Ethnopharmacological Validation of Selected Coleus and Plectranthus spp. For Skin-Related Applications Through In Vitro Biological Assays

Coleus Lour. and Plectranthus L’Hér. (Lamiaceae) species are recognized as promising sources of bioactive compounds for skin health, supported by their traditional use in skin-related conditions; however, scientific validation of these traditional uses remains limited for several species. In this work, the biological activities of eight Coleus and Plectranthus species (C. barbatus, C. cylindraceus, C. grandidentatus, C. hadiensis, C. madagascariensis, P. ambiguus, P. ecklonii, and P. fruticosus) were evaluated to support their ethnomedicinal relevance. Extracts were assessed for general toxicity (Artemia salina model), antimicrobial activity (well diffusion and microdilution methods) and antioxidant capacity (DPPH, TBARS and cellular assays). In addition, anti-inflammatory activity (ability to suppress nitric oxide), cytotoxicity in skin cell lines (HaCaT and HFF-1) and inhibition of skin-related enzymes (elastase, tyrosinase and collagenase) were evaluated. Antibacterial activity was predominantly observed against Gram-positive bacteria, with no general toxicity observed. P. ambiguous and P. ecklonii showed moderate-to-high antioxidant activity, while anti-inflammatory effects were observed for C. hadiensis and C. madagascariensis and P. ambiguous. None of the extracts showed cytotoxicity. Enzyme inhibition assays highlighted C. cylindraceus and P. ecklonii. HPLC-DAD analysis confirmed the presence of rosmarinic acid. Overall, the findings support the traditional use of Coleus and Plectranthus species for skin-related conditions and highlight their potential as sources of bioactive compounds for dermatological and cosmeceutical applications.