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INTRODUCTION
Acne vulgaris, commonly known as acne, is one of the most prevalent skin conditions. This chronic inflammatory disorder of the pilosebaceous skin affects the chest, back, and face. Eighty-five percent of individuals are affected, particularly teenagers (Canha et al., 2020). The three primary causes of acne include increased sebum production, pore blockage-induced hyperkeratinisation, and the subsequent release of inflammatory chemicals into the skin. As various types of skin bacteria are removed from the follicle, bacterial colonization within the follicles activates additional commensals in the skin (Chen et al., 2020). The three main Gram-positive bacteria implicated in skin bacterial colonization are Staphylococcus aureus, Staphylococcus epidermidis, and Cutibacterium acnes (previously known as Propionibacterium acnes). The pathogenesis and progression of acne are significantly influenced by C. acnes, which may trigger the immune response cascade and initiate inflammatory processes in infected cells (Fourniere et al., 2020).
Cosmetics are products applied to the face, neck, and hands to enhance natural beauty while preserving skin health and maintaining the body's natural structure and function (Ko, 1998). The use of herbal cosmetics is becoming increasingly popular, as dermatologists endorse their safe application and minimal side effects, making them clinically effective (Kumar et al., 2012). Herbal medicines remain an integral part of traditional healthcare, particularly when conventional approaches fall short in treating chronic conditions. Bauhinia racemosa, for example, has demonstrated diverse pharmacological activities including anti-inflammatory, hepatoprotective, antioxidant, and antimicrobial effects (Tripti and Sahu, 2015). Numerous skincare products are available on the market, including sunscreen, anti-aging treatments, anti-wrinkle creams, anti-acne solutions, and those featuring natural ingredients (Joshi and Pawar, 2015).
Common cosmetics, including lotions, creams, and fragrances, are applied to the skin for aesthetic and cleansing purposes. As a result, they enhance our appearance without disrupting physical makeup (Larsson et al., 2007). Furthermore, these products include an emulsion and gel that improve solubility and skin penetration by allowing hydrophobic bioactive components to enter the aqueous phase (Malavi et al., 2022). The benefits of both emulsions and drug gels are combined when an emulgel is used, offering a dual-controlled drug-release system (Dantas et al., 2016; Kumar et al., 2016).
Overall, after oxygen, silicon is the second most abundant element on Earth and the third most plentiful trace element in the human body (Jugdaohsingh et al., 2008; Reffitt et al., 1999). Silica offers advantages over conventional gel bases due to its porous structure, high surface area, and ability to enhance skin penetration, making it superior to carbopol-only systems for delivering hydrophobic herbal actives (Morais et al., 2021). Emulgels are two-phase solutions that are ideal for acne-prone skin because of their non-greasy and lightweight textures.
The primary objective of this research is to create and test an herbal emulgel containing silica, tulsi oil, and neem oil (Chauhan et al., 2010; Bhattacharya and Walia, 2020). These herbal ingredients are effective in treating acne due to their antibacterial, anti-inflammatory, and antioxidant properties. This study is novel in its integration of Tulsi and Neem oils-both known for their antimicrobial and anti-inflammatory potential-into a silica-based emulgel, aiming to exploit their synergistic effect for acne therapy.
MATERIALS AND METHODS
Materials
Jojoba oil, tulsi oil, and neem oil were procured from Paras Chemicals Ltd., Additional reagents, including silica gel, tween 80, span 20, and ethanol, were sourced from the School of Pharmacy, VU chemical storehouse.
Preparation Methods
Extraction of Tulsi Oil: Fresh Ocimum sanctum leaves were thoroughly washed and dried for 36 hr. The dried leaves were cut into small pieces and subjected to solvent extraction in a stirred-type batch reactor using methanol. The extracted oil was collected at specific intervals (Chauhan et al., 2010).
