Hypoglycaemic activity of preheated (roasting) Aframomum citratum (C. Pereira) K. Schum and Tetrapleura tetraptera (Schumach Thonn.) fruits beverage on Streptozotocin-induced rats

Tetrapleura tetraptera and Aframomum citratum fruits are used as spices and in the traditional pharmacopeia in Cameroon. They are mostly combined and preheated for many purposes while cooking. The effects of roasting on the phenolic content of spices, phenolic profile of a beverage made with the mix of roasted spices and its hypoglycaemic activity on diabetes complications were investigated. Aqueous extract (infusion: 100°C; 1/5 g/ml) was prepared, and the total polyphenols and flavonoids contents before and after heat treatment were quantified. Four formulations of T. tetraptera/A. citratum (95/5; 90/10; 85/15; 80/20) were assessed and the in vitro glucose adsorption capacity of the extracts was studied to retain the most effective formulation (AEF). Phenolic and derivatives compounds of AEF were analysed using HPLC-DAD methodology. The AEF hypoglycaemic activity (250 mg/kg bw) and the various complications of hyperglycaemia after Streptozotocin induction (55 mg/kg) were examined on rats. Significant (p<0.05) improvements in phytochemical content were noticed for T. tetraptera and AEF extracts after heat treatment. Among the phenolic compounds identified, flavone, protocatechic, chlorogenic, p-Coumaric acids, and naringin showed the highest concentrations. Significantly, the effect of AEF is the same as the administration of AEF-Glibenclamide (Glibenclamide) and Acarbose after 4 h when assessing the anti-hyperglycaemic test. The influence of Glibenclamide (the reference drug) is significantly improved by AEF, and this synergy has the best anti-hyperglycaemic, hypoglycaemic, hypotriglyceridaemic potential and boosts catalase, superoxide dismutase activities while reducing Malondialdehyde (liver, pancreas, haemolysates) and hydroperoxide (liver, plasma, and kidney) contents compared with the use of single AEF. Key words: Tetrapleura tetraptera, Aframomum citratum, anti-diabetic, hyperglycaemia, roasting, pharmacopeia, hypoglycaemia, infusion, HPLC-DAD, Streptozotocin