Bactericidal and antioxidant properties of essential oils from the fruits Dennettia tripetala G. Baker

The antibacterial and antioxidant properties of the essential oils (EOs) of unripe and ripe fruits of Dennettia tripetala and their potential for the management of infectious and oxidative-stress diseases were investigated in-vitro in this study.

Essential oil obtained from the fruit in Clevenger modified apparatus, was characterized by high resolution GC-MS, while antioxidant and antibacterial properties were tested by spectrophotometric and agar diffusion methods respectively.

The EO demonstrated strong antibacterial properties when subjected to multi -drug resistant bacterial strains: Enterococcus faecium (ATCC19434), Escherichia coli (ATCC 700728), Staphylococcus aureus (NCINB 50080), Listeria ivanovii (ATCC 19119), Enterobacter cloacae (ATCC13047) and four previously confirmed multi resistant bacterial isolates from our laboratory stock culture. The unripe fruit oil (UFO) demonstrated greater activity than the ripe fruit oil (RFO) against most of the tested bacteria with minimum inhibition concentrations (MIC) ranging between 0.05-0.20 mg/mL while that of the ripe fruit oil (RFO) ranged from 0.10-0.20 mg/mL. The IC₅₀ for RFO (0.62 ± 0.12 mg/mL) showed that it has higher antioxidant strength than UFO and vitamin C (0.87 ± 0.23 and 3.39 ± 0.12 mg/mL) but a lower activity compared to β-carotene (0.32 ± 0.22 mg/mL) in scavenging 2, 2-diphenyl-1-picrylhydrazyl radicals (DPPH^•). The EOs also demonstrated strong ability in scavenging three other different radicals (ABTS, lipid peroxide and nitric oxide radicals) in concentration dependant -manner.

Findings from this study suggest that apart from the local uses of the plant extracts, the EO has strong bioactive compounds, noteworthy antibacterial, antiradical properties and may be good candidates in the search for lead constituents for the synthesis of novel potent antibiotics.