Emulgel Preparation: After moderate stirring, Carbopol 934 was dissolved in filtered water, and the pH was adjusted to between 6 and 6.5. Span-20 was dissolved in liquid paraffin to create the oil phase, while Tween-20 was added to filtered water to form the aqueous phase. The medication was dissolved in ethanol, and the preservatives were dissolved in propylene glycol before being combined with the aqueous phase. The two phases were independently heated to 70ºC to 80ºC and then mixed while being constantly stirred. The final emulgel was created by blending the gel and the resulting emulsion in a 1:1 ratio (Bhattacharya and Walia, 2020) (Figure 1).
Figure 1: Emulgel preparation process. Development of an Optimal Topical Formulation: A suitable formulation should ensure effective topical targeting, smooth consistency, ease of application, non-greasy feel, stability, and washability. The silica-based emulgel was optimized to meet these criteria. Four batches (F1-F4) were developed with varying ingredient concentrations (Table 1).
| Ingredients | F1 | F2 | F3 | F4 |
|---|---|---|---|---|
| Tulsi oil %v/v | 0.1 | 0.2 | 0.3 | 0.4 |
| Jojoba oil %v/v | 0.4 | 0.5 | 0.6 | 0.7 |
| Neem oil q.s. (mL) | 10 | 10 | 10 | 10 |
| Silica gel %w/v | 2.5 | 3 | 3.5 | 4 |
| Carbopol %w/v | 0.2 | 0.3 | 0.4 | 0.5 |
| Preservatives | 0.001 | 0.001 | 0.001 | 0.001 |
| Water | q.s. | q.s. | q.s. | q.s. |
RESULTS AND EVALUATION METHODS OF THE FORMULA
Evaluation of the physicochemical parameters and standardization of herbs.
(a) Humidity:, 2 g of the sample were weighed, dried at 105ºC for 2 hr, cooled in a desiccator, and reweighed. The weight loss was recorded as moisture content.
Formula: Moisture% = (Weight before drying - Weight after drying) / Initial weight × 100
(b) Total ash:, 3 g of the sample were incinerated at 600ºC for 3 hr. The remaining ash content was weighed and calculated as a percentage.
Formula: Total Ash % = (Weight of Ash) / (Weight of Sample) × 100
(c) Acid insoluble ash:, After treatment with hydrochloric acid, the ash was filtered, dried, and burned again. The amount of acid-insoluble ash in the residue was determined by weighing it.
Formula: Acid Insoluble Ash % = (Weight of Acid-Insoluble Ash) / (Weight of Sample) × 100
(d) Characterization of oil:, Properties of the oils used are listed in Table 2.
| Properties | Jojoba oil | Tulsi oil | Neem oil |
|---|---|---|---|
| Saponification value | 61.5 | 187 | 190 |
| Colour | Pale yellow | Clear | Clear |
| Odor | Characteristic | Characteristic | None |
| State | Liquid | Liquid | Liquid |
| % yield | - | 13% | - |
Saponification value:, The saponification value indirectly indicates the molecular weight and fatty acid chain length, measuring the potassium hydroxide required to saponify 1 g of oil.
Formula: Saponification Value = 28.05 × (Blank Reading - Sample Reading) / Weight (Kokate et al., 2017; Indian Pharmacopoeia, 2018).
(e) The physicochemical evaluation of Tulsi leaves is summarized in Table 3.
| Characteristics | Herb | Requirements | Results | Remarks |
|---|---|---|---|---|
| Moisture % by mass, Max. | Tulsi leaf | 16.26 | 15.88 | Passes |
| Total ash (on dry basis), % by mass, Max. | Tulsi leaf | 15.21 | 14.75 | Passes |
| Acid insoluble ash (on a dry basis), % by mass, Max. | Tulsi leaf | 17.6 | 16.8 | Passes |
Evaluation of the prepared formulation
Each formulation was tested for pH, viscosity, spreadability, and washability to determine the optimal batch.
(a) pH Determination:, A measured quantity of oil was diluted with water, and pH was recorded using a pH meter (Figure 2).
(b) Viscosity Measurement:, Viscosity was determined using a Brookfield digital viscometer.
