Keywords: Capsicum, hair loss, in vivo biological assay, rosemary, standardized herbal extracts
Abstract
INTRODUCTION:
Alopecia, a common condition causing hair loss, leads to decreased self-esteem worldwide. Natural extracts such as rosemary (Rosmarinus officinalis L.) and capsicum (Capsicum annuum L.), traditionally used for various medicinal purposes in Egypt, are widely utilized in treatments for androgenetic alopecia and hair care products. However, these extracts lack market standardization and clear specifications, leading to inconsistent and unpredictable effects.
OBJECTIVES:
This study aims to investigate the effects of standardized rosemary and capsicum extracts on testosterone-induced androgenetic alopecia in rats to ensure consistent quality and safety in marketed hair care products.
MATERIALS AND METHODS:
The study involved preparing standardized rosemary and capsicum extracts and developing simple, accurate, sensitive, rapid, and reproducible methods for both. The extracts were tested on adult male Wistar rats with testosterone-induced alopecia, using a 2% finasteride solution as a reference standard. Visual and microscopic evaluations were conducted to measure three hair follicle parameters: diameter, length, and density.
RESULTS:
This study demonstrated the potent effects of standardized rosemary and capsicum extracts on hair growth parameters over 21 days; the application of 0.075% of standardized capsicum extract significantly improved hair growth parameters, including follicle density, length, and diameter. Furthermore, standardized rosemary extracts at 3% and 5% concentrations showed significant improvements across all measured parameters, particularly in hair follicle density.
CONCLUSIONS:
This study highlights the potential of standardized rosemary and capsicum extracts in promoting hair growth parameters, including hair follicle density, length, and diameter. It will pave the way for more effective natural-based androgenetic alopecia treatment.
Introduction
Alopecia is a widespread condition causing hair loss that affects millions of individuals worldwide. Among the various forms of alopecia is testosterone-induced hair loss which is called androgenic alopecia that results from hormonal imbalances.[1]Alopecia can have a significant impact on self-esteem and overall well-being.[2] Beyond conventional treatments such as finasteride and minoxidil, there has been a growing interest in natural remedies for managing alopecia.[3] Among these remedies are rosemary (Rosmarinus officinalis L.)[4] and capsicum (Capsicum annuum L.), both of which have received considerable attention for their traditional medicinal use and recent studies supporting their effectiveness in treating alopecia.[5] Hence, both extracts were selected according to their reported data, which indicate that rosemary extract inhibits 5-alpha-reductase[6] and has antioxidant properties,[7] stimulating the nuclear factor erythroid 2-related factor 2 (Nrf-2) pathway to provide additional oxidative damage protection for the hair follicle.[8] Furthermore, capsicum has been shown to promote hair growth through various mechanisms. It enhances hair follicle activity by stimulating the release of substance P, boosting the production of insulin-like growth factor-I (IGF-I), and activating sensory neurons thus enhancing the hair follicle function. Moreover, it improves hair density and reduces oxidative stress, showing significant potential in treating alopecia.[10,11,12,13] Although hundreds of products and formulas containing rosemary are available in the market, they all lack standardization using marker compounds. However, the lack of standardization in these natural remedies often leads to inconsistent results thus standardized extracts serve as a quality benchmark to ensure consistent efficiency and repeatability, foster trust, and enable research and development to formulate more effective hair care products. This study involves preparing standardized extracts of rosemary and capsicum and investigating their effects on testosterone-induced alopecia in male Wistar rats in comparison with a standard finasteride solution (in vivo experiment). This approach promotes the development of natural-based hair care products.
Materials and Methods
Extract preparation and standardization
Collection and identification of plant
Rosemary (R. officinalis) dried leaves and capsicum (Capsicum annuum) dried fruits were obtained from Cairo University Farm in July 2019 and authenticated by Mrs. Therese Labib, a botanical specialist at Orman and Qubba Botanic Gardens. Voucher specimens (Nos. 20.12.2022 and 21.12.2022) were stored in the Department of Pharmacognosy Herbarium, Faculty of Pharmacy, Cairo University, Egypt. The dried leaves and fruits were ground into a coarse powder and stored in a sealed container at room temperature.
