Indian culinary plants enhance glucose-induced insulin secretion and glucose consumption in INS-1 β-cells and 3T3-L1 adipocytes

Six Indian plants, commonly used as culinary plants, herbs or spices (kikar; jamun; neem; harad; fenugreek; bitter gourd), were screened and compared for their antidiabetic potential in vitro. Aqueous plant extracts were prepared and assessed for their effect on the insulin secretion activity of rat pancreatic INS-1 β-cells and glucose consumption in mouse 3T3-L1 adipocytes in order to study their specific mechanisms of action. The effect of the plant extract concentration (25–1000 μg/ml) on insulin release and glucose consumption was also studied. All the extracts had a significant stimulatory effect on the insulin secretion of INS-1 cells. In the presence of kikar extract (100 μg/ml), an increase of 228% in insulin release was recorded compared to the control (5.6 mM glucose) whereas that was 270% and 367% in the presence of kikar and jamun extracts (500 μg/ml), respectively. 3T3-L1 cells treated with jamun extract (100 μg/ml) exhibited the highest increase in glucose consumption by the cells (94%, compared with the control) followed by harad (53%) and fenugreek (50%) extracts. A significant inhibitory effect of the fenugreek, kikar and jamun extracts on glucose diffusion across a dialysis membrane suggested that these extracts could partly act by decreasing glucose absorption in the small intestine. The results showed that a combination of these plants in diet could help in the management of both type 1 and type 2 diabetes.