Abstract
Plectranthus ecklonii Benth. is traditionally used in South Africa for treating stomach aches, nausea, vomiting and meningitis. Bioassay-guided fractionation of the ethyl acetate extract of the plant led to the isolation of two known compounds, parvifloron D and parvifloron F, neither of which has been previously reported for this species. The compounds exhibited minimum inhibitory concentrations of 15.6 and 31.2 μg/mL, respectively against Listeria monocytogenes, whereas the values against a drug-sensitive strain of Mycobacterium tuberculosis were 190 and 95 μg/mL, respectively. The ethyl acetate extract of P. ecklonii and its isolated compounds were tested for their activity on tyrosinase inhibition. The concentration at which half the tyrosinase activity was inhibited (IC50) by the extract was found to be 61.7 ± 2.7 μg/mL. The antibacterial activity of the extract and its isolated compounds correlates with the traditional use of the plant for various ailments such as stomach aches, diarrhea and skin diseases. The fifty percent inhibitory concentrations of parvifloron D and parvifloron F against vero cell lines were found to be 2.9 μg/mL and 1.6 μg/mL, respectively. This is the first report of the bioactivity of P. ecklonii extract and its constituents.