Journal of Ethnopharmacology 67 (1999) 367 – 372 Short communication A comparative evaluation of some blood sugar lowering agents of plant origin R.R. Chattopadhyay Biometry Research Unit, Indian Statistical Institute, 203, Barrackpore Trunk Road, Calcutta -700 035, India Received 15 January 1998; received in revised form 11 May 1999; accepted 17 May 1999 Abstract A comparison of blood sugar lowering activity of four important medicinal plants (Azadirachta indica, Gymnema sylestre, Catharanthus roseus and Ocimum sanctum) were carried out against normal and streptozotocin-induced diabetic rat models. The plant extracts decreased the blood sugar level in varying degrees. Blood sugar lowering unit (BLU) of activity of each leaf extract and tolbutamide was calculated by ED 50 values. Statistical analysis revealed significant (P 0.05) variation among the treatments as well as doses with regard to their blood sugar lowering capacity. A. indica leaf extract was found to have the most potent blood sugar-lowering activity followed by C. roseus, G. sylestre and O. sanctum. © 1999 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Blood sugar lowering activity; Azadirachta indica ; Gymnema sylestre ; Catharanthus roseus ; Ocimum sanctum; Compara- tive study www.elsevier.com/locate/jethpharm 1. Introduction Various types of antidiabetic drugs are avail- able in the market for the treatment of diabetes mellitus, but none can be termed as an ideal one, due to their toxic side effects and, sometimes, diminution in response after prolonged use. Hence a search for herbal antidiabetic agents has been initiated. The plants Azadirachta indica A Juss. (Meliaceae, Neem), Ocimum sanctum Linn. (Labiatae, Tulsi), Gymnema sylestre, R. Br. (As- clepiadaceae; Meshasringi) and Catharanthus roseus (L.) G. Don (Apocynaeceae; Nayantara) have been commonly used to treat diabetes in the Indian system of medicine from time immemorial (Kirtikar and Basu, 1933; Chopra et al., 1956). Preliminary studies revealed that the hydroalco- holic extract of the leaves of these plants pos- sessed significant blood sugar lowering activity in normal, glucose fed hyperglycemic, exogenous in- sulin treated and streptozotocin induced diabetic rats (Chattopadhyay et al., 1987a, 1991; Chatto- padhyay, 1993; Chattopadhyay et al., 1993a). The further effect of each leaf extract on glucose up- take and glycogen deposition by isolated rat hemidiaphragm revealed their strong blood sugar- 0378-8741/99/$ - see front matter © 1999 Elsevier Science Ireland Ltd. All rights reserved. PII:S0378-8741(99)00095-1