Effect of extraction methods on phytochemical constituents and antioxidant activity of de