Studies On Inhibition Of Persimmon Leaf Flavonoids On Tyrosinase Activity

Persimmon leaf is the fresh or dried persimmon leaf,its bitter in taste,has the hemostatic,anti-cancer of health care function,the main effective ingredients are persimmon leaves flavonoids.Tyrosinase Inhibitor?TI?by inhibiting Tyrosinase activity which restrain melanin formation.Therefore,TI can reduce food Browning level and can be used as fresh-keeping agent,The purpose of this article is to persimmon leaves of flavonoids fabrication process is optimized,research on the tyrosinase inhibitory effect and the application in fresh-keeping.1 Total flavonoid were extracted from persimmon leaf with cellulase.Based on single factor tests,the optimum extraction conditions of total flavonoids from persimmon leaf were obtained through Box-Benhnken central combination design and RSM.The optimum extraction conditions were confirmed byresponse surface method as follows: cellulose concentration 9mg,enzymatic hydrolysis temperature 52?,pH 4.8,and time 130 min.Under these conditions,the extraction rate was 2.47%.2 AB-8 resin possesses much higher adsorption and desorption capacity.The optimum conditions are: the pH value of sample is 6,current velocity 2BV/h,concentration of sample3mg/mL,70% alcohol as eluant for desorption,current velocity 2BV/h and eluant volume 3BV.An enriched total flavonoids extract with 34% purity can be separated from crude persimmon leaf extract?about 9% purity?in this way.Conclusion: It is feasible to separate and purify persimmon leaf flavonoids with AB-8 resin.3 The inhibitory of persimmon leaf flavonoids on tyrosinase activities were examined with L-Tryosine as substrate.The results showed that persimmon leaf flavonoids had obvious inhibitory activity on tyrosinase,IC₅₀ was 2.38mg/mL.Persimmon leaf flavonoids showed reversibly inhibitors to tyrosinase and the type of inhibition belonged to be mixed-type,K_I was0.33 and K_IS was 0.48.4 Its oxidation resistance and complex with Cu²⁺ were investigated.The results showed that persimmon leaf flavonoids had obvious inhibitory activity on tyrosinase.The antioxidant study and complex with Cu²⁺ study showed that persimmon leaf flavonoids had activity of scavenging DPPH·?O^2-· and·OH,had strong abilities of complex with Cu²⁺.The inhibitory of persimmon leaf flavonoids on tyrosinase activities was relation with its antioxidant and abilities of complex with Cu²⁺.5 Fresh-keeping of PLF on fresh-cut apple was studied.The content of Vc and TSS,and the changes of Browning Degree of fresh-cut apple were studied during the storage.The resultsshowed that PLF showed good fresh-keeping when concentration of sample 0.1mg/mL,soak time 5min;PLF showed good fresh-keeping;the mechanism was related to its inhibitory on tyrosinase activities and its oxidation resistance.This is probably the PLF with preservation role of the mechanism.