Table 1.

Clinical trials of antidiabetic flavonoids.

Molecules	Models	Experiment	Doses/Periods	Key findings	Authors
Resveratrol	19 T2D patients	A randomized study Double-blind trial (Phase III)	2 × 5 mg/day 4 weeks	Decreased insulin resistance Improved insulin sensitivity	[30]
	62 patients with T2D	A prospective, open-label, randomized, controlled trial	250 mg/day 3 months	Normalized glycaemia and HbA1c levels	[31]
	Non-obese postmenopausal women	A randomized, double-blind, placebo-controlled trial	75 mg/day 12 weeks	Increased resveratrol plasma concentration No effect on insulin sensitivity	[32]
	66 patients with type 2 diabetes mellitus (T2DM)	A randomized placebo-controlled double-blinded parallel clinical trial	1 g/day 45 days	Lowered fasting glycaemia levels, HbA1c, and resistance to insulin	[33]
	12 participants with metabolic syndrome (MetS)	A randomized, double-blind, placebo-controlled clinical trial	500 mg 3 times a day 90 days	Decreased insulin AUC Decreased total insulin secretion	[34]
	8 overweight and sedentary men		A single dose (300 mg) on two separate occasions	Attenuated post-absorption insulin concentrations No changes in insulin signaling	[35]
	60 non-alcoholic subjects with fatty liver disease (FLD)	A double-blind, randomized, placebo-controlled clinical study	2,15 g (twice daily) 3 months	Improved levels of glycaemia, LDL cholesterol, and total cholesterol	[36]
	14 patients with T2D	A double-blind, randomized, crossover design	500 mg (twice daily) 5 weeks	No effect on postprandial and fasting glycaemia, or HbA1c	[37]
	34 subjects suffering from polycystic ovary syndrome	A randomized double-blind, placebo-controlled trial	1500 mg/day 3 months	Lowered fasting insulin content (31.8 %) Augmented insulin sensitivity index (66.3 %)	[38]
	38 obese and overweight subjects	A randomized double-blind study	Resveratrol (80 mg/day) EGCG (282 mg/day) 12 weeks	No impact on insulin-stimulated glucose disposal	[39]
	17 subjects with T2D	A randomized double-blind crossover study	150 mg/day 30 days	No improvement in insulin sensitivity	[40]
	Middle-aged men suffering from metabolic syndrome	A randomized, placebo-controlled, double-blind, parallel group clinical trial	150 and 1000 mg/day 16 weeks	No improvement in glucose homeostasis	[41]
	45 overweight or slightly obese volunteers	A Randomized placebo-controlled trial	150 mg/day 4 weeks	No effect on insulin and plasma glucose levels	[42]
	13 men with T2D	A randomized, placebo controlled, cross-over trial	150 mg/day 1 month	No effect on insulin sensitivity	[43]
	472 elderly diabetic patients	A single-blind randomized controlled clinical trial	500 mg/day 6 months	Improvemed insulin resistance Improvemed blood glucose parameters (decreased G6Pase and HbA1c)	[44]
	110 diabetic patients	A randomized, placebo-controlled trial	200 mg/day 24 weeks	Improved blood glucose as well as insulin synthesis and resistance levels	[45]
Catechin	T2D patients not receiving insulin The participants ingested green tea containing either 582.8 mg of catechins (catechin group; n = 23) or 96.3 mg of catechins (control group; n = 20) per day	A double-blind controlled study	582.8 and 96.3 mg per day 12 weeks	Augmented insulin and adiponectin production No effect on glucose and HbA1c	[46]
	Healthy postmenopausal women (Phase III)		615 mg/350 mL per day 4 weeks	Improved redox homeostasis Improved postprandial glycemic status	[47]
Rutin	50 participants suffering from T2DM	A double blind, placebo-controlled trial	500 mg/day 3 months	Lowered the levels of fasting glycaemia, insulin, insulin resistance, and HbA1c	[48]
	34 healthy adult participants	A randomized, placebo-controlled, double blind crossover study	200 mg/day 3 weeks	Lowered postprandial glycaemia levels	[49]
Epicatechin	37 healthy women and men	A randomized, double-blind, placebo-controlled study	100 mg/day 4 weeks	Improved insulin resistance Enhanced fasting plasma insulin	[50]
	Erythrocyte membrane AChE in normal and type 2 diabetic patients		–	Pronounced insulin-like effect	[51]
Quercetin	37 healthy women and men	A randomized, double-blind, placebo-controlled study	160 mg/day 4 weeks	No impact on insulin resistance	[50]
Hesperidin and Diosmin	127 diabetic patients with neuropathy and MetS	A randomized controlled trial	1 g/day (for each) 12 weeks	Improved glycaemia, LDL, and triglyceride rates Increased magnitude of enhancement when the two molecules are combined	[52]