Formulation and Evaluation of Polyherbal Hair Oil Containing Nagarmotha, Curry Leaves, Amla, Hibiscus, Fenugreek, and Coconut Oil

Hair care represents one of the most ancient traditions in human grooming and therapeutics. Across Asia, particularly in the Indian subcontinent, the application of herbal oils to the scalp has been practiced for millennia, with Ayurvedic texts such as the Charaka Samhita and Sushruta Samhita extensively documenting the formulation and use of medicated oils (taila kalpana) for promoting hair growth, preventing premature greying, and maintaining scalp health [1, 2]. Hair loss (alopecia) and scalp disorders including dandruff (seborrheic dermatitis), scalp dryness, and follicular inflammation represent significant dermatological concerns globally. Studies indicate that androgenetic alopecia affects approximately 50% of men by age 50 and nearly 25% of women by age 60, whereas telogen effluvium and nutritional deficiency-related hair loss are increasingly prevalent due to modern lifestyle changes [3]. Despite the availability of synthetic pharmacological agents such as minoxidil and finasteride, these treatments are associated with systemic side effects, cost burdens, and limited long-term efficacy, driving renewed interest in plant-derived therapeutic alternatives [4]. Plant derived cosmeceuticals offer multifaceted bioactivities including antioxidant, anti-inflammatory, antimicrobial, and 5α-reductase inhibitory properties, which collectively address the pathophysiology of hair loss and scalp disorders without significant adverse effects [5]. The formulation of polyherbal hair oils enables synergistic interactions between phytoconstituents, potentially producing enhanced therapeutic outcomes compared to single herb preparations [6]. The herbs selected in the present study Nagarmotha (Cyperus rotundus Linn.), Curry Leaves (Murraya koenigii Spreng.), Amla (Phyllanthus emblica Linn.), Hibiscus (Hibiscus rosa-sinensis Linn.), and Fenugreek (Trigonella foenum-graecum Linn.) have individually demonstrated pharmacological activities relevant to hair care, including antifungal, hair growth promoting, antioxidant, and anti-inflammatory properties, as substantiated by a growing body of in vitro, ex vivo, and clinical studies [7–12]. Coconut oil (Cocos nucifera) was selected as the base owing to its excellent penetration into the hair shaft, its capacity to reduce protein loss from hair, and its widespread traditional use in Indian hair care [13]. The objectives of the present study were to: (i) Prepare three polyherbal hair oil formulations (F1, F2, F3) with varying extract concentrations (ii) Evaluate the formulations for organoleptic and physicochemical parameters (iii) Assess the accelerated stability of the formulations over a six-month period in accordance with International Council for Harmonisation (ICH) guidelines Q1A(R2).

MATERIALS AND METHODS

Plant Material Collection

Fresh plant material comprising rhizomes of Cyperus rotundus, leaves of Murraya koenigii, fresh fruits of Phyllanthus emblica, fresh flowers and leaves of Hibiscus rosa-sinensis, and seeds of Trigonella foenum-graecum were procured from a certified botanical garden and authenticated by a qualified pharmacognosist. Virgin coconut oil (cold-pressed) meeting the specifications of the Indian Pharmacopoeia 2022 was obtained from a certified pharmaceutical grade supplier. All solvents and reagents used were of analytical reagent (AR) grade.

Preparation of Herbal Extracts

Each plant material was shade-dried at ambient temperature (25–30°C), coarsely powdered (sieve No. 40), and subjected to hot continuous extraction using a Soxhlet apparatus with 70% ethanol as the solvent. Extraction was continued for 18–24 cycles. The resultant extracts were filtered, concentrated under reduced pressure using a rotary evaporator at 45°C, and dried to yield semi-solid extracts. The yield (% w/w) was calculated on a dry weight basis. Extracts were stored at 4°C in amber colored glass containers until use [14].

