Phytochemical Investigation of Compounds from Vepris Glandulosa Leaf Extracts and Their Antibacterial Activities

Abstract

Historically mankind has relied on plants for curing various bacterial diseases with great success but with modernization mankind turned to synthetic drugs which had great success initially but overtime began facing challenges such as resistance, toxicity and low drug discovery in recent times. Mankind had no option but to turn to plants for medicine because plants have an abundance of natural products which if exploited could be used for man’s benefit. Plants from the genus Vepris are known to be good sources of medicines curing a variety of bacterial diseases such as syphilis, gonorrhea and brucellosis. Vepris glandulosa is a tree that is endemic to Kenya was collected at Muguga South Forest Reserve. It is known ethno botanically to cure complications such as malaria, pains, fever and brucellosis. There are no known documented phytochemical and antibacterial assays done on Vepris glandulosa and the study helped to bridge that gap. The crude leaf extract of V. glandulosa obtained after soaking in hexane was subjected to phytochemical qualitative analysis which showed presence of saponins, tannins, phenol, flavonoids, alkaloids and terpenoids. The crude extract was subjected to repeated column and thin layer chromatography for isolation and purification. Compound 1 was as a white threadlike crystal isolated at 10 % ethyl acetate, 90 % hexane. Compound 1 was subjected to 1H NMR,

13C NMR, COSY, DEPT, HSQC and HMBC analyses. Spectral data from these spectroscopic techniques showed compound 1 as a Lupane type pentacyclic triterpene characteristics with 6 quaternary, 6 methine, 7 methyl and 11 methylene carbons. There were olefinic carbon resonance of exocyclic double bond that appeared at δc 79.01 ppm for carbon bonded to an OH group, δc 150.95 ppm for the quaternary carbon and δc 109.3 ppm for the methylene carbon which had olefinic of δH 4.57 and δH 4.68. The 13C NMR showed thirty carbon signals and 1H NMR integration values gave 50 proton signals with a molecular formula of C30H50. Compound 1 was confirmed to be Lupeol after literature comparison. Zone of inhibition assay on the crude extract showed moderate sensitivity against Staphylococcus aureus with 13.66 mm while resistance was observed for Klebsiella pneumoniae, Streptococcus pyogenes, Pseudomonas aeruginosa with zone of inhibition values falling below 13 mm. Minimum Inhibitory Concentration values were 6 μg/ml for P. aeruginosa and 4 μg/ml for S. aureus. The Minimum Bactericidal Concentration values were 8 μg/ml for both S. aureus and P. aeruginosa. These values showed that the crude extract has bactericidal activity against both P. aeruginosa and S. aureus. The Minimum Inhibitory Concentration and Minimum Bactericidal Concentration assays are sufficient in concluding that the crude extract is a viable antibacterial agent because clinicians use their results to determine choice of chemotherapy. It is recommended that further phytochemical and antibacterial assays be done on Vepris glandulosa leaf extracts and also stem bark and root extracts.