Caffeine and Phenolic Compounds in Cola nitida (Vent.) Schott and Endl and Garcinia kola Heckel Grown in Côte d’Ivoire

Abstract

Kola nuts are usually eaten fresh and represent a substantial source of income for many households and certain public authorities. Their importance lies in their content of some secondary metabolites of interest used in industries for the production of energy drinks and pharmaceuticals. The aim of this study is to reveal and determine the content of polyphenols (flavonoids in particular) and caffeine in nuts from Côte d’Ivoire. According to their phenotypical characteristics, four lots of nuts were collected (Red Cola nitida (RCN); White Cola nitida (WCN); Purple Cola nitida (PCN) and Garcinia kola (WGK)). After drying, different extractions were carried out using several solvents: water, acidified water (0.01N citric acid), methanol, ethanol, acetone 60% and methanol/acetic acid 1% solution. Phytochemical screening showed that kola nuts contain antioxidants such as flavonoids, tannins and alkaloids in varying proportions according to the species. Spectrophotometric analysis revealed that total polyphenols and flavonoids are important in C. nitida nuts compared to those of G. kola. Phenolic contents are 26.76±0.54; 23.08±1.06; 17.06±1.03 and 14.90±0.64 mg/g FW for WCN, RCN, PCN and WGK respectively. As for flavonoids, levels are 803.03±14.48, 697.13±12.76, 647.76±21.16 and 355.74±17.03 mg/kg FW for WCN, RCN, PCN and WGK respectively. It noted that acetone 60% is the efficient solvent for extraction. Statistical analyzes indicate the significant influence at P=.05 of solvent and nuts morphotype on the level of extractable for total polyphenols (P=.000000) and flavonoids (P=.000000) respectively. Concerning caffeine, reversed-phase HPLC analysis indicates that concentrations are higher in C. nitida extracts with a slight predominance for RCN (10812.5±6.27 mg/kg FW). We note a small amount of this metabolite (80.08 ±2.91 mg/kg) in G. kola. The mean intakes of nutrients are 3.99 and 1217.13 mg of polyphenol/day for an equivalent daily intake of 0.6 g (cola amount consumed per day in West Africa) and 183 g (amount of fruit consumed per day). About caffeine, intakes are 4.31 and 1313.05 mg/day for 0.6 and 183 g respectively. These findings indicate that kola seeds are enriched in important compound and can be used as a possible source of antioxidant for African population’s customs and European industries.