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 (125) and stembark (628) 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 ¼ 7.8 mg/mL) and moderately active towards Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922 and Klebsiella pneumoniae ATCC 31488 (MIC ¼ 62.5 mg/mL). Compound 2 showed potency against P. aeruginosa ATCC 27853 (MIC ¼ 1.0 mg/mL) while 4 and 7 were selective towards K. pneumoniae ATCC 31488 (MIC ¼ 7.8 and 1.0 mg/mL, respectively). These findings suggest that prenylation of flavonoids may contribute to improving their broad-spectrum antimicrobial activities.