Online RP-HPLC-DPPH Screening Method for Detection of Radical-Scavenging Phytochemicals from Flowers of Acacia confusa

摘要

Acacia confusa is traditionally used as a medicinal plant in Taiwan.In this study,phytochemicals and antioxidant activities of extracts from flowers of A.confusa were investigated for the first time.In addition,a rapid screening method,online RP-HPLC-DPPH system,for individual antioxidants in complex matrices was developed.Accordingly,six antioxidants including gallic acid (1),myricetin 3-rhamnoside (2),quercetin 3-rhamnoside (3),kaempferol 3-rhamnoside (4),europetin 3-rhamnoside (5),and rhamnetin 3-rhamnoside (6) were detected using the developed screening method.Of these,compounds 2,3,and 5 were found to be major bioactive phytochemicals,and their contents were determined as 11.3,6.7,and 8.7 mg/g of crude extract,respectively.By comparison with quercetin,a well-known antioxidant,these compounds had the order of compound 2 > compound 5 > quercetin > compound 3 for DPPH radical-scavenging activity.Their IC50 values were 3.0,3.2,4.5,and 7.4 mu M,respectively.Moreover,the same order was observed for superoxide radical-scavenging activity,and their IC50 values were 2.6,2.7,4.3,and 5.3 pM,respectively.However,for lipid peroxidation,quercetin,an aglycon,showed the best inhibitory activity.The IC50 values of quercetin,compound 2,compound 5,and compound 3 were 46.7,88.5,90.7,and 124.6 mu M,respectively.These results indicated that a rhamnoside at the C3 position of flavonoids had a negative effect on radical-scavenging activity and antilipid peroxidation.In contrast,the number of hydroxyl groups on the B-ring exhibited a positive relationship with their inhibitory activities.