Chemicals
Capsaicin (≥95% purity, Sigma M2028) and rosmarinic acid (RA; ≥95% purity, Sigma M20283) were used as reference standards. Testosterone was obtained from Chemical Industries Development Co. (SID), Giza, Egypt, and finasteride from Global-Napi Pharmaceuticals, 6th October City, Egypt. Both drugs and extracts were mixed with coconut oil to formulate the solution.
Preparation of the specified rosemary and capsicum extracts
Dried rosemary leaves and capsicum fruits (500 g each) were extracted with 70% ethanol (EtOH) (1.5 L × 3) using sonication (Emla Transsonic TS 540, Germany). The extraction process was repeated three times till exhaustion. Each of the collected extracts was concentrated (with a rotary evaporator at a temperature of 55ºC) to 500 ml to give a specified extract (drug/extract ratio 1:1). The capsicum extract yielded 68 g (13.6%), and the rosemary extract yielded 162 g (16.2%). Each 1 ml of capsicum extract contained 0.138 g of solid extract, while rosemary contained 0.324 g.
High-performance liquid chromatography apparatus
High-performance liquid chromatography (HPLC) analysis was performed using an Agilent Technologies 1100 Series HPLC system (Agilent Technologies, Palo Alto, CA, USA).[18]
High-performance liquid chromatography condition for rosemary extract
The HPLC analysis of rosemary extract used gradient elution with acetonitrile (A) and 0.3% phosphoric acid in water (B), an ultraviolet (UV) detector at 325 nm, and a flow rate of 1 ml/min. The gradient started at 18% to 25% (A in B) for 5 min, increased to 32% (A in B) in 14 min, then to 100% (A) in 1 min, continuing for 5 min. The standard RA (0.5 mg/50 ml MeOH/W) showed a major peak at Rt 11.4 min.
High-performance liquid chromatography condition for capsicum
Several studies[14,15] have detailed HPLC methods for quantifying capsaicin in capsicum species. However, these methods were neither simple nor easily applicable. Therefore, we developed a simple, sensitive, and reproducible HPLC method using gradient elution of acetonitrile (A) and 0.3% phosphoric acid in water (B). The analysis was performed with a UV detector at 222 nm and a flow rate of 1 ml/min, starting with 50% (A in B) to 100% (A) in 5 min, continuing at 100% (A) for another 5 min. The standard capsaicin (0.7 mg/25 ml MeOH/W) showed one major peak at a retention time of 6.19 min.
Standardization of extracts
Standardization of rosemary extract
A stock solution of RA was prepared by dissolving 1.5 mg in 10 mL of methanol (150 µg/mL). Serial dilutions (30, 60, 75, 90, and 150 µg/mL) were prepared, and 20 µL of each was injected in triplicate under the same conditions as the extract. Peak areas were recorded to establish a standard calibration curve by plotting peak areas against concentrations. Linearity was assessed using linear regression, with a correlation coefficient (r2) of 0.9989 and the lowest detectable concentration of 3 µg/mL, as shown in Supplementary File.
Standardization of capsicum extract
A stock solution of capsaicin was prepared by dissolving 1.1 mg in 10 mL of methanol, resulting in a 110 µg/mL concentration. Serial dilutions (4.4, 8.8, 17.6, 22, 44, and 110 µg/mL) were prepared, and 20 µL of each was injected in triplicate. Peak areas were recorded to establish a standard calibration curve by plotting mean peak areas against concentrations. Linearity was assessed using linear regression, with a correlation coefficient (r2) of 0.9989 and the lowest detectable concentration of 4 µg/mL, as shown in Supplementary File.
