Comparative Study for the Volatile Oil Constituents and Antimicrobial Activity of Rhanterium epapposum Oliv. Growing in Qassim, Saudi Arabia

Background: Rhanterium epapposum is an herbaceous plant widely distributed in the Gulf region and used by Bedouins as antiseptic for wounds, skin infections and in gastrointestinal disturbances. Aim: The study aimed to compare the results obtained from volatile oil analysis of R. epapposum growing in Buraydah, Qassim with reported data of the same plant growing in Riyadh “Al-Majmaah” and Northern border region of Saudi Arabia. Both cold and hot extracts of the R. epapposum were used to find the best extraction method to be adopted as an antimicrobial agent. Methods: Volatile oils were distillated using Clevenger apparatus and analyzed by GC-MS. The plant powder was extracted by cold maceration and hot contentious extraction methods. Furthermore, antimicrobial activity was conducted using the agar diffusion method. Results: The hydro-distillation of R. epapposum growing in Qassim region yielded 0.5 % w/w of the total volatile oils. Moreover, forty-three compounds of 97.68% of the volatile oil components were identified while modephene, caryophyllene, linalyl acetate and epizonarene were the major components of volatile oils. Nevertheless, the volatile oils diversity and concentrations were found to be different in R. epapposum growing in Buraydah, as compared with the plant growing in Riyadh and the northern border region of Saudi Arabia which almost due to the differences in the environmental condition. Among all extracts, ethyl acetate hot extract showed the best inhibition to bacterial strains while fugal strain Candida albicans growth was better inhibited by hot n-hexane extract. Conclusion: Volatile oils were active against all microbial strains. Hot extracts were more active against bacterial strains while the opposite effects were found against Candida albicans which was generally inhibited by the cold extracts.