(c) Spreadability Assessment:, Spreadability was analyzed using a glass slide apparatus, where the time required for the slides to separate under a given weight was recorded. The results are presented in Table 4 (Figure 3).
| Formulation | Consistency | Texture | Spreadability | Washability | pH | Viscosity |
|---|---|---|---|---|---|---|
| F1 | Poor | Smooth | Poor | Poor | 5.0±0.3 | 0.0164 |
| F2 | Poor | Smooth | Poor | Poor | 5.0±0.3 | 0.0164 |
| F3 | Good | Smooth | Good | Good | 5.0±0.1 | 0.0191 |
| F4 | Good | Smooth | Good | Good | 5.0±0.2 | 0.0171 |
A measure of cream was applied to the fixed glass slide to evaluate its spreadability. 1 kg of weight was placed on the movable glass slide, which was connected to a pan, for 5 min while positioned over the fixed glass slide. After adding 50 g of weight to the pan, the time for the slides to separate was recorded. The results are presented in Table .
Where
S = Spreadability,
W = Weight attached to the top slide,
L = Length of slide (Smith and Johnson, 2023).
It was found that Formula number 4 has all the qualities that topical application needs, and below are the ingredients used in specific quantities mentioned.
Optimized Formulation:, The formulation exhibited a non-greasy, smooth texture with excellent washability (Figure 4). The ingredients of Batch F4 are detailed in Table 5.
| Sl. No. | Ingredients used | Quantities (%) |
|---|---|---|
| 1 | Tulsi oil (%v/v) | 0.4% |
| 2 | Jojoba oil (%v/v) | 0.7% |
| 3 | Neem oil(%v/v) | 10% |
| 4 | Silica gel (%w/v) | 4% |
| 5 | Tween 80 | 1.3% |
| 6 | Span 20 | 0.5% |
| 7 | Carbopol 934 | 0.5% |
| 8 | Liquid paraffin | 7.5% |
| 9 | Propylene glycol | 5% |
| 10 | Ethanol | 2.5% |
| 11 | Methyl paraben | 0.001% |
| 12 | Propyl paraben | 0.003% |
| 13 | Purified water | q.s. |
DISCUSSION
The physicochemical evaluation of Tulsi leaves confirmed compliance with quality standards, showing a moisture content of 15.88%, total ash of 14.75%, and acid-insoluble ash of 16.80%. The oils used- Tulsi, Neem, and Jojoba- demonstrated favorable saponification values and clarity, supporting their use in topical preparations.
Among the four formulations developed, Batch F4 exhibited the most desirable characteristics, including an appropriate pH (~5.0±0.2), spreadability (13.6 g·cm/s), and viscosity (0.0171 Pa·s), as well as excellent washability and no visible signs of skin irritation.
The therapeutic effect of Tulsi oil is primarily attributed to its active constituent eugenol, which is reported to have antibacterial and anti-inflammatory properties. Similarly, Neem oil contains nimbidin, a known antimicrobial agent. These phytochemicals, when combined in a stable emulgel matrix, may act synergistically to reduce inflammation and bacterial colonization in acne-prone skin, based on previously reported literature.
The incorporation of silica gel significantly enhanced the emulgel's structural and dermal penetration characteristics. As a porous, biocompatible carrier, silica facilitates the sustained release and improved bioavailability of lipophilic actives, ensuring prolonged skin retention and therapeutic action.
While the formulation results suggest promising potential, several limitations must be acknowledged. No in vivo clinical trials were conducted, and the accelerated stability and microbial limit tests- important for commercial translation- were not included. These gaps provide direction for future studies on regulatory compliance and clinical validation.
CONCLUSION
This study successfully developed and evaluated a silica-based herbal emulgel incorporating Tulsi, Neem, and Jojoba oils. Among the tested batches, formulation F4 was found to be optimal, demonstrating favorable pH, spreadability, viscosity, and washability. Using silica gel improved the consistency and enhanced the delivery of phytoconstituents. The combination of herbal actives, eugenol from Tulsi and nimbidin from Neem, offers promising potential for antimicrobial and anti-inflammatory activity, as supported by literature, making it a promising candidate for topical acne therapy. Further work should include clinical trials, long-term stability testing, and regulatory safety assessments to validate the formulation's commercial and therapeutic applicability.