The positive glycation inhibitory and antioxidative activities of these tropical herbs suggest a possible role in targeting ageing, diabetic complications and oxidative stress related diseases.
In this study, seven exotic/indigenous medicinal plants of Mauritius, namely Coix lacryma-jobi (Poaceae), Aegle marmelos (Rutaceae), Artocarpus heterophyllus (Moraceae), Vangueria madagascariensis (Rubiaceae), Azadirachta indica (Meliaceae), Eriobotrya japonica (Rosaceae) and Syzigium cumini (Myrtaceae) were studied for possible effects on starch breakdown by alpha-amylase in vitro. The results showed that only Artocarpus heterophyllus significantly (p < 0.05) inhibited alpha-amylase activity in vitro. To confirm the observed effects, a further biochemical assay was undertaken to investigate the effects of Artocarpus heterophyllus on alpha-amylase activity using rat plasma in vitro. It was found that the aqueous leaf extract significantly (p < 0.05) inhibited alpha-amylase activity in rat plasma. The highest inhibitory activity (27.20 +/- 5.00%) was observed at a concentration of 1000 microg/mL. However, in both cases dose dependency was not observed. Enzyme kinetic studies using the Michaelis-Menten and Lineweaver-Burk equations were performed to establish the type of inhibition involved. In the presence of the plant extract the maximal velocity (Vmax) remained constant (1/150 g / L/s) whereas the Michaelis-Menten constant (Km) increased by 5.79 g / L, indicating that the aqueous leaf extract of Artocarpus heterophyllus behaved as a competitive inhibitor. Results from the present study tend to indicate that Artocarpus heterophyllus could act as a 'starch blocker' thereby reducing post-prandial glucose peaks.
Five traditionally used antidiabetic native medicinal plants of Mauritius, namely, Stillingia lineata (SL), Faujasiopsis flexuosa (FF), Erythroxylum laurifolium (EL), Elaeodendron orientale (EO), and Antidesma madagascariensis (AM), were studied for possible α-amylase and α-glucosidase inhibitory property, glucose entrapment, and amylolysis kinetics in vitro. Only methanolic extracts of EL, EO, and AM (7472.92 ± 5.99, 1745.58 ± 31.66, and 2222.96 ± 13.69 μg/mL, resp.) were found to significantly (P < 0.05) inhibit α-amylase and were comparable to acarbose. EL, EO, AM, and SL extracts (5000 μg/mL) were found to significantly (P < 0.05) inhibit α-glucosidase (between 87.41 ± 3.31 and 96.87 ± 1.37% inhibition). Enzyme kinetic studies showed an uncompetitive and mixed type of inhibition. Extracts showed significant (P < 0.05) glucose entrapment capacities (8 to 29% glucose diffusion retardation index (GDRI)), with SL being more active (29% GDRI) and showing concentration-dependent activity (29, 26, 21, 14, and 5%, resp.). Amylolysis kinetic studies showed that methanolic extracts were more potent inhibitors of α-amylase compared to aqueous extracts and possessed glucose entrapment properties. Our findings tend to provide justification for the hypoglycaemic action of these medicinal plants which has opened novel avenues for the development of new phytopharmaceuticals geared towards diabetes management.
PurposeThis article focuses on some of the reported medicinal values of bitter melon, an exotic vegetable forming part of the cuisine of various countries.Design/methodology/approachAvailable data in the literature strongly support the anti‐hypoglycaemic properties of Bitter melon. A literature view was carried out and the data were used to validate our findings regarding the effects of extracts of Momordica charantia on uptake of sugar.FindingsOur work adds on to the growing evidence of the anti‐diabetic properties of bitter melon.Practical implicationsIn view of evidence reported in the literature regarding the medicinal properties of vegetables, the importance of vegetables in a well balanced diet should therefore be strongly advocated.Originality/valueThis paper adds on to the evidence of the use of Momordica charantia as a medicinal plant in traditional medicine in the control of blood sugar level.
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