GC-MS Analysis and Antibacterial Effects of Vernonia glaberrima n-Hexane Extracts alone and in Combination with Standard Antibiotics

Abstract

The occurrence of drug resistant bacteria warrant investigation on herbal plants for effective antibacterial agents. Vernonia glaberrima leaf (VGL) and stem (VGS) hexane extracts were subjected to analysis by gas chromatography-mass spectrometry (GC-MS) and subsequently evaluated for antibacterial activity alone and in combination each with Sparfloxacin (SPX) and Ciprofloxacin (CPX) on selected bacteria including resistant species. GC-MS analysis revealed fatty acid esters, triterpenoids and aromatic derivatives largely identified as responsible for the broad-spectrum antibacterial activity. Both the VGL and VGS demonstrated potent antibacterial activities on P. aeruginosa (29 mm and 27 mm), respectively. However, combination of SPX with VGL potentiated the effects on E. coli and S. typhi by synergistic interaction. Similarly, the efficacy of CFX in combination with VGS on MRSA (30 mm) was significantly enhanced by additive action. It was observed that VGS potentiation of CFX on P. aeruginosa (32 mm) was the most effective antibacterial inhibition recorded in the study. Thus, combination of SPX and CFX each with the extracts has revealed remarkable properties for alternative or complementary therapeutic strategy. Our findings elicit enormous potentials of V. glaberrima hexane extracts as treatment adjuncts for combating drug resistant bacteria. It will be interesting to evaluate in vivo effects of extracts in combination with antibiotics against drug resistant bacteria.