Gorelick, J., Judea Regional Research and Development Center, Kiryat Arba, Israel
Rosenberg, R., Institute of Soil Water and Environmental Sciences, Volcani Center, POB 6, 50-250, Israel
Smotrich, A., Judea Regional Research and Development Center, Kiryat Arba, Israel
Hanuš, L., Institute for Drug Research, Hebrew University Medical Faculty, Jerusalem 91120, Israel
Bernstein, N., Institute of Soil Water and Environmental Sciences, Volcani Center, POB 6, 50-250, Israel
Jonathan, G., Judea Regional Research and Development Center, Kiryat Arba, Israel
Rivka, R., Institute of Soil Water and Environmental Sciences, Volcani Center, POB 6, Israel
Avinoam, S., Judea Regional Research and Development Center, Kiryat Arba, Israel
Lumír, H., Institute for Drug Research, Hebrew University Medical Faculty, Jerusalem, Israel
Nirit, B., Institute of Soil Water and Environmental Sciences, Volcani Center, POB 6, Israel

Withania somnifera, known in India as Asghawhanda, is used traditionally to treat many medical problems including diabetes and has demonstrated therapeutic activity in various animal models as well as in diabetic patients. While much of W. somnifera's therapeutic activity is attributed to withanolides, their role in the anti-diabetic activity of W. somnifera has not been adequately studied. In the present study, we evaluated the anti-diabetic activity of W. somnifera extract and purified withanolides, as well as the effect of various elicitors on this activity. W. somnifera leaf and root extracts increased glucose uptake in myotubes and adipocytes in a dose dependent manner, with the leaf extract more active than the root extract. Leaf but not root extract increased insulin secretion in basal pancreatic beta cells but not in stimulated cells. Six withanolides isolated from W. somnifera were tested for anti-diabetic activity based on glucose uptake in skeletal myotubes. Withaferin A was found to increase glucose uptake, with 10. μM producing a 54% increase compared with control, suggesting that withaferin A is at least partially responsible for W. somnifera's anti-diabetic activity. Elicitors applied to the root growing solutions affected the physiological state of the plants, altering membrane leakage or osmotic potential. Methyl salicylate and chitosan increased withaferin A content by 75% and 69% respectively, and extracts from elicited plants increased glucose uptake to a higher extent than non-elicited plants, demonstrating a correlation between increased content of withaferin A and anti-diabetic activity. © 2015 Elsevier Ltd.