Antioxidative activity and α-glucosidase inhibitory activity of ethanol extracts of leaves of different cultivars of jaboticaba

QIU Shanlian; LIN Baomei; ZHENG Kaibin; ZHANG Shaohua; LIN Shuangshuang; ZHANG Shuhe; ZHENG Feiyan; LI Shanshan

doi:10.13925/j.cnki.gsxb.20170141

Abstract：[Objective] The study compared the antioxidant activity,α-glucosidase inhibitory activity,and the contents of total polyphenols and flavonoids of ethanol extracts from young and old leaves in 4 different cultivars of jaboticaba,and to analyze their correlations.[Methods] The fresh young and old leaves of 4 cultivars of jaboticaba,‘Sabah’ ‘Sijizaosheng’ ‘ Fukuoka’ and ‘Argentina’,were collected from Fujian-Taiwan Jiyong Cooperative Farm of Fruits and Vegetables,Longhai,Fujian.Leaves were crashed in 70％ ethanol at a mass ratio of 1 ∶ 10 for 1 min by a shredder.The liquor was shaken for 16 h at 28 ℃ and 180 r·min-1 and centrifuged for 15 min at 6 000 r·min-1.The supernatant was collected and applied to determine the scavenging effects on DPPH·,· OH and ABTS+ free radicals,the inhibition effect on α-glucosidase activity,as well as the contents of total polyphenols and flavonoids.Difference significance and the correlations between the content of active substances (polyphenols and flavonoids) and antioxidant activity,α-glucosidase inhibitory activity were analyzed using SPSS 19.0 software.[Results] Extracts of young and old leaves from different cultivars had different levels of antioxidant capacity and a strong α-glucosidase inhibitory activity.The results of all tested samples showed a linear relationship between the ability of scavenging DPPH·,· OH and ABTS+ free radicals and the concentrations the components.According to the IC50 values obtained from linear regression equation,the scavenging ability towards DPPH · free radicals was in the order of young leaves of ‘Sabah’ (ySa) ＞ young leaves of ‘Sijizaosheng’ (ySi) ＞ young leaves of ‘Argentina’ (yAr) ＞ young leaves of ‘Fukuoka’ (yFu) ＞ old leaves of ‘Sijizaosheng’ (oSi) ＞ old leaves of ‘Sabah’ (oSa) ＞ old leaves of ‘Argentina’ (oAr) ＞ old leaves of ‘Fukuoka’ (oFu);the order of the ability of scavenging hydroxyl radicals was ySa ＞ ySi ＞ yAr ＞ oSi ＞ yFu ＞ oSa ＞ oAr ＞ oFu;the ability of scavenging ABTS+ radicals is in the order of ySa ＞ ySi ＞ yAr ＞ oSi ＞ yFu ＞ oAr ＞ oSa ＞ oFu.Thus,the three antioxidant tests exhibited the highest antioxidant activity in the extract of ySa,followed by that of ySi and yAr.The extract of oFu exhibited the lowest antioxidant activity.The capacity of scavenging · OH of all extracts with an IC50 in the range of 127.80-960.63 mg· L-1,was much higher than the positive control of ascorbic acid (VC,IC50=2 658.62 mg· L-1).The α-glucosidase inhibitory rate was linearly correlated with the logarithm values of extract concentration for all the tested samples.The IC50 value of α-glucosidase inhibitory activity of the 8 samples ranged from 1.99 to 38.71 mg· L-1.The inhibitory activity of all extracts from jaboticaba leaves in this study was much higher than that of acarbose (IC50=3 133.47 mg· L-1),and was in the order of ySa ＞ ySi ＞ oSi ＞ yFu ＞ yAr ＞ oSa ＞ oAr ＞ oFu.Similar to the antioxidant activity,ySa showed the strongest α-glucosidase inhibitory activity,followed by ySi,and oFu had the lowest activity.The contents of polyphenols and flavonoids of extracts ranged from 53.92 to 274.72 mg· g-1 and 49.84 to 214.82 mg· g-1,respectively.The content of polyphenols was in the order of ySa ＞ ySi ＞ yAr ＞ oSi ＞ yFu ＞ oAr ＞ oSa ＞ oFu,but the content of flavonoids was in the order of yAr ＞ ySi ＞ oSa ＞ yFu ＞ ySa ＞ oAr ＞ oSa ＞ oFu.The contents of polyphenols and flavonoids in the young leaves were significantly higher than those in the old leaves of the same cultivar (P＜0.01).Correlation analysis revealed that the DPPH·,· OH and ABTS+ free radicals scavenging abilities were highly,significantly and positively correlated with the contents of polyphenols (P＜0.01,0.933 1＜r＜0.958 0).The inhibitory activity on α-glucosidase was also significantly and positively correlated with the contents of polyphenols (P=0.009 6,r=0.836 5).However,the antioxidant capacity and α-glucosidase inhibitory activity had no significant correlation with flavonoids (P＞0.05).[Conclusion] The results indicated that there were significant differences in antioxidant activity,α-glucosidase inhibitory activity,and the contents of total polyphenols and flavonoids among the ethanol extracts from young and old leaves of different cultivars of jaboticaba.The antioxidant activity,α-glucosidase inhibitory activity,and the contents of total polyphenols and flavonoids in the young leaves were obviously higher than in the old leaves for each cultivar in this study.These bioactivities had a significant positive correlation with the content of polyphenols.The extract of ySa had the highest antioxidant activity,α-glucosidase inhibitory activity,and content of total polyphenols among the 4 cultivars,followed by ySi.