Cellular and molecular regulation of skin by ginseng and its bioactive Constituents: A review of studies from 2021 to 2025

Abstract

The skin functions as the first line of defense against external and internal stressors, containing pathogen invasion, ultraviolet (UV) radiation, and the loss of collagen and hydrogen, all of which could finally cause skin damage and cellular senescence. Over time, a large plenty of strategies, including herb therapies, have been developed to protect skin health. Ginseng is a well-known traditional herbal medicine that has been widely applied in various diseases. In recent years, ginseng and its bioactive compounds attracted increasing attention in dermatological and cosmeceutical research because of their modulatory effects on inflammation, melanogenesis, skin barrier function, and skin regeneration. Five years ago, a paper summarized the skin-protective properties and mechanisms of Korean Red Ginseng in different types of skin cells. Since then, another lustrum has passed, during which some new functions and insights related to ginseng in skin have been reported. Therefore, this paper reviews studies published over the past five years that investigate the effects and mechanisms of ginseng-derived compounds in keratinocytes, melanocytes, and fibroblasts. Moreover, the corresponding animal models are organized and discussed. This review provides an updated and structured reference to support future phytopharmacological and cosmeceutical development of ginseng-based studies for skin health.

Graphical abstract

1. Introduction

In the current environment, people undergo increasing intensity and diversity of environmental hazards, such as radiation, pollutants, and pathogens. These threats cause extensive skin damage, leading to inflammation, barrier dysfunction, and even aging. As the largest organ of our body, skin is the foremost line of defense, comprising three layers: epidermis, dermis, and subcutaneous tissue [1].

The epidermis can be organized into five strata, containing stratum corneum, lucidum, granulosum, spinosum, and stratum basale from superficial to deep layer. Among these layers, the stratum lucidum is an additional layer that is found only in the thick epidermis of the palms and soles. Within these layers reside four types of skin cells: Keratinocytes, Melanocytes, Langerhans cells, and Merkel cells. Keratinocyte is the predominant type in the epidermis, accounting for about 90 % of epidermal cells. It originates from the stratum basale, which is also the basal layer of the epidermis. Keratinocyte is most pivotal because it can produce a crucial protein called keratin [2]. Keratin can strengthen our skin and protect the skin from outside damage. Keratinocytes, divided by the stem cells, will migrate from the basal layer to the superficial layer to act different roles. The keratinocytes in the stratum spinosum are responsible for the structural integrity and elasticity of the skin. Whereafter, keratinocytes produce numerous keratins in the stratum granulosum, called keratinization. At the same time, keratinocytes become flat and fragile, as well as the nuclei are degraded [1]. Keratinocytes almost die after they enter the stratum lucidum because of lacking nutrients and oxygen. These dead keratinocytes are extruded to the surface of the skin, known as corneocytes, which form a hard shell to protect the skin from injury. This mature process of keratinocyte is addressed as terminal differentiation and takes around 25–45 days [3]. Melanocytes, located in the stratum basale as well, regulate the skin color through producing melanin, a dark pigment. And the organelle which secrete melanin is called a melanosome. Melanosome could be transferred from melanocytes to surrounding keratinocytes through cell release and uptake, leading to skin pigmentation and photoprotection [4]. The other two types of epidermal cells are Langerhans cells and Merkel cells [5]. Merkel cells are also called tactile epithelial cells because they are sensitive to light, touch, and other sensations [6]. The epidermis also contains appendages, including hair follicles, nails, and sweat glands.

The dermis is the middle layer of the skin, which can support the epidermis, keep the flexibility and moisture, regulate the body temperature, and remain multiples of sensations. The dermis consists fibroblast, macrophages, mast cell and so on. Besides, other specialized structures like hair follicles and various glands are also settled in the dermis. Among them, fibroblast is the leading cell type in the dermis, which can produce collagen and elastin. Other cell types, like macrophages and mast cells, are related to inflammation and immune responses. According to the functions, the dermis contains papillary dermis and reticular dermis. Papillary dermis is located on the reticular dermis, which is thinner than the latter. It contains fibroblasts and collagen fibers. While reticular dermis comprises many glands, hair follicles, and so on [7]. The immune cells, like macrophages and mast cell are located in both papillary dermis and reticular dermis [8].

The last layer of skin is subcutaneous tissue, which connects and protects underlying structures, stores fat, and maintains body temperature. Actually, subcutaneous tissue is made of fibroblasts, adipocytes, and immune cells like macrophages as well [9].

Currently, several natural products, including green tea, Aloe vera, and Centella asiatica, display excellent properties on skin health, such as anti-aging, wound-healing, and antioxidant activities [10]. Besides these plants mentioned above, other herbs also exhibit various skincare benefits, particularly ginseng. Ginseng is a traditional Chinese medicine that has been used for more than two millennia. According to the region of cultivation, ginseng could be classified into four types. The first type is Panax ginseng C.A. Meyer, also known as Korean Ginseng, which is mainly cultivated in northern China and Korea. The second type is Panax notoginseng Burk, which grows in southern China and is called Sanqi or Sanchi as well. The remaining two types are American ginseng (Panax quinquefolium L.) and Japanese ginseng (Panax japonicus C.A. Meyer). According to processing methods, Panax ginseng C.A. Meyer can be classified into three forms: white ginseng (WG), red ginseng (RG), and black ginseng (BG). WG refers to fresh ginseng roots that are dried under sunlight, exhibiting a white or beige color. RG is steamed at 95–100 °C for a reasonable period (usually 2–3 h), followed by drying until the moisture content is reduced below 15 %, resulting in a reddish-brown color. In addition, Korean red ginseng (KRG) is identical to RG. The third form, BG, undergoes repeated steaming and drying (often 9 times) until it becomes black in color. The pharmacological value of ginseng has been scientifically investigated, including numerous bioactive components such as ginsenoside, amino acids and peptides, polysaccharides, as well as various other active constituents [[11], [12], [13], [14], [15], [16], [17], [18], [19]]. Therefore, ginseng and its ingredients could be used to relieve inflammation, improve immunity, and even inhibit tumor growth [12,[20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36]]. Additionally, the extracts of ginseng and their individual compounds exhibit outstanding benefits in skin health, including antioxidant, anti-aging, anti-inflammatory, moisturizing, and wound-healing effects [14,16,23,30,[37], [38], [39], [40], [41], [42]]. In light of this, a review published five years ago summarized the regulatory role of ginseng in skin-related cells [43]. Given a substantial amount of research on ginseng and its effects on the skin published in the past five years, we aim to summarize these complex studies according to skin-related cell types and present them in a structured manner for the benefit of readers. Therefore, this review will focus on the regulatory role of ginseng and its bioactive components in primary skin cell types, including keratinocytes, melanocytes, and fibroblasts.