Formulation of Polyherbal Hair Oil

Three formulations F1, F2, and F3 were prepared by dissolving weighed quantities of each herbal extract in a minimum volume of propylene glycol (acting as a co-solvent and humectant), followed by gradual incorporation into the pre heated (60°C) coconut oil base under continuous stirring using an overhead mechanical stirrer (500 rpm, 30 min). Vitamin E (tocopherol), BHT, and rosemary essential oil were added during the cooling phase (below 40°C) to prevent thermal degradation of the antioxidants. The formulations were stirred until homogeneous and allowed to cool to room temperature. The exact composition of each formulation is detailed in Table 1.

Table 1: Formulation composition of polyherbal hair oil (F1, F2, F3) per 100 g batch

Evaluation Parameters

Organoleptic Evaluation

Colour: The colour of each formulation was assessed visually under diffused natural light and recorded against a white background by three independent observers. Results were expressed descriptively.

Odour: The odour of each formulation was evaluated by trained panel members (n=5) under standardized conditions and scored on a 5 point hedonic scale: 1 (very unpleasant) to 5 (very pleasant). Mean scores ± SEM were recorded [15].

Taste: Although hair oils are for external use, taste evaluation was conducted for completeness as per regulatory guidelines for cosmeceuticals products, noting any bitterness imparted by the phytoconstituents. A small quantity (~0.1 mL) was placed on the tip of the tongue by trained panellists, and taste was recorded descriptively.

pH Determination

The pH of each formulation was determined using a calibrated digital pH meter (Systronics Model µ pH System 362, India) at 25 ± 0.5°C. A 10% v/v dispersion of the oil in distilled water was prepared with the aid of Tween 80 (2%), vortexed for 2 min, and the pH was measured in triplicate. The pH meter was calibrated using standard buffer solutions (pH 4.0 and 7.0) prior to each measurement [16].

Viscosity Measurement

Apparent viscosity was determined using a Brookfield DV-E rotational viscometer equipped with spindle No. 64 at 25 ± 0.5°C. Measurements were performed at 60 rpm in triplicate, and results were expressed in millipascal-seconds (mPa·s). Temperature was maintained using a circulating water bath. All readings were taken after 1 minute of equilibration at the set spindle speed [17].

Specific Gravity

Specific gravity was determined using a 25 mL pycnometer. The pycnometer was first weighed empty (W1), then filled with distilled water (W2), and finally filled with the sample (W3). Specific gravity was calculated using the formula: SG = (W3 − W1) / (W2 − W1). Measurements were conducted at 25°C in triplicate [18].

Refractive Index

The refractive index was determined at 25°C using an Abbe refractometer (ERMA Inc., Japan). A small drop of oil was placed on the prism surface, and the reading was taken in triplicate after temperature equilibration. The instrument was calibrated with distilled water (RI = 1.333 at 25°C) prior to measurements [18].

Acid Value

Acid value was determined as per the method described in the Indian Pharmacopoeia 2022 (IP 2022). Approximately 5 g of oil was dissolved in 50 mL of a neutralized ethanol-diethyl ether (1:1 v/v) mixture. The solution was titrated with 0.1 N KOH using phenolphthalein as the indicator. Acid value was calculated as: AV = (56.1 × V × N) / W, where V = volume of KOH consumed (mL), N = normality of KOH, and W = weight of sample (g) [19].

Peroxide Value

Peroxide value was determined by the iodometric method. Approximately 5 g of oil was dissolved in 30 mL of acetic acid–chloroform (3:2 v/v) solution and treated with 0.5 mL of saturated potassium iodide solution. After standing in the dark for exactly 1 minute, 30 mL of distilled water and starch indicator were added. Liberated iodine was titrated with 0.01 N sodium thiosulphate. Peroxide value was expressed in milliequivalents of active oxygen per kilogram of oil (meq/kg) [19, 20].

