PHYSICOCHEMICAL PROPERTIES AND BIOLOGICAL ACTIVITIES OF OIL EXTRACTS FROM SEEDS AND LEAVES OF GARDEN CRESS (Lepidium sativum L.)

Garden cress is a fast growing annual herb that is native to Ethiopia. Its seeds are rich source of proteins, dietary fiber, omega-3 fatty acids, iron, other essential nutrients and phytochemicals. The aim of the present study was to investigate the physicochemical properties and biological activities of the oils from garden cress seeds and leaves using solvent extraction methods. The oil extraction was done in Soxhelt apparatus using petroleum ether as a solvent. The physicochemical properties of the oil extracts were done based on determination of oil content, specific gravity, acid value; percent free fatty acid and peroxide values. The antioxidant activity was investigated based on determination of ascorbic acid, DPPH and hydrogen peroxide free radical scavenging activities. The antimicrobial experiment was arranged as 2x1x4x3 factorial design in three replications. A complete randomized design was used to determine the antimicrobial activities using disc diffusion and broth dilution method. The least concentration of extract that show antimicrobial activity was selected for further determining the MIC, MBC and MFC. The results indicated that significant differences were observed between seed and leaf oils in all measured parameters. It was found that oil yield and specific gravity were significantly higher for seed oil extract than leaf oil extract. The acid value, free fatty acid value and peroxide value were significantly higher for leaf oil extract. The mean zone of inhibition at highest concentration (3μl/ml) against bacterial test pathogens ranged from 15.53±0.45 mm to 18.50±0.45 mm, while it ranged from 12.57±0.55 to 18.50±0.50 mm against fungal test pathogens. The leaf oil extract has exhibited the strongest bactericidal activity with MIC of 0.05μl/ml and MBC of 0.05 μl/ml against S. aureus. Garden Cress leaf oil extract has demonstrated strongest antifungal activity with of MIC, 0.25μl/ml and MFC of 0.50μl/ml against A. niger. It can be concluded from the result of the present study that Lepidium sativum seed and leaf oil extract have both antimicrobial and antioxidant activities but leaf oil extracts have highest antibacterial and antifungal activities. Further studies were needed on other pathogens.