LAUSR

Abstract In South Africa, traditional medicine remains a key source of health care, however majority of the plants used as medicines by traditional health care practitioners have not been investigated for their in vitro biological activity. The purpose of the present study was to examine the antityrosinase, anti-acne, antioxidant and cytotoxic potential of 25 ethanolic extracts from 16 different plant families which were collected in the Jongilanga community in the Mpumalanga province. The tyrosinase inhibitory activity was evaluated using the mushroom tyrosinase enzyme to determine potential plant extracts that could treat skin hyperpigmentation. Six of the plant extracts showed a fifty percent inhibitory concentration (IC50) lower than 200 μg/mL, of which Acacia nilotica (L.) Delile (12.97 ± 1.07 μg/mL) showed the highest activity, followed by Schotia brachypetala Sond. (35.07 ± 0.71 μg/mL) and Combretum collinum Fresen. (47.92 ± 1.13 μg/mL). The anti-acne potential of the extracts was evaluated by determining their antibacterial activity against Cutibacterium acnes. The highest activity was noted for Harpagophytum procumbens (Burch.) with a minimum inhibitory concentration (MIC) of 31.25 μg/mL, followed by S. brachypetala (125 μg/mL) and C. collinum, Ozoroa sphaerocarpa R. Fern & A. Fern and Pterocarpus rotundifolius DC. which all showed MIC values of 250 μg/mL. The antioxidant studies revealed that the majority of the plant extracts showed strong DPPH radical scavenging activity. The 2,3-Bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxyanilide salt (XTT) method was used to assess the cytotoxic effect of the plant extracts, of which only two extracts showed strong cytotoxicity against the non-cancerous human keratinocyte (HaCat) cell line namely; H. procumbens and Ipomoea oblongata Hook. The remaining extracts showed low to moderate cytotoxicity. The promising antityrosinase activity of A. nilotica, S. brachypetala and C. collinum as well as the promising antibacterial activity of O. spaerocarpa, P. rotundifolius and S. brachypetala, together with their low to moderate cytotoxicity against HaCat cells, merits further investigation of these species.