In vivo pharmacological study
Animals
Adult male Wistar rats (150–200 g) were procured from the animal house at the Faculty of Pharmacy, Cairo University. They were maintained under optimal conditions: temperature of 25°C ± 2°C, 60% ±10% humidity, and a 12/12 h light/dark cycle, with unrestricted access to food and water. The study protocol was approved by the Institutional Research Ethics Committee for Animal Experimentation (MP No. 2494) and adhered to the National Institutes of Health Guide for Care and Use of Laboratory Animals (2011).
Androgenetic alopecia induction
Androgenetic alopecia was induced by subcutaneous injection of 0.1 ml of testosterone propionate (5 mg/mL) diluted in coconut oil for 21 days.[16]
Experimental design
In this study, 60 rats were divided randomly into 10 groups of 6 animals each. Group 1 served as the control group and received no treatment, while Group 2 was administered testosterone only. Group 3 received testosterone and vehicle (coconut oil), Group 4 was treated with testosterone and 2% finasteride, Group 5 was treated with testosterone and 0.01% capsicum extract, Group 6 was treated with testosterone and 0.025% capsicum extract, Group 7 was treated with testosterone and 0.075% capsicum extract, Group 8 was treated with testosterone and 1% rosemary extract, Group 9 was treated with testosterone and 3% rosemary extract, and Group 10 was treated with testosterone and 5% rosemary extract. Solutions (0.5 mL each) were applied topically to the shaved back skin area (2 cm × 3 cm) once daily for 21 days for groups 3–10. The hair growth in each group was visually evaluated and recorded photographically after 7, 14, and 21 days. Two rats from each group were randomly selected and euthanized at each time interval by cervical dislocation under light anesthesia for further histopathological examination.
Histopathological analysis
The morphological parameters of hair follicles were assessed using skin samples from the dorsal area of rats at 7, 14, and 21 days. Samples were fixed in 10% formalin for 48 h, dehydrated, and sectioned longitudinally and crosswise. Hematoxylin and eosin staining was performed. Six nonoverlapping fields were analyzed for follicular length using longitudinal sections aligned with hair growth, while cross-sections evaluated follicular hair density and mean diameter. All measurements and data analyses were conducted using a full HD microscopic imaging system with the Leica Application suite for histological analysis.
Statistical analysis
The data are expressed as means ± standard error. Statistical analysis was conducted using GraphPad Prism software (version 6; GraphPad Software, Inc., San Diego, CA, USA). A one-way analysis of variance followed by Tukey’s multiple comparison test was performed, with a significance level set at P < 0.05. Graphical presentations were also generated using the same software.
Results
High-performance liquid chromatography analysis and standardization
The quantification of major active compounds in each bioactive extract revealed precise parameters necessary for consistent therapeutic applications. HPLC analysis of rosemary extract contained 0.605 g% of RA, while in capsicum extract, capsaicin was determined as 0.16 g%. This quantification was achieved by employing a calibration curve established for the extract’s standardization.
Qualitative hair growth study
Visual evaluations at 7, 14, and 21 days revealed significant hair loss in groups treated with testosterone alone or with the vehicle. In contrast, rats treated topically with 2% finasteride, as well as various concentrations of rosemary and capsicum extracts, exhibited improved hair growth compared to testosterone-only groups, as shown in Figure 1.
Figure 1.
Hair growth assessment in testosterone-induced alopecia rat model. Comparison between different treatment groups — control, testosterone only, testosterone + rosemary extract, and testosterone + capsicum extract — was conducted at days 7, 14, and 21. Photographic evaluation illustrates the progression of hair regrowth in each group over time
Quantitative hair growth study
The provided data offer a comprehensive analysis of the effects of various herbal treatments on hair follicle parameters, including diameter, length, and density. The study examined the impact of these interventions at three different time points: days 7, 14, and 21. The treatments assessed testosterone, testosterone + vehicle, finasteride, rosemary extracts, and capsicum extracts at various concentrations. The values illustrate the percentage or fold changes relative to the control or testosterone group, highlighting the effectiveness of each treatment in influencing hair follicle characteristics.
