Conglomeratin: a new antibacterial flavonol derivative from Macaranga conglomerata Brenan (Euphorbiaceae).

ABSTRACT

A new prenylated kaempferol, conglomeratin (1), alongside 7 known compounds including flavonoids (2 and 3), ellagic acid derivatives (4 and 5), triterpenoids (6 and 7), and a coumarin (8) were isolated from the leaves (1 - 5) and stem bark (6 - 8) of Macaranga conglomerata. Their structures were elucidated using spectroscopic and spectrometric techniques. The antibacterial assay was performed using disc diffusion method against Gram-positive and Gram-negative microorganisms. Compound 1 was significantly active against Pseudomonas aeruginosa ATCC 27853 (MIC = 7.8 µg/mL) and moderately active towards Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922 and Klebsiella pneumoniae ATCC 31488 (MIC = 62.5 µg/mL). Compound 2 showed potency against P. aeruginosa ATCC 27853 (MIC = 1.0 µg/mL) while 4 and 7 were selective towards K. pneumoniae ATCC 31488 (MIC = 7.8 and 1.0 µg/mL, respectively). These findings suggest that prenylation of flavonoids may contribute to improving their broad-spectrum antimicrobial activities.