Chemical constituents, antimicrobial and antioxidant activities of the essential oil of leaves of Dombeya buettneri K. Schum. (Sterculiaceae)

Abstract

The essential oil of the leaves of Dombeya buettneri was investigated for chemical composition, antioxidant and antimicrobial activities. The oil was separated by Gas Chromatography (GC) and analysed by Gas Chromatography/Mass Spectrometry (GC-MS) methods. Antimicrobial activity was evaluated by broth dilution method to determine the minimum inhibitory concentration (MIC) on Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922 and Candida albicans ATCC 18804 while antioxidant activity was determined by three methods (DPPH, FRAP and ABTS).

The GC-MS detected a total of 23 compounds (93.9% identification) which were dominated by Apocarotenes (64.9%) and Non-terpene derivatives (20.2%), the main compounds identified being hexahydrofarnesylacetone (32.5%), dihydroedulan IIA (9.6%), (E) –geranylacetone (7.8%), β-selinene (5.4%) and 2-pentyl furan (4.6%). The oil showed a good antimicrobial activity with respective MIC and MBC of 6.25 and 12.50%v/v on Staph. aureus, 12.5 and 25.0 %v/v on E. coli; MIC and MFC on Candida albicans were 12.5 and 25.0%v/v respectively. The free radical antioxidant activity (DPPH expressed as % inhibition) at 25, 50 and 100 mg/mL were 8.0993±0.827, 14.7657±0.8151 and 19.449±0.6678 respectively. The antioxidant potential (FRAP) was 0.076713±0.012275 mg/FeSO4.eq/g. The result of 2, 2-azobis-3-ethylbenzothiazoline-6-sulfonate radical scavenging ability (ABTS) showed the oil to possess free radical scavenging ability of 0.37759±0.0025 mg/AA Equiv./g.

The leaves of Dombeya buetnneri possess essential oils that are rich in phytochemicals with good antimicrobial and antioxidant activities; which can be of significant application in food, drug and cosmetic industries.