Anti-bacterial properties and GC-MS analysis of extracts and essential oils of selected plant product

Abstract

Nyaitondi OD, Wanjau R, Nyambaka H, Hassanali A. 2018. Anti-bacterial properties and GC-MS analysis of extracts and essential oils of selected plant product. Biofarmasi J Nat Prod Biochem 16: 44-58. Plants are traditionally used for the treatment of bacterial infections though they are not clinically regulated due to lack of awareness and sufficient data to support the reported therapeutic claims. Some plants used as food and vegetables are hardly considered in such studies. This study aimed to investigate the antibacterial properties associated with garlic, ginger, turmeric, lemon, and onion in the form of juices, methanol extracts, and essential oils. These materials were tested against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Salmonella typhi. Identification of suspected antibacterial compounds was made by comparison of retention indices and the mass spectra with those in National Institute of Standards and Technology (NIST) libraries using GC-MS analyses. Garlic juice was bactericidal against all tested strains. Lemon/garlic juice exhibited significantly higher activity against E. coli and S. typhi. Turmeric/lemon/garlic methanol extracts blend was most active against S. aureus. Preliminary screening of the essential oils indicated significant antibacterial activity of lemon/garlic essential oil blend against P. aeruginosa. GC-MS analysis of the active samples confirmed the presence of compounds containing-OOH,-OH,-N,-Cl,-F,-NH2 and-S groups which are associated with bacterial inhibition in conventional antibiotics. The 10 major constituents obtained from samples suspected to contain antibacterial activity, include limonene; 3-vinyl-1,2-dithiacyclohex-4- ene; α-zingiberene; diallyl disulphide; 2-butanone,4-(-hydroxy-3-methoxyphenyl); 3-chlorothiophene; methanehydrazonic acid,N-[3- (methylthio)-1,-2,4-thiadiazol-5-yl]-,ethyl ester; n-hexadecanoic acid; γ-sitosterol and propanamide,2-amino-3-phenyl. Juices of garlic, lemon and lemon/garlic blend were found to be active against one or more of the bacteria tested unlike methanol extracts and essential oils, and they should be used in raw form as heating and drying is likely to render them inactive. Further studies on methanol extract and fresh juice of lemon/garlic blend need to be undertaken to elucidate the active principles in these extracts and may lead to the discovery of novel antimicrobial agents and models for the new generation of synthetic antibiotics.