This study compared dipeptidyl peptidase-4 (DPP-4) inhibitory activity of citrus bioflavonoid nutraceuticals compared with three gliptins. Citrus bioflavonoid standards and three commercially available citrus bioflavonoid supplements (Thompson's Super Bioflavonoid Complex^®(SB), Ethical Nutrients Bioflavonoids Plus Vitamin C^®(EN), and Country Life Citrus Bioflavonoids and Rutin^®(CB)) were considered in this study. Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis was undertaken to identify and quantitate the citrus bioflavonoids present in each supplement. The DPP-4 inhibitory activity was determined by fluorometric assay. All of the tested individual citrus flavonoids demonstrated DPP-4 inhibitory activity, with IC₅₀ values ranging from 485 μM (rutin) to 5700 μM (hesperitin and eriodictyol). Similarly, the flavonoid supplements had IC₅₀ values of 16.9 mg/mL (EN), 3.44 mg/mL (SB) and 2.72 mg/mL (CB). These values compare with gliptin IC₅₀ values of 0.684 μM (sitagliptin), 0.707 μM (saxagliptin) and 2.286 μM (vildagliptin). The supplement flavonoid content varied from 11.98% (CB) to 5.26% (EN) and 14.51% (SB) of tablet mass, corresponding to daily flavonoid doses of around 300, 150 and 400 mg, respectively, with CB and SB containing rutin at levels of 7.0% and 7.5% of tablet mass, respectively. While our data demonstrated that citrus bioflavonoid based supplements do possess DPP-4 inhibitory activity, they are several orders of magnitude less potent than gliptins. Further studies using higher concentrations of citrus bioflavonoids, as well as investigations into antioxidant properties which may add additional benefit are warranted.

Item Type:	Refereed Article
Keywords:	flavonoid, DDP-4, citrus, gliptin, ultra performance liquid chromatography, DPP-4 inhibitory assay, dipeptidyl peptidase-4
Research Division:	Biomedical and Clinical Sciences
Research Group:	Pharmacology and pharmaceutical sciences
Research Field:	Pharmaceutical sciences
Objective Division:	Health
Objective Group:	Other health
Objective Field:	Other health not elsewhere classified
UTAS Author:	Gupta, A (Mr Ankit Gupta)
UTAS Author:	Jacobson, GA (Professor Glenn Jacobson)
UTAS Author:	Burgess, JR (Professor John Burgess)
UTAS Author:	Nichols, DS (Dr David Nichols)
UTAS Author:	Narkowicz, CK (Dr Christian Narkowicz)
UTAS Author:	Al-Aubaidy, HA (Dr Hayder Al-Aubaidy)
ID Code:	126974
Year Published:	2018
Web of Science® Times Cited:	17
Deposited By:	Pharmacy
Deposited On:	2018-07-05
Last Modified:	2019-04-10
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