Composition,Antioxidant Capacity And Digestive Enzyme Inhibitory Activity Of Phenolics From Five Immature Broad Beans

ObjectiveThis study was based on the immature broad beans of five varieties cultivated by the Dali Academy of Agricultural Science,Yunnan Province.The phenolic composition,antioxidant capacity and inhibitory effects onα-glucosidase and lipase in the seed coats and cotyledons at three edible stages were studied in this paper,which will provide a theoretical basis for the rational harvest of broad beans according to different needs,and provide a scientific basis for the rational and comprehensive use of broad beans to develop nutritional health care products.MethodsThe contents of TP,TF and CT in the phenolic extracts were determined by spectrophotometry.The individual phenolic composition and content of phenolic extracts were analyzed by high performance liquid chromatography（HPLC）.The antioxidant capacities of phenolic extracts were evaluated by DPPH and ABTS⁺free radical scavenging capacity and Ferric reducing ability of plasma（FRAP）assay in vitro.The inhibitory activity of phenolic extracts onα-glucosidase and lipase was evaluated using an in vitro enzyme inhibition test.ResultsThe contents of TF,TP and CT in seed coats and cotyledons of five immature broad bean were in the range of 1.62～4.71 and 0.03～0.27 mg GAE/g DW,5.16～13.25 and 0.14～0.63 CAE/g DW,and 2.19～7.91 and 0.10～0.34 mg CAE/g DW,respectively.With the continuous maturity of broad beans,the variation trend of TP,TP and CT content in seed coats and cotyledons of different varieties are different.The experimental results of the individual phenolic composition of seed coats and cotyledons from five immature broad beans showed that the seed coats was rich in phenolics and epicatechin and catechin were the major phenolic compounds.Whereas the cotyledons contain few individual phenolic compounds with catechin,epicatechin and quercetin prominent.The results of the antioxidant capacities showed that the DPPH and ABTS⁺free radical scavenging capabilities of phenolic extracts from seed coats ranging from 11.73～24.27 and 36.30～73.96μmo L TE/g DW,respectively,and the cotyledons were in the range of 0.18～0.61 and 0.30～1.05μmo L TE/g DW,respectively.The FRAP values of the phenolic extracts from seed coats and cotyledon were in the range of 32.64～98.49 and 0.30～4.74μmo L Fe（Ⅱ）/g DW,respectibely.The antioxidant capacity of the seed coats is significantly higher than that of cotyledons,and significant positive correlations between phenolics and antioxidant capacity were observed.The results of the enzyme inhibition test revealed that the inhibitory activity of the phenolic extracts onα-glucosidase showed a logarithmic function relationship,while on the pancreatic lipase showed a linear relationship within the range of the test concentration.The IC₅₀values of the inhibitory effects of the phenolic extracts from faba bean seed coats onα-glucosidase and pancreatic lipase were in the range of 37.62～335.30μg/mL and 3.60～6.61 mg/mL,respectively,while from cotyledons were in the range of 0.59～6.44 mg/mL and 2.55～7.41 mg/mL.In a whole,the inhibitory activity of the seed coat on digestive enzymes is stronger than that of the cotyledon.ConclusionsDuring the development of broad beans,the composition and content of phenolics in seed coats and cotyledons from different broad bean varieties possessed different change trends,as well as the antioxidant capacity and enzyme inhibition capacity.Generally speaking,the phenolics were abundant in seed coat of broad bean.Therefore,the seed coat of broad bean is a potential source of functional raw materials and it should be reasonable harvest and use according to the different needs.