Wright, Colin W.Kirby, G.CPhillipson, J.DWarhurst, D.C.Lang'at-Thoruwa, C.Watt, R.A.2009-10-062009-10-062003Wright, C., kirby, G.C., Phillipson, J.D. and Warhurst, D.C. et al. (2003). Enhancement of the antiplasmodial activity of quassin by transformation into a gamma-lactone. Journal of Natural Products. Vol. 66, No. 11, pp. 1486-1489.http://hdl.handle.net/10454/3616NoThe 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).enBitter principle quassinGamma-lactone quassilactoneIn vitro antiplasmodialQuassinArticlehttps://doi.org/10.1021/np030107a