Targeting periodontitis with shikonin: Molecular insights and therapeutic prospects – A narrative review

Abstract

Shikonin (SHI) is a naturally occurring naphthoquinone predominantly isolated from the roots of Lithospermum erythrorhizon and other species within the Boraginaceae family. Traditionally recognized for its therapeutic potential, SHI has garnered considerable scientific interest due to its broad pharmacological profile and relatively low toxicity. Together with its enantiomer alkannin, SHI shows anti-inflammatory, antibacterial, antioxidant, anticancer, wound-healing, and antithrombotic activities. Recent advancements in extraction technologies, notably ultrasound-assisted ionic liquid–aqueous two-phase systems, have achieved SHI yields of up to 97%, thereby enhancing its accessibility for pharmaceutical applications. SHI is biosynthesized in the endoplasmic reticulum of plant cells through the coordinated activity of the shikimate and mevalonate pathways, with cytochrome P450 enzymes playing a pivotal role in its synthesis. Its relevance in periodontology is increasingly recognized, owing to its capacity to inhibit osteoclastogenesis, promote periodontal tissue and bone regeneration, modulate host immune responses, and suppress pathogenic microorganisms such as Porphyromonas gingivalis. Moreover, SHI’s inhibition of pyruvate kinase M2, a key regulator of glycolytic and inflammatory pathways, highlights its potential in the modulation of immunometabolic processes. A systematic search of PubMed, Web of Science, and Scopus using the keywords “shikonin AND periodont*” identified 384 publications. Following screening, 40 studies were selected and thematically categorized: SHI’s pharmacological properties, its role in periodontal tissue homeostasis, and its therapeutic potential in clinical periodontology. In summary, SHI appears as a promising candidate for adjunctive periodontal therapy, meriting further investigation into its mechanistic actions and clinical applications in oral health preservation.

INTRODUCTION

Shikonin (SHI) is a phytonutrient extracted from the roots of Lithospermum erythrorhizon. It is a naphthoquinone also present in several plants of the Boraginaceae family.[1] Its pharmacological properties are multifaceted and are extensively utilized as a component of herbal medicine owing to its therapeutic efficacy. SHI and its enantiomer alkannin have been investigated for their comprehensive biological effects, such as antibacterial, anti-inflammatory, anticancer, antioxidant, wound-healing, and antithrombotic activities.[2]

In recent years, interest in SHI has increased due to its possible application in the treatment of chronic inflammatory disorders, including periodontitis. Scientific developments have enhanced the techniques for isolating and extracting SHI from the botanical sources. Azuma et al.[3] developed a chromatographic technique using hexane, resulting in approximately 2% SHI extracted from Lithospermum erythrorhizon roots. Huang et al.[4] employed ultrasound-assisted ethanol extraction from Arnebia euchroma, resulting in a yield of 1.26%. Tsermentseli et al.[5] utilized molecularly imprinted polymers for solid-phase extraction, achieving a 72% recovery rate from Alkanna tinctoria root extracts in hexane. The most effective method, devised by Sun et al.,[6] employed an ultrasound-assisted ionic liquid in conjunction with an aqueous two-phase system, achieving yields of 90%–97%. These sophisticated approaches enhance accessibility to SHI for pharmacological and biological research.

From a biochemical perspective, SHI biosynthesis occurs within the endoplasmic reticulum of plant cells. Cytochrome P450 enzymes are especially crucial in catalyzing the final modifications necessary for producing bioactive SHI.[1] The increasing availability of SHI through both improved extraction techniques and synthetic biology approaches makes it a practical candidate for further development in clinical applications.

In terms of therapeutic potential, SHI has shown significant promise in managing chronic inflammatory and degenerative conditions.[7] It has also garnered attention in the field of food safety, where it is utilized in smart packaging systems to detect freshness by responding to oxidative changes.[8] SHI’s multifunctional profile includes the suppression of osteoclast activity, promotion of bone and tissue regeneration,[9] reduction of pro-inflammatory cytokine levels, and antimicrobial action, particularly against oral pathogens such as Porphyromonas gingivalis. It exerts its beneficial effects through multiple mechanisms, including inhibition of pyruvate kinase M2 (PKM2),[10] a glycolytic enzyme involved in energy metabolism and inflammation.

