Altholactone exhibited the anti-fungal activity with a high MIC value of 128 μg ml(-1) against Cryptococcus neoformans and Saccharomyces cerevisiae. Fifteen ester derivatives of altholactone 1-15 were modified by esterification and their structures were confirmed by spectroscopic methods. Most of the ester derivatives exhibited stronger anti-fungal activities than that of the precursor altholactone. 3-Bromo- and 2,4-dichlorobenzoates (7 and 15) exhibited the lowest minimal inhibitory concentration (MIC) values against C. neoformans at 16 μg ml(-1), while the 4-bromo-, 4-iodo-, and 1-bromo-3-chlorobenzoates (11-13) displayed potent activity against S. cerevisiae with MIC values of 1 μg ml(-1). In conclusion, this analysis indicates that the anti-fungal activity of altholactone is enhanced by addition of halogenated benzoyl group to the 3-OH group.
Keywords: Altholactone; Polyalthia crassa; anti-fungal activity; ester derivative; halogenated benzoate.