Differential Anti-Acne Activities of Citrus hystrix Peel Extracts: 5α-Reductase Inhibition, Anti-Inflammatory, and Antimicrobial Effects.

Acne vulgaris is a multifactorial skin disorder involving sebaceous gland dysfunction, hormonal imbalances, bacterial overgrowth, and inflammation. While various cosmeceutical products target these mechanisms, there remains a strong demand for natural alternatives with multi-target actions. Citrus hystrix, a traditional medicinal plant, exhibits notable anti-inflammatory properties, suggesting its potential for acne treatment. This study assessed the in vitro biological activities of C. hystrix peel extracts and essential oil by examining their effect on Propionibacterium acnes and inflammatory targets. In vitro assays demonstrated that extract polarity significantly affected the observed bioactivities, resulting in distinct activity profiles among the extracts. The hexane extract (34.12% ± 2.56%) and essential oil (43.65% ± 8.44%) exhibited greater 5α-reductase inhibition at 100 mg/mL compared to the ethanolic extract (15.64% ± 1.66%). Conversely, the ethanolic extract more effectively inhibited IL-1β, nitric oxide, and PGE2 production. In addition, P. acnes growth inhibition was observed across all samples. These findings highlight C. hystrix as a promising multi-target anti-acne agent. Further research should explore formulation strategies, skin penetration, and clinical efficacy.