Antidiabetic Properties of a Spice Plant Nigella sativa

Seeds of Nigella sativa (black cumin/kalonji) used in pickles as spice, have also been traditionally used in treatment of many diseases including diabetes and hypertension. Among many activities exhibited by N. sativa and its constituents in animal experiments, antidiabetic property is most important. Thymoquinone (TQ), a volatile oil, is one of its active constituents but antidiabetic activity has also been shown by its aqueous extract and defatted extract. N. sativa may be beneficial in diabetic individuals and those with glucose intolerance as it reduces appetite, glucose absorption in intestine, hepatic gluconeogenesis, blood glucose level, cholesterol, triglycerides, body weight and simulates glucose induced secretion of insulin from beta-cells in pancreas; improves glucose tolerance as efficiently as metformin; yet it has not shown significant adverse effects and has very low toxicity. In streptozotocin (STZ) induced diabetic rats it causes gradual partial regeneration of pancreatic beta-cells, increases the lowered serum insulin concentrations and decreases the elevated serum glucose. N. sativa has antioxidant activity and protective role of TQ against development of type I diabetes may be via NO inhibitory pathway. It also exerts an insulin-sensitizing action in hepatocytes. Seeds of N. sativa have been safely consumed by human patients in many clinical trials which however were not aimed to assess its antidiabetic activity. In future clinical studies may show potential of N. sativa, its constituents or their synthetic analogues, in prevention and control of diabetes.