Antioxidative property of Thai fruits

Phytochemicals in plants have been reported to prevent oxidative stress related diseases such as cancer, cardiovascular disease, cataracts, brain and immune-system dysfunction and inflammation. Polyphenolic compounds are commonly found in plants both edible and nonedible parts. The aim of this study was to evaluate different varieties of Thai fruits for their total polyphenolic content and their antioxidant property in order to find potential sources of edible and natural antioxidants. In this study, the total polyphenolic contents in 28 varieties of fruits were determined by Folin-Ciocalteu method. Antioxidant property of tested fruits were determined by using 2,2-diphenyl-1- picrylhydrazyl (DPPH) method. Specific free radical scavenging activities; superoxide anion scavenging activity, hydroxyl radical scavenging activity and the protective effect of fruits on hemolysis of human red blood cells (RBCs) were also elucidated. Total polyphenolic contents in fruits varied widely from 3.243 ± 0.303 to 2120.526 ± 141.244 mg GAE/g wet weight: low levels (< 30 mg GAE/g wet weight) were found in watermelon, rose apple, fragrant banana, grape pulp, lemon juice, mango (Rad), papaya, rambutan, pineapple, banana (Kai), jackfruit, durian, orange juice, mango (Kiow-Sa- Wooei), pomelo, and sa-la; moderate levels (30-80 mg GAE/g wet weight) were found in mangosteen pulp, longan, mango (Nam-Dok-Mai), ma-fai, zalacca, indian mulberry, apple, litchi, guava, longkong pulp, orange, carambola, custard apple, jujube, santol (white pulp), plum mango, and grape skin (White Malaca); high levels (> 80 mg GAE/g wet weight) were found in grape skin (White Spain), banana (Nam-Var), longkong seed, grape skin (Pok-Dum), santol (brown pulp), and mangosteen hull. The DPPH radical scavenging of fruit extracts measured as IC₅₀ varied from 0.149 to 513.974 mg/ml: mangosteer1 hull, grape skin, santol, banana (Nam-Var), plum mango, mango, longkong seed~ carambola, guava, ma-fai, litchi, apple, jujube, zalacca, sa-la, mangosteen pulp, longan, indian mulberry, custard apple, orange, and pomelo showed strong activity to scavenge the DPPH radical (IC₅₀ < 20 mg/ml); moderate antioxidant activity was found in durian, longkong pulp, grape pulp, banana (Kai), papaya, rambutan, orange juice, pineapple, fragrant banana, rose apple, and lemon juice (IC₅₀ from 20 - 100 mg/ml); low antioxidant activity (IC₅₀ > 100 mg/ml) was found in jackfruit and watermelon. The superoxide scavenging abilities of the six fruit extracts generated in a PMS/NADPH system are as follows: mango (Nam-Dok-Mai) > longkong seed > banana (Nam-Var) > guava > longkong pulp > durian. The hydroxyl radicals were generated by the Fenton system. T he order 0f hydroxyl radical scavenging capabilities of six fruit extracts are mango (Nam-Dok-Mai) > longkong pulp > banana (Nam-Var) > longkong seed > guava > durian. The protective effect of fruits on hemolysis of human RBCs, induced by 2,2’- azobis (2-methylpropionamidine) dihydrochlonde (APPH) radicals was investigated. The results demonstrated that among the six fruit extracts, mango (Nam-Dok-Mai) possesses the strongest effect (91% inhibition) to prevent human erythrocyte membrane from hemolysis while durian has the weakest effect (58% inhibition) against human erythrocyte hemolysis; banana, guava, longkong pulp, and longkong seed have moderate capability (71-81% inhibition) to prevent human erythrocyte membrane from hemolysis.