2. Regulatory effects of ginseng and its active components on keratinocytes

2.1. Protective effects of ginseng and its active components on keratinocytes against UV radiation

As we introduced before, keratinocytes form an armour to protect the skin from outside damage, such as UV radiation, pathogenic organisms, and harmful chemicals [44]. In the past five years, some studies related to ginseng have been published to demonstrate the protective effects against UV radiation. UV has three types containing UVA, UVB, and UVC. UVA has the longest wavelength, whereas UVC has the shortest but strongest energy [45]. To simulate natural UV radiation, UVB is commonly applied as an inducer in experiments evaluating the protective effects of ginseng. Shin et al. reported that Halophyte red ginseng complex extract (HRCE) could rescue the cell viability, collagen type I (COL-1), and elastin of human keratinocytes (HaCaT) irradiated by UVB. Meanwhile, UVB exposure up-regulated the protein level of Matrix Metalloproteinases (MMP)-1 and MMP-9, whereas HRCE reduced their expression and down-regulated the phosphorylation of c-Jun N-terminal kinase (JNK), mitogen-activated protein kinase p38 (p38), extracellular signal-regulated kinase (ERK), as well as nuclear factor kappa B (NF-κB) induced by UVB. In male hairless mice, UVB exposure increased the epidermal thickness and transepidermal water loss (TEWL), while HRCE treatment alleviated these effects. The changes in elastin and collagen protein levels observed in UVB-exposed mice were consistent with those seen in HaCaT cells. Therefore, HRCE could prevent the degradation of collagen and elastin from UVB radiation in both in vitro and in vivo models [46]. Additionally, KRG strengthened the skin barrier and hydrogen-related genes, such as Hyaluronan Synthase 2 (HAS-2), Serine Palmitoyltransferase Long Chain Base Subunit 2 (SPTLC2), Ceramide synthase 3 (CerS3), and loricrin in human keratinocytes. Moreover, KRG up-regulated telomerase and promoted cell migration through NF-κB activation, regardless of UVB exposure [47]. Another study on RG demonstrated that single or combined treatment with red ginseng extract (RGE) and velvet antler extract (VAE) enhanced the viability of HaCaT as well as reduced UVB-induced apoptosis in both HaCaT and SKH-1 hairless mice. At the same time, inflammatory cytokines induced by UVB exposure, such as cyclooxygenase-2 (COX-2), interleukin-1 beta (IL-1β), and tumor necrosis factor (TNF-α), were suppressed by RGE and VAE treatment. AP-1-mediated MAPKs and NF-κB signaling pathways, as well as the caspase signaling cascade, were inhibited. The effects of anti-oxidation and skin barrier were also strengthened by RGE and VAE [48]. Not only RG, BG also showed protective effects against UVB radiation. Kim et al. reported that fermented black ginseng extract (FBGE) can suppress UVB-induced expression of MMP-1, MMP-9, COX-2, IL-8, TNF-α and prostaglandin E2 (PGE2), which were mediated by nc886-PKR signaling pathway [49]. In addition to the previously mentioned red and black ginseng extracts, Chen et al. screened 14 extracts and found that dermal application of Panax ginseng extract for 9 weeks could reduce the degradation of collagen as well as inhibit apoptosis in both UVB-irradiated keratinocytes and BALB/c mice [50]. Furthermore, the observed damage was attributed to endoplasmic reticulum (ER) stress and was mediated by the up-regulation of vacuole membrane protein 1 (VMP1). Lee et al. also performed a similar experiment in which SKH-1 hairless female mice were exposed under UVB irradiation for 10 weeks to evaluate the protective role of fermented and aged mountain-cultivated ginseng sprouts (FAMCGSs) [51]. Unlike previous studies, FAMCGSs were administered orally. Similar to the study by Shin et al., the biomarkers exhibited the great anti-photoaging properties of FAMCGSs. Son et al. proved that processed ginseng leaves (PGL) containing ginsenosides also exhibited anti-photoaging effects [52]. Not only leaves, but the berries derived from Panax ginseng also exhibited anti-photoaging functions. Tan et al. reported that Ginseng berry rare saponins (GFRS) prevent UVB injury through activating Nuclear factor erythroid 2-related factor 2 (Nrf2)/Heme-oxygenase 1 (HO-1)/Glutathione peroxidase 4 (GPX4) pathways and suppressing ferroptosis both in vitro and in vivo [53]. Choi et al. reported that ginseng root-derived exosome-like nanoparticles (GrDENs), identifying 10 ginsenosides, mitigated apoptosis and inhibited the expression of MMP-related genes and inflammatory cytokines by targeting MEK1/2 and AP-1 signaling axis [54]. Li et al. examined the protective effects of ginsenosides mixture [55] and ginseng oligosaccharide extract [56] in both HaCaT and BALB/c mice under UVB exposure. The Ginsenosides promoted the skin barrier and hydration-related genes, such as filaggrin (FLG), involucrin (IVL), and Aquaporin 3 (AQP3). While ginseng oligosaccharide extract not only can rescue the proteins above, but also restore the expression of desquamation-related genes, such as serine protease inhibitor Kazal type-5 (SPINK5), kallikrein related peptidase 5 (KLK5), KLK7, and desmoglein 1 (DSG1). Liu's group extracted ginseng glycoproteins and ginsenosides to evaluate the anti-photoaging activities in diabetic rats instead of hairless mice. The results demonstrated that both ginseng glycoprotein and ginsenosides can relieve oxidative stress and collagen degradation induced by the combination of diabetes and UVB exposure [57].

Given much research on ginseng-related extracts, several individual compounds derived from ginseng have been investigated as well, particularly ginsenosides. Ginsenosides can be categorized into four types, including protopanaxatriol (PPT)-type, protopanaxadiol (PPD)-type, ocotillol-type, and oleanolic acid-type [58]. Oh et al. reported that inflammatory cytokines secreted by keratinocytes under UVB radiation could stimulate fibroblasts to produce MMPs, which would impair skin integrity and lead to wrinkle development. Whereas, S-Rg2, a PPT-type ginsenoside without any toxicity under 100 μM in Hs68 cells, can significantly reduce the expression of MMPs at 50 μM [59]. Besides that, Jeong et al. demonstrated that combination treatment with S-Rg2 and piceatannol reduced the ROS and facilitated the repair of UVB-induced DNA damage, thereby exhibiting great anti-photoaging and antioxidant effects [60]. In addition to PPT-type ginsenosides, four PPD-type ginsenosides also exhibited protective activity against UVB. Lee et al. observed that ginsenoside Rd alleviated UVB-induced ROS generation and MMPs production in HaCaT cells [61]. Moreover, Rd enhanced the production of total glutathione (GSH) and superoxide dismutase (SOD). Another PPD-type ginsenoside, S-Rg3, incorporated into a hydrogel (Rg3-Gel) at a concentration of 10 μg/mL for safety, not only suppressed ROS and MDA, but also increased the activity of antioxidant enzymes such as SOD and GSH-Px. Additionally, Rg3-Gel modulated apoptotic pathways by downregulating Bcl-2 and upregulating Bax and Caspase-3 in HaCaT under UVB exposure [62]. Rk1 has been found to exhibit nearly all the antioxidative, anti-inflammatory, and collagen-protective properties reported ginsenosides as demonstrated in UVB-irradiated HaCaT and BALB/c nude mice. Moreover, phosphatidylinositol 3-kinase (PI3K)/serine-threonine Protein Kinase (AKT)/NF-κB signaling pathways were suppressed in Rk1 [63]. As a secondary metabolite of three ginsenosides (Rb1, Rb2, and Rc), Compound K (CK) underwent various examinations for its UV protective properties. Park et al. demonstrated that CK enhanced the protein level of SPINK5, which was subsequently inhibited by downstream targets such as tissue KLKs and protease-activated receptor 2 (PAR2), in both UVB-exposed HaCaT at 15 mJ/cm² and SKH-1 hairless mice at 100 mJ/cm². CK administration alleviated TWEL and epidermal thickness, and improved skin hydration as well. The similar results were also observed in SKH-1 mice topical administrated 1 % 1-chloro-2,4-dinitrobenzene (DNCB) [64]. More interestingly, Kim et al. evaluated the anti-photoaging effects of CK in primary normal human keratinocytes (NHKs), HaCaT cells, and human skin equivalents subsequently induced by IL-17A and UVB. Senescence-Associated β-Galactosidase (SA-β-Gal) assay revealed obvious inhibition in cellular senescence following CK treatment. Then, CK downregulated the mRNA and protein levels of pro-inflammatory cytokines through blocking p38 and NF-κB signaling pathways, while the genes of Filaggrin, Keratin 10, and Collagen 17 were rescued by CK as well [65]. Combined treatment with CK and retinol showed good skin-protective properties in both UVA-induced HaCaT and zebrafish [66]. UV radiation can also can involve in inflammasome activation, a process containing two steps. The first step of inflammasome activation is the priming step, the enhancement of inflammasomes related genes. Then, the second step is the maturation of cytokines, called the activation step. Ahn et al. used IL-1β to evaluate the functions of KRG, saponin fraction (SF), and non-saponin fraction (NS) on the process of inflammasome activation. To simulate the priming phase, cells were pre-treated with poly I:C, followed by UV radiation to initiate activation. Interestingly, when KRG, SF, and NS were administrated after UV radiation, the production of IL-1β cannot be inhibited in HaCaT cells. Whereas if KRG and its sub-fractions were treated during the priming step, IL-1β can be significantly blocked. This suggested that KRG and its sub-fractions primarily targeted and modulated the early priming step of inflammasome activation [67]. Moreover, maltol, a non-saponin derived from KRG, can selectively suppress the inflammasome activation induced by Staphylococcus aureus in HaCaT cells through interrupting the priming step of inflammasome activation and reducing the production of mitochondrial reactive oxygen species. Moreover, in S. aureus-injected mice, maltol restrained the expression of IL-1β and IL-6 in the peritoneal cavity [68].

