[Mechanisms of action of acetonic and hexanic extracts of leaves of Vernonia colorata (Willd.) Drake (Composeae) on blod glucose regulation]. / Mecanismes d'action des extraits acetonique et hexanique de feuilles de Vernonia colorata dans la regulation de la glycemie.

INTRODUCTION: This study aimed to investigate the mechanism of action of acetonic and hexanic extracts of the leaves of Vernonia colorata on blood glucose regulation. MATERIALS AND METHODS: Experiments were performed in normoglycaemic, type 1 and 2 diabetic rats. The effects of acetonic and hexanic extracts on blood glucose were evaluated. The antagonism effect of hexanic extract on the decrease of blood glucose induced with glibenclamide and metformin was also tested. RESULTS: The hexanic extract of the leaves of V. colorata (HELVC) dose dependently increased the blood glucose in normoglycaemic rats. At the dose of 30 and 100 mg/kg, the glycaemia varied from 0.84 +/- 0.02 to 1.11 +/- 0.10 g/l and 0.68 +/- 0.02 to 1.31 +/- 0.30 g/l (p<0.05, n = 5). Such glibenclamide, the acetonic extract of the leaves of V. colorata (AELVC) induced hypoglycaemia in normoglycaemic rats. The HELVC prevents significantly the AELVC and glibenclamide induced hypoglycaemia. The chronic administration of the AELVC and HELVC as well as glibenclamide in type 1 diabetic rats did not change significantly the level of blood glucose. In type 2 diabetic rats, the single dose administration of metformin (300 mg/kg, per os) decreased the glycaemia which is completely prevented by a HELVC pretreatment. CONCLUSION: These results suggest that: i) The respective hypo- and hyperglycaemic effects of AELVC and HELVC require the presence of the pancreatic beta cells. ii) The AELVC would act by a sulfonylurea-like mechanism as glibenclamide to induce an hypoglycaemic effect.

[Healing activity of methanolic extract of the barks of Spathodea campanulata Beauv (Bignoniaceae) in rat experimental burn model]. / Activite cicatrisante de l'extrait methanolique des ecorces de Spathodea campanulata Beauv (Bagnoniaceae) sur un modele de brulures experimentales chez le rat.

Spathodea campanulata Beauv. (Bignoniaceae) is widely distributed through Africa and found in particular in Cameroon and Senegal. It is used in traditional herbal medicine for the treatment of ulcers, filaria, gonorrhea, diarrhea and fever. S. campanulata was also known in Cameroon traditional medicine to have a healing activity in burn wounds. The aim of the present study was to assess the burn healing effectiveness of the methanolic extract of the barks of S. campanulata ointment (MEBSCO) in comparison to those of Centella asiatica and Peru's balm in experimental burn model in rats. Experimental burn was made in rat under chloral anaesthesia with electric iron (200 degrees C) on the right and left side of the medianus line. Topical applications of MEBSCO (2%, 10% and 49%) dose-dependently decreased the score damage of the burn site. Treatment with 10% and 49% of MEBSCO varied the score damage from 5 to 1 +/- 0.4 and 5 to 0.2 +/- 0.5 (p < 0.05, n = 5) respectively, at day 15 after experimental burn. As well as C. asiatica (1%) and Peru's balm (1%) ointments, MEBSCO (10% and 49%) induced a complete burn healing on the 19-20th post burn day. This study shows for the first time, the burn healing effectiveness of MEBSCO in experimental burn model. It also provides a rational use of the S. campanulata barks in traditional medicine to promote burn healing.

Hypoglycaemic and antidiabetic activity of acetonic extract of Vernonia colorata leaves in normoglycaemic and alloxan-induced diabetic rats.

The aqueous extract of Vernonia colorata (Willd.) Drake (Composeae) leaves is used by African traditional medicine practitioners as a remedy for the treatment of diabetes. Our previous studies have shown the hypoglycaemic activity of the aqueous extract of Vernonia colorata leaves (300 mg/kg, per os) in normoglycaemic rats. The aim of the present study was to investigate the hypoglycaemic and antidiabetic activity of acetonic and hexanic extracts of the leaves of Vernonia colorata in order to further discriminate the type of extract which provides a better antidiabetic activity. Experiments were performed in normoglycaemic and alloxan-induced diabetic rats. The acetonic extract of the leaves of Vernonia colorata (AELVC) (100 mg/kg, per os) induced a significant decrease of blood glucose in normoglycaemic rats. The glycaemia varied from 4.72+/-0.11 to 3.72+/-0.22 mmol/l (p<0.05, n=5) 3 h after AELVC administration per os. In contrast, the hexanic extract of the leaves of Vernonia colorata (HELVC) increased significantly the glycaemia in normoglycaemic rats. Like glibenclamide, AELVC has an antihyperglycaemic effect in oral glucose tolerance test (OGTT) and alloxan-induced diabetic rats. These results have shown that: (i) AELVC and HELVC have an opposite effect on basal blood glucose in normoglycaemic rats, suggesting that the mechanisms of action of both above-mentioned extracts are different; (ii) AELVC has also an antidiabetic activity in hyperglycaemic rat models.

