In Vitro Antioxidant Activity Of Anthocyanins In Vaccinium Uliginosum L.

This study used Vaccinium uliginosum L. fruit from Greater Khingan Mountains as raw material, we investigated the antioxidant activity of crude extract and refined extract under different conditions by scavenging DPPH free radicals, hydroxyl free radicals, ABTS radicals and ferric reducing antioxidant power (FRAP) assay.The result showed, the crude extract showed better antioxidant capacity with the initial pH1. As the pH value increased the crude extract showed bwer antioxidant capacity. DPPH radical scavenging activity was greatly improved under pH5but unable to be determined when pH exceeded8.The activity of scavenging OH free radical reached a peak value in pH5and pH10. ABTS free radical scavenging activity obviously increased with the pH8,10. The ferric reducing antioxidant power (FRAP) assay reached a maximum in pH7,9. The antioxidant activity of crude anthocyanins from Vaccinium uliginosum L. decreased with the increasing of temperature. However, it was found that the antioxidant activity of crude anthocyanins after water bathed at100℃increased gradually with the increasing of pH (over7). Finally, the antioxidant activity of crude anthocyanins after water bathed at100℃were found to be more effective than water bathed at60and80℃.Similar to the crude extract, the antioxidant activity of refined extract from Vaccinium uliginosum L. dropped with pH increased (pHl-4), slightly improved pH5and then gradually decreased; temperature of the sample solution had the obvious effect of ABTS·+scavenging capacity. When pHl-6, the ABTS·+scavenging capacity had the similar trend with temperature and capacity in order of60℃,80℃and100℃. In addition to the pH8and pH10, others have similar trend and effects, but the extract after60℃had better antioxidant activity. The impact of temperature on the activity of scavenging OH free radical is not significant. In addition to the pH5and pH7, others have similar trend and effects, but the extract after60℃had better antioxidant activity. When pH<10the antioxidant activity than pH>10.Correlation between the content of monomer anthocyanins, secondary color of anthocyanins and polymeric anthocyanin with the antioxidant activity of anthocyanins was analyzed. The results showed that the antioxidant capacity of the anthocyanins was mainly affected by the impact of the content of monomeric anthocyanin at low pH. However, the content of the polymeric anthocyanins and secondary color anthocyanins showed more greater impact on the antioxidant activity of anthocyanins with high pH and high heating temperature.The results show that the DPPH· scavenging capacity of Vaccinium uliginosum purified extracts was best at pHl, then reduced with the increase of pH; Treated whit the acidic conditions, the ABTS·+scavenging capacity Vaccinium uliginosum maintain stable and relatively high with the heating time and the pH changes; however, the ABTS·+scavenging capacity Vaccinium uliginosum decreased with the increase of the heating time and the pH under the alkaline conditions; FRAP method to measure the total antioxidant activity,6min,8min,10min, the antioxidant activity of purified extracts with the increase of pH.Treated with the artificial gastric juice, the anthocyanin extract still showed good antioxidant activity and showed a good linear relationship with the change of the concentration of anthocyanin with increasing pH value. The effect of temperature on the DPPH·and ABTS·+scavenging capacity was the same (60℃>80℃>100℃). In contrast, treated with100℃, the reducing power of the anthocyanins in the gastric juice (FRAP method) was generally higher than that treated with60℃and80℃.