Table 3.
Protective effects of flavonoids against diabetic complications—clinical evidence.
| Flavonoid name | Administration, Dosage form | Experimental design | Treatment | Duration | Results | References | |
|---|---|---|---|---|---|---|---|
| Upregulation | Downregulation | ||||||
| Hesperetin | Oral, dietary supplement | Double-blind RCT in 31 patients with T2DM | 1 capsule daily (each contains 500 mg hesperetin) | 6 weeks | Increased the serum TAC | Greater reduction in the percent change of SBP, DBP, mean arterial BP and inflammatory markers (TNF-α, IL-6, and hs-CRP) in Hesperidin group comparing to the control group | (68) |
| ECGC | Oral, dietary supplement | Double-blind, RCT in 50 patients with T2DM | Each capsule contains 150 mg, twice daily | 8 weeks | 1. Decreased levels of FBG 2. Reduced levels of hs-CRP | (69) | |
| Anthocyanins | Oral, freeze-dried blueberries | Double-blind, parallel RCT in 52 patients with T2DM | 22 g with 11 g taken with each of breakfast and evening meals along with typical diet | 8 weeks | 1. Reduction in the levels of HbA1c and fructosamine 2. Reduced levels of serum TC, LDL-C and triglycerides | (70) | |
| Silymarin | Oral, tablets (each contain 140 mg of silymarin) | Double-blind, 2-arm parallel RCT in 30 patients with T2DM and diabetic nephropathy | 3 × 140 mg silymarin | 3 months | 1. Higher decrement of UACR in the silymarin group than placebo group 2. Decreased urinary levels of TNF-α and urinary and serum levels of MDA | (71) | |
| Flavones/flavonols, flavanones/dihydroflavonols, and phenolic compounds | Oral, Iranian propolis capsules (each contains 500 mg of propolis) | Double-blind RCT in 50 patients with T2DM | 2 × 500 mg daily | 90 days | Increased level of HDL-C | 1. Reduction in HbA1C and insulin 2. Decreased levels of IL1-β, hs-CRP and TNF-α 3. Reduction in the blood urea nitrogen | (72) |
| Diosmin, Centella asiatica and Melilotus officinalis | Oral, dietary supplement | RCT with 35 patients with T2DM and diabetic CME | 1 pill daily (containing 300 mg of diosmin, 15 mg of Centella asiatica and 160 mg of Melilotus officinalis) | 36 months | A greater retinal sensitivity was present at month 12, 24, and 36 compared to the placebo group | (73) | |
RCT, randomized controlled trial; T2DM, type-2 diabetes mellitus; SBP, systolic blood pressure; DBP, diastolic blood pressure; BP, blood pressure; TNF-α, Tumor Necrosis Factor alpha; IL-6, interleukin-6; hs-CRP, high-sensitivity C-reactive protein P; ECGC, epigallocatechin-3-gallate; FBG, fasting blood glucose; HbA1C, glycosylated hemoglobin A1C; TC, total cholesterol; LDL-C, low-density lipoprotein cholesterol; UACR, Urinary albumin-creatinine ratio; MDA, malondialdehyde; HDL-C, high-density lipoprotein cholesterol; IL-1β, interleukin-1β; CME, cystoid macular edema.