EFFECTS OF HIGH PRESSURE OR ULTRASONIC TREATMENT ON EXTRACTION YIELD AND ANTIOXIDANT ACTIVITY OF PERICARP TISSUES OF LONGAN FRUIT

Abstract

High pressure extraction (HPE) and ultrasonic extraction (UE) has exhibited great potential for extracting bioactive compounds from plant tissues. Experiments were conducted to comparatively investigate the effects of 500 MPa HPE, 40 kHz UE and convention extraction (CE) on extraction yield, total phenolic content and antioxidant activity from longan fruit pericarp. The antioxidant activities of these extracts were then analyzed employing various antioxidant model systems including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, reducing power, total antioxidant capacity, superoxide anion radical scavenging activity and inhibitory ability against lipid peroxidation. In addition, three phenolic compounds, namely gallic acid, corilagin and ellagic acid, were identified and quantified using the high-performance liquid chromatography method. Compared with CE and UE samples, HPE sample exhibited higher extraction efficiency in terms of extraction yield, phenolic content and antioxidant activity. PRACTICAL APPLICATIONS Longan (Dimocarpus longan Lour.) is an attractive fruit and is widely distributed throughout the southern parts of China. Longan fruit pericarp (LFP) accounts for approximately 20% by weight of the whole fresh fruit and is comprised of significant amount of phenolic compounds and polysaccharides which are natural antioxidants. This work showed that high pressure extraction technique has a high efficiency in extracting phenolic compounds from longan fruit pericarp tissues and the HPE sample shows a strong antioxidant activity of the phenolic compounds, which may help longan industry to develop new extraction methods for better utilization of phenolic compounds as natural antioxidants.