Quality Evaluation And Study Of Biological Activity Of Okra Leaf Tea

Okra(Abelmoschuseulentus(L.)Moench)is a native plant from Africa.Its tender pod is main edible part,which is nutritious and have various healthy functions.Okra leaf also contains a variety of nutrients.At present,the research about it mainly focused on the analysis of components,the extraction of bioactive components and the evaluation of antioxidant activity.While the study on its deep processing was relatively few.Although the tea made of okra leaf has been reported,it has not been comprehensively analyzed from the perspective of tea,which will influence the development and utilization of okra leaf resources.In this paper,the okra leaf tea was gotten from fresh okra leaves.The quality components of okra leaf tea were meassured and analyzed,and its brewing conditions were optimized.At the same time,the extraction kinetics of aqueous extracts of okra leaf tea were studied,and the biological activity of aqueous extracts at different temperatures were analyzed.The main research contents and results were as follows:1.The results indicated that the contents of each component basically met the national standards.The total ash was higher than the national standards for variety,the crude protein was the highest,and the ratio of potassium to sodium was also higher;The flavor components included polyphenols,free amino acids and caffeine.And the phenol ammonia ratio was relatively low,and it tasted light and refreshing.Flavonoid glycosides with quercetin and kaempferol as aglycones were the main polyphenolic compounds.The taste was dominant by y-aminobutyric acid(GABA)and glutamic acid,whose proportion were higher and the threshold values were lower.The color components were composed of chlorophyll and carotenoids.A total of 28 aroma components were identified,and content of aldehyde compounds reached 47.53%,and dimethyl sulfide,D-Limonene and ?-ionone were characteristic aroma substances of it.2.The brewing conditions were screened by sensory evaluation and color difference analysis.Further on,taking the contents of polyphenols and GABA as the indexes,the brewing conditions of okra leaf tea were optimized by single factor and orthogonal test.The the best brewing condition was achieved:ratio of tea to water was 1:70,brewing time was 7 min,and brewing temperature was 95 ?.The contents of polyphenols and GABA reached 14.58 mg/g and 2.77 mg/g respectively.The flavor components of tea soup,such as soluble total sugar and free amino acids,and the characteristic aroma components such as cedrol,?-ionone and geranyl acetone made the tea soup mellow and fragrant.3.The concentrations of the bioactive components by magnetic stirring extraction were higher than that by conventional static extraction,and the concentrations of each bioactive component increased with the improvement of temperature.The concentrations increased rapidly first,and then increased slowly or tended to be flat.Only polyphenols decreased after 10 minutes by magnetic stirring extraction.The kinetics equations of pseudo-second-order and first-order were used to fit the water extraction process of okra leaf tea.It was found that the bioactive components were extracted more easily by magnetic stirring extraction,and the extraction rate and amounts increased with the improvement of temperature.The model has been verified to have good accuracy and predictive ability.4.Aqueous extracts of okra leaf tea could effectively scavenge DPPH·,·OH,O2.-and nitrite,and inhibit ACE activity,but the effect of inhibiting a-glucosidase was general.And the biological activity of aqueous extracts increased with the improvement of temperature.Polyphenols,polysaccharides,free amino acids and GABA increased,while flavonoids decreased with the improvement of temperature(P>0.05).Besides the ability of scavenging-OH was only significantly related to polyphenols and polysaccharides(p<0.05),and the ability of scavenging DPPH·,O2.-,and nitrite was highly correlated with polyphenols,polysaccharides,free amino acids and GABA(p<0.01).The effect of inhibiting a-glucosidase was highly correlated with polysaccharides(p<0.01),and the effect of inhibiting ACE was more correlated with free amino acids and GABA.