Diameter of hair follicle
After 7 days, the diameter of hair follicles in the testosterone and testosterone + vehicle groups showed marked decreases of 70% and 61%, respectively, compared to the control group. In contrast, treatment with 2% finasteride and 3% and 5% rosemary extract successfully increased the diameter by 2-fold, 1-fold, and 1.2-fold, respectively. Meanwhile, 0.01%, 0.025%, and 0.075% capsicum extracts showed increases of 1.1-, 1.3-, and 1.5-folds, respectively, compared to the testosterone-treated group.
After 14 days, the diameter of hair follicles in the testosterone and testosterone + vehicle groups were notably decreased by 54% and 39%, respectively, compared to the control group. However, treatments with 2% finasteride, 3%, 5% rosemary extract, and 0.075% capsicum extract showed to increase the diameter by 100%, 55.2%, 91%, and 76.3%, respectively, compared to the testosterone group.
Finally, on day 21, the treatment with testosterone and testosterone + vehicle groups resulted in a significant decrease in follicle diameter by 56% and 54%, respectively, compared to the control group. In comparison, administration of 2% finasteride, 5% rosemary extract, and 0.025% and 0.075% capsicum extracts caused a notable increase in the diameter by 80%, 46.2%, and 45.7%, 73%, respectively, compared to the testosterone group. The highest increases in follicle diameter were observed with 2% finasteride and 5% rosemary extract, highlighting their significant effectiveness in Figures 2 and 3 and Table 1.
Figure 2.
Photomicrographs: Cross-sections from the dorsal skin of rats in various groups at 7, 14, and 21 days using hematoxylin and eosin staining. These sections were analyzed to assess follicular hair density and the diameter of hair follicle
Figure 3.
Comparison of hair follicle diameters in skin sections from all groups: (a) Treatment after 7 days, (b) after 14 days, (c) after 21 days. Data were expressed as means of 6 rats (2 for each time interval) ± standard error, and comparisons between different groups were carried out using one-way analysis of variance followed by Tukey’s multiple comparisons test. a: Significantly different from control group. b: Significantly different from testosterone group. c: Significantly different from vehicle. d: Significantly different from finasteride
Table 1.
Comparison of hair follicle diameter in skin sections between groups at different time intervals
| Group | Day 7 | Day 14 | Day 21 |
|---|---|---|---|
| Control versus testosterone | Significant | Significant | Significant |
| Control versus vehicle | Significant | Significant | Significant |
| Control versus 2% finasteride | NS | NS | Significant |
| Control versus 0.01% Cap. | Significant | Significant | Significant |
| Control versus 0.025% Cap. | Significant | Significant | Significant |
| Control versus 0.075% Cap. | NS | Significant | Significant |
| Control versus 1% Ros. | Significant | Significant | Significant |
| Control versus 3% Ros. | Significant | Significant | Significant |
| Control versus 5% Ros. | Significant | NS | Significant |
| Testosterone versus 2% finasteride | Significant | Significant | Significant |
| Testosterone versus 0.01% Cap. | Significant | NS | NS |
| Testosterone versus 0.025% Cap. | Significant | NS | Significant |
| Testosterone versus 0.075% Cap. | Significant | Significant | Significant |
| Testosterone versus 3% Ros. | Significant | Significant | NS |
| Testosterone versus 5% Ros. | Significant | Significant | Significant |
| Vehicle versus 2% finasteride | Significant | Significant | Significant |
| Vehicle versus 0.01% Cap. | Significant | NS | NS |
| Vehicle versus 0.025% Cap. | Significant | NS | Significant |
| Vehicle versus 0.075% Cap. | Significant | Significant | Significant |
| Vehicle versus 5% Ros. | Significant | Significant | Significant |
| 2% Finasteride versus 0.01% Cap. | NS | Significant | Significant |
| 2% Finasteride versus 0.025% Cap. | NS | Significant | NS |
| 2% Finasteride versus 0.075% Cap. | NS | NS | NS |
| 2% Finasteride versus 1% Ros. | Significant | Significant | Significant |
| 2% Finasteride versus 3% Ros. | Significant | Significant | Significant |
NS=Nonsignificant, Cap.=Capsicum, Ros.=Rosemary
Length of hair follicles
The results showed a marked decrease in the length of hair follicles for the testosterone and testosterone + vehicle groups by 62% and 63%, respectively, after 7 days compared to the control group. However, treatments with 2% finasteride, 3% and 5% rosemary extract, and 0.025% and 0.075% capsicum extract successfully increased the length by 1.6-folds, 1.3-folds, 1.4-folds, 1.1-folds, and 1.4-folds, respectively, compared to the testosterone group.
