ANTIOXIDANT CAPACITY AND PHENOLIC COMPOUNDS IN LITCHI (LITCHI CHINENSIS SONN.) PERICARP

Abstract

Phenolic contents and antioxidant activities in fruit pericarp of eight litchi (Litchi chinensis Sonn.) cultivars ('Nuomici', 'Feizixao', 'Guiwei', 'Edanli', 'Yuhebao', 'Dingxiang', 'Wuye' and 'Lanzhu') were studied. Antioxidant activities were elucidated by the 1,1-diphenyl-2-piceyhydrazyl (DPPH) decoloration test and hydroxide free radical scavenging (HFRS) assay. Litchi fruit pericarp (LFP) contains rich phenolic compounds including phenolic acids, flavonoids and proanthocyanidins, and exhibits a powerful antioxidant activity in retarding oil deterioration and antiradical activity in vitro. Among these cultivars, phenolic acids in dry pericarp ranged from 1.0 to 2.4 g 100 g -1 DW, total flavonoids from 1.5 to 3.8 g 100 g -1 DW, and proanthocyanidins from 1.6 to 4.4 g 100 g -1 DW. These compounds are the highest in 'Nuomici', 'Feizixiao' and 'Edanli', moderate in 'Yuhebao' and 'Wuye', and lowest in 'Guiwei', 'Dingxiang' and 'Lanzhu'. The radical scavenging rate ranged from 18 to 72% in DPPH system and from 22 to 57% in HFRS system. Their antiradical activities were positively correlated with phenols, while their activities against lipid oxidation showed no correlation with phenol levels. 'Nuomici' and 'Edanli' displayed the lowest peroxide values (POV) and therefore the highest lipid antioxidant activity and their activity increased with concentrations in the range of 0.1 to 0.8%. 'Feizixiao', though showed high phenolic content and radical scavenging rate, displayed a very poor ability in suppressing lipid oxidation.