Abstract:

The DPPH radical scavenging effects of different solvent extracts from different parts of Ligustrum lucidum fruit growing in Nanjing were comparatively investigated. Moreover, the effects of sunlight illumination and growth period on the DPPH free radical scavenging activity of ethanol extract from whole Ligustrum lucidum fruit were examined, and the lyophilized ethanol extract from whole Ligustrum lucidum fruit was subjected to sensory evaluation and comparison with VC and tea ployphenols in free radical scavenging capacity. Polar and non-polar solvents were employed to extract Ligustrum lucidum fruit, and the extracts derived from polar solvent extraction showed stronger DPPH free radical scavenging capacity. Solvents and fruit parts both made a difference to DPPH free radical scavenging capacity. The same solvent extracts from different fruit parts obtained with methanol, ethanol or water were ranked in the following order starting with the strongest: peel ＞ whole fruit ＞shell ＞ kernel. For acetone, ethyl acetate and ethanol extracts, the order was peel ＞ whole fruit ＞ kernel ＞ shell. All five solvent extracts from whole fruit showed a positive correlation between DPPH free radical scavenging activity and concentration in the lower concentration range, and the slopes were much higher than those in the higher concentration range. However, the concentration-effect relationship in the higher concentration range was complicated and closely associated with solvent type. The highest DPPH free radical scavenging activity of Ligustrum lucidum fruit was observed at the early ripening stage, followed by different decreases at the middle and post ripening stages. The ethanol extract from Ligustrum lucidum fruit exposed to sunlight revealed significantly higher DPPH free radical scavenging activity than that from Ligustrum lucidum fruit unexposed to sunlight. The lyophilized ethanol extract from whole Ligustrum lucidum fruit had a DPPH free radical scavenging capacity (IC50= 5.38－10.46) equivalent to that (IC50 = 8.59) of VC but lower than that (IC50 = 1.70) of tea polyphenols. The solid water-soluble ethanol extract in dark brown is a potential effective antioxidant.

Key words: Ligustrum lucidum friut, extract, antioxidant activity, antioxidant compound, DPPH radicals, scavenging rate