Phytochemical screening, quantification of tannin, flavonoid and in vitro antimicrobial activity of different forms and varieties of coconut water

Abstract

Tender coconut water (Cocos nucifera) is a natural beverage and sports drink in tropical countries due to the presence of high mineral content and other nutritional properties. The aim of this study was to investigate the nutritional and phytochemical analysis and in vitro antimicrobial activity for eight different forms and varieties of tender coconut water with a maturity stage of 5-7 months. Tender coconut water of Nawasi, Ran thembili, Green dwarf, Brown dwarf, Yellow dwarf, King coconut, CRIC 60, and CRIC 65 were collected in sterile bottles and liquid-liquid extraction was carried out in different separating funnels using the nonpolar solvent n-hexane for qualitative analysis. Nutritional and phytochemical screening was carried out for n-hexane extract and fresh coconut water. The findings from the nutritional and phytochemical screening show the presence of carbohydrates, reducing sugars, amino acids, phenols, tannins, flavonoids, terpenoids, alkaloids and glycosides. Quantification of tannin was determined using Folin ciocalteu assay and flavonoid was determined using Aluminium chloride assay. Ran thembili (Tall variety) shows significantly higher total tannin content (22.32 ±0.909 µg TAE/ mL) and Nawasi (Tall variety) shows significantly higher total flavonoid content (1.229 ± 0.114 µg QUE/ mL). When agar well diffusion assay was used to determine the antibacterial and antifungal activity of fresh coconut water, Pseudomonas aeroginosa showed an inhibition zone for Nawasi (2.5±0.109 cm), Ran thembili (2.783± 0.223 cm), Green dwarf (2.45±0.152 cm), Brown dwarf (2.45±0.188 cm), Yellow dwarf (2.383 ± 0.24 cm), King coconut (2.567±0.294 cm), CRIC 60 (2.33± 0.234 cm), and CRIC 65 (2.417± 0.214 cm) while Streptomycin (positive control) shows an inhibition zone of (5.03±0.34 cm) and the diameter of the well was 0.9 cm. Microorganisms such as Staphylococcus, E.coli, Enterococcus, Klebsiella, Proteus, Bacillus, Mucor, Aspergillus, Penicillium, and Fusarium were not inhibited by coconut water. The components in the coconut water of all the varieties inhibit the growth of Pseudomonas aeroginosa while not inhibiting the growth of other microorganisms tested. Preliminary nutritional and phytochemical analysis of coconut water shows the existence of biologically active compounds.