IDF21-0138 Antidiabetic and anti-radical effects of Garcinia kola seeds in dexamethasone-induced-hyperglycemic rats

Abstract

Background: Seeds of Garcinia kola are consumed as stimulant due to its bitter and astringent taste. In traditional medicine, the maceration of seeds or roots are used to treat various diseases including liver diseases, cough, diabetes and complications. Several studies have been conducted to validate or not the empirical use of G. kola. Aim: Here using in vivo model we assessed some pharmacological properties of the hydroalcoholic extract of G. kola in dexamethasone-induced-hyperglycemic rat, hypoglycemia, anti-hyperglycemia, spasmolytic and laxative activities, then in vitro model to assess antiradical activity. Method: The decoction of the hydroalcoholic extract of G. kola seeds was obtained by introducing 250 g of powder into an Erlen Mayer by supplementing the total volume to 1L with water-ethanol mixture (30:70), then brought to boil at 80°C for 15 min. After cooling and filtration with Watman paper No. 4, the filtrate was concentrated with rotavapor. The extract was reconstituted in a 100% DMSO solution for purification and then prepared at 1% at concentrations of 0.5mg/mL and 1mg/mL for administration to animals at doses of 50 and 100 mg/kg. To evaluate antidiabetic properties, 30 rats of Wistar strain were used. The animals were divided into 5 groups of 6 rats each. Hyperglycemia was induced by a single intravenous injection of 4 mg/kg of dexamethasone for 3 days. Animals with glycemia no more than 120 mg/dL after 12 h fasting were considered as hyperglycemic then used for experiments. Glibenclamide® 2.5 mg/kg was used as a positive control. To evaluate the effect of G. kola on intestinal transit in normo-glycemic and hyperglycemic rat, we used 30 rats. Each group consisted of 3 normo-glycemic rats and 3 hyperglycemic rats. Imodium® and Fructin® were used as positive controls respectively for the evaluation of the spasmolytic and laxative effect of G. kola. Anti-radical activity of G. kola was assessed in vitro by inhibition of the activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH). Results: At doses 50 and 100 mg/kg G. kola significantly (P<0.001) regulate dexamethasone induced hyperglycemia after from a week treatment compared to the control normo-glycemic and hyperglycemic. The extract at both doses significantly (P<0.001) inhibited the spasmolytic activity in both normo-glycemic and hyperglycemic rats compared to Imodium®. In rats made hyperglycemic, only dose 100 mg/kg significantly (P<0.05) increase laxative effects when compared to the negative control. The potentiation of this effect was dose-related because no significant difference (P>0.05) was observed in both normo-glycemic and hyperglycemic rats in comparison to the reference laxative drug (Fructin®). In vitro anti-radical activity of G. kola revealed vitamin C-like anti-radical activity. Indeed, it appears from the histopathological study of liver, kidney and pancreas that extract restored the histological integrity of these organs initially altered by dexamethasone. Discussion: These pharmacological effects of G. kola could be attributed to numerous flavonoids, as plant extract revealed a total flavonoid 2.94±0.33 mgEq/100mg extract. Several studies demonstrated the involvement of flavonoids in the regulation of blood sugar and diabetes complications.