Anti-Mycobacterial Activity of Flavonoid and Pyrimidine Compounds.

We evaluated the anti-mycobacterial effect of a flavonoid 5,7-dihydroxy-2-(4-hydroxyphenyl) 4-chromen-4-one () and two pyrimidines, 4-hydroxy-2-dimethylamino-5-nitroso-6-aminopyrimidine () and 2-chloro-5--nonylpyrimidine () in vitro against (, H37Ra) and , using a Microplate Alamar Blue Assay (MABA). The effects of the compounds - in combination with first- and second-line anti-TB drugs isoniazid, rifampicin, cycloserine, and clarithromycin on the growth of and were also evaluated in in vitro assays. As a single agent, compounds and exhibited modest activity while compound was the most effective against and . When compounds - were evaluated at lower than 50% of their inhibitory concentrations in a two-drug combination with isoniazid or rifampicin, they showed additive to synergistic interactions. This inhibitory effect was improved when each of the three compounds was tested together in a three-drug combination with two of the first-line anti-TB drugs. Compounds - also demonstrated strong synergistic interaction in combination with cycloserine and clarithromycin in inhibiting the growth of and , respectively. This study demonstrated that compounds - have potential to be developed as effective anti-TB agents with combined use.