Optimization of Polyphenols Extraction Method from Kola Nuts (Cola nitida Vent. Schott & Endl.) Using Experimental Design

Abstract

Aims: The aim of this study is to optimize extraction process of phenolics compounds from kola nuts by using experimental design. Study Design: Kola nuts were collected in October 2014-February 2015 in south of Côte d’Ivoire. Harvested kola nuts were transferred to the laboratory until used in the experiments Place and Duration of Study: This study was carried out during season 2014-2015 in the Laboratory of Biochemistry and Food Science, Félix Houphouët-Boigny University, Côte d’Ivoire. Methodology: Nuts were divided into two groups and subdivided to obtain four groups according to their variety (traditional or improved) and morphotype or cultivar (white and red). After drying and powder processing, the effect of six parameters (solvent type, solid-liquid ratio, extraction mode, variety, cultivar and extraction time) on polyphenol extraction from kola nuts were studied. Firstly, a Plackett-Burman design (8 experiments) was used to highlight the most important factors which influence the extraction process. Then, a full factorial design (2k, k=4) was used to optimize the extraction conditions. Results: Results showed that solvent, ratio (w/v), extraction mode and variety of nuts had significant effect on polyphenols extraction. The predicted optimal conditions for the highest polyphenol content from kola nuts were found with infusion of traditional variety at 1/100 (w/v) ratio with aqueous ethanol 50% (v/v). In the predicted optimal conditions, experimental values were 350 mg/L GAE, 1460 mg/L QE and 264.33 mg/L CE for total polyphenol, total flavonoid and condensed tannin, respectively. Experimental data were very close to the predicted values. Conclusion: The extractive capability of kola nuts polyphenol is considerably depended on the solvent type, the extraction mode, the solid-liquid ratio (w/v) and nuts variety. Thus, kola nuts can be considered as a natural source of phenolics compounds with good antioxidant capacity. This optimization of the extraction parameters of phenolics compounds from kola nuts is very original, it is the first on a current scale of research on kola nut.