In vitro antiplasmodial and cyclin- dependent protein kinase (pfmrk) inhibitory activities of selected flavonoids in combination with chloroquine (CQ) and artemisinin

H. M. Akala¹, C. N. Waters¹, A. Yenesew², C. Wanjala³ and T. Ayuko Akenga⁴*

¹Kenya Medical Research Institute, Walter-Reed Laboratories, P. O. Box 54840 - 00100 G. P. O. Box, Nairobi, Kenya.

²Department of Chemistry, University of Nairobi, P. O. Box 30197 - 00100 G. P. O. Nairobi, Kenya.

³Department of Physical Sciences South Eastern University College (SEUCO) P.O.Box 170-90200, Kitui, Kenya.

⁴Office of the Deputy Principal (Academic Affairs), Bondo University College

(BUC), P. O. Box 210-40601, Bondo, Kenya.

*Corresponding author. E-mail: tezakenga@yahoo.co.uk,

takenga@bondo-uni.ac.ke.

Accepted 2 February, 2010

    Abstract

In this study, we report in vitro chloroquine (CQ) and artemisinin combination studies of eight flavonoids against Plasmodium falciparum strains. The flavonoids were previously isolated from Erythrina sp. (Family Leguminosae) growing in Kenya. Synergism was observed for chloroquine/ Sigmoidin E (5) combination at ratios of 5:1 and 3:1 respectively, while other chloroquine/flavonoids combinations showed variable response; either additive or even antagonistic effects. The artemisinin/abyssynone IV (1) combination also showed synergistic interaction at a ratio of 5:1. Further investigations revealed that Abyssinone IV (1) and Abyssinone V (2) were effective inhibitors of plasmodial growth and differentiation regulatory enzyme, pfmrk.

Key words: Combination studies, CQ, artemisinin, flavonoids, sigmoid E, synergism, antagonism, pfmrk.