In vitro studies of eggplant (Solanum melongena) phenolics as inhibitors of key enzymes relevant for type 2 diabetes and hypertension.
ABSTRACT National Diabetes Education Program of NIH, Mayo Clinic and American Diabetes Association recommend eggplant-based diet as a choice for management of type 2 diabetes. The rationale for this suggestion is the high fiber and low soluble carbohydrate content of eggplant. We propose that a more physiologically relevant explanation lies in the phenolic-linked antioxidant activity and alpha-glucosidase inhibitory potential of eggplant which could reduce hyperglycemia-induced pathogenesis. Results from this study indicate that phenolic-enriched extracts of eggplant with moderate free radical scavenging-linked antioxidant activity had high alpha-glucosidase inhibitory activity and in specific cases moderate to high angiotensin I-converting enzyme (ACE) inhibitory activity. Inhibition of these enzymes provide a strong biochemical basis for management of type 2 diabetes by controlling glucose absorption and reducing associated hypertension, respectively. This phenolic antioxidant-enriched dietary strategy also has the potential to reduce hyperglycemia-induced pathogenesis linked to cellular oxidation stress. These results provide strong rationale for further animal and clinical studies.
Journal of Functional Foods 04/2013; 5(2):981-986. DOI:10.1016/j.jff.2013.01.008 · 4.48 Impact Factor
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ABSTRACT: Aqueous extracts of Highbush blueberries grown in New Zealand were investigated for their total phenolic concentration, antioxidant activity and potential to contribute to the dietary management of type II diabetes. There were significant differences (P < 0.05) between blueberry genotypes for these measurements. ‘Elliott’ had the highest total phenolic concentration (2.24 mg gallic acid equivalent/g frozen berries). Across all eight varieties, ‘Burlington’ showed the highest antioxidant capacity as determined by ferric reducing antioxidant power (2.52 mg FeSO4 equivalent/g frozen berries) and 2,2′-diphenyl-1-picrylhydrazyl assay (IC50 = 3.41 mg/mL). Most blueberry extracts inhibited α-amylase and α-glucosidase activity in vitro, with ‘Bluecrop’ and ‘Jersey’ having the highest inhibitory activity for both enzymes. There were no significant correlations between enzyme inhibitory activities and total phenolic concentration or antioxidant capacities across all genotypes, suggesting that such inhibitory activity was influenced by some particular phytochemicals in blueberries. Of the eight genotypes tested, ‘Bluecrop’ and ‘Burlington’ may be potential candidates for early management of hyperglycemia.Practical ApplicationsBlueberries (Vaccinium spp.) are commonly available in New Zealand. In addition, various members of this species have been reported to be used as a traditional medicine for diabetic treatment for many years. In the present study, the ability of New Zealand Highbush blueberries to inhibit carbohydrate hydrolyzing enzymes (α-amylase and α-glucosidase) was explored in relationship to their phenolic content and antioxidant activity. All aqueous extracts tested exhibited the capacity to inhibit pancreatic α-amylase and yeast α-glucosidase enzymes in vitro and these beneficial effects appear to be due to some specific bioactive compounds in blueberries, in particular glucosylated anthocyanins. Our preliminary observation provides a rationale for further animal and clinical studies of a possible use of blueberry for the management of hyperglycemia.Journal of Food Biochemistry 02/2015; 39(1). DOI:10.1111/jfbc.12094 · 0.85 Impact Factor