Background Most of the edible portions like peel and skin of some fruits is discarded while consuming it, though they are rich in several health beneficial phytochemicals or nutrients. Many reports from literature are about fruit pulp of (Sapota) Manilkara zapota (L) P. Royen having high radical scavenging and antioxidant potential, but the studies relating to peel extracts are scanty. Regardless of its commendable phytoconstituents which could have free radical scavenging potential, this fruit peel is as yet still needed to be assessed for in vitro antidiabetic prospects. Hence, the present study aims at evaluating in vitro free radical scavenging and α-glucosidase enzyme hindrance abilities of this fruit peel. Results With a maximum considerable % extractive yield (18.90%) in 70% ethanol, this study has demonstrated that 70% ethanolic extract of Manilkara Zapota (L.) P. Royen Fruit Peel (MZFP) has the highest in vitro free radical scavenging potential as compared to extracts of other solvents viz. n-hexane, chloroform, acetone, absolute ethanol, and water by DPPH and H2O2 assays. In order to optimize the extraction condition parameters, MZFP sample evaluated with three different concentrations of ethanol (40%, 70%, 100%), extraction times (6 h, 9 h, 12 h), and temperatures (40 °C, 50 °C, 60 °C) to get the highest radical scavenging potential. The MZFP when extracted with 70% ethanol, at 50 °C for 12 h, showed higher DPPH (IC50 = 0.34 and 88.42% inhibition at 1 mg/ml) and H2O2 (IC50 = 32.69 and 65.78% inhibition at 50 μg/ml) radical scavenging potential than absolute and 40% ethanolic extracts, when ascorbic acid was used as a reference standard. While further evaluation for in vitro α-glucosidase enzyme inhibition, 70% ethanolic MZFP extract demonstrated high inhibition activity (IC50 = 104.23 ± 1.75 μg/ml) than absolute ethanolic extract (IC50 = 111.65 ± 1.57 μg/ml) with a significant difference (p < 0.05), when acarbose was taken as reference inhibitor (IC50 = 86.93 ± 0.74 μg/ml). Conclusions Overall results indicated that MZFP 70% ethanolic extract exhibited promising in vitro radical scavenging and α-glucosidase enzyme inhibition potential. Thus, suggesting further studies with isolated phytochemicals from peel to explore its potentials for antidiabetic activity through in vitro α-glucosidase enzyme inhibition.

Background A perusal of the literature suggested that Manilkara zapota (L.) P. Royen stem bark (MZSB) is enriched with several bioactive phytoconstituents but had not been yet screened for its in vitro and in vivo antidiabetic potentials. Thus, the present study aimed to investigate the effects of 70% ethanolic extract of Manilkara zapota (L) P. Royen stem bark (EMZSB) in DPPH- and H2O2-scavenging assay, in vitro α-glucosidase inhibition assay, ameliorating diabetes and its complications in alloxan-induced diabetes in Wistar rats. Results With a maximum extractive yield of 9.16% w/w, EMZSB has shown the presence of various phytochemicals like flavonoids, phenolic compounds, tannins, anthraquinone glycosides, steroids, terpenoids, and alkaloids. EMZSB has elucidated a considerable in vitro free radical scavenging potential by DPPH and H2O2 assays when compared with absolute ethanolic extract of Manilkara zapota (L) P. Royen stem bark (AEMZSB), while ascorbic acid was taken as the standard. Further, EMZSB demonstrated high in vitro α-glucosidase enzyme inhibition potential (IC50 = 119.79 ± 1.52 µg/mL) than AEMZSB (IC50 = 129.92 ± 2.29 µg/mL) with a significant difference (p < 0.01), when acarbose was taken as reference inhibitor (IC50 = 86.43 ± 1.26 µg/mL). During acute toxicity studies EMZSB was safe up to 2000 mg kg−1 doses while, found causing moribund status followed by mortality in mice at 3000 mg kg−1 and above doses. A preliminary antidiabetic study with EMZSB-250 mg kg−1 in normal rats showed no sign of hypoglycemia; however, a dose-dependent antihyperglycemic effects were observed in oral glucose tolerance test in glucose-loaded rats. In vivo assessment with EMZSB-250 mg kg−1 in alloxan-induced rats demonstrated significant blood glucose-lowering effects with perfection in serum lipid profile, body weight enhancement, cardiovascular risk indices, nephroprotective effects, augmentation in liver glycogen content, and histopathological evidence of normal architecture of kidneys with no marks for nephritis. Conclusions EMZSB-250 showed significant antidiabetic effects and ameliorated diabetic complications by improving glycemic control and accompanying biochemical alteration.

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