Screening plant products for Ralstonia solanacearum inhibition and characterization of antibacterial compounds in Garcinia indica and Tamarindus indica

Abstract

Bacterial wilt caused by Ralstonia solanacearum is a soil borne disease affecting several plant species of different genera. Management of this disease with various strategies provided limited success. Plant product in the management of bacterial wilt is one of the minimum explored areas. In the present study attempts were made to exploit the antibacterial properties of the locally available plant species for the inhibition of R. solanacearum and also to characterize the phytochemicals in two of the promising plant species by Gas Chromatography–Mass Spectrometry (GC–MS). Thirty-two plants species were screened for their antimicrobial activity against R. solanacearum using eight organic solvents. Out of the 264 tested extracts 123 showed zones of inhibition under in vitro condition. It was observed that alcohol extracts showed better activity against R. solanacearum as compared to other solvents. Two plant species viz. Garcinia indica and Tamarindus indica were highly inhibitory to the pathogen. The phytochemical analysis indicated the presence of saponins, terpenoids, alkaloids, flavonoids and tannins in the extracts. Fractions from solvent–solvent partitioning indicated that alcohol based fraction (Fraction III) was inhibitory to the pathogen. GC–MS analysis of Fraction-III revealed the presence of phytoconstituents viz. 4H-pyran-4-one,2,3-dihydro-3,5-dihydroxy-6-methyl and 2-Furancarboxaldehyde, 5 (hydroxymethyl) in G. indica; butanoic acid, and myo-inositol, 4-C-methyl in T. indica. The present study is the first report on the use of G. indica and T. indica in inhibiting R. solanacearum and the antimicrobial constituents of the extracts.