Antibacterial activity of Melastoma candidum D. Don

Melastoma candidum D. Don is a plant of the Melastomataceae family that has been used as folk medicine in Taiwan. In this study, the antibacterial activity of M. candidum extracts was investigated. Water, acetone, ethanol (95 ml/100 ml), and ethyl acetate extracts of M. candidum exhibited antibacterial activity, especially the acetone and ethanol (95 ml/100 ml) extracts. Over one-third of MICs for those two extracts were close to or equal to that of amoxicillin. MICs and minimum bactericidal concentrations (MBCs) for the acetone extract were 0.02–0.64 mg/ml and 0.08–2.56 mg/ml, respectively; while for the ethanol (95 ml/100 ml) extract, corresponding values were 0.04–1.28 mg/ml and 0.16–5.12 mg/ml, respectively. The acetone M. candidum extract exhibited good thermal stability subsequent to heating from 70 to 121 °C for 15–60 min; further, no dramatic changes in the MICs in a range of pH 5–8 were noted. Overall, M. candidum acetone extract revealed a good bactericidal effect, good thermal stability (heating at 121 °C for 15 min), and broad antibacterial activity in the pH range of 5–8.