Bioactive compounds and functional potential of <i>Uapaca kirkiana</i> (Muell. arg.) fruits

Abstract

Consumption of Uapaca kirkiana indigenous fruit by the local populace is growing in popularity because of the acclaimed health and  functional benefits. The aim of the study was to determine the bioactive compounds and functional properties of the U. kirkiana fruit. Besides the fruit’s pulp yield, the bioactive phytochemical constituent, physicochemical properties and functional characteristics of the pulp were analysed. The sugar, starch, minerals, and ascorbic acid constituents of the fruit pulp were, respectively determined using the following instruments: brix refractometer, megazyme kit, inductive coupled plasma-optical emission spectrometer and 2,6- dichlorophenolindophenol (DCPIP) titration test. The total phenolic content (TPC), tannin, and flavonoid contents were evaluated using Folin Ciocalteau test, tannin binding test and vanillin test, respectively. The average weight of the U. kirkiana fruits harvested from three  regions having different climatic conditions ranged from 23.56 to 34.20 g per fruit. The mean pulp weight was from 12.15 g/100 g to 15.09 g/100 g per fruit. The biochemical and functional parameters obtained include total titratable acid (0.3 - 0.48 g/kg), antioxidant
activity (34.96 - 36.68%), vitamin C (15.74 - 16.63 mg/100 g), dry matter content (28.81 - 29.38%), pH (4.3 - 4.6) and sugar content (20.29 - 21.87 g/100 g). Fructose was the dominant sugar (10.12-11.0 g/100 g). Preliminary phytochemical screening of the pulp indicated the presence of tannins, flavonoids, amino acids and carbohydrate content. Total phenolic content ranged from 67.0 to 82.5 µg GAE/g. The essential elements constituent evaluation of the pulp revealed that Fe content was 11.3 - 12.2 mg/100 g, K (383.07 - 439.8 mg/100 g), Mg (28.7 - 35.1 mg/100 g), Ca (16.4 - 17.3 mg/100 g), P (13.4 - 15.1 mg/100 g), Na (9.08 - 9.78 mg/100 g), Cu (0.8 - 0.94 mg/100 g) and Zn (0.87 - 0.94 mg/100 g). This study, besides establishing U. kirkiana fruit as a good source of micronutrients (Fe, Cu, Zn), reveals that the fruit is also an excellent source of phenolic compounds, vitamin C and sugars, hence use as a dietary supplement may combat some nutritional deficiencies. We, therefore, recommend U. kirkiana fruits to be used to produce nutritive functional foods with health  benefits such as probiotic jams and as an additive.

Key words: Indigenous fruit, micronutrients, phenolic, pulp, phytochemicals, U.kirkiana, megazyme kit