2.2. Roles of ginseng and its active components in keratinocyte responses to other stress conditions

After discussing the protective effects of ginseng against UV radiation, its additional stress factors are further addressed. Kim et al. reported that KRG relieved the skin damage stimulated by immersion in a 45 °C water bath. KRG rescued impaired skin barrier markers such as AQP3, CerS3, and occludin, while inhibiting the expression of MMPs and pro-inflammatory cytokines. Meanwhile, immunoblots suggested that KRG repaired the thermal stress-induced damage through suppressing NF-κB signaling [69]. Particulate matter (PM) is another kind of skin-harmful substance. Moon et al. assessed the protective effects of saponins from KRG on NHKs under PM10-induced stress, which improved the cell viability and attenuated oxidative stress. The MMPs and pro-inflammatory cytokines were also suppressed [70]. Kang et al. reported that KRG prevented 50 μg/mL PM2.5-induced senescence in both HaCaT and NHKs via down-regulating p16^INK4A, an important senescence marker. Epigenetic experiments revealed that KRG reversed PM2.5-stimulated alterations in DNA and histone-modifying enzymes, thereby inhibiting the expression of p16^INK4A in transcription levels [71]. Lee et al. used DNCB to induce AD in NC/Nga mice [72], while Wu et al. topically applied calcipotriol (MC903) to the ears of female BALB/c mice to establish an AD model [73]. Lee et al. indicated that the combination treatment of KRG and probiotics can strengthen the prevention of AD-induced skin lesions. Whereas, Wu et al. relieved allergic inflammation and improved skin barrier through co-treatment of tetrandrine, icariin and PPT-type ginsenoside Rg1. Besides, the formulations of KRG were investigated as well. Pfleger et al. developed a KRG-loaded vehicle containing oil-in-water nanoemulsions (NEs) and hydroalcoholic gels (2 % w/w KRG) to evaluate biocompatibility and radical scavenging ability, exhibiting good DPPH scavenging abilities [74]. Another ginseng-derived nanoparticles (GDNPs) accelerated the cell proliferation and wound healing both in HaCaT cells and ICR mice through activating ERK and AKT/mTOR signaling pathways [75].

In addition to KRG, other ginseng-related products also exhibited a protective role on human keratinocytes. Ramadhania et al. reported that Black ginseng fermented by Aspergillus niger strain KHNT-1 (FBG), BG, and WG exhibited the anti-aging properties in H₂O₂-treated HaCaT [76]. The individual compound, syringaresinol (SYR) derived from Panax ginseng berry, also suppressed the aging caused by H₂O₂ through up-regulating autophagy [77].

For wound healing, Gintonin, which contains lysophosphatidic acids (LPAs), accelerated the wound healing-related cellular responses through activating LPA receptor and Vascular Endothelial Growth Factor (VEGF)-mediated AKT/ERK signaling pathways [78]. Furthermore, Won et al. demonstrated that Gintonin (10 μg/mL) also can also enhance wound healing effects by activating the phosphorylation of the epidermal growth factor receptor (EGFR) and inducing the expression of heparin-binding EGF-like growth factor (HB-EGF) [79]. Two additional PPD-type ginsenosides, Rb1 and its metabolite 20(R)-ginsenoside Rg3 (R-Rg3) (IC50 more than 150 μM), promoted proliferation and migration in HaCaT cells at concentrations below 28 μM, suggesting wound-healing potential [80,81]. Moreover, R-Rg3 also accelerated the wound closure in BALB/c mice at a concentration of 100 μM [80]. Not only ginsenosides, polydeoxyribonucleotide (PDRN) derived from the adventitious roots of Korean ginseng can speed wound healing both in HaCaT cells and in an artificial skin model as well [82].

2.3. Regulatory functions of ginseng and its active components in healthy keratinocytes

After introducing the protective roles of ginseng and its constituents against various stress-induced damage in keratinocytes, their regulatory role on healthy keratinocytes was also exhibited. Kim et al. found that BIOGF1K, a ginsenoside-rich fraction primarily composed of CK, dramatically strengthened skin barrier integrity in HaCaT cells [83]. In this investigation, transepithelial electrical resistance (TEER) related to tight junctions (TJ) was measured by ohmic resistance to evaluate skin barrier integrity. BIOGF1K notably increased TEER within 600 min, suggesting enhanced skin barrier integrity through improving TJ.

Another secondary metabolite ginsenoside, PPT, revealed the clear mechanisms in supporting skin barrier and hydration in HaCaT. PPT up-regulated the mRNA expression of FLG, TGM-1, Claudin, and Occludin at 20 μM. Meanwhile, for skin hydration maintenance, PPT induced the expression of HAS-1, -2, -3, and AQP3. Luciferase assay and immunoblots revealed that PPT activated Src-mediated NF-κB and MAPKs signaling pathways [84]. Further upstream investigation revealed that PPT stimulated the autophosphorylation of EGFR and human epidermal growth factor receptor 2 (HER2), which were confirmed by gene overexpression and cellular thermal shift assay (CETSA) [85].

In addition to wound healing, PDRN enhanced the skin barrier through stimulating adenosine A2A receptor and following the focal adhesion kinase (FAK)/AKT/MAPKs signaling. Meanwhile, the mRNA levels of fibronectin (FN1), FLG, and Antigen Kiel 67 (Ki-67) were up-regulated, highlighting its role in promoting skin barrier function [82].

3. Modulatory effects of ginseng and its active compounds on melanocytes

As we introduced before, melanocyte is another important cell type responsible for melanin secretion. Therefore, the process by which melanocytes synthesize and secrete melanin is known as melanogenesis [1]. Melanogenesis can be activated by both physical and chemical stimuli, such as UV and α-Melanocyte-stimulating hormone (α-MSH). During this process, the pivotal enzyme is tyrosinase, which catalyzes the conversion of the amino acid tyrosine into melanin. Because of this, tyrosinase is used as a critical marker to evaluate the effects of compounds on melanogenesis.

