To seek out a cheap source of dietary polyphenols and antioxidants along with anti-amylase and antiglucosidase activities, ethanol extracts of eleven cheap Bangladeshi fruits were investigated. The extracts were also examined for anti-allergic activity using rat peritoneal exudate cells exposed to the calcium ionophore A23187. Phyllanthus emblica (emblic myrobalan) had the highest total polyphenol content (339 mg gallic acid equivalent (GAE)/g), followed by Syzygium cumini (Indian blackberry; 192.3 mg GAE/g), and Aegle marmelos (wood apple; 53.7 mg GAE/g). P. emblica, and S. cumini also exhibited the most potent DPPH radical scavenging activity, with an IC 50 of 2.1 and 8.6 μg/mL respectively. These extracts also showed promising reducing powers with P. emblica having the greatest such activity (optical density (O.D.) 1.66), followed by S. cumini (O.D. 1.34), at a concentration of 0.2 mg/mL. The extracts of Artocarpus heterophyllus (jackfruit) and S. cumini showed promising chelating activities. At a concentration of 1 mg/ mL, Dillenia indica (chalta) showed the highest inhibition of α-amylase activity (60%), and A. marmelos, D. indica, P. emblica, Spondias dulcis (hog-plum) & S. cumini completely inhibited α-glucosidase activity (100%). Apart from A. heterophyllus, D. indica and Phyllanthus acidus (star-gooseberry), all other extracts inhibited the release of histamine from the peritoneal exudate cells, with S. cumini having the strongest effect. These fruits therefore have activities beneficial to physiological health. Keywords: antioxidant, anti-amylase, anti-glucosidase, anti-allergy, antihistamine release, fruits, polyphenol *To whom correspondence should be addressed. Email: aoshima@yamaguchi-u.ac.jp
IntroductionFruits are major sources of health promoting agents. Of these agents, antioxidants are most important because they inhibit the initiation of lipid peroxidation, which is related to aging and the pathogenesis of diseases such as cardiovascular disorders, cancer, inflammation, and brain dysfunction (Ames, 1983;Shon et al., 2004). Various epidemiological studies have suggested that consumption of fruit and vegetables is associated with reduced risk of cardiovascular diseases and cancers (Kris-Etherton et al., 2002), neurodegenerative diseases such as Parkinson's and Alzheimer's diseases (Di Matteo and Esposito, 2003), as well as with inflammation and aging (Ames et al., 1993).Natural products are reportedly beneficial to physiological health. Various flavonoids and non-flavonoids have been reported as showing radical scavenging activity (Sawa et al., 1999): flavone, and flavonoids inhibit α-amylase and α-glucosidase activities (Havsteen, 1983;Kim et al., 2000); polyphenols have anti-hyperglycemic effects (Hossain et al., 2002;Hanamura et al., 2006), and inhibit the development of diabetes (Zunimo et al., 2007). Since glucose release from food sources is the main factor affecting post-prandial hyperglycaemia, retardation of the digestion of starch by key gastrointestinal enzymes can be of benefit to...