The antimicrobial activity of 3,5,7-trihydroxyflavone isolated from the shoots of Helichrysum aureonitens

Extracts from Helichrysum aureonitens are used topically by the indigenous people of South Africa against infections. The antimicrobial activity-guided fractionation by bioautography of the acetone extract from the aerial parts of H. aureonitens led to the isolation of 3,5,7-trihydroxyflavone (galangin). Evaluation of the antibacterial activity of the compound against ten randomly selected bacteria indicated significant activity against all the Gram-positive bacteria tested with the minimum inhibitory concentration (MIC) ranging from 0.1 to 0.5 mg/ml. The compound was not active on Gram-negative bacteria except for Enterobacter cloacae which was significantly inhibited at an MIC of 0.1 mg/ml. Galangin indicated considerable activity against the fungi tested with the exception of Cladosporium herbarum. Penicillium digitatum and P. italicum appeared to be particularly susceptible at a concentration of 0.01 mg/ml.