By day 14, the length of hair follicles in the testosterone and testosterone + vehicle groups had decreased significantly by 68% and 59%, respectively, compared to the control group. In contrast, treatments with 2% finasteride, 3% and 5% rosemary extract, and 0.025% and 0.075% capsicum extract significantly boosted the length by 2-folds, 1.4-folds, 1.5-folds, 1.5-folds, and 1.7-folds, respectively, compared to the testosterone group.
Finally, on day 21, a significant decrease in the length of hair follicles was observed in the testosterone and testosterone + vehicle groups, by 78% and 70%, respectively, compared to the control group. However, topical administration of 2% finasteride, 1%, 3%, and 5% rosemary extract, and 0.01%, 0.025%, and 0.075% capsicum extract showed a marked enhancement in length by 3.2-folds, 1.4-folds, 2.1-folds, 2.7-folds, 1.5-folds, 2.4-folds, and 2.8-folds, respectively, compared to the testosterone group, as shown in Figures 4 and 5 and Table 2.
Figure 4.
Photomicrographs longitudinal sections from the dorsal skin of rats from various groups at 7, 14, and 21 days using hematoxylin and eosin staining. These sections were analyzed to assess follicular length
Figure 5.
Comparison of follicular length in longitudinal skin sections from all groups: (a) Treatment after 7 days, (b) after 14 days, (c) after 21 days. Data were expressed as means of 6 rats (2 for each time interval) ± standard error, and comparisons between different groups were carried out using one-way analysis of variance followed by Tukey’s multiple comparisons test. a: Significantly different from control group. b: Significantly different from testosterone group. c: Significantly different from vehicle. d: Significantly different from finasteride
Table 2.
Comparison of hair follicle length in skin sections between groups at different time intervals
| Group | Day 7 | Day 14 | Day 21 |
|---|---|---|---|
| Control versus testosterone | Significant | Significant | Significant |
| Control versus vehicle | Significant | Significant | Significant |
| Control versus 2% finasteride | Significant | Significant | NS |
| Control versus 0.01% Cap. | Significant | Significant | Significant |
| Control versus 0.025% Cap. | Significant | Significant | Significant |
| Control versus 0.075% Cap. | Significant | Significant | Significant |
| Control versus 1% Ros. | Significant | Significant | Significant |
| Control versus 3% Ros. | Significant | Significant | Significant |
| Control versus 5% Ros. | Significant | Significant | Significant |
| Testosterone versus vehicle | NS | Significant | NS |
| Testosterone versus 2% finasteride | Significant | Significant | Significant |
| Testosterone versus 0.01% Cap. | Significant | Significant | Significant |
| Testosterone versus 0.025% Cap. | Significant | Significant | Significant |
| Testosterone versus 0.075% Cap. | Significant | Significant | Significant |
| Testosterone versus 1% Ros. | Significant | Significant | Significant |
| Testosterone versus 3% Ros. | Significant | Significant | Significant |