3.1. Ginseng and its constituents suppress melanogenesis in vitro

RG is one of the most important Panax ginseng products in Asia, and steamed ginseng dew (SGD) can be processed during the RG production. Zhang et al. employed phytochemical extraction methods to isolate RG and SGD through different organic solvents. They found that the ethyl acetate extract of RG, along with n-butanol and chloroform extracts of SDG, exhibited significant tyrosinase inhibition [86]. Normally, B16F10, a murine melanoma cell line derived from C57BL/6J mice, was applied to evaluate the effects of compounds on melanogenesis in vitro. Meanwhile, α-MSH is commonly used as an inducer in B16F10 cells. Tan et al. reported that the extract of GFRS, treated with citric acid at 100 °C, significantly suppressed tyrosinase activity and melanin content under α-MSH induction. Moreover, heat treatment with citric acid converted Rd into S-Rg3, Rg5, and Rk1, thereby improving the efficiency of anti-melanogenesis [87]. Similar results were also obtained from new green berry cultivar K-1 (GK-1) [88] and Panax notoginseng [89] in B16 cell line. In addition, Park et al. also used another method to evaluate the anti-melanogenesis activity with hydroponic ginseng (HG) fermented with Bacillus Strains in B16F10 cells [90]. The black dot appeared in L-3,4-dihydroxyphenylalanine (L-DOPA) staining after treating α-MSH, indicating the enhancement of tyrosinase activity. Whereas HG reduced these black dots. At the same time, the genes related to melanogenesis, including tyrosinase, tyrosinase-related protein (TYRP)-1, TYRP-2, and microphthalmia-associated transcription factor (MITF), were inhibited by HG. The extract of KRG [91] and Korean red ginseng oil (KGO) [92] block the protein levels of these genes as well. Beyond KRG mixtures, several individual ginsenosides have been shown to inhibit melanogenesis. Ginsenoside Rb1 and Rd can be catalyzed by an enzyme to produce compounds such as gynostapenoside XVII, LXXV, ginsenoside F2, and CK, all of which exhibited strong anti-melanogenic effects [93]. Not only the inhibitory roles of ginsenoside Rf and Re in melanogenesis were checked, but their mechanisms were also investigated as well. Ginsenoside Rf inhibited melanogenesis through down-regulating adenylate cyclase (AC)/adenosine cyclic 3′, 5′-monophosphate (cAMP)/protein kinase A (PKA) and nitric oxide (NO)/guanylate cyclase (GC)/guanosine cyclic 3′, 5′-monophosphate (cGMP)/protein kinase G (PKG) signaling cascades [94]. In contrast, Re up-regulated AKT and ERK phosphorylation, and induced MITF degradation through the proteasome [95]. Two compounds were found to alleviate melanogenesis. One compound is acremonidin E isolated from Penicillium sp. SNF123, that is a symbiotic fungus with Panax ginseng. The coincident results were obtained in α-MSH-induced B16F10 and human melanoma cell line MNT-1 after treating with Acremonidin E. Moreover, the treatment of acremonidin E in co-cultured MNT-1 and HaCaT system revealed the regression of MNT-1 dendrites, which indicated the suppression of melanosome transfer between melanocytes to keratinocytes in human epidermis [96]. Another compound, SYR, isolated from ginseng berries, also exhibited similar properties [97]. Liu et al. reported that the phenolic acids derived from Panax ginseng, including salicylic acid (SA) (3.1 μg/mL), protocatechuic acid (PA) (4.2 μg/mL), p-coumaric acid (p-CA) (1.2 μg/mL), vanillic acid (VA) (68.5 μg/mL), and caffeic acid (CA) (1.4 μg/mL) can relieve hyperpigmentation [98]. Similar to acremonidin E, SA also can interrupt melanogenesis and block the transport of melanosome. Meanwhile, both HEM and HaCaT were irradiated by UVB, and two transport related proteins melanophilin and myosin Va were inhibited as well. The results showed that SA down-regulated AC/cAMP/PKA/CREB/MITF signaling cascade in melanocytes and UVB-induced PAR2/Ca²⁺/PI3K/AKT/MAPKs signaling pathways in keratinocytes [99]. For the other four components, PA, p-CA, and VA suppressed melanogenesis in B16F10 cells, whereas CA induced hyperpigmentation [98]. Another case of UVB-induced HEM was reported by Cho et al., and the melanogenesis was restrained by extracellular vesicles (EVs) [100].

Melanogenesis not only can be induced by UVB and α-MSH, but also can be stimulated via other chemicals. For example, fermented black ginseng not only can inhibit melanin production in B16F1 cells [101], but also can block in 3-isobutyl-1-methylxanthine (IBMX)-stimulated B16F10 cells [76]. However, the latter black ginseng was fermented by Aspergillus niger strain KHNT-1. Previously, Chen et al. demonstrated that ginsenoside Rf can inhibit α-MSH-induced melanogenesis in B16F10 cells [94]. While Lee et al. found that Rf also weakened melanin formation in another mouse melanocytes Mel-Ab stimulated by Forskolin (FSK). In addition, Rf down-regulated MITF and the phosphorylation of CREB [102]. Kim et al. reported that FSK-induced melanin secretion in B16 cells can be suppressed by a decoction named GMC made of Ginseng Radix Alba and Mori Radicis Cortex at a ratio of 3:2. This inhibition was also visualized by Fontana–Masson staining [103]. PM also induced melanin production in NHMs and NHKs co-cultured models. However, the overproduction of melanin can be eliminated by KRG saponins [70]. In addition, the cream made of Rh1, S-Rg2, and Hydrangea macrophylla flower extract can mitigate tyrosinase activity in human melanoma cells SK-MEL-2 [104], whereas panaxynol derived from Panax ginseng sprout strongly suppressed melanogenesis in Melan-a cells [105].

Next, the effects of ginseng and its active components in artificial skin models were addressed. Lee et al. employed 70 mJ/cm² UVB to irradiate ex vivo skin tissue stripped from a female donor. The immunoblots and histological analysis were evaluated, respectively. Results indicated that Rf alleviated UVB-induced melanin secretion. Meanwhile, the protein expression of MITF, Tyr, TYRP 1, and TYRP2 induced by UVB was blocked as well [102]. Kim et al. reported that acremonidin E [96] and SYR [97] suppressed melanin content and distribution in artificial pigmented human epidermis (Melanoderm™). Additionally, the accumulated melanin and dendrites were inhibited by SYR as well.

In addition to melanogenesis assays, SYR attenuated α-MSH-induced ROS production in B16F10 cells, and restrained the expression of NADPH oxidase 4 (NOX4), a key cytosolic ROS marker [97]. Ginseng and its active components not only can inhibit melanogenesis, but also can protect melanocytes from H₂O₂ injury. Tang et al. reported that CK derived from Panax notoginseng Burk protected oxidative injury from H₂O₂ in human primary skin epidermal melanocytes (HEMn-MPs). The MTT assay indicated that CK was not toxic to the cells at concentrations below 2.5 μg/mL. Meanwhile, CK dramatically ameliorated oxidative stress through improving cell death and enhancing GSH and oxidized glutathione at 1.25 μg/mL [106]. Moreover, Rk1 induced the expression of SOD, CAT, and GSH-Px and prevented human PIG1 melanocytes from H₂O₂ oxidative lesion through up-regulating PI3K/AKT/Nrf2/HO-1 signaling cascade [107].

3.2. Ginseng and its constituents suppress melanogenesis in vivo

Currently, four animal models have been employed to evaluate the effects of compounds on melanogenesis. The most commonly used model is zebrafish, followed by HRM-2 hairless mice and C57BL/6 mice. Guinea pigs were also utilized.

In zebrafish models, GFRS, containing ginsenoside S-Rg3, Rg5, and Rk1, dramatically inhibited endogenous melanin production and tyrosinase activity. Compared with arbutin, GFRS exhibited the stronger anti-melanogenic effects [87]. Re and Rf [94] also suppressed melanogenesis in zebrafish. The zebrafish embryos were fertilized 9 h ahead and incubated with Re and tyrosinase inhibitor 1-phenyl-2-thiourea (PTU) for another 26 h, which is named 9-h post-fertilization (9-hpf) to 35-hpf. After 35 h of incubation, the zebrafish embryos were imaged under a stereomicroscope, revealing reduced body pigmentation in Re- and PTU-treated groups [95]. Wang et al. demonstrated that protopanaxatriol saponins (PTS) (Rg1, Re, and Notoginsenoside R1) from Panax notoginseng produced greater anti-melanogenic effects than protopanaxadiol saponins (PDS) (Rb1 and Rd). PDS displayed higher toxicity than PTS, although both of them can reduce tyrosinase activity. Meanwhile, the PTS significantly decreased melanin content in zebrafish embryos, whereas the effects of individual Rg1, Re, and R1 were relatively weak [89]. Extract from Panax ginseng sprouts (GSs) [105], salicylic acid [99], and ginseng-derived oligosaccharide also reduced the melanin content and tyrosinase activity in zebrafish.

Another two animal models are HRM-2 hairless mice and C57BL/6 mice. Saba et al. employed UVB to irradiate HRM-2 hairless mice and evaluated the melanin formation on the dorsal skin at 1st, 3rd, and 5th week. The results revealed that KRG and KGO started to alleviate the melanin secretion from the 3rd week. Meanwhile, KRG and KGO also reduce the wrinkle formation and collagen degradation [91,92]. H&E staining showed no obviously damages on the back of C57BL/6 mice for four weeks. PTS and PTS combined with ethosome were applied topically on mice, which exhibited significant inhibition on melanin production [89]. Huang et al. evaluated the anti-proliferation effects of Re in C57BL/6 mice subcutaneously injected with B16F10 cells. The xenograft tumors, as well as related genes such as MITF, Bcl-2, HIF-1α, and Ki67 were suppressed at 25 mg/kg. Whereas the cleaved caspase-3 and tumor vascular normalization were enhanced as well [95].

