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In vitro activity of (-)-deoxypergularinine, on its own and in combination with anti-tubercular drugs, against resistant strains of Mycobacterium tuberculosis

Nam, Kung-Woo, Jang, Woong Sik, Jyoti, Md. Anirban, Kim, Sukyung, Lee, Byung-Eui, Song, Ho-Yeon
Phytomedicine 2016 v.23 no.5 pp. 578-582
Mycobacterium tuberculosis, Vincetoxicum atratum, active ingredients, alkaloids, drugs, isoniazid, minimum inhibitory concentration, multiple drug resistance, new products, plant extracts, rifampicin, roots, screening, synergism, tuberculosis
The increasing incidence of multidrug-resistant tuberculosis (MDR-TB) infections has created a need for new effective drugs that also target extensively drug-resistant tuberculosis (XDR-TB) and/or augment the activities of existing drugs against tuberculosis.This study searched natural products for a new lead compound that targets MDR/XDR-TB.An active compound was purified from the roots of Cynanchum atratum Bunge (Asclepiadaceae) after screening 1640 plant extracts, and its inhibitory effects against MDR/XDR strains and synergistic effects with existing anti-TB drugs were assessed using the resazurin, MGIT, and checkboard assays.(-)-Deoxypergularinine, purified from the roots of C. atratum, inhibited not only M. tuberculosis but also MDR/XDR strains. The minimum inhibitory concentrations (MICs) of (-)-deoxypergularinine for H37Ra, H37Rv, MDR, and XDR strains were all about 12.5µg/ml. Moreover, combinations of (-)-deoxypergularinine with the first-line standard drugs rifampicin or isoniazid afforded six- and eight-fold reductions in drug MIC values, respectively, against strain H37Ra.(-)-Deoxypergularinine exerts anti-tubercular activities not only against normal tuberculosis strains but also MDR/XDR strains, and synergic effects with rifampicin and isoniazid for the H37Ra strain. The alkaloid may be valuable for targeting M/XDR M. tuberculosis.