Leonidah Kerubo Omosa1*, Evans Kenanda Okemwa2
1Department of Chemistry, School of Physical Sciences, University of Nairobi, P. O. Box 30197, 00100, Nairobi, Kenya.
2Department of Chemistry, School of Pure and Applied Sciences, Kisii University, P.O. Box 408-40200 Kisii, Kenya
Introduction: Multidrug resistance remains a major obstacle hindering successful antimalarial chemotherapy. In the current study, 50% methanol in dichloromethane extract and six compounds from the stem bark of Zanthoxylum gilletii were explored for their antiplasmodial potential against three strains of Plasmodium falciparum. Materials and Methods: The extract was obtained by cold percolation using 50 % MeOH in CH2Cl2 and the antiplasmodial activities were assayed using a non–radioactive Malaria SYBR Green I assay to determine a concentration that inhibits growth of 50% of parasites in culture (IC50). Results and Discussion: Chromatographic separation of the crude extract yielded six known compounds including: one lignan, sesamin (1), an alkamide, fagaramide (2), three benzo [c] phenanthridine alkaloids, 8–acetonyldihydrochelerythrine (3), dihydrochelerythine (4), norchelerythrine (5) and one pentacyclic triterpenoid, lupeol (6). The extract and sesamin (1) showed promising antiplasmodial activities against the chloroquine resistant (W2), chloroquine sensitive (D6) and 3D7 strains of P. falciparum, with IC50 values of 2.52, 1.48 and 1.43 μg/mL and 5.4, 9.1 and 8.3 μM, respectively. To the best of our knowledge, this is the first report on antiplasmodial activities of the stem bark extract (50% MeOH in CH2Cl2) and compound 1–3 and 6. Furthermore, three of the isolated compounds; 1, 3, 6 are reported from this species for the first time.
Conclusion: The good antiplasmodial activities exhibited by the stem bark of Z. gilletii against three different strains of P. falciparum may be attributed to the presence of 1-3 exhibiting good activities against all strains of P. falciparum.
Key words: 8–Acetonyldihydrochelerythrine, Sesamin, Antimalarial potencies, Zanthoxylum gilletii.