Finally, in Guinea pigs, Tang et al. demonstrated that Sanqi-CK markedly rescued the dysregulated depigmentation caused by rhododendrol [106]. Topical treatment of Rhododendrol for 21 days could produce cytotoxic ROS, which reduced melanin contents and TYRP1 level. Whereas Sanqi-CK improved this abnormal disappearance and prevented the melanocytes from oxidative stress.

4. Impact of ginseng and its components on skin fibroblasts

In addition to keratinocytes and melanocytes, ginseng was also applied in studying the protective impacts on skin fibroblasts. Most studies were focused on the inflammation and senescence under UV- or H₂O₂-induced damage. Therefore, the studies of ginseng on skin fibroblasts were systematically sorted out according to the stressors.

4.1. Protective effects of ginseng and related ingredients on skin fibroblasts under UV-induced injury

The scientists also want to make it clear how ginseng modulates skin fibroblasts exposed to UV. Heo et al. separated the seed of Panax ginseng C.A. Meyer into ginseng seed embryo (GSE) as well as ginseng seed coat (GSC), and assessed their protective effects in Hs68 cells under UVB exposure [108]. The results exhibited that GSE and GSC rescued the cell viability inhibited by UVB. Moreover, both GSE and GSC dramatically inhibited the UVB-induced ROS, MMP-1, and MMP-3, but regenerated the fibrillar collagens through down-regulating MAPKs/AP-1 and Suppressor of mother against decapentaplegic 7 (Smad7) signaling cascades and up-regulating transforming growth factor-β (TGF-β) and Smad2/3 signaling pathways. Similar results were also displayed in Hs68 cells treated by GSs with kelp fermentates [109].

HDF cells are another major cell types which are used abundantly in study skin fibroblasts. Previously, Ramadhania et al. compared the functions of FBG, BG, and WG in different types of skin cells [76]. FBG showed the greatest inhibition in UVB-induced elastase, which is associated with collagen degradation and elastin loss. Moreover, FBG showed dramatic effects on the suppression of MMP-1 and MMP-9, while enhancing the expression of COL-1. Similar results were obtained in CCD-986sk cells as well [101]. Furthermore, the functions of Rh2, SYR, and Gintonin were investigated in UV-damaged HDFs as well. Individual administration of Rh2 accelerated proliferation and wound healing activities at low concentration (less than 50 μM). For the extracellular matrix, Rh2 rescued the expression of collagen 1 and elastin as well as inhibited the mRNA level of MMP-2 and protein level of MMP-3. Meanwhile, Rh2 showed an anti-oxidative role through up-regulating NRF-2 and HO-1. In addition to these, UV irradiation changed the morphology of mitochondria, interfered with its functions, and initiated the mitophagy, which was ameliorated by Rh2 [110]. UVB-induced NO and ROS production were alleviated by gintonin, exhibiting the anti-aging effects [111]. Additionally, Ngo et al. reported that the combination treatment of 50 % ethanol extracts consisting of enzyme-processed Panax ginseng and Gastrodia elata at the ratio of 1:10 could alleviate the pro-COL-1 destroyed by UVB as well as block the production of MMP-1 and IL-6. Their isolated ingredients, ginsenoside F2 and α-gastrodin, showed similar properties as well [112]. SYR repressed MMP-1 and pro-COL-1 induced by UVA in both HaCaT and HDF cells through MAPK/AP-1 signaling pathways [113].

Other cell types related to fibroblasts were also applied to evaluate ginseng-related compounds under UVA radiation. Xu et al. found that wild ginseng adventitious root protein mixture (ARP) remarkably repressed the apoptosis induced by UVA in NIH3T3 cells. UVA-induced cell cycle arrest and DNA damage were alleviated by ARP as well [114]. UVA not only resulted in cell cycle arrest, but also caused oxidation in HFF-1 cells. Sun et al. proved that the phenolic acids derived from the forest ginseng (FG) blocked the DNA oxidative damage through Nrf2 signaling pathways [115]. Both two ginseng related extracts can enhance the secretion of COL-1 as well. Ginseng-derived peptides (GPs) reported by Xia et al. reversed collagen production in human skin fibroblasts (HSF) and 3D dermal model [116]. Additionally, Li et al. used UVB-exposed L929 cells and zebrafish to indicate the anti-oxidative and anti-wrinkle properties of GFRS [117].

4.2. Protective effects of ginseng and related constituents on skin fibroblasts under H₂O₂-induced stress

Not only UV radiation, but H₂O₂ also acts as a common stimulator for oxidative stress-induced senescence. Hwang et al. introduced that SYR also enhanced the wound healing along with H₂O₂ in both Hs68 cells and ex-vivo human skin tissues [118]. While in HDF cells, the polysaccharides derived from fermented Panax notoginseng roots (FPNP) could repress the oxidation resulting from H₂O₂ and attenuate the degradation of collagen and elastin. FPNP can activate the expression of TGF-β and Smad2/3, whereas down-regulated Smad7 [119]. The rejuvenation of cellular senescence has always been a popular research topic, yet no studies have explored the role of ginsenosides until Ginsenoside S-Rg3 was identified as a potential compound for reversing aging. Jang et al. revealed that S-Rg3 could partially invert senescent HDFs through activating peroxiredoxin at 10 μM [120]. One year later, they reported that S-Rg3 reduced ROS production and reversed H₂O₂-induced senescence by activating the Ca²⁺ membrane channel protein ORAI1, thereby promoting AMPK-mediated autophagy at the same concentration [121]. Ginseng oligopeptides (GOPs) and Panax notoginseng fermented extract (pnFE) were evaluated in H₂O₂-induced NIH3T3 cells and MSFs, respectively. Both GOPs and pnFE reduce the ROS and MDA production, whereas enhanced the activities of SOD, GSH-Px, and CAT. In addition, GOPs also regulated cell cycles, inhibited aging-related proteins p16 and p21, prevented cell cytotoxicity and DNA damage, and prolonged telomerase activities. The functions of mitochondria in H₂O₂-induced NIH3T3 cells were also ameliorated through NAD⁺/SIRT1/PGC-1α pathway [122]. Additionally, the safety and stability of pnFE were evaluated by red blood cell test and hen's egg test-chorioallantoic membrane assay [123], which was confirmed as a potential product in cosmetics. Similar anti-aging results were found in Panax notoginseng oligosaccharides (PNO) by Zhai et al. in NIH3T3 cells [124]. The expression of several proteins, like proliferating cell nuclear antigen (PCNA), cyclin E, cyclin D1, and cyclin-dependent kinase 4 (CDK4) were also enhanced.

4.3. Protective effects of ginseng and related components on skin fibroblasts under other stress conditions

TNF-α is another type of stimulator for skin fibroblasts, which can induce inflammatory responses. ROS triggered by TNF-α led the oxidation in skin fibroblasts and finally caused senescence. Four ginseng-related products were investigated in HDFs under TNF-α stimulating, those are tissue-cultured mountain-grown ginseng (TG) [125], solid-state fermented ginseng with Aspergillus cristatus (GFFG), Withagenin A Diglucoside from Indian Ginseng (WAD) [126], and the hot water extract of fresh P. ginseng roots (HWEG) [127] containing ginsenoside Rf. Similar to other ginseng-related extracts under UV and H2O2 induction, these extracts suppressed the production of MMP-1 and ROS stimulated by TNF-α, and enhanced the secretion of pro-COL-1. Moreover, WAD inhibited the expressions of HO-1, IL-6, IL-8, and COX-2 through decreasing the phosphorylation of MAPK/AP-1 signaling pathways.

