Potential antimicrobial compounds in flower extract of Plumeria alba

Abstract

This study was carried out to investigate the antimicrobial activity of methanolic flower extract of Plumeria alba and identification of the possible antimicrobial compounds through GC–MS analysis. Antimicrobial efficacy of the methanolic extract of 5 ppm to 1000 ppm concentrations was assessed against five fungal (Trichoderma viride, T. reesei, T. harzianum, T. hamatum and T. koningii) and five bacterial species (Escherichia coli, Salmonella sp., Pseudomonas sp., Bacillus sp. and Staphylococcus sp.). In general, all the concentrations of the extract significantly reduced growth of all the fungal and bacterial species. However, there was a significant variation in susceptibility of different fungal and bacterial species to the applied concentrations of the extract. The extract was the most effective against T. reesii followed by T. viride, T. harzianum, T. hamatum and T. koningii causing 11–97%, 36–90%, 24–86%, 7–77% and 9–76% reduction in their growth. Similarly, there was 23–93%, 12–92%, 36–90%, 19–90% and 8–84% reduction in growth of Bacillus sp., Staphylococcus sp., E. coli, Pseudomonas sp., and Salmonella sp., respectively, due to different concentrations of methanolic extract. GC–MS analysis of the extract showed the presence of 21 constituents. The most abundant compound was benzofuran, 2,3-dihydro- (27.95%). Other important compounds included cyclononanone (14.59%), 9-octadecyne (14.29%), 9,12,15-octadecatrienoic acid, methyl ester, (Z,Z,Z)- (10.28%), benzyl alcohol (5.57%), 1-decanol, 2-hexyl- (5.44%), 2,6-octadien-1-ol, 3,7-dimethyl-, acetate, (Z)- (3.76%), 4H-pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl- (2.48%) and heptadecane (2.43%). It is concluded that methanolic extract of P. alba flowers has the potential to control both fungal as well as bacterial growth.