Background: Due to side-effects and lost efficacy of common drugs on new resistance strains of Mycobacterium tuberculosis (Mtb), investigation on novel drugs and natural compounds from rich source of endemic plants is required. Thus, in the present study, the anti-mycobacterial effect of 22 Iranian endemic or rare plant extracts on multi-drug resistance (MDR) and extensively-drug resistance (XDR) Mtb isolates was evaluated.
Methods: 22 Iranian endemic and rare plant species from 9 families were collected and extracted by methanol. Their inhibitory-effects were then evaluated against Mtb H37Rv strain, seven clinical MDR-TB and two XDR-TB isolates using resazurin microtiter assay (REMA) method. Best of them were then fractionalized by five different polar solvents (Petroleum-Ether, Dichloromethane, Ethyl-Acetate, n-butanol and water). To find anti-mycobacterial fractions, inhibitory effect of isolated fractions were tested on Mtb H37Rv.
Results: Out of the 22 plants, 14 plant extracts demonstrated anti-mycobacterial activity with minimum inhibitory concentration (MIC) ranging from 4 to 30µg/mL against Mtb H37Rv. Eight plant extracts also exhibited anti-mycobacterial activity against MDR and XDR clinical strains of Mtb by MICs, 15-60μg/ml. Crinitaria grimmii and Linum album were the best anti-mycobacterial plants. Among fractions of Crinitaria grimmii, dichloromethane and n-butanol and for Linum album, dichloromethane and Ethyl-Acetate fractions displayed more anti-mycobacterial effect comparing to crude extract on Mtb.
Conclusion: The present study confirms the potential role of some plants to treat respiratory diseases as our results have demonstrated that these plants exhibit anti-mycobacterial activity in the acceptable range against Mtb. Thus, these plants could be good sources and alternatives of plant metabolites for anti-TB-drug development.