Chemical Composition, Synergistic Antimicrobial and Antioxidant Potential of Hibiscus rosa-sinensis L. Leaves Essential Oil and Its Major Compound

This study aimed to investigate the chemical composition, antioxidant and synergistic antimicrobial potential of Hibiscus rosa-sinensis L. (China rose) leaves essential oil and its major compound, Dioctyl phthalate (DOP). The essential oil was extracted from leaves by hydro-distillation using the Clevenger apparatus. The essential oil was characterized by Gas Chromatography-Mass Spectrometry (GC/MS) analysis which revealed the presence of DOP as a major compound. The essential oil and DOP were tested for antibacterial activity against Klebsiella sp. and Pseudomonas aeruginosa using the disc plate method, antifungal activity against Fusarium oxysporum by agar well diffusion method, and antioxidant activity by 2,2-diphenyl-1-picrylhydrazyl (DPPH), nitric oxide (NO) and 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) free radical scavenging assays. The synergistic antimicrobial interaction of essential oil and DOP was also tested against standard antimicrobials: tetracycline, chloramphenicol, fluconazole, and clotrimazole. The maximum antimicrobial potential was exhibited by China rose leaves essential oil with minimum inhibitory concentrations (MIC) of 18.5, 11.5, and 23.0 mu g/mL against Klebsiella sp., P. aeruginosa, and F. oxysporum respectively. Moreover, the essential oil exhibited synergistic interaction with standard antimicrobials with a 3.75 to 10 times decrease in their MIC values. The essential oil also exhibited median inhibitory concentration (IC50) values of 780, 800, and 860 mu g/mL in DPPH, NO, and ABTS free radical scavenging assays respectively. Hence it can be concluded that China rose leaves essential oil has a huge significance in pharmaceutical industries as an alternative to synthetic antioxidants and antimicrobials in near future.