Accelerated Stability Testing

Stability studies were conducted in accordance with ICH Q1A(R2) guidelines. Samples were stored in sealed amber glass bottles and placed in stability chambers set at three conditions: (i) 25°C/60% RH (long-term), (ii) 40°C/75% RH (intermediate), and (iii) 45°C/75% RH (accelerated). Samples were withdrawn at 0, 1, 3, and 6 months and analyzed for pH, viscosity, colour, odour, acid value, and peroxide value. Phase separation and rancidity were also visually assessed [21].

Results and Discussion

4.1 Organoleptic and Physicochemical Evaluation

The organoleptic and physicochemical parameters of all three formulations (F1, F2, F3) are presented in Table 2. All formulations exhibited characteristic herbal odour attributed primarily to the essential oil components of curry leaves and rosemary, and to the volatile terpenoids of nagarmotha. The colour progressively deepened from F1 (pale yellow) to F3 (dark brown) with increasing extract concentrations, consistent with the high phenolic and flavonoid content of amla and hibiscus extracts [7, 9]. The pH values of F1, F2, and F3 were 5.8 ± 0.05, 5.5 ± 0.04, and 5.2 ± 0.06, respectively, all within the acceptable range of 4.5–7.0 for scalp application. The slightly acidic pH mimics the physiological scalp pH (4.5–5.5), thereby supporting the integrity of the hair cuticle and minimizing disruption of the scalp's acid mantle [16]. The progressive decrease in pH with increasing extract concentration is attributable to the higher content of organic acids, particularly ascorbic acid from Amla and gallic acid from Nagarmotha and Amla [7].

Viscosity values ranged from 42.3 ± 1.2 mPa·s (F1) to 55.1 ± 1.8 mPa·s (F3), within the acceptable specification of 30–80 mPa·s for hair oils. The higher viscosity of F2 and F3 compared to F1 is attributable to the elevated concentration of semi-solid herbal extracts, which contribute to the overall rheological profile. F2 demonstrated the most optimal spreadability and scalp coverage during in-use assessment [17]. Specific gravity and refractive index values were consistent across formulations and within the IP 2022 specifications for fixed oils. Acid values (≤ 1.35 mg KOH/g) and peroxide values (≤ 1.72 meq/kg) were well below the permissible limits (AV ≤ 2.0; PV ≤ 5.0), confirming good oxidative stability at baseline [19].

Table 2: Physicochemical evaluation parameters of polyherbal hair oil formulations (n=3, Mean ± SD)

All values are mean ± SD, n = 3; pH measured as 10% v/v dispersion in distilled water.

Stability Analysis

Accelerated stability testing is critical for predicting the shelf life and performance of cosmeceuticals formulations under real-world storage conditions. Results of the stability study at 40°C/75% RH over 6 months are summarized in Table 3. All three formulations remained physically stable over the six-month study period, with no observed phase separation, precipitation, or gross rancidity. Minor darkening of colour was noted in F2 at 3 months at 40°C, likely due to Maillard type browning reactions between amino acids from fenugreek and reducing sugars from amla extract; however, this change was within acceptable organoleptic limits and did not affect product performance [20]. pH values remained within the specified range throughout the study period, with maximum deviations of 0.08 pH units, indicating adequate buffering capacity conferred by the phenolic acids and organic acids within the extracts. Viscosity showed marginal increases (< 5%) at elevated temperatures for F2 and F3, consistent with increased intermolecular interactions between the phytoconstituents at higher temperatures [17]. Acid values and peroxide values showed small but statistically non-significant increases over time, remaining well below established safety thresholds. The inclusion of Vitamin E and BHT as antioxidants effectively retarded oxidative degradation of the unsaturated fatty acids in coconut oil, consistent with published literature [13, 21]. F2 demonstrated the most favorable overall stability profile, combining adequate herbal extract concentration for pharmacological efficacy with excellent physicochemical stability over the six-month accelerated study period.

Table 3: Accelerated stability testing results at 40°C/75% RH over 6 months