[Antidiabetic activity of the leaves of Vemonia colorata (Wilid.) Drake (Composees) in alloxan-induced diabetic rats]. / Activité antidiabétique des feuilles de Vernonia colorata (Willd.) Drake (Composees) sur un modèle de diabète alloxanique chez le rat.

Vemonia colorata is distributed through Africa (Benin, Cameroon, Senegal, Togo etc...). Its leaves are commonly used by african tradipractitioners for treating diabetes. However, the antidiabetic activity of the leaves of V. colorata had never been investigated in experimental conditions. The present study aimed to test the aqueous extract of the leaves of V. colorata for its effects in normoglycaemic and alloxan-induced diabetic rats in comparison to glibenclamide antidiabetic activity. Such glibenclamide, the aqueous extract of V. colorata (300 mg/kg, per os) induced a significant hypoglycaemic effect in normoglycaemic rats. The blood glucose varied from 0.77 +/- 0.01 to 0.58 +/- 0.01 g/l (p < 0.05, n = 5). It also reduced significantly the fasting glucose level of the hyperglycaemic rats induced with oral administration of glucose (4 g/kg). In alloxan-induced diabetic rats, glibenclamide (0.2 mg/kg, per os) lowered significantly the blood glucose from 2.40 +/- 0.30 to 0.70 +/- 0.40 g/l (p < 0.05, n = 5). As well as glibenclamide, the aqueous extract of V. colorata (300 mg/kg, per os) decreased the blood glucose in alloxanic rats from 2.80 +/- 0.10 to 1.00 +/- 0.20 g/l (p < 0.05, n = 5). The aqueous extract of the leaves of V. colorata possesses both hypoglycaemic and antidiabetic effect in normoglycaemic and alloxan-induced diabetic rats. This may indicate the ethnopharmacological basis of the use of V. colorata leaves in traditional medicine for treating diabetes.

[Antidiabetic activity of Zizyphus mauritiana Lam (Rhamnaceae)]. / Etude de l'activité antidiabétique de Zizyphus mauritiana Lam (Rhamnaceae).

In traditonnal medicine, several plants were used in diabetes treatment. Among them, the aqueous extract from the leaves of Zizyphus mauritiana Lam (Rhamnaceae) was studied. The extract was administrated per os to Wistar rats made diabetics either temporarily by oral glucose tolerance test (first case) or definetely by subcutaneous injection of alloxan (second case). It was observed a striking decrease of the hyperglycemic arrow (p < 0.05) in the first case, with 300 mg/kg administrated 90 minutes before starting the test. In the second case, the results obtained with a dose of 300 mg/kg once or twice a day were identical as those with glibenclamide at 0.2 mg/kg per day. So, the antidiabetic activity of Zizyphus mauritiana Lam was experimentally born out but it has to be standardized for common use.

[Toxocological study of Guiera senegalensis Lam (Combretaceae)]. / Etude toxicologique de Guiera senegalensis Lam (Combretaceae).

The study was based on an aqueous extract derived from a 60 degrees ethanolic tincture containing 0.032 g of dry matter per ml. The leaves of Guiera senegalensis Lam (Combretaceae) were collected in December 1991 at Nguekhokh a village within 20 km from Mbour (Senegal). The extract was administered for six months through daily forced-feeling at 2 g/kg to Wistar male and female rats whose weight at the beginning of the experiment tanged between 140 g and 180 g. The urine was analysed during the study and the animals were weighed every four weeks. At the end of the experiment, the animals were slaughtered and various analyses carried out. Haematological features in relation with erythropoiesis, haemoglobinogenesis and leucopoiesis, were studied in relation with renal and hepatic functions; biochemical features too. Some organs (heart, lungs, kidneys, brain, cerebellum, spleen and liver) were removed and examined in order to detect possible lesions following the experiment. Judging by the results, Guiera senegalensis Lam (Combretaceae), as used in the experiment, did not show any significant toxicity.