Table 2.
List of medicinal herbs affecting the absorption of carbohydrates from the gastrointestinal environment by inhibiting α-glucosidase and α-amylase.
| Herb | Botanical name | Part used | Type of extract | Chemical constituent | Animal model | Outcome (effects) |
|---|---|---|---|---|---|---|
| Leafflower | Phyllanthus urinaria | Leaves | 50% aqueous methanolic extract | Corilagin, gallic acid and macatannin B | – | Corilagin, gallic acid and macatannin B demonstrated low inhibitory activity against amylase (21%, 23% and 33% respectively in 1 mmol.L−1 concentration) |
| Cinnamon | Cinnamomum zeylanicum | Bark | Methanol extract | Tannins, flavonoids, glycosides, terpenoids, coumarins and anthraquinones | STZ-induced diabetic rats |
In vitro: Inhibition of yeast and mammalian α-glucosidase (IC50 = 5.83 μg ml−1 & 670 μg ml−1 respectively) In vivo: Decreased postprandial hyperglycemia by 78.2% and 52.0% compared to normal rats |
| Black seed | Nigella sativa | Seeds | Aqueous extract | Flavonoids, unsaturated fatty acids, nigellone, thymoquinone (TQ), p-cymene and carvone | – |
In vitro: Inhibition of sodium-dependent glucose transport In vivo: Chronic treatment improved glucose tolerance and reduced body weight similarly as metformin |
| China aster | Callistephus chinensis | Flower | 70 % ethanol extract | Apigenin, apigenin-7-O-β-D- glucoside, hyperin, kaempferol, kaempferol-7-O-β-D- glucoside, luteolin, naringenin and quercetin | – | Inhibition of α-glucosidase by quercetin (IC50 = 2.04 μg ml−1) comparable to that of acarbose (IC50 = 2.24 μg ml−1) |
| Basil | Ocimum basilicum | Leaves | Aqueous extract | Cardiac glycosides, flavonoids, glycosides, reducing sugars, saponins, steroids and tannins | – | Inhibition of α-amylase: rat intestinal maltase and sucrase, porcine pancreatic amylase (IC50 = 21.31 mg ml−1, 36.72 mg ml−1 & 42.50 mg ml−1 respectively) |
| Jute | Corchorus olitorius | Leaves | Free & bound extracts | Caffeic acid, chlorogenic acid and isorhamnetin | – | Inhibition of α-amylase, α-glucosidase & ACE (IC50 = 17.5 μg mL−1, 11.4 μg mL−1 & 15.7 μg mL−1, respectively) |
| Mistletoe fig | Ficus deltoidea | (a) Leaves (b) Flowers |
(a) Ethanolic, methanolic extracts (b) Crude extracts |
Vitexin, isovitexin, proanthocyanidin, flavonoids, 3-flavanol monomers and flavones glycosides | STZ-induced diabetic rats |
In vitro: Inhibition on α-glucosidases and improvement on basal and insulin-mediated glucose uptake into adipocytes cells In vivo: Reduction in the postprandial blood glucose level by 19.7% with 200 mg kg−1 & 100 mg kg−1 of vitexin & isovitexin respectively |
| Bitter oleander | Holarrhena antidysenterica | Seeds | Hydro-methanolic (2:3) extract | Gallic acid and quercetin | Starch loaded normoglycemic rats |
In vitro: Inhibition of α-glucosidase (IC50 = 0.52 mg ml−1) In vivo: Decreased postprandial hyperglycemia |
| Olive | Olea europaea L | Leaves | Alcoholic extract | Oleuropein, hydroxytyrosol, oleuropein aglycone, and tyrosol |
In vivo: STZ-induced diabetic rats RCT: Type II DM patients |
In vivo: Reduction in starch digestion and absorption RCT: Lower HbA1c (8.0%–1.5% vs. 8.9%–2.25% in placebo) and fasting plasma insulin levels (11.3–4.5 vs. 13.7–4.1 in placebo) |
| Soybean | Glycine max (L.) Merrill | Soybean | Free and bound phenolic extracts | Phenolic compounds | – | Inhibition of α-amylase, α-glucosidase & ACE |