Without the senescence stimulators, ginseng-related products themselves still brought benefits to skin fibroblasts. In HDFs, ginseng non-edible callus-derived extracellular vesicle (GNEV) accelerated the regeneration by enhancing the protein levels of TGF-β, COL1A1, and Smad2/3 [128]. The extract of KRG can induce the accumulation of collagen, elastin, and fibrillin, while down-regulating the ratio of F-actin and G-actin, which reversed elasticity. Not only S-Rg3, Rb2 was found to induce autophagy as well. Yang et al. revealed that Rb2 reversed the senescence in old HDFs by converting LC3-I to LC3-II and LC3 puncta from 20 to 40 μM. Meanwhile, DNA damage-regulated autophagy modulator 2 (DRAM2) was found to be the potential target of Rb2 [129]. Oh et al. illuminated the keratinocytes in UVB and collected the medium for inducing MMP-1 in Hs68 cells. S-Rg2 not only suppressed the secretion of MMP-1, but also inhibited the inflammatory cytokines induced by the medium above. Src/ERK/JNK and NF-κB signaling pathways were blocked by S-Rg2 as well [59].

5. Discussion

Skin is one of the most important organs in our body, which acts as the first protective barrier against external injury. Meanwhile, the degradation of collagen and elastin indicates the human senescence. Additionally, the hyperpigmentation and hypopigmentation resulting from abnormal melanocytes could influence people's appearance and moods. Therefore, removing these disadvantages from the human body has become an interesting topic in both scientific research and everyday life. Among various approaches, oral taking or topical application of natural products are relatively economical and widely accepted strategies compared with aesthetic medical interventions. Ginseng is an outstanding traditional medicine that is not only used for the treatment of several diseases but also for promoting overall health [20]. Five years ago, we reviewed the research of Korean ginseng in several skin-related cells [43]. However, the previous review has some limitations due to the limited number of available studies. Therefore, in the current review, we not only classify the different types of ginsengs and their products according to the skin cell types, but also sort out corresponding stress models (Table 1). Moreover, animal models are summarized to indicate the applications as well (Table 2).

Table 1.

The role of ginseng related products on skin cells.

Cell type	Stress model	Compound	Biological responses	Regulated genes or hallmarks	Target/signaling	Ref.
Keratinocyte	UVB-induced HaCaT	HRCE	Collagen & elastin degradation	COL-1, MMP-1, MMP-9	MAPKs, NF-κB (−)	[16]
		KRG	DNA damage & Apoptosis Skin barrier damage Hydrogen loss Oxidative injury Inflammation	TERT, Bcl-2, Bax, PARP, Caspases, CERS3, SPTLC2, HAS-2, Loricrin, Involucrin, FLG, CAT, GPx, SOD, Nrf2, HO-1, NQ01, COX-2, IL-1β, IL-6	MAPKs (−) NF-κB (+)	[17] [18] [37]
		FBGE	Skin barrier damage, Inflammation	MMP-1, MMP-9, COX-2, IL-8, TNF-α, PGE2	Nc886-PKR-MAPKs (−)	[19]
		P. ginseng extract	Collagen degradation, Apoptosis	ATF4, CHOP, BIP, p53, p21, HMGB1, Collagen 1, Bcl-2, Bax	VMP1 (+)	[20]
		PGL (Rg3, Rk1)	Photoaging	MMP-2, MMP-9	(−)	[22]
		GFRs	Oxidative injury	Nrf2, HO-1	Nrf2/HO-1/GPX4 (+)	[23]
		GrDENs	Apoptosis, Wrinkle, Inflammation	Caspases, MMPs, COX-2, IL-6	AP-1/MAPKs (−)	[24]
		Ginsenosides	Skin barrier damage	FLG, IVL, Cldn-1, AQP3	MAPKs (+)	[25]
		GSO		FLG, IVL, AQP3	DSG1, KLK7 (+)	[26]
		Rg2	DNA damage	DDR, PIC, MMPs	P53, p21 (−)	[30]
		Rg3	Oxidative injury, Inflammation, Apoptosis	GSH-PX, SOD, TNF-α, COX-2, iNOS, IL-1β, Bcl-2, Bax, Caspase-3	Apoptosis pathway (−)	[32]
		Rd	Photo-oxidative injury	MMPs, GSH, SOD	(−)	[31]
		Rk1	Collagen degradation, Inflammation, Oxidative injury	MMPs, Collagen, TNF-α, IL-1β, −6, −8, ROS, MDA, GSH-PX, SOD, CAT	PI3K/AKT/NF-κB (−)	[33]
Keratinocyte	UVB-induced HaCaT	CK	Skin barrier damage	SPINK5, KLK5, KLK7, PAR2	(−)	[34]
		Salicylic acid	Phagocytosis effect	Melanophilin, Myosin Va	PAR2/Ca2+/PI3K /AKT/MAPKs (−)	[69]
	UVA-induced HaCaT	CK	Photo-aging, Apoptosis	P53, p21, p63, Caspase-8, Caspase-9, PARP	(−)	[36]
	S. aureus-infected HaCaT	Maltol	Inflammation	IL-6, IL-1β	(−)	[38]
	Heat stimulated HaCaT	KRG	Skin barrier damage, Aging, Inflammation	AQP3, CERS3, OCL, MMP1, 2, 3, IL-6, IL-8	MAPKs (+) NF-κB (−)	[39]
	H2O2-induced HaCaT	FBG, BG, WG	Oxidative injury, Wrinkle, Skin barrier damage	HO-1, CAT, SOD-1, HAS-2, AQP3	EGFR (+)	[46] [46]
		SYR	Oxidative injury, Autophagy	MMP-2, MMP-9, LC3B	(+)	[47]
	Normal HaCaT	GDNPs	Skin barrier and hydrogen enhancement	MMP-1, FN1, elastin-1, COL1A1	ERK, AKT/mTOR (+)	[45]
		PPT		FLG, TGM-1, Claudin, Occludin HAS-1, -2, -3, AQP3	EGFR, HER2/MAPKs, NF-κB (+)	[54] [55]
		BIOGF1K		KRT1, KRT10, TEER, IVL	(+)	[53]
		Gintonin	Wound-healing	VEGF	LPA receptor, EGFR, AKT/ERK (+)	[48] [49]
		Rb1, Rg3		TNF-α, TNF-β, IL-10, CXCR7, VEGF, Collagen	(+)	[51]
		PDRN		FN1, FLG, Ki67	FAK/AKT/MAPKs (+)	[52]
	UVB and IL-17A induced NHEKs	CK	Inflammation, Senescence	CXCL8, IL-6, IL-8, TNF-α, CSF2, KRT10, COL17A1,	P38, p65, IκB (−)	[35]
	PM10-induced NHEKs	KRG	Oxidative injury, Inflammation	IL-1α, IL-1β, IL-8	(−)	[40]
	PM2.5-induced NHEKs		Senescence	p16INK4A	Epigenetic regulation (−)	[41]
Melanocytes	α-MSH induced B16F10	Salicylic acid	Melanogenesis, Melanosome transport	Tyrosinase, TYRP1, TYRP2, Melanosome	MC1R/cAMP/PKA PI3K/AKT (−)	[69]
		GFRS(Rg3, Rg5, RK1)	Melanogenesis	Tyrosinase	MC1R/TYR/MITF LC3B/p62/Atg4B (−)	[57]
		Gyp XVII, GypLXXV, GF2, CK			MITF (−)	[63]
		HG		MITF, Tyrosinase, MITF Melanin content, Tyrosinase, TRP-1, TRP-2, TYR,	(−)	[60]
		KRG, KGO				[61] [62]
		Re		Tyrosinase, MITF, TRP-1, TRP-2	AKT/ERK/MDM2 /IKKα/p21 (+)	[65]
		Phenolic acid (SA, PA, P-CA, CA,VA)		TYR, TYRP1, TYRP2	MC1R/cAMP/PKA Wnt/MAPKs (−)	[68]
		Rf		Tyrosinase, Melanin content, TYRP1, TYRP2	AC/cAMP/PKA (−), NO/GC/cGMP/PKG (−)	[64]
	UV and FSK-induced Mel-Ab cells	Rf			cAMP/CREB/MITF (−)	[72]
	FSK-induced B16F10	Ginseng Radix Alba		Tyrosinase, Melanin content	(−)	[73]
	IBMX-induced B16F10	FBG, BG, WG		Tyrosinase, Melanin content, TYRP1, TYRP2, MITF	(−)	[46]
	B16F10, MNT-1, Melanoderm	Acremonidin E, SYR		Tyrosinase, Melanin content, TRP1, Morphology, Dendrite formation	(−)	[66,67]
	α-MSH-induced B16	BGK-1, PTS	Melanogenesis	Tyrosinase, Melanin content	NF-κB (−)	[58,59]
	Tyrosine with B16F1	FBG	Melanogenesis, Senescence	Tyrosine, Melanin content,	(−)	[71]
Melanocytes	UVB-induced HEMs	GrEVs	Pigmentation Senescence	Melanin content, TYR, TYRP2, RAB27, HMGB1, SA-β-Gal	(−)	[70]
	PM 10-induced HEMs	KRG	Melanogenesis	Tyrosinase, Melanin content, MITF	(−)	[40]
	H2O2-induced HEMs	San-qi CK	Depigmentation	Tyrosinase, Melanin content, TYR, TYRP1, GSH, Glutathione	(+)	[76]
	Human PIG1	Rk1	Depigmentation Apoptosis	SOD, CAT, GSH-Px, Bax, Bcl2, Caspase-3	PI3k/AKT/Nrf2/HO-1 (+)	[77]
	Melan-a	Panaxynol	Melanogenesis	Tyrosinase	AKT/ERK/MITF (−)	[75]
	SK-MEL-2, 3D models	Rh1, Rg2		Tyrosinase, Melanin content	(−)	[74]
Fibroblasts	UVB-induced Hs68	GSE, GSC, GSs	photoaging	MMP-1, MMP-3, ROS, Collagen, TGF-β	MAPK/Ap-1 (−) TGF-β/Smad (+)	[78,79]
	H2O2-induced Hs68	SYR	Wound healing	TGF-β, VEGF-c, eNOS, Collagen I	(+)	[88]
	UV CM-induced Hs68	Rg2	Inflammation	MMP-1, IL-1β, IL-6, TNF-α	Src/ERK/JNK (−) AKT/NF-κB (−)	[29]
	UVA- induced HDFs	SYR	Photoaging	MMP-1, MMP-9, procollagen type I, COX-2, TNF-α, IL-1β	MAPK/Ap-1 (−)	[83]
	UVB-induced HDFs	FBG, BG, WG	Wrinkle	Elastase, MMP-1, MMP-9, COL-1	(−)	[46]
		KRGM gintonin	Oxidation, Wound healing, Senescence	ROS, [Ca2+]i transient	LPA 1/3 receptors (+)	[81]
		EPG, GF2	Oxidation, photoaging	MMP-1, IL-6, procollagen type I	MAPK/Ap-1 (−)	[82]
	UV-induced HDFs	Rh2	Proliferation, ECM injury, Oxidation	Collagen type I, Elastin, HO-1, MMP-3, NRF-2, Caspase-3, Drp1, Fis1, MFF, Opa I, MFN2	PKB/ERK (+) TNFR1, EGFR/p38 (−)	[80]
Fibroblasts	H2O2-induced HDFs	FPNP	Collagen and elastin injury	CAT, SOD, GSH-Px, MMP-1, ELN, COL-1	TGF-β/Smad (+)	[89]
	TNF-α-induced HDFs	TG, GFFG, WAD, HWEG (Rf)	Inflammation	MMP-1, ROS, HO-1, procollagen type I, IL-6, IL-8, COX-2	MAPK/Ap-1 (−)	[95] [96] [97]
	Old HDFs	Rg3	Senescence	HSP60, PRDX1-3, CDKN1A, ACC, BECM1, LC3B, NRF2, HMOX1, SQSTM1	ROS (−) p53/p21/p16 (−) ORAI1/AMPK/BECN1 (+)	[90,91]
		Rb2		CDK4, Cyclin D, Cyclin E, LC3B	p53/p21/p16 (−) AMPK/mTOR (+)	[99]
	Normal HDFs	GNEV	Skin regeneration	TGF-β, SMAD-2, SMAD-3, COL1A1	TGF-β/Smad (+)	[98]
	UVA-induced NIH3T3	ARP	DNA damage	Bax, Bcl-2, Collagen type I	AKT (+)	[84]
	H2O2-induced NIH3T3 & MSFs	GOPs, pnFE	Senescence	ROS, MDA, GSH-Px, CAT, p16INK4A, p21Waf1/Cip1, IL-6, IL-1β	NAD+/SIRT1/PGC-1α (−)	[92,93]
	Old NIH3T3	PNO		COL-1, PCNA, Cyclin E, Cyclin D1, CDK 1	p21/p16 (−) TGF-β/Smad (+) MAPKs (+)	[94]
	CCD-986SK	FBG	Wrinkle	Elastase, procollagen type I c-peptide, MMP-1, MMP9, SOD	(−)	[71]
	UVB-induced L929	GFRs				[87]
	UVA-induced HFF-1	FGE	Photoaging	GSH, GPx, SOD, CAT, MDA	Nrf2 (+), p53/p21/p16 (−)	[85]
	UVA-induced HSF	GPs		Collagen type I, MMP-1, IL-6, TNF-α	(−)	[86]

