Comparative study of antimicrobial activity of essential oils of selected plants of Rutaceae and TLC bioautographic studies for detection of bioactive compounds

Abstract

The present study aimed to determine the antimicrobial activity of essential oils extracted from Citrus maxima, Citrus aurantium, Citrus aurantifolia and Limonia acidissima of the Rutaceae and identification of bioactive compounds in oils using thin-layer chromatography (TLC) bioautography and gas chromatography–mass spectrometry (GC–MS) analysis. Antimicrobial screening was done with 10 μL of the oil sample using a disc diffusion method against five Gram-positive and ten Gram-negative bacteria, and a fungal strain, Candida albicans. Among the four oils, C. maxima and C. aurantifolia showed potential antimicrobial properties against the majority of the tested organisms, even when compared with positive controls ciprofloxacin (for bacteria) and ketoconazole (for fungi) antibiotics. In the study, the most sensitive organism to the essential oils was found to be Acinetobacter baumannii and the most resistant organisms were Enterococcus faecalis and Pseudomonas aeruginosa. Bioautography and GC–MS analysis revealed that E-citral, Z-citral, nerol, geraniol, eucalyptol, linalool, eugenol, methyl cinnamate, terpinen-4-ol, α-terpineol, geranyl acetate and myristic acid were the compounds possessing antimicrobial activity present in the oils.

Keywords:

• essential oil
• Rutaceae
• hydro-distillation
• antimicrobial activity
• thin-layer chromatography
• TLC bioautography
• GC–MS analysis

Acknowledgements

We would like to thank Mrs K.V. Vijaya Lakshmi, HOD, Mr B. Yogeswara Rao, Mr V. Sanyasi Rao and V. Mohan Rao Technical Staff, Department of Microbiology, MRPG College, Vizianagaram, for their cooperation in the work, IMTECH, Chandigarh for providing test organisms and Dr S. Vijayalakshmi, Research Scientist, SAIF, IIT Mumbai., for providing the GC–MS facilities.