Insulin-releasing and insulin-like activity of the traditional anti-diabetic plant Coriandrum sativum (coriander)

Coriandrum sativum (coriander) has been documented as a traditional treatme nt of diabetes. In the present study, coriander incorporated into the diet (62.5g/kg) and drinking water (2.5 g/l, prepared by 15min decoction) reduce d hyperglycaemia of streptozotocin-diabetic mice. An aqueous extract of cor iander (1 mg/ml) increased 2-deoxyglucose transport (1.6-fold), glucose oxi dation (1.4-fold) and incorporation of glucose into glycogen (1.7-fold) of isolated murine abdominal muscle comparable with 10(-8) M-insulin. In acute 20 min tests, 0.25-10 mg/ml aqueous extract of coriander evoked a stepwise 1.3-5.7-fold stimulation of insulin secretion from a clonal B-cell line. T his effect was abolished by 0.5 mM-diazoxide and prior exposure to extract did not alter subsequent stimulation of insulin secretion by 10 mM-L-alanin e, thereby negating an effect due to detrimental cell damage. The effect of extract was potentiated by 16.7 mM-glucose and 10 mM-L-alanine but not by 1 mM-3-isobutyl-1-methylxanthine. Insulin secretion by hyperpolarized B-cel ls (16.7 mM-glucose, 25mM-KCl) was further enhanced by the presence of extr act. Activity of the extract was found to be heat stable, acetone soluble a nd unaltered by overnight exposure to acid (0.1 M-HCl) or dialysis to remov e components with molecular mass < 2000 Da. Activity was reduced by overnig ht exposure to alkali (0.1 M-NaOH). Sequential extraction with solvents rev ealed insulin-releasing activity in hexane and water fractions indicating a possible cumulative effect of more than one extract constituent. These res ults demonstrate the presence of antihyperglycaemic, insulin-releasing and insulin-like activity in Coriandrum sativum.