Table 2.

The role of ginseng related products on animals.

Model	Compound	Biological responses	Regulated genes or hallmarks	Target/signaling	Ref.
UVB-induced male hairless mice	HRCE	Skin edema, dryness	Skin thickness, TWEL	(−)	[16]
UVB-induced SKH-1 hairless mice	KRG	Apoptosis, Inflammation Skin barrier damage, Oxidative injury	Bcl-2, Bax, PARP, Caspases, Loricrin, Involucrin, FLG, CAT, GPx, SOD, Nrf2, HO-1, COX-2, IL-1β, IL-23, IL-17	AP-1/MAPKs (−) NF-κB (+)	[18]
	FAMCGS	Photoaging	Skin thickness, Collagen density, TWEL, Skin moisture content, roughness, elasticity	(−)	[21]
	CK	Skin barrier damage	Skin thickness, KLK5, DSC1, SPINK5, PAR2	(−)	[34]
UVB-induced HR-1 hairless mice	PGL	Photoaging	Skin thickness, TWEL, wrinkle, MMP-2, MMP-9	(−)	[22]
UVB-induced HRM-2 hairless mice	KRG, KGO	Skin barrier damage, Melanogenesis	Wrinkle, MMP-2, MMP-9, IL-1β, Skin thickness, collagen, melanin content	(−)	[61,62]
UVB-induced BALB/c mice	P. ginseng extract	Collagen degradation, Apoptosis	ATF4, CHOP, BIP, Collagen 1, MMP-1a, −2, −9, Skin thickness	VMP1 (+)	[20]
	GFRs	Collagen degradation, Oxidation	SOD, CAT, GSH-Px, H2AX, FLG	Nrf-2, HO-1, GPX4 (+)	[23]
	PTS	Melanogenesis	Melanin content, tyrosinase	Autophagy (−)	[59]
	Ginsenosides	Skin barrier damage	Skin thickness, FLG, IVL, Cldn-1, AQP3	MAPKs (+)	[25]
	GSO			DSG, KLK7 (+)	[26]
	RK1		MMPs, Collagen, TNF-α, IL-1β, −6, −8, ROS, MDA, GSH-Px, SOD, CAT	PI3K/AKT/NF-κB (−)	[33]
UV-irradiated male SD rats	Ginsenoside, glycoprotein		MDA, GSH-Px, SOD, MMPs, HYP, TNF-α, IL-1β, IL-6	(−)	[27]
BALB/c mice	20(R)-Rg3	Wound-healing	COL1A2, ACTC1	(+)	[50]
MC903-induced female BALB/c mice (Atopic dermatitis)	Rg1	Allergic reaction, Skin barrier dysfunction	Skin thickness, IL-1β, IL-4, ZO-1, Claudin	MAPKs (−)	[43]
DNCB-induced Nc/Nga mice	KRG	Skin lesion	TWEL, IFN-γ, TSLP	(−)	[42]
Tris-HCl induced ICR mice	GDNPs	Wound-healing	Skin thickness, TGF-β, Ki67, COX-2, iNOS	NF-κB (+)	[45]
S. aureus-injected female C57BL/6	Maltol	Inflammation	IL-1β, IL-6	(−)	[38]
B16F10-injected C57BL/6	Re	Melanoma proliferation	Tumor volume, Weight, MITF, HIF-1α, Bcl2, Ki67+, Caspase3, CD31, α-SMA	(−)	[65]
C57BL/6	Rg3	Senescence	PCNA, Ki67+	(−)	[91]
Zebrafish	Re, Rf, GFRS, Phenolic acid (SA, PA, P-CA, VA, CA), Panaxynol, Salicylic acid	Melanogenesis	Tyrosinase, Melanin content	(−)	[64] [57] [68] [69,75]
Rhododendrol-induced leukoderma guinea pig model	Sanqi-CK	Depigmentation	Skin color, TYRP1	(+)	[76]
HPO-induced ex vivo human and pig skin	SYR	Wounding healing	TGF-β, VEGF, eNOS, PCNA	(+)	[88]

