Anti-oxidative Stress Effect And Its Mechanism Of Litchi Pulp Polyphenols

Litchi, a delicious and nutritious fruit, has been considered as "the king of fruit" Studies have shown that litchi displayed antioxidant, anti-ageing, hypolipidemic, and hepatoprotective effects, but little is known about the basis of active components and action mechanism. It has been reported that polyphenols in fresh fruits and vegetables are responsible for their health benefits such as tumor inhibition. Despite a lot of research on polyphenols in litchi pericarp in the fresh-keeping field, data are lacked on polyphenols in litchi pulp.In order to investigate the compositions and bioactivity of litchi pulp polyphenols, litchi polyphenols extracts (LPE) with different polarity were obtained by fractional extraction, and antioxidant activity of each fraction was determined, The antioxidant activity of LPE was analyzed by determining the redox status of serum and liver of restraint-stressed mice, Hepatic function and the structure and function of liver mitochondria were also estimated. The results are as follows:1. Comparison of the content and antioxidant activity of litchi pulp polyphenols with different polarity:Sixty percent aqueous ethanol and eighty percent aqueous acetone were used separately to extract polyphenols and the extracts were fractionally extracted with ethyl acetate, n-butanol and water. Antioxidant activity of polyphenols extracts fractioned by solvents with different polarity was determined by DPPH scavenging, FRAP and ABTS methods. The results showed that:the ABTS antioxidant activity of the polyphenol extracted by 80% acetone was significantly stronger than that by 60% ethanol(P<0.05), and polyphenol content of the two litchi polyphenol extracts was not significantly different. The water layer had the highest polyphenol content, followed by n-butyl alcohol layer. The ethyl acetate of polyphenol extract exhibited the highest antioxidant activity, followed by n-butyl alcohol extract. The activity of acetone extract polyphenol was significantly higher than the ethanol extract of polyphenols (P<0.05).2. Antioxidation Effect of polyphenols of litchi pulp on Mice loaded with restraint stress:Mice models of peroxidation were induced by 18-hour restraint stress, To observe the antioxidation effect of LPE on mice loaded with restraint stress, researched the changes of antioxidants and antioxidative enzymes in mice,The alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities of serum were measured by Reitamn-Frankel assay, malondialdehyde (MDA) level by thiobarbituric acid method, glutathione(GSH) content, glutathione peoxidase (GSH-Px), total antioxidant capacities(T-AOC), superoxide dismutase(SOD) by colorimetric method. The results shows that:Compared with the model group, the AST activity in serum of low(200mg/kg.d), medium(400 mg/kg.d) and high(800 mg/kg.d) LPE treatmeat groups were significantly reduced(P<0.05), the T-AOC and GSH content in liver of medium and high treatmeat groups were significantly increased(P<0.05), the ALT activity in serum of high treatmeat group were significantly reduced(P<0.05), the SOD activity in serum and liver of high treatmeat group were significantly increased(P<0.05), MDA content in serum and liver of high treatmeat groups were significantly reduced(P<0.05), XOD,GSH-Px and CAT activities in serum were significantly increased(P<0.05).3.Anti-oxidative stress effect and its mechanism of polyphenols of litchi pulp: We observed mitochonndrial function through optical microscope, examined the respiratory chain complex and Na+-K+-ATPnase through spectrophotometry instrument, measured mitochondria membrane potential through the Flow Cytometer, examined the changes of the expression of liver SDHA-D through the method of RT-PCR. The results shows that:Compared with the model group, the mitochondrial function in liver of low(200mg/kg.d), medium(400 mg/kg.d) and high(800 mg/kg.d) LPE treatmeat groups were improved, the ROS content in mitochondria of liver was significantly reduced(P<0.01), mitochondria membrane potential of liver was significantly reduced(P<0.01), total ATPnase was significantly increased(P<0.05); Compared with the model group, the respiratory chain complexⅡin liver of high LPE treatmeat groups were reduced, Na+-K+-ATPnase was significantly increased (P<0.05); The respiratory chain complexⅠ,Mg2+-ATPase and expression of liver SDHA-D were not significantly changed(P>0.05).The main originality of this research is as follows:This paper analysed the polyphenol content and antioxidant activity of the polyphenols fractions by liquid-liquid extraction, proposed that antioxidant activity of ethyl acetate fraction of litchi polyphenol was the highest.Anti-oxidative stress effect of LPE was studied with loaded Mice mice models in the first time.Restraint stress selectively affected the second chain of respiratory chain. LPE alleviated the status of oxidative stress through improving the mitochondrial function of restraint mice.