Formulation Development and Quality Evaluation of a Topical Cream Containing a Polyphenol-Rich Extract from Spilanthes acmella Murr.

Abstract

This study aimed to develop and evaluate a stable oil-in-water (O/W) topical cream incorporating a polyphenol-rich extract from Spilanthes acmella Murr. (S. acmella), a plant recognized for its antioxidant potential. The extract, obtained via reflux extraction with 80% ethanol, demonstrated notable free radical scavenging activity in the DPPH (2,2-diphenyl-1-picrylhydrazyl) assay, exhibiting an IC₅₀ (Inhibitory concentration 50) value of 563.26 µg/mL. The cream was prepared using the hot emulsification method. Formulation variables, including oil phase concentration and composition (olive oil and cetyl alcohol), the emulsifier system (Tween 80/Span 80 blend), stirring duration, and humectant type, were systematically optimized to achieve the desired physicochemical stability and aesthetic properties. The optimized formulation contained 10% S. acmella extract, a 15% oil phase, a 10% emulsifier mix, and 10% glycerin. Three pilot batches were produced, all yielding a smooth, homogeneous, grayish-green cream with a pH of 5.69 ± 0.20, which is consistent with the physiological pH of human skin. The cream demonstrated good stability under stress conditions, excellent spreadability (29.87 ± 0.33 cm²), and a consistent total polyphenol content of 56.82 ± 0.69 mg gallic acid equivalents per gram. Microbial limit tests confirmed the product’s microbiological safety, and in vivo dermal irritation tests in rabbits (ISO 10993-10) showed no signs of skin irritation. Overall, the formulated cream was found to be stable, safe, and rich in antioxidant compounds, suggesting its potential as a promising dermo-cosmetic product.