Exploring antioxidant properties and antidiabetic potential of ten underutilized Sri Lankan fruits

Managing and treating diabetes mellitus is one of the scientific community's biggest challenges. This study aimed to determine phytochemicals, antioxidants, and antidiabetic properties of different solvent extracts of fruit plants as a source of natural products. The total flavonoid content (TFC) and total phenolic content (TPC) were determined using standard methods. Antioxidant activities were determined using in vitro ferric reducing power (FRAP), oxygen radical absorbance capacity (ORAC), DPPH radical scavenging, and ABTS radical scavenging assay methods. The antidiabetic activities of the fruit extract were assessed using in vitro anti-amylase,anti-glucosidase , and anti-glycation assays. Among different fractions of crude (CR), hexane (HX), ethyl acetate (EA), and aqueous (AQ), the highest TPC and TFC values were found in the HX fraction and EA fraction of Garcinia xanthochymus, respectively. The highest FRAP, ORAC, DPPH, and ABTS activities were found in the CR extract of G. xanthochymus, EA of G. xanthochymus, EA of Flacourtia indica, and HX fraction of G. xanthochymus, respectively. The highest anti-amylase inhibition was found in EA of G. xanthochymus, EA fraction of Careya arborea, and HX fraction of Syzygium zeylanicum compared to the standard drug Acarbose. The highest anti-glucosidase enzyme activities were found in the EA fraction of Elaeocarpus angustifolia, followed by the EA fraction of Cynometra cauliflora, the EA fraction of S. zeylanicum, the CR extract of F. indica, the AQ fraction of C. cauliflora, the EA fraction of C. arborea, the EA fraction of G. xanthochymus, the CR extract of C. cauliflora, and the CR extract of E. angustifolia compared to Acarbose. Antiglycation activities were higher in the HX fraction of S. zeylanicum, the EA fraction of G. xanthochymus, and C. arborea than in Rutin. None of the extracts showed inhibition for human salivary α-amylase enzyme. The ethyl acetate (EA) fractions of G. xanthochymus and C. arborea, along with the hexane (HX) fraction of S. zeylanicum, exhibited strong in vitro antioxidant and antidiabetic activities. These results indicate their potential as promising therapeutic candidates for the management of diabetes mellitus. However, further in vivo investigations are warranted to elucidate their mechanisms of action and assess their clinical applicability.