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This study demonstrates the Dipeptidyl peprtidase-4 (DPP-4) inhibition activity of citrus bioflavonoid nutraceuticals as compared to known gliptins. Citrus bioflavonoid standards and three commercially available citrus bioflavonoid supplements (Thompson's Super Bioflavonoid Complex (SB), Ethical Nutrient Citrus Plus Vitamin C (EN), and Country Life Citrus Bioflavonoid & Rutin (CB)) were considered in this study. Ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) analysis was undertaken to identify the citrus bioflavonoids present in each supplement and the DPP-4 inhibitory activity was determined using the DPP-4 fluorometric assay. The UPLC-MS showed the retention time of standards eriocitrin 3.67 min, naringin 4.53 min, hesperidin 4.71 min, eriodictyol 5.87 min, naringenin 6.91 min, hesperetin 7.15 min. The DPP-4 inhibition of SB showed the best possible inhibition which was 99% in response to other supplements, while the DPP-4 inhibition with reference compounds and a starting concentration of 10 mg/ml was best shown for sitagliptin at 91% and vildagliptin at 91%. The citrus bioflavonoids standards were also tested for DPP-4 inhibition. Eriocitrin showed the maximum inhibition at 97%. Our data demonstrated that citrus bioflavonoids based supplements do possess DPP-4 inhibition activity. The SB had the highest activity. In particular, the naringin and hesperidin compounds have the best individual activity in comparison to that of the gliptins. Natural gliptin-like alternatives may make these supplements a promising group of natural products for use in improving blood glucose levels in prediabetes and early stages of type 2 diabetes.
PMID: 29698678 [PubMed - as supplied by publisher]