Given the synergistic effects of SHI on inflammation, bone resorption, and microbial control, it emerges as a compelling therapeutic agent in periodontitis management. Periodontitis, a chronic inflammatory condition affecting the supporting structures of the teeth, involves a complex interplay of microbial insults, host immune responses, and tissue degradation.[11] The disease not only leads to the destruction of the periodontal ligament and alveolar bone but also is implicated in systemic conditions such as cardiovascular diseases, diabetes, and adverse pregnancy outcomes. Therefore, identifying effective adjuncts to conventional periodontal therapies is critical.

Over the decades, numerous reviews have explored the pharmacology, biosynthesis, and broad-spectrum activities of SHI. However, this review specifically focuses on the role of SHI in periodontal tissue homeostasis and its emerging potential as a therapeutic strategy in the prevention and treatment of periodontal disease. The goal is to highlight both its molecular mechanisms and practical applications in clinical periodontology.

METHODOLOGY

A comprehensive literature search was conducted using three major scientific databases – PubMed, PubMed Central, Web of Science, and Scopus – to gather relevant publications on the topic of SHI and its association with periodontal disease. The search strategy employed the keywords “shikonin AND periodont*” to ensure a broad yet focused retrieval of literature related to both SHI and various aspects of periodontal health and disease. This search initially yielded a total of 384 articles. After screening the articles, 40 were included in this narrative review. The information from these articles has been organized into three principal areas: (i) the overall therapeutic attributes of SHI, encompassing its anti-inflammatory, antibacterial, and antitumor capabilities, (ii) role of SHI in preserving periodontal tissue homeostasis, encompassing its influence on host immunological responses, and (iii) the prospective therapeutic applications of SHI in the management of periodontal disease.

SHIKONIN – MEDICINAL PROPERTIES

SHI has shown significant antitumor, antibacterial, anti-inflammatory, antioxidant, and wound-healing properties in both in vitro and in vivo research [Figure 1].[12]

Figure 1.

Therapeutic properties of shikonin: Shikonin has anti-tumor, antibacterial, anti-inflammatory, and antioxidant properties

SHI has been documented to inhibit ultraviolet B (UVB)-induced damage in keratinocytes by downregulating the expression of pro-inflammatory cytokines such as IL-1, IL-6, and TNF-α. In bone marrow-derived dendritic cells, SHI reduces the production of IL-4, IL-5, and TNF-α, indicating its ability to modulate both innate and adaptive immune responses.[12] This modulatory effect on cytokine production plays a central role in its therapeutic potential in inflammatory diseases.

Antimicrobial effect

The antimicrobial properties of SHI are of relevance to oral health, given the microbial etiology of periodontitis. SHI disrupts microbial cell membrane integrity by integrating into the lipid bilayer, increasing membrane permeability, and resulting in the leakage of intracellular components.[13] Transmission electron microscopy studies of SHI-treated MRSA have shown unambiguous evidence of cytoplasmic membrane rupture and cellular lysis.

SHI’s antimicrobial spectrum includes Gram-positive bacteria such as Staphylococcus aureus and Bacillus subtilis[13] and extends to viruses such as herpes simplex virus and fungi including Candida albicans.[14] In bacteria, SHI inhibits ATPase activity and disrupts critical metabolic enzymes, while in fungi, it induces mitochondrial dysfunction, thereby impairing cellular respiration.[14] Furthermore, SHI interferes with quorum-sensing mechanisms, which are essential for biofilm formation and antibiotic resistance in bacteria.[15] These multifaceted antimicrobial actions make SHI an ideal candidate for managing infections in periodontal pockets.

Antitumor mechanism of SHI

SHI’s antitumor activity is underpinned by its ability to modulate key pathways involved in cell proliferation, survival, and apoptosis. It promotes apoptosis through intrinsic mitochondrial pathways – marked by increased expression of Bax and cleaved caspases – and extrinsic pathways involving death receptors. Simultaneously, it downregulates antiapoptotic proteins such as Bcl-2, tipping the balance toward programmed cell death.[16]

Reactive oxygen species (ROS) generation is another key mechanism through which SHI induces cytotoxicity in cancer cells.[17] Excessive ROS disrupts mitochondrial membrane potential and leads to DNA damage. Moreover, SHI inhibits PKM2,[18] a pivotal enzyme in cancer cell metabolism and proliferation. It also interferes with the cell cycle by suppressing cyclins and cyclin-dependent kinases, thereby arresting cells in either the G2/M or G0/G1 phase of proliferation.[19] These actions collectively make SHI an effective antiproliferative agent.

