Formulation And In Vitro Evaluation Of A Polyherbal Anti-Acne Patch Incorporating Selected Extracts

Herbal medicines have long been valued for their therapeutic efficacy, broad phytochemical diversity, and comparatively low incidence of adverse effects, and they continue to occupy a significant place in global healthcare alongside conventional pharmacotherapy. Plant-derived actives such as alkaloids, flavonoids, tannins, and polyphenols contribute antimicrobial, antioxidant, and anti-inflammatory activities that make botanical extracts attractive candidates for dermatological formulations.

The skin, as the body's largest organ, provides both a physical barrier and a route for localized drug delivery. Transdermal and topical patches exploit this property to deliver active constituents directly to the site of action, offering improved patient compliance, sustained release, and reduced systemic exposure compared with oral therapy. Facial or topical patches formulated with botanical extracts have gained particular attention for cosmetic and dermatological applications, including the management of acne.

Acne vulgaris is one of the most common inflammatory skin disorders, arising from excessive sebum secretion, hyperkeratinisation of the pilosebaceous follicle, colonisation by organisms such as Cutibacterium acnes and Staphylococcus epidermidis, and the resulting inflammatory cascade. Conventional anti-acne therapy relies heavily on antibiotics and keratolytic agents, but growing antimicrobial resistance and cutaneous side effects have created demand for safer, plant-based alternatives with antimicrobial, antioxidant, and anti-inflammatory properties.

Punica granatum   (pomegranate) peel is rich in punicalagins and anthocyanins with documented antioxidant and antibacterial activity; Azadirachta indica  (neem) leaf contains azadirachtin and nimbin with broad antimicrobial action; Glycyrrhiza glabra  (liquorice) root contains glycyrrhizin with anti-inflammatory and antimicrobial properties; and Camellia sinensis  (green tea) leaf is a rich source of catechins, particularly epigallocatechin gallate (EGCG), with potent antioxidant activity. The present study was undertaken to formulate a polyherbal anti-acne patch combining extracts of these four plants and to evaluate its physicochemical properties, in vitro antimicrobial activity, and antioxidant potential.

2. MATERIALS AND METHODS

2.1 Plant material and authentication

Fresh pomegranate peel, neem leaves, liquorice roots, and green tea leaves were collected and authenticated prior to processing.

2.2 Preparation of extracts

Each plant material was washed, shade-dried for four weeks, and pulverized to a fine powder. For each plant, 200 g of powder was macerated in a hydroalcoholic solvent system (560 mL ethanol: 240 mL distilled water) for three days. The macerate was filtered, and the filtrate was concentrated on a hot plate; the resulting dried extract was stored in a desiccator until use.

2.3 Formulation of the polyherbal patch

Patches were prepared by the solvent-casting method. HPMC E5 (3 g) was dispersed in 50 mL distilled water and allowed to swell for 1–2 h to form the film-forming base. Pomegranate peel extract (1 g), neem extract (0.5 g), liquorice extract (0.5 g), and green tea extract were dissolved in 5 mL ethanol and combined with glycerine, propylene glycol, and methyl paraben, then incorporated into the swollen polymer base under continuous stirring (300–500 rpm, 15–20 min) using a magnetic stirrer. The volume was adjusted to 100 mL with distilled water, and the homogeneous solution was cast into petri plates, dried at room temperature for 24 h, and cut into uniform 1 × 1 cm patches. Composition details are summarised in Table 1.

Table 1. Composition of the polyherbal anti-acne patch.

2.4 Physicochemical characterization

The formulated patches were evaluated for organoleptic characters (colour, odour, texture), thickness (digital vernier caliper), weight uniformity (analytical balance, n = 10), folding endurance (repeated folding of a 2 × 2 cm specimen until failure), moisture content (loss-on-drying at 105 ± 2 °C), surface pH (contact pH electrode after surface hydration), swelling index (weight gain in phosphate buffer pH 7.4), drug content uniformity (UV-visible spectrophotometry after extraction and filtration), adhesion (peel/attachment time on skin or membrane), skin irritation (visual scoring over 24–72 h), and short-term stability under ambient (25 ± 2 °C/60 ± 5% RH) and accelerated storage conditions.

2.5 Preliminary phytochemical screening

Each extract was subjected to standard qualitative colour and precipitation tests for alkaloids (Dragendorff's, Wagner's, Mayer's, Hager's reagents), flavonoids, terpenoids and steroids (Salkowski and Liebermann–

Burchard tests), tannins and phenolics (ferric chloride, potassium dichromate, lead acetate tests), saponins (froth test), glycosides (Legal's, Borntrager's, Baljet's tests), carbohydrates (Molisch's, Fehling's, Benedict's tests), proteins (Biuret, Ninhydrin, Xanthoproteic tests), fixed oils and fats (spot and saponification tests), anthraquinones, coumarins, gums, mucilage, and resins.

2.6 In vitro antimicrobial activity

Antimicrobial activity was determined by the agar well (cup-plate) diffusion method on Mueller–Hinton agar against an acne-associated test organism. Wells (6 mm) were loaded with 100 µL each of clindamycin solution (standard), polyherbal patch extract (test), and sterile solvent (negative control). Plates were incubated at 37 °C for 24 h, and the zone of inhibition was measured with a calibrated scale.

2.7 In vitro antioxidant activity (DPPH assay)

Antioxidant activity was assessed using the DPPH free-radical scavenging assay. A DPPH working solution (absorbance ≈ 0.97 ± 0.02 at 517 nm) was combined with the polyherbal extract or ascorbic acid standard, incubated in the dark for 30 min, and the absorbance was read at 517 nm. Percentage radical scavenging activity was calculated as:

%RSA = (A₀ − Aₛ) / A₀ × 100

where A₀ is the absorbance of the DPPH control and Aₛ is the absorbance of the sample or standard.

3. RESULTS

3.1 Organoleptic characters

The formulated patches were transparent to slightly yellowish-amber in colour, with a mild characteristic herbal odour and a thin, flexible, uniform film texture.

3.2 Preliminary phytochemical screening

Alkaloids, flavonoids, terpenoids, tannins, saponins, glycosides, phenolics, and carbohydrates were detected across the peel, leaf, and root extracts, with flavonoids consistently showing strong positive reactions in all four extracts (Table 2). Anthraquinones were absent in all extracts tested.

Table 2. Preliminary phytochemical screening of the four plant extracts. (−) absent; (+) present; (++) moderately present; (+++) strongly present.

3.3 Physicochemical parameters

The formulated patch met acceptable pharmaceutical benchmarks for topical films across all tested parameters (Table 3), including a near-neutral-to-slightly-acidic surface pH compatible with skin physiology and a high drug content uniformity.

Table 3. Physicochemical evaluation of the polyherbal anti-acne patch.

3.4 In vitro antimicrobial activity

The polyherbal patch produced a zone of inhibition of 20 mm against the test acne-associated organism, compared with 18 mm for clindamycin and no inhibition (0 mm) for the negative control (Table 4).

Table 4. Zone of inhibition by the agar well diffusion (cup-plate) method.

3.5 In vitro antioxidant activity

At the tested concentration (100 µg/mL), the polyherbal extract exhibited 80.95% DPPH radical scavenging activity, compared with 88.45% for the ascorbic acid standard (Table 5).

Table 5. DPPH free-radical scavenging activity of the polyherbal extract versus ascorbic acid.