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Background: Fire is important for the maintenance of African savanna ecosystems, particularly humid savanna. Despite the importance of fire behavior to our understanding of fire's ecological effects, few studies have documented fire behavior and its determinants in humid West African savannas and, in particular, whether fire behavior depends on season of the year. We analyzed fire behavior in the Guinean savanna of Lamto (Ivory Coast) during a 4-year field experiment. The fire regimes tested consisted of three different burning seasons: early-season fire, mid-season fire, and late-season fire. Nine 0.5 ha plots were burned annually to determine the rate of spread and fire intensity. Fuel characteristics and weather conditions were measured to assess their impact on fire behavior. Results: Understory grass height, total fresh fuel load, and moisture content had greater values in early-season fire than in mid-season and late-season fire. The rate of spread and intensity of both mid-season fire (0.14 +/- 0.03 m s(-1) and 3920 +/- 740 kW m(-1), respectively) and of late-season fire (0.12 +/- 0.02 m s(-1) and 3134 +/- 482 kW m(-1), respectively) were significantly greater than those of early-season fire (0.04 +/- 0.01 m s(-1) and 1416 +/- 252 kW m(-1), respectively). The best predictors of fire behavior were fuel moisture content and air humidity; these two explanatory variables were the sole significant predictors for fire intensity, rate of fire spread, and flame height. Conclusions: Given that there is no difference between intensity of mid-season and late-season fire, we suggest that the generally reported higher impact of late-season fire on trees in the West African humid savannas is due not to fire intensity per se, but rather to a more sensitive phenological stage of trees (e.g., leafless in mid-season), and to a longer time of exposure to lethal temperatures (> 60 degrees C) in the late dry season. These data provide important insights into fire behavior in the Guinean savanna-forest mosaic ecoregion, informing fire management.

This study reports the effect of a dichloromethane fraction of the stem bark of Piliostigma reticulatum, a plant with anti-diarrhoeal properties, on the concentrations of electrolytes and the weight of water in castor oil-induced diarrhoea model in rats. The concentrations of ions in the supernatant of the small intestine content, obtained after centrifugation of the intraluminal fluid, were measured by flame photometry. The fraction showed a dose-dependent decrease of electrolytes concentration of [Na+], [K+], [Cl-] and [Ca2+], compared to the vehicle control. The ion concentrations were significantly reduced by the fraction at 125, 250 and 500 mg/kg, in the same range of inhibi-tion obtained in rats treated by loperamide (5mg/kg), used as the reference anti-diarrhoeal drug. Quantity of water in faeces was also significantly reduced by the dichloromethane fraction at 250 and 500 mg/kg, and by loperamide. Results from the study showed that the dichloromethane frac-tion obtained from a crude extract of the stem bark of P. reticulatum possesses anti-secretory activity. These results suggest that the anti-diarrhoeal properties of the plant could partly be mediated by its anti-secretory activity and could therefore justify its use in traditional medicine to treat diarrhoea.

Piliostigma reticulatum (Caesalpiniaceae) is used in Africa as a traditional medicine for the treatment of many diseases, such as malaria, tuberculosis and diarrhoea. We investigated the antidiarrhoeal properties of a crude ethanol extract from the stem bark of Piliostigma reticulatum (EEPR) in Wistar albino rats to substantiate its traditional use and to determine its phytochemical constituents. The antidiarrhoeal activity of the plant extract was evaluated in a castor oil-induced diarrhoea model in rats and compared with loperamide. The effect of the extract on gastrointestinal motility was also determined by the oral administration of charcoal meal and castor oil-induced intestinal fluid accumulation (enteropooling). EEPR showed remarkable dose-dependent antidiarrhoeal activity evidenced by a reduction of defecation frequency and change in consistency. Extracts at 250, 500 and 1000 mg/kg body weight significantly reduced diarrhoeal faeces. EEPR also significantly inhibited gastrointestinal motility and castor oil-induced enteropooling at 500 and 1000 mg/kg, similar to the inhibition obtained in control rats treated by atropine. Phytochemical screening revealed the presence of tannins, flavonoids, polyphenols and reducing sugars in the stem bark of P. reticulatum. No mortality or visible signs of general weakness were observed in the rats following administration of the crude extract in doses up to 6000 mg/kg body weight in an acute toxicity study. Our results show that the stem bark of P. reticulatum possesses antidiarrhoeal activity and strongly suggest that its use in traditional medicine practice could be justified.Key words: Antidiarrhoeal activity; Castor oil; Diarrhoea; Piliostigma reticulatum

Holarrhena floribunda is a common plant that has traditionally been used in Africa to treat many diseases such as fever, dysentery, sterility and diabetes. This study was set out to evaluate the hypoglycaemic properties of ethanolic leaf extract of Holarrhena floribunda and various fractions of this extract in normal fasted and fed-hyperglycaemic rats. Blood glucose levels (g L-1) were deter-mined at the following times: 1) after a 12 hours period prior to drug administration, 2) An hour after the oral administration of the extract (250-1000 mg kg-1), its fractions (1000 mg kg-1), Glibenclamide (10 mg kg-1) or the vehicle and 3) one and four hours after the oral overload of anhy-drous glucose (4 g kg-1 body weight). The extract showed a remarkable dose-dependent down-regulation of blood glucose in fasted rats at 1000 mg kg-1 (p