| Testosterone versus 5% Ros. | Significant | Significant | Significant |
| Vehicle versus 2% finasteride | Significant | Significant | NS |
| Vehicle versus 0.01% Cap. | Significant | Significant | Significant |
| Vehicle versus 0.025% Cap. | Significant | Significant | Significant |
| Vehicle versus 0.075% Cap. | Significant | Significant | Significant |
| Vehicle versus 1% Ros. | Significant | Significant | Significant |
| Vehicle versus 3% Ros. | Significant | Significant | Significant |
| Vehicle versus 5% Ros. | Significant | Significant | Significant |
| 2% finasteride versus 0.01% Cap. | Significant | Significant | Significant |
| 2% finasteride versus 0.025% Cap. | Significant | Significant | Significant |
| 2% finasteride versus 0.075% Cap. | Significant | Significant | NS |
| 2% finasteride versus 1% Ros. | Significant | Significant | Significant |
| 2% finasteride versus 3% Ros. | Significant | Significant | Significant |
| 2% finasteride versus 5% Ros. | Significant | Significant | NS |
NS=Nonsignificant, Cap.=Capsicum, Ros.=Rosemary
Density of hair follicles (number of hair follicles)
The density of hair follicles at day 7 in the testosterone and testosterone + vehicle groups decreased significantly by 84% and 81%, respectively, compared to the control group. While treatments with 2% finasteride, and 1%, 3%, and 5% rosemary extract, as well as 0.01%, 0.025%, and 0.075% capsicum extract, increased the density by 3.8-folds, 1.2-folds, 3.5-folds, 3.7-folds, 1.7-folds, 2.2-folds, and 3.9-folds, respectively, compared to the testosterone group.
By day 14, the density of hair follicles had markedly decreased by 82% and 69% in the testosterone and testosterone + vehicle groups, respectively, compared to the control group. However, significant increases in density were observed with treatments of 2% finasteride and 1%, 3%, and 5% rosemary extract, as well as 0.01%, 0.025%, and 0.075% capsicum extract, by 2.9-folds, 3.3-folds, 3.9-folds, 2.2-folds, 2.6-folds, 3.9-folds, and 3.9-folds, respectively, compared to the testosterone group.
Finally, on day 21, the density of hair follicles in the testosterone and testosterone + vehicle groups was significantly reduced by 60.75% and 51.3%, respectively, compared to the control group. At the same time, 2% finasteride, 5% rosemary extract, and 0.075% capsicum extract were able to increase the density by 1.1-folds, 46%, and 1.1-folds, respectively, compared to the testosterone group, as illustrated in Figure 6 and Table 3.
Figure 6.
Comparison of number of hair follicles in skin sections from all groups. (a) Treatment after 7 days, (b) after 14 days, (c) after 21 days. Data were expressed as means of 6 rats (2 for each time interval) ± standard error, and comparisons between different groups were carried out using one-way analysis of variance followed by Tukey’s multiple comparisons test. a: Significantly different from control group. b: Significantly different from testosterone group. c: Significantly different from vehicle. d: Significantly different from finasteride
Table 3.
