Abstract:
This study sought to investigate the starch composition, antioxidant potential, phenolic
phytoconstituents, glycemic indices, α-amylase and α-glucosidase inhibitory activities of some
Nigerian fruits. Thirteen fresh fruits were sourced for and the fruits juices were extracted, freeze dried
and then reconstituted for analysis. The sugar, starch, amylose and amylopectin contents as well as
glycemic indices, antioxidant properties and the ability of the fruits to inhibit starch hydrolyzing
enzymes were determined. Also, the phenolic constituents of the fruits were characterized using
HPLC-DAD. The starch, sugar, amylose and amylopectin contents ranged between 3.01-3.89g/100g,
35.34-60.91g/100g, 0.84-1.46g/100g and 1.68-2.86g/100g respectively while the glycemic indices
range from 28.01-68.34 with African star apple (28.01) having the least glycemic index while
Watermelon (68.34) had the highest. Furthermore, the fruits exhibited high antioxidant properties as
exemplified by their DPPH, ABTS + , • OH and NO radical scavenging abilities. Likewise, the HPLC
analysis revealed the presence of quercetin, gallic acid, catechin, epicatechin, rutin and chlorogenic
acid in most of the fruits with resveratrol found only in breadfruit, isoquercitrin in carrot, orientin in
guava, cyanidin-3-O glycoside and cyanidin in African star apple. The fruits also demonstrated α-
amylase and α-glucosidase inhibitory property with Soursop (IC 50 =18.52μg/mL), guava
(IC 50 =19.77μg/mL) and african star apple (IC 50 =20.86μg/mL) showing the highest inhibitory potential
among the thirteen fruits. Similarly, the same trend was followed for α-glucosidase inhibitory activity.
The fruits’ low glycemic indices, antioxidant properties and inhibition of α-amylase and α-glucosidase
activities could be possible mechanisms for their use in the management and prevention of type-2
diabetes and as well justify their recommendation for the diabetics.
