Enhancement of the antiplasmodial activity of quassin by transformation into a gamma-lactone.
Lang'at-Thoruwa, Caroline;
Kirby, Geoffrey C;
Phillipson, J David;
Warhurst, David C;
Watt, Robert A;
Wright, Colin W;
(2003)
Enhancement of the antiplasmodial activity of quassin by transformation into a gamma-lactone.
Journal of natural products, 66 (11).
pp. 1486-1489.
ISSN 0163-3864
DOI: https://doi.org/10.1021/np030107a
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The naturally occurring bitter principle quassin (1) was converted chemically into the gamma-lactone quassilactone (13) in an attempt to enhance its antiplasmodial activity. The in vitro antiplasmodial activity of 13 against Plasmodium falciparum (K1) (IC(50) = 23 microM) was 40-fold greater than that of 1. However, one of the intermediates, compound 8, the 15beta-hydroxy,16-O-m-chlorobenzoyl analogue of 1, was 506-fold more active than 1 against P. falciparum (IC(50) = 1.8 microM) and only 3-fold less potent than chloroquine. In addition, 8 displayed the best cytotoxic/antiplasmodial ratio (112) of all of the compounds tested. In the course of this work a dimer, neoquassin ether (6), linked at C-16 was also prepared; 6 was found to have weak antiplasmodial activity (IC(50) = 9.7 microM).