Comparison of hair follicles number (density) in skin sections between groups at different time intervals
| Group | Day 7 | Day 14 | Day 21 |
|---|---|---|---|
| Control versus testosterone | Significant | Significant | Significant |
| Control versus vehicle | Significant | Significant | Significant |
| Control versus 2% finasteride | Significant | Significant | Significant |
| Control versus 0.01% Cap. | Significant | Significant | Significant |
| Control versus 0.025% Cap. | Significant | Significant | Significant |
| Control versus 0.075% Cap. | Significant | Significant | Significant |
| Control versus 1% Ros. | Significant | Significant | Significant |
| Control versus 3% Ros. | Significant | Significant | Significant |
| Control versus 5% Ros. | Significant | Significant | Significant |
| Testosterone versus vehicle | NS | Significant | Significant |
| Testosterone versus 2% finasteride | Significant | Significant | Significant |
| Testosterone versus 0.01% Cap. | Significant | Significant | NS |
| Testosterone versus 0.025% Cap. | Significant | Significant | NS |
| Testosterone versus 0.075% Cap. | Significant | Significant | Significant |
| Testosterone versus 1% Ros. | Significant | Significant | NS |
| Testosterone versus 3% Ros. | Significant | Significant | NS |
| Testosterone versus 5% Ros. | Significant | Significant | S |
| Vehicle versus 2% finasteride | Significant | Significant | S |
| Vehicle versus 0.01% Cap. | Significant | Significant | NS |
| Vehicle versus 0.025% Cap. | Significant | Significant | Significant |
| Vehicle versus 0.075% Cap. | Significant | Significant | Significant |
| Vehicle versus 1% Ros. | Significant | Significant | Significant |
| Vehicle versus 3% Ros. | Significant | Significant | NS |
| Vehicle versus 5% Ros. | Significant | Significant | Significant |
| 2% finasteride versus 0.01% Cap. | Significant | Significant | Significant |
| 2% finasteride versus 0.025% Cap. | Significant | Significant | NS |
| 2% finasteride versus 0.075% Cap. | NS | NS | NS |
| 2% finasteride versus 1% Ros. | Significant | Significant | Significant |
| 2% finasteride versus 3% Ros. | NS | Significant | Significant |
| 2% finasteride versus 5% Ros. | NS | NS | Significant |
NS=Nonsignificant, Cap.=Capsicum, Ros.=Rosemary
Discussion
Androgenetic alopecia causes progressive miniaturization of the hair follicle, leading to hair loss through different mechanisms of action.[17] Rosemary (R. officinalis) and capsicum (C. annuum) extracts were selected according to their reported data in which one of the researchers has identified rosemary’s active ingredients, carnosol, and 12-methoxycarnosic acid. These have been shown to improve hair regrowth by inhibiting 5-alpha-reductase in rats, thus preventing androgenetic alopecia.[6] Additionally, carnosol’s antioxidant properties have been found to improve the resistance of the dermal papillae against oxidative stress, a factor linked to hair loss.[7] Furthermore, a study conducted in 2017 suggested that compounds activating the Nrf-2 pathway – the master regulator of the body’s natural antioxidant systems – can be considered as potential treatments for hair loss and for preventing oxidation-induced alopecia.[8] Moreover, a clinical comparative study showed that rosemary oil (containing 3.7 mg 1,8-cineole per ml) was equally effective as minoxidil (2%) in promoting hair growth, with mild side effects.[4] Another clinical study evaluated the efficacy of a lotion containing R. officinalis, Salvia officinalis, Salvia sclarea, Thymus satureioides, and Pogostemon patchouli in combination with electromagnetic pulses for the treatment of androgenetic alopecia. The results indicated that the lotion not only prevented hair loss but also led to a significant increase in hair density after 3 and 6 months.[9] Concerning capsicum, research demonstrates that the co-application of capsaicin and minoxidil can significantly enhance hair growth in mice, suggesting a synergistic effect of these two compounds on promoting hair follicle activity.[10] Moreover, capsaicin and isoflavones, the primary bioactive compounds in capsicum, have been shown to promote hair growth by increasing the production of IGF-I in hair follicles.[11] This effect observed in both mice and humans with alopecia is facilitated by capsaicin’s activation of sensory neurons, which increases the release of calcitonin gene-related peptide, a known enhancer of IGF-I production.