In keratinocytes, HaCaT and NHEKs are major cell lines to study the functional role of different types of ginsengs and their products. Among these studies, UV radiation, especially UVB, is the most widely used stress model [45]. Several reasons contribute to the frequent selection of UV as an experimental inducer, including its precise controllability in wavelength and dosage, the simplicity of machines, and the convenience of experimental operation. The biological responses of UV induction are inflammation, skin barrier damage, and oxidative stress. Therefore, several representative biomarkers have been examined, including TNF-α, COX-2, iNOS, IL-1β, and IL-6 as indicators of inflammation, COL-1, MMPs, HAS-2, Loricrin, Involucrin, and FLG as markers of skin barrier disruption, as well as GSH-PX, SOD, MDA, and CAT as hallmarks of oxidative injury (Fig. 1D). MAPKs and NF-κB, as well as apoptosis signaling pathways, were investigated. In addition to UV irradiation, other stress inducers, including H₂O₂, PM, and bacterial infection, were also evaluated respectively. Ginseng and its derived components not only can alleviate the damage by the stimulators above, but also can strengthen the barrier integrity and hydration as well as accelerate cell regeneration. Meanwhile, these effects are mediated through modulating RTKs and LPA receptors (Fig. 1A) [78,79,85]. Several animal models were utilized to evaluate the protective role of ginseng on the outermost layer of skin, with SKH-1 hairless mice being the most commonly used model. Because these mice possess an intact immune system, they are considered as an ideal model for studying drug safety, skin wound healing, photoaging, and tumorigenic responses [48,51,64]. Additionally, HR-1 and HRM-2 hairless mice were occasionally employed. However, HRM-2 mice can secrete a large amount of melanin that is used to study the melanogenesis as well [92]. Beyond hairless mouse models, BALB/c, ICR, and C57BL/6 mice were also used to evaluate the skin protective activities (Fig. 1A and D).

Fig. 1.

The mechanisms of ginseng-derived compounds in each cell types.

A, B, and C. The regulatory role of ginseng-derived compounds in (A) keratinocytes, (B) Melanocytes, and (C) Fibroblasts. D. The biological responses of skin problems and their related hallmarks.

In melanocytes, the most topic that is studied is to investigate the anti-melanogenesis role in ginsengs [98]. Currently, the cell lines chosen most for studying melanogenesis are B16F10 and HEMs. Other cell lines, such as Mel-Ab, MNT-1, B16F1, and PIG1 were used as well. Among them, the popular model is α-MSH induced B16F10 cells. Several hallmarks that ginseng related products suppressed are tyrosinase, melanin content, TYRP1, and TYRP2 (Fig. 1D). Meanwhile, ginseng related products can ameliorate the melanogenesis through targeting MC1R/cAMP/PKA/MITF pathways (Fig. 1B). Additionally, other inducers for melanogenesis model are used, such as UV [102], FSK [102,103], and IBMX [76]. The most commonly used animal model for melanin secretion is zebrafish [87,94,98,99,105]. Because zebrafish are low cost and allow direct, real-time visualization of pigmentation and melanosome distribution. Moreover, the melanogenesis in zebrafish is rapid and highly conserved. Several ginseng-related compounds, such as ginsenoside Re, Rf, as well as panaxynol, can suppress the tyrosinase activity and melanin content in zebrafish. Meanwhile, some ginseng-related products can remove depigmentation of skin diseases. Sanqi CK can enhance the melanin secretion under the H₂O₂-induced HEMs and rhododendrol-induced leukoderma guinea pig [106], Rk1 also exhibited similar results in human PIG1 cells [107].

Two fibroblast-related cell lines, Hs68 and HDFs, were popularly used to examine the biological effects of ginseng. Similar to keratinocytes, both UV and H₂O₂ were also applied to stimulate the inflammatory and oxidative injury in fibroblasts. Multiple signaling pathways, such as RTKs/Src/MAPKs and PI3K/AKT/NF-κB, were also regulated by ginseng-related compounds. Meanwhile, two additional signaling cascades, ORAI1/AMPK/BECN1 [121] and TGF-β/Smad2/3 [109,110,119] were up-regulated, thereby inducing autophagy and skin regeneration (Fig. 1C and D). In addition, fibroblasts at both low and high passage numbers were collected to evaluate the anti-aging effects of ginsenosides [121].

In addition, the structure-activity relationship of ginsenosides exhibited great relevance to skin health. Key structural parts include the aglycon backbone, the number of sugar moieties, the stereochemistry at C-20, and the double bonds [100]. Ginsenosides with fewer sugar residues (such as CK or S-Rg3) showed better activities in skin protection. Different aglycon backbones (such as PPD-type and PPT-type) have relatively distinct focuses. Moreover, 20(S) isomers may exhibit better skin protection abilities than 20(R) isomers. The presence of double bonds may lead to good antioxidant and anti-aging activities. Meanwhile, reducing sugar chains (such as CK) may enhance skin penetration and lipid solubility, thereby improving therapeutic efficacy.

Compare with five years before, recent studies have expanded beyond traditional animal models to increasingly incorporate ex vivo skin systems, including the 3D dermal model. It is a good evolution because these models not only can enhance the efficient and reproducible evaluation of outcomes, but also reduce the reliance on experimental animals, thereby alleviating their suffering and following the rules of experimental ethics. Despite these advances, several challenges remain. For example, current cosmetic products mainly use ginseng extracts rather than individual constituents. One reason is that many potent ginsenosides (such as CK, Rh2, and S-Rg3) are very rare, resulting in high production costs for the cosmetic industry. Meanwhile, some ginsenosides exhibit low bioavailability and poor stability, leading to limited solubility, restricted permeability, and rapid metabolic degradation. Additionally, some challenges remain in clinical translation, as some results obtained from cell lines and animal models fail to translate effectively to humans. Biomarkers used to assess cellular responses across different skin types remain relatively limited, and many studies rely on previously established evaluation frameworks. Although it is the easiest way to study each compound, it lacks the update and creativity. In addition, many reports emphasize phenotypic outcomes rather than describing upstream molecular targets and signaling networks. Hence, the mechanisms underlying the diverse skin-related activities of ginseng-derived compounds remain incompletely clarified. In addition, it remains unclear whether these individual constituents would interact other conventional drugs, particularly when used as adjuvants. Future studies using advanced skin models combined with detailed molecular analyses will be critical to better understand how ginseng and its bioactive constituents affect skin biology.

Conflicts of interest

The authors declare that no conflicts of interest exist.

Data availability

Datasets related to this article can be found at https://www.ncbi.nlm.nih.gov/pubmed, hosted at the U.S. National Institutes of Health's National Library of Medicine (NIH/NLM).