Study On Condition Of Enzymatic Conversion Of The Flavonoids From Toon A Sinensis Leaves

Toona sinensis (A. Juss.) Room, a perennial deciduous tree distributed widely in China, is a plant resource that can be concurrently used as medicine and food and its leaves are rich in flavonoids which arc known to possess various biological and pharmacological functions, such as anti-oxidative. antibacterial, antiviral, anti-inflammatory activities and so on. The extracting, purification, enzymatic conversion and acidolysis test of the flavonoids from Toona sinensis leaves were studied in this paper. The composition and content changes of the Toona sinensis leaf flavonoidal glycosides and aglycones after enzymatic conversion and acidolysis and the antioxidant capacities were also studied.The parameters of the optimal water extracting technology for the flavonoids of Toona sinensis leaf were that the ratio of sample to extracting solution was1:25(w/v),2hour of extracting time, twice for extraction after the single factor experiments and orthogonal experiments were finished. The purity of the Toona sinensis leaf flavonoids was14.89%. The ethanol concentration was adjusted to80%and the extract was precipitated for12h to remove most proteins, polysaccharides and other water-fast impurities from the water extract. The purity was increased to23.19%.Then the sample was further extracted2times by the water saturated n-butanol and the extraction rate achieved93.61%.Response surface analysis was used to determine the optimized conditions for the enzymatic conversion of the flavonoids from Toona sinensis leaves. The results showed that the optimized conditions were enzyme dosage0.4838g/g, substrate concentration8.77mg/mL, reaction time7.08hand the conversion rate achieved93.23%.Study on the composition and content changes of the Toona sinensis leaf flavonoidal glycosides and aglycones after enzymatic conversion and acidolysis by TLC and HPLC showed that the water-solubility of the products reduced and the solubility in the organic solvent increased correspondingly. Compared with the standard, there was no kaempferol, but a little quercetin aglycone before the conversion. After enzymatic conversion, the rutin content reduced by0.905%, while the quercetin and kaempferol contents increased by1.228%and1.334%, respectively. After acid treatment, the quercetin content increased by2.115%and the kaempferol content increased by5.424%. The Toona sinensis leaf flavonoids were hydrolyzed completely after acid treatment. The quercetin and kaempferol contents after enzymatic conversion were58.06%and24.59%of those after acid treatment, respectively.The antioxidant capacity was studied by evaluating the reducing power, FRAP value and DPPH radical scavenging capacity and the results showed that the antioxidant capacity of the Toona sinensis leaf flavonoids before enzymatic conversion was between Vc and BHT, higher than the Toona sinensis leaf flavonoids after enzymatic conversion, the Toona sinensis leaf flavonoids after aeidolysis and rutin. The antioxidant capacity of quercetin was also higher than rutin. The results of beta-carotene bleaching method evaluating the antioxidant capacity showed that the antioxidant capacity of the Toona sinensis leaf flavonoids before enzymatic conversion was higher than the Toona sinensis leaf flavonoids after enzymatic conversion but lower than the Toona sinensis leaf flavonoids after acidolysis.