[12] Further, a review paper has shown that capsaicin has significant potential to promote hair growth by enhancing follicle health and reducing oxidative stress.[13] These data indicated that both rosemary and capsicum extracts have a promising effect in treating alopecia, but they were carried out on unstandardized extract, which may lead to unreproducible results. To address this, we prepared a standardized extract for each of the selected drugs to provide precise quantification of the active compounds, which is critical for ensuring consistent biological efficacy. We developed a new, simple, accurate, rapid, and applicable method for analyzing RA in rosemary extract and capsaicin in capsicum extract in contrast with the previously reported HPLC. This method ensures consistency in the active components, enhancing the repeatability and efficacy of the extracts in treating hair loss to be used in formulas and products in the market. The qualitative and quantitative findings of this study offer insightful data into the effectiveness of capsicum and rosemary standardized extracts in comparison with conventional treatments like finasteride. Notably, the visual evaluation at 7, 14, and 21-day intervals indicated that testosterone treatment alone or with vehicle (control groups) led to hair loss, while the application of finasteride and varying concentrations of rosemary (3 and 5%) and capsicum (0.075%) extracts significantly improved hair growth and appearance. These observations suggested a strong potential for these natural extracts as alternative treatments for hair loss. The 5% rosemary and 0.075% capsicum extracts showed the most significant increases, highlighting their potent effects in enhancing hair follicle diameter. Similarly, the length of hair follicles was significantly improved with the application of both extracts. The results on day 21 demonstrated a significant increase in follicle length with 5% rosemary and 0.075% capsicum extracts. Finally, in terms of hair follicle density in rats, the highest increase in hair follicle density was observed with 3% and 5% rosemary extract and 0.075% capsicum extract at day 21 compared to the testosterone group. Although these findings suggest that these extracts exhibit significant potential as hair growth-promoting agents, further research is needed to explore the clinical applications and mechanisms of action of these extracts on humans. Nevertheless, these findings suggest that rosemary and capsicum extracts hold promise as potential therapeutic agents for hair loss treatment.
Conclusions
This study provides valuable insights into the role of herbal drug extracts in hair growth. The results highlight the potential of standardized rosemary and capsicum extracts in promoting hair parameters, including follicle density, length, and diameter. Future investigations should focus on clinical applications.
Conflicts of interest
There are no conflicts of interest.
Supplementary File
Linear regression of rosmarinic acid standard solution
| Mean peak area (mAU) |
Mean peak area | |||
|---|---|---|---|---|
| 1st run | 2nd run | 3rd run | ||
| RA concentration (μg/mL) | ||||
| 30 | 1636 | 1628 | 1626 | 1630 |
| 60 | 3180 | 3152 | 3172 | 3168 |
| 75 | 4021 | 4028 | 4020 | 4023 |
| 90 | 4802 | 4875 | 4834 | 4837 |
| 150 | 8361 | 8336 | 8449 | 8382 |
| Specified extract | ||||
| 60.05 μg/mL | 3652 | 3587 | 3555 | 3598 |
RA=Rosmarinic acid
Calibration curve of standard rosmarinic acid
Linear regression of capsaicin standard solution
| Mean peak area (mAU) |
Mean peak area | |||
|---|---|---|---|---|
| 1st run | 2nd run | 3rd run | ||
| Capsaicin concentration (μg/mL) | ||||
| 4.4 | 120 | 118 | 117 | 118.33 |
| 8.8 | 238 | 238 | 240 | 238.67 |
| 17.6 | 492 | 482 | 485 | 486.33 |
| 22 | 607 | 593 | 622 | 607.33 |
| 44 | 1206 | 1244 | 1264 | 1238.00 |
| 110 | 3042 | 3080 | 3052 | 3058.00 |
| Specified extract | ||||
| 8.9 | 248 | 254 | 240 | 247.33 |
Calibration curve of standard capsaicin
High-performance liquid chromatography fingerprint of capsicum specified extract: (a) Total extract, (b) Capsaicin
High-performance liquid chromatography fingerprint of rosemary specified extract: (a) Total extract, (b) Rosmarinic acid
Funding Statement
Nil.
References
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