The therapeutic abilities of Tetrapleura tetraptera and Aframomum citratum fruits used as spices are attributed to their bioactive molecules, including polyphenols. Sometimes used together and heated, they can undergo denaturation. The aim of the current study is to optimize the extraction of phenolic compounds and antioxidant potential of a roasted mix of Tetrapleura tetraptera and Aframomum citratum (95/5: w/w) fruits using RSM in a home food consumption context. The mix of spices was chosen according to the highest content of TPP and preliminary studies were performed to select the influencing variables. Roasting temperatures (130–170 °C), roasting times (10–15 min) and brewing times (8–15 min) were investigated with a rotatable central composite design. Experimental results were fitted to the second-order polynomial model where multiple regressions and ANOVA were used to determine the coefficients of the model and the optimal conditions for the considered responses. The two spices are good sources of phenolic compounds, and they also show significant (p < 0.05) dose-dependent radical scavenging activities (DPPH assay and inhibition of β-carotene discoloration) and reductive activities (FRAP assay and Phosphomolybdenum method). They significantly inhibit bovine serum albumin and 5-LOX denaturation. Brewing time and roasting time significantly (p < 0.05) influence the responses and there is a strong (R 2 = 0.93) correlation between the TPP and TAC of the beverage. The quadratic model fit well and the different factors used to test its accuracy and fitness were in satisfactory ranges. For TPP extraction (38.90 mgGAE/g dw) and TAC (50.75 mg TE/g dw) expression, the optimal conditions were reached at a roasting temperature of 150 °C, roasting time of 12.62 min, brewing time of 11.91 min and a desirability of 0.95. The novel information on the optimisation of the process can be further used by scientists, consumers and herbalists for effective handling of fruits during the extraction process.

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 antihyperglycaemic, 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.

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Description. Hard shelled fruits, Tetrapleura tetraptera and Aframomum citratum nonwood forest products are used as spices and for many medicinal recipes. Mostly used together, they undergo heat treatment before being milled when cooking Mbongo Tchobi, a black spicy stew from central and coastal regions in Cameroon. Objectives. Evaluate the impact of roasting these spices on the physicochemical properties (dry matter, ash, raw protein, total sugar, raw fibre, pH, aw, total energy, total fat), phytochemical content (total polyphenol, total flavonoids) and the antioxidant activities (total antioxidant activity, FRAP, DPPH and lipid peroxidation inhibition assays) of their aqueous extracts in a home food consumption context. Method. Tetrapleura tetraptera and Aframomum citratum fruits from Ngola locality in Yokadouma (east region in Cameroon) locality were collected, sorted, cleaned and dried (72 h, 45 °C) in an oven. Cut into small pieces, a part was heated using roasting parameters deduced from preliminary tests (140 °C/10 min; 180 °C/20 min and 150 °C/12 min respectively for T. tetraptera, A. citratum and a formulation 95/5 of the two spices). The heated and unheated spices were ground and an infusion was prepared from boiling water in the proportion of 1/5 (g·ml-1) for both types of spices. Physicochemical and phytochemical characteristics (dry matter, total ash, fat, sugar, crude fibre and energy contents, pH, aw, total flavonoids and polyphenols) as well as the antioxidant activities of the aqueous extracts of the two spices and a mix of the two spices were evaluated before and after the heat treatment. Results. Heat treatment significantly (p < 0.05) reduces fat and total sugars contents but improves raw fiber contents for all spices. Phenolic content is more important for heated spices and percentage differences before and after heat treatment are between 8.0 and 23.2% for both spices. Extracts obtained with heated spices possess the best antioxidant potential. Strong significant positive correlations have been established between the phenolic compounds and the reductive antioxidant activities and negative correlations with the antiradical antioxidant activities as they are expressed as IC50 (mg·ml-1). Conclusions. In most of the features studied, the heated formulation (95/5) possesses the highest characteristics studied. The choice of heating these spices under the roasting parameters identified should be guided by the desire of improving their antioxidant potential because of the nutritional losses observed after heat treatment.