The Chemical Composition of Volatile Oil and Biological Activity of Rhododendron caucasicum

The aim of this research was to investigate the effect of different extraction methods and chemical composition of the essential oil and solid-phase microextraction (SPME) from Rhododendrum caucasium Pall. The volatiles of R. caucasicum have been isolated by hydro distillation (HD) and SPME. The compositions of the volatiles were characterized by GC-FID/MS. A total of twenty-five and thirty-one compounds were identified constituting over 89.25%, and 90.33% of volatiles obtained with HD and SPME, respectively. The main volatile constituents of R. caucasicum were found to be calarene (46.13% (HD) and 54.91% (SPME)) and sandaracopimaradiene (25.93% (HD) and 8.16% (SPME)). Furthermore, the obtained essential oil (EO) and solvent extracts (n-hexane and methanol) of R. caucasicum were tested against the following nine bacteria: Escherichia coli, Yersinia pseudotuberculosis, Pseudomonas aeruginosa, Enterococcus faecalis, Staphylococcus aureus, Bacillus cereus, Mycobacterium smegmatis, Candida albicans, and Saccharomyces cerevisiae. The EO showed moderate antimicrobial activities with the inhibition zone from 6 to18 mm against E. faecalis, S. aureus, B. cereus and M. smegmatis, respectively. Methanol extract gave better antimicrobial activity against the P. aeruginosa, E. faecalis, S. aureus, and B. cereus with the almost 15 mm inhibition zones.