Studies On Inhibition Effects Of Extracts From Gracilaria Asiatica And Ulva Pertusa Kjellm On The Tyrosinase Activity

Tyrosinase(EC 1.14.18.1)is a copper-constaining redoxidase enzyme which has complex constructure, widely distributed in microorganisms, animals, plants and human beings. It is a key enzyme involved in the melanin biosynthesis, which has a unique double catalytic functions. Over these years, the study on tyrosinase inhibitors has been a major concern of domestic and international academics. So, the study of screening new naturally tyrosinase inhibitors would provide a theoretical basement for the medical cosmetology, food industry and agriculture resist insects fields. There are vast sea areas as well as rich marine resources in china, and the seaweed growing techniques are in the world leading level. Gracilaria asiatica and Ulva pertusa kjellm are large economic algae resources rich in the huanghai sea and the bohai sea areas. Their rich nutrition ingredients and active substances had applied to medical care, food culture and ecological restored aspects.This article made a deep research on the tyrosinase inhibition of the ethanol extracts that extracting from Gracilaria asiatica and Ulva pertusa kjellm. The optimum ultrasonic extracting conditions of the substances from the seaweeds were confirmed by single factor and orthogonal experiment; the inhibitory mechanism and types of the extracts on tyrosinase were studied using enzyme kinetic method. The contents and results were as follows.1 The antienzyme components were extracted from Gracilaria asiatica with the ultrasonic technology, using single factor and orthogonal experiment method to optimize the extracting conditions. The optimum extracting conditions were ultrasonic time 20min, ultrasonic power 100w, the liquid-solid ratio 16mL:1g, ethanol concentration 70%. The Gracilaria asiatica ethanol extracts was leached with organic solvents to obtain the ethyl acetate fraction, the petroleum ether fraction and the substance in water. The results showed that all of the three components had different inhibition on the activity of the tyrosinase. The concentration of Gracilaria asiatica extracts corresponding to 50% inhibition (IC50) was 0.6mg/mL, 22.32 mg/mL and 7.85 mg/mL, respectively, the ethyl acetate fraction showed a prominent inhibition. The inhibition kinetics analysis based on the Lineweaver-Burk plots showed that the inhibition of the Gracilaria asiatica ethyl acetate fraction and the petroleum ether fraction belongs to noncompetitive inhibition, the KI(KIS) was 0.86 mg/mL and 1.96 mg/mL, respectively; the substance in water belongs to competitive inhibition, the KI was 0.81mg/mL.2 The optimum extracting conditions with ultrasonic technology to extract the antienzyme components from Ulva pertusa kjellm were ultrasonic time 8min, ultrasonic power 100w, the liquid-solid ratio 20mL:1g, the ethanol concentration 70%. The organic solvents leached experiments showed that the petroleum ether fraction from Ulva pertusa kjellm had no inhibition on the activity of tyrosinase, the ethyl acetate fraction and the substance in water can inhibit the activity of tyrosinase. The concentration of extracts corresponding to 50% inhibition (IC50) was 1.75mg/mL and 11.53mg/mL, respectively, the ethyl acetate fraction showed a prominent inhibition. The Lineweaver-Burk plots showed that the ethyl acetate fraction belongs to noncompetitive inhibition, the KI(KIS) was 1.92mg/mL; the substance in water belongs to competitive inhibition, the KI was 1.11mg/mL.3 Synthesizing the tyrosinase inhibition of the two algaes, the extracts from Gracilaria asiatica and Ulva pertusa kjellm both have different antienzyme active components, and the distinct antienzyme components are both on the ethyl acetate fraction, its active ingredients may be the similar substance.