Anti-inflammatory mechanism of shikonin

SHI’s anti-inflammatory effects are primarily mediated through the inhibition of key intracellular signalling pathways, particularly the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and mitogen-activated protein kinases (MAPK) cascades. NF-κB is a master regulator of inflammatory gene expression. SHI blocks NF-κB activation by preventing the degradation of IκB-α, thereby inhibiting the nuclear translocation of the p65 subunit and subsequent transcription of pro-inflammatory genes.[20]

In addition, SHI inhibits the MAPK family of kinases, particularly extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38. These pathways are known to promote the synthesis of pro-inflammatory cytokines, COX-2, and inducible nitric oxide synthase.[20] SHI also suppresses the NLRP3 inflammasome, a multiprotein complex responsible for the maturation of interleukin-1 (IL-1) β and IL-18.[21] This comprehensive anti-inflammatory profile underscores SHI’s potential as a powerful agent for controlling inflammation-related diseases, including periodontitis.

ROLE OF SHIKONIN IN PERIODONTAL TISSUE HOMEOSTASIS

Periodontal tissue homeostasis is a delicately balanced process involving coordinated immune responses, extracellular matrix maintenance, and cellular integrity to protect against microbial challenges. Disruption of this equilibrium leads to periodontitis, characterized by destruction of the periodontal ligament, alveolar bone loss, and eventual tooth loss. Central to the pathogenesis of periodontitis is the overexpression of pro-inflammatory cytokines such as IL-1 β, IL-6, and tumor necrosis factor-alpha (TNF-α), along with elevated levels of matrix metalloproteinases (MMPs) and cyclooxygenase-2 (COX-2), which drive tissue breakdown and hinder repair. Key pro-inflammatory cytokines such as IL-1 β, IL-6, and TNF-α are elevated in periodontal lesions and contribute to tissue degradation and bone resorption.[22] These cytokines stimulate osteoclast activity, inhibit fibroblast function, and increase MMP expression. SHI has demonstrated potent anti-inflammatory effects in various disease models.[12] SHI can downregulate key inflammatory mediators and enzymes implicated in periodontal tissue degradation by targeting intracellular signaling pathways. Furthermore, SHI’s ability to modulate oxidative stress and suppress cytokine expression positions it as a promising candidate for maintaining periodontal tissue integrity and restoring homeostasis [Figure 2]. In lipopolysaccharide (LPS)-stimulated human periodontal ligament cells (hPDLCs), SHI significantly downregulated IL-1 β, IL-6, and TNF-α at both mRNA and protein levels.[12] SHI was shown to inhibit NF-κB activity,[20] a transcription factor central to the regulation of inflammatory gene expression in periodontitis. Inhibition of NF-κB signaling prevents transcription of pro-inflammatory mediators, thus mitigating the inflammatory response in periodontal tissues.

Figure 2.

Role of shikonin in periodontal tissue homeostasis: Shikonin can modulate host response which, along with its anti-microbial properties, will help in maintaining periodontal tissue integrity and restoring periodontal tissue homeostasis when used as an adjunct to mechanical and regenerative therapy

Regulation of matrix metalloproteinases

MMPs are the key enzymes responsible for extracellular matrix degradation. In particular, MMP-2 and MMP-9 are elevated in inflamed periodontal tissues and gingival crevicular fluid.[23] Their overexpression leads to degradation of collagen and other matrix components, facilitating tissue destruction and disease progression. SHI has been found to significantly reduce MMP-2 and MMP-9 expression in hPDLCs stimulated with LPS.[12] Similar anti-MMP activity was observed in tumor cell lines, where SHI suppressed MMP-9-mediated invasion and metastasis.[24] By inhibiting MMP expression, SHI helps preserve connective tissue architecture and slows disease progression.

