Optimization of water-extract of phenolic and antioxidant compounds from Kinkéliba (Combretum micranthum) leaves

The hot water extract of dry kinkéliba leaves (DKL) is a traditionally widely delighted and consumed beverage in West Africa, especially during the fasting periods. It is believed to possess various health benefit effects such as diuretic, purgative, digestive, anti-viral and anti-malarial properties. However, the preparation of this beverage has not been optimized so far, which may underestimate its health benefit potential. In this study, the traditional preparation of the beverage, by decoction, was optimized in order to maximize the amounts of health benefit polyphenolic and other antioxidant compounds. The results showed that an optimal preparation with maximum solubilization of polyphenols required the brewing of approximately 20-25 g of DKL in boiling water for about 15-20 min. These conditions afforded an optimized extract (OEDKL) with a total phenolic content of 215.0 mg GAE/g and arabinogalactan-rich pectic polysaccharide content of 553.0 mg/g. Moreover, the OEDKL exhibited a high antioxidant capacity, as evaluated by DPPH [93.0% IP and EC50 = 15.0 (g/g)], ABTS (112.0 μmol TE/ g), or FRAP (376.0 μmol TE/g) assay, which was correlated with the total phenolic content (R 2 = 0.897-0.991). Nevertheless, the pectic material detected within the beverage was likely to contribute to its interesting antioxidant properties. Therefore, it was suggested that the total antioxidant capacity of the OEDKL could result from synergistic interactions among the various antioxidant compounds present, including polyphenols and fractionated pectic materials.