Bioassay-guided isolation of antibacterial compounds from mesua grandis (king) kosterm

Abstract

Medicinal plants have been used across the world and since the beginning of civilizations, yet, 80% of the community in the developing countries still depends on traditional medicine as a main source of medication. Plant species in the genus Mesua of Clusiaceae family are well known for their uses in traditional medicine. Mesua grandis can be found in Terengganu, Perak and Pahang states and locally known as Penaga layan. This project investigated the antimicrobial properties of M. grandis using disc diffusion and broth microdilution methods. Column chromatography techniques were then used to isolate the active compounds using bioassay-guided isolation approach. The n-hexane, dicloromethane and methanol crude extracts of M. grandis were tested against Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, Escherichia coli, Candida albicans and Cryptococcus neoformans. All three crude extracts were able to inhibit the growth of S. aureus, B. cereus and E. coli at a concentration of 1 mg/disc, while none were active against P. aeruginosa, C. albicans as well as C. neoformans at tested concentration of 1 mg/disc and 2 mg/disc. The n-hexane crude extract (S. aureus, 10.5 ± 0.4 mm; B. cereus, 9.2 ± 0.2 mm; E. coli, 15.2 ± 0.2) was applied through column chromatography and several compounds including one active compound were obtained. The compound was identified as 2,2-dimethyl-6-(2-methylbutanoyl)-10-phenylpyrano[2,3-f]chromen-8(2H)-one and was found to be a bacteriostatic agent. The molecular formula of the compound was C25H24O5 (Mw = 404.45 Da) and was active against S. aureus, B. cereus and E. coli at the MIC value of 12.3 ?g/mL, 333.3 ?g/mL and 333.3 ?g/mL, respectively. In conclusion, M. grandis was found to be promising source of antibacterial agents.