Proximate analysis and evaluation of total phenolic compounds in Azanza garckeana fruit for use as gelatin crosslinking agent

Abstract

Azanza garckeana (A. garckeana) is a wild edible fruit native in Africa, widely distributed in the East and Southern Africa. The species grow naturally in semi-arid areas. The consumption of the fruit is linked to many phytochemicals present within the fruit, one of these being phenolic compounds. Several studies have been conducted on A. garckeana, but, study on the phenolic content of the pulp and the seed coat has been overlooked. However, to link the effect of these phenolics, the complete quantification of the whole fruit is mandatory. The objective of this research was therefore to conduct proximate analysis and to determine the Total Phenolic Content (TPC) in different constituents of A. garckeana fruit for use as a natural crosslinking agent in gelatin resin. Firstly, the phytochemical yield was determined and this was done through separating the fruit into different components (i.e., pulp, seed and the seed coat) defatting and extracting using methanol. The extracts were filtered, concentrated and the yield was calculated. Secondly, phytochemical screening for phenolics and clean-up was done prior to the determination of TPC. TPC was estimated based on Folin Ciocalteu’s method using SpectraMax M2 UV-vis spectrophotometer. The linearity of the Folin Ciocalteu method was verified through the method of least squares which was applied through different concentrations of standard gallic acid. TPC was calculated from the gallic acid standard curve and the results expressed as mg/g gallic acid equivalents (Standard curve equation: y = 2.9503x + 0.0348; Correlation coefficient: R² = 0.997). The extraction yield was found to be 0.57, 0.18 and 0.14g/g for the pulp, seed and the seed coat, respectively. All phytochemical screening tests revealed a positive test for phenolics. The TPC varied from 18.14 to 20.78 and 24.92mgGAE/g in the seed coat, seed and the pulp, respectively. High TPC (24.92mgGAE/g) was found in the fruit pulp.