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BioMed Research International
Volume 2014, Article ID 835013, 10 pages
http://dx.doi.org/10.1155/2014/835013
Research Article

In Vitro Antiplasmodial Activities and Synergistic Combinations of Differential Solvent Extracts of the Polyherbal Product, Nefang

1Centre for Research on Medicinal Plants and Traditional Medicine, Institute of Medical Research and Medicinal Plants Studies (IMPM), P.O. Box 6163, Yaoundé, Cameroon
2Department of Pharmacology and Pharmacognosy, University of Nairobi, P.O. Box 19676-00202, Nairobi 0800, Kenya
3Early Drug Discovery Program, Institut Pasteur Korea, Republic of Korea
4Centre for Neglected Diseases Drug Discover, Institut Pasteur Korea, Republic of Korea

Received 12 February 2014; Accepted 4 April 2014; Published 27 April 2014

Academic Editor: Paulo A. Nogueira

Copyright © 2014 Protus Arrey Tarkang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Nefang, a polyherbal product composed of Mangifera indica (bark and leaf), Psidium guajava, Carica papaya, Cymbopogon citratus, Citrus sinensis, and Ocimum gratissimum (leaves), is a potential therapy against P. falciparum malaria. In vitro antiplasmodial activities of its constituent solvent extracts were analyzed on CQ-sensitive (3D7) and multidrug resistant (Dd2) P. falciparum strains. The interactions involving the differential solvent extracts were further analyzed using a variable potency ratio drug combination approach. Effective concentration 50 (EC50) values were determined by nonlinear regression curve-fitting of the dose-response data and used in calculating the fractional inhibitory concentration 50 (FIC50) and combination indices (CI) for each pair. The derived EC50 values (3D7/Dd2, μg/mL) are Nefang-96.96/55.08, MiB-65.33/34.58, MiL-82.56/40.04, Pg-47.02/25.79, Cp-1188/317.5, Cc-723.3/141, Cs-184.4/105.1, and Og-778.5/118.9. Synergism was obtained with MiB/Pg (CI = 0.351), MiL/Pg (0.358), MiB/Cs (0.366), MiL/Cs (0.482), Pg/Cs (0.483), and Cs/Og (0.414) when analyzed at equipotency ratios. Cytotoxicity testing of Nefang and the solvent extracts on two human cell lines (Hep G2 and U2OS) revealed no significant toxicity relative to their antiplasmodial activities (SI > 20). Taken together, our data confirm the antimalarial activities of Nefang and its constituent plant extracts and identified extract pairs with promising synergistic interactions for exploitation towards a rational phytotherapeutic and evidence-based antimalarial drug discovery.