Modulation of cyclooxygenase-2 and prostaglandin synthesis

COX-2 is an inducible enzyme that catalyzes the conversion of arachidonic acid to prostaglandins. Upregulated in periodontal inflammation, COX-2 contributes to vasodilation, pain, and leukocyte infiltration.[25] Inhibition of COX-2 has been linked to reduced periodontal bone loss in experimental models. SHI has shown the ability to suppress COX-2 expression in multiple cell types. In LPS-treated hPDLCs, SHI significantly reduced COX-2 mRNA and protein levels,[12] indicating that it can modulate the prostaglandin-mediated inflammatory cascade.

Interference with nuclear factor-κB and extracellular signal-regulated kinase signaling pathways

The NF-κB and ERK pathways are critical in the regulation of inflammation, immune response, and tissue remodeling. Activation of NF-κB involves phosphorylation and degradation of IκB, releasing p65/p50 subunits to the nucleus, where they activate target gene transcription.[26] In hPDLCs, SHI inhibited phosphorylation of NF-κB p65 and IκB degradation, leading to decreased nuclear translocation and activity of NF-κB.[27] In addition, SHI significantly reduced ERK phosphorylation[28] without affecting JNK or p38 MAPK pathways, suggesting selective modulation of inflammatory signaling. Targeting the ERK/NF-κB axis may offer a precise strategy for reducing periodontal inflammation while avoiding broad-spectrum immunosuppression.

Potential modulation of chemokines and toll-like receptor pathways

Chemokines such as CCL5 participate in immune cell recruitment and are upregulated in periodontitis. Computational studies have shown that SHI has high binding affinity for CCL5 and AKT1 – key mediators of toll-like receptor (TLR) signaling.[29] TLRs recognize bacterial components like LPS and activate downstream inflammatory pathways through NF-κB and MAPKs.

By targeting CCL5 and AKT1, SHI may interfere with leukocyte recruitment and cytokine amplification loops in periodontal tissues. This raises the possibility of SHI being a novel modulator of innate immune signaling in the periodontium.

Antioxidant and antimicrobial properties

Oxidative stress plays a pivotal role in the pathogenesis and progression of periodontal disease by inducing cellular and molecular damage within periodontal tissues. Oxidative stress contributes to periodontal tissue damage by promoting lipid peroxidation, protein degradation, and DNA damage.[30]

Oxidative stress arises when the production of ROS overwhelms the antioxidant defense mechanisms of the host, leading to an imbalance that fosters a pro-inflammatory microenvironment.[31] Excessive ROS can promote lipid peroxidation, resulting in damage to cellular membranes and impaired barrier function. Moreover, oxidative stress contributes to protein degradation by modifying amino acid side chains and disrupting enzymatic activities crucial for maintaining tissue integrity.[31] DNA damage caused by ROS, including strand breaks and base modifications, can lead to cellular senescence or apoptosis, further worsening periodontal tissue destruction and impeding repair mechanisms.[32] This cumulative damage undermines the structural and functional stability of the periodontium, facilitating disease progression and bone resorption.

SHI has demonstrated potent antioxidant properties that can counteract the detrimental effects of oxidative stress in periodontal disease. SHI has shown potent antioxidant activity, reducing ROS levels and enhancing antioxidant enzyme activity in various cell models.[5] SHI has been shown to significantly reduce ROS levels[33] by directly scavenging free radicals and enhancing the activity of endogenous antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). These enzymes are essential for neutralizing reactive molecules and safeguarding periodontal tissues from oxidative damage. Moreover, SHI has been documented to modulate oxidative stress-induced signaling pathways, including NF-κB,[20] and it can affect MAPK pathways, which are recognized for mediating inflammatory responses in periodontal disease.

In addition to its antioxidant properties, SHI shows antibacterial efficacy. SHI demonstrates specific actions against periodontal pathogens such as P. gingivalis. SHI can suppress the invasiveness of P. gingivalis-infected OSCC cells through the suppression of IL-8 and MMP release.[34] This mechanism may also be used for the management of periodontal tissue destruction induced by the pathogen-stimulated host response. Li et al. have shown that acetylshikonin is effective against P.gingivalis and Fusobacterium nucleatum,[35] which are two significant pathogens associated with periodontal disease. By suppressing the proliferation and survival of these bacteria, SHI may aid in reestablishing microbial equilibrium and diminishing the bacterial burden in periodontal pockets.

The combination of anti-inflammatory and antibacterial properties of SHI offers a comprehensive strategy for periodontal care. Although numerous traditional therapies focus on either the microbial component or the host’s inflammatory response, SHI’s integrated capacity to diminish ROS, decrease pro-inflammatory cytokines, and curtail bacterial growth presents a comprehensive therapeutic approach. The multifaceted mechanism of action makes SHI a prospective complement or adjunct to existing periodontal therapies, especially for individuals with chronic inflammation or resistance to standard antimicrobials. Ongoing investigation into the molecular processes of SHI, coupled with clinical trials, will be crucial to comprehensively substantiate its efficacy in the prevention and treatment of periodontal disorders.

THERAPEUTIC STRATEGIES AND CLINICAL POTENTIAL

SHI may serve as an efficacious agent in the management of periodontal disease. Research into its potential application has proven that SHI can promote wound healing and diminish inflammation. The following applications of SHI in periodontal disease may be investigated further to obtain an efficient phytonutrient to combat periodontal disease.

Topical application in periodontal pockets

Periodontal pockets, which form as a result of connective tissue and bone loss around the teeth, provide an ideal site for localized drug delivery. The topical delivery of SHI through liposome[36] gels, biodegradable strips, or sustained-release fibers enables direct targeting of the affected tissues, ensuring a high local concentration of the therapeutic agent while significantly minimizing systemic exposure and associated side effects.[37] This is especially critical for compounds like SHI, which exhibit strong biological activity and may cause off-target effects when administered systemically. Due to its lipophilic nature, SHI shows good affinity for biological membranes, but its solubility and bioavailability can be challenging. Hence, incorporating SHI into biodegradable polymer matrices or advanced delivery systems such as nanoparticles, liposomes, or micelles may significantly enhance its penetration through the gingival epithelium and allow for sustained, controlled release over time. Studies in other inflammatory conditions have shown that nanoparticle-encapsulated SHI not only increases tissue retention but also improves therapeutic outcomes, a strategy that can be extrapolated to periodontitis.[36] Moreover, the development of SHI-loaded delivery systems responsive to pH or enzymatic activity in periodontal pockets can provide intelligent, site-specific drug release, optimizing therapeutic efficacy.

Adjunct to scaling and root planing

The current gold standard for nonsurgical treatment of periodontitis is scaling and root planing (SRP), which mechanically removes plaque biofilm and calculus from tooth surfaces. However, in many cases, residual inflammation persists even after SRP, especially in deep pockets or inaccessible anatomical sites. Integrating SHI therapy as an adjunct to SRP may significantly improve the clinical outcomes by targeting the underlying inflammation and promoting healing. SHI has demonstrated potent anti-inflammatory effects by inhibiting key mediators such as IL-1 β, IL-6, TNF-α, and COX-2, as well as matrix-degrading enzymes like MMP-2 and MMP-9, all of which are implicated in periodontal tissue destruction. In addition, SHI’s ability to inhibit the NF-κB and ERK signaling pathways – both pivotal in propagating inflammation – further supports its therapeutic use following mechanical debridement. Importantly, in vitro studies have shown that SHI does not impair the viability of human periodontal ligament fibroblasts, indicating its biocompatibility and safety when applied to periodontal tissues.[38] This makes SHI a suitable candidate for clinical application post-SRP, where its anti-inflammatory and tissue-protective effects can complement mechanical therapy to enhance periodontal regeneration and reduce pocket depth more effectively than SRP alone.

Use in regenerative therapies

In the field of periodontal regeneration, the restoration of lost bone and soft tissues is still a significant challenge. SHI’s biological profile suggests a strong potential for integration into regenerative therapies. Given its ability to inhibit MMPs and pro-inflammatory cytokines, SHI can help preserve extracellular matrix components that are crucial for wound healing and scaffold integration. In guided tissue regeneration, SHI could be incorporated into biomaterials such as collagen membranes, hydrogels, or synthetic scaffolds designed to promote selective repopulation of periodontal tissues. These SHI-loaded scaffolds may not only modulate the local inflammatory response but also encourage fibroblast proliferation and bone-forming activity.[38,39] Furthermore, the antioxidant properties of SHI may reduce oxidative stress in the periodontal microenvironment, further supporting tissue repair. Preliminary research in other tissue models has shown that SHI enhances wound closure[38] and angiogenesis,[39] both of which are essential for successful periodontal regeneration. Thus, SHI’s incorporation into advanced biomaterials represents an innovative direction in regenerative periodontology, potentially accelerating healing and improving outcomes in complex periodontal defects.

SUMMARY OF THE ROLE OF SHIKONIN IN PERIODONTAL HEALTH AND DISEASE

Overall therapeutic attributes of shikonin

SHI displays potent anti-inflammatory, antimicrobial, antioxidant, and antitumor properties. It inhibits NF-κB and MAPK pathways, reducing pro-inflammatory mediators like IL-1 β, IL-6, TNF-α, COX-2, and iNOS. SHI disrupts microbial membranes and interferes with quorum sensing, showing strong activity against periodontal pathogens such as Porphyromonas gingivalis and Fusobacterium nucleatum. Its antioxidant action lowers ROS and boosts SOD, CAT, and GPx levels. In addition, SHI induces apoptosis and cell-cycle arrest in tumor cells, highlighting broad therapeutic potential.

Role of SHI in preserving periodontal tissue homeostasis

SHI modulates host immune responses to maintain periodontal balance. It downregulates pro-inflammatory cytokines and inhibits NF-κB activation, reducing inflammation in periodontal ligament cells. By suppressing MMP-2, MMP-9, and COX-2, SHI limits collagen degradation and tissue breakdown. Its antioxidant capacity mitigates ROS-induced damage, preserving the integrity of the periodontal ligament, cementum, and alveolar bone.

Prospective therapeutic applications of shikonin in periodontal disease

SHI shows promise as a local adjunct in periodontal therapy. Topical or nanoparticle-based delivery systems enable targeted action in periodontal pockets, minimizing systemic exposure. Used with SRP, it can reduce residual inflammation and enhance healing. Incorporation into regenerative scaffolds may further promote tissue repair and bone regeneration. While generally biocompatible, dose optimization and clinical trials are essential for its safe and effective use in periodontitis management.

SAFETY AND LIMITATIONS

While SHI is generally considered safe in traditional medicine, its cytotoxicity at high concentrations and poor aqueous solubility present challenges.[40] Dose optimization, biocompatible formulations, and efficacy assessment are necessary for clinical translation for any herbal formulation.[41,42] Moreover, cell-specific and dose-dependent effects of SHI have been seen, which warrant further studies to delineate the context-specific mechanisms. Long-term animal studies and randomized clinical trials are essential to assess safety, efficacy, and pharmacokinetics in periodontal therapy for all formulations,[41,42] including SHI.

CONCLUSION

SHI represents a promising phytotherapeutic agent for managing periodontitis due to its multifaceted biological activities. By targeting inflammatory cytokines, MMPs, COX-2, and the NF-κB/ERK signaling pathways, SHI can effectively reduce inflammation, prevent tissue destruction, and potentially support regenerative processes in the periodontium. With further development of targeted delivery systems and clinical validation, SHI may emerge as a valuable adjunct in the modern periodontal therapeutic arsenal.

Key findings

• SHI is a multifunctional bioactive compound with potent anti-inflammatory, antimicrobial, antioxidant, and regenerative potential relevant to periodontal therapy

• It acts through multiple mechanisms: NF-κB/MAPK inhibition, ROS reduction, MMP/COX-2 suppression, and microbial membrane disruption

• In periodontal tissues, SHI helps restore homeostasis by controlling inflammation, oxidative stress, and microbial load

• Localized delivery systems (e.g. gels and nanoparticles) are key to harnessing its benefits while minimizing toxicity

• As an adjunct to SRP and a part of regenerative biomaterials, SHI holds promise for future clinical use in managing chronic periodontitis

• Further studies should focus on optimizing formulations, dosage, and delivery for clinical translation.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.