Antifungal Compounds of Tribulus terrestris Root for the Control of Pyricularia oryzae, the Cause of Rice Blast Disease

Pyricularia oryzae is a fungal pathogen that causes blast disease in rice. In the present study, methanolic root extract of a medicinal herb Tribulus terrestris was assessed for its antifungal activity against this fungal pathogen. Roots of T. terretris were collected from Lahore, Pakistan and shade dried. The dried and crushed roots were extracted in methanol for two weeks and the effect of 1, 2, 3, 4 and 5% concentrations of the extract was checked in vitro against P. oryzae using malt extract broth as a growth medium. All the applied concentrations of the extract exhibited significant antifungal activity and declined P. oryzae biomass by 45-56% over control. The extract was analyzed by GC-MS to identify the possible antifungal constituents. Sixteen compounds were detected in the root extract in GC-MS analysis. Among these, three compounds namely neotigogenin (29.30%), hexadecanoic acid, methyl ester (19.70%) and cis-13-octadecenoic acid, methyl ester (18.10%) were found the highly abundant ones. Likewise, three compounds namely methyl stearate (6.65%), stigmasterol (6.05%) and 9,12-octadecadienoic acid (Z,Z)-, methyl ester (7.11%) were categorized as moderately abundant ones. Different fatty acid methyl esters together with stigmasterol identified in the root extract have shown antifungal activity in various previous studies and might be responsible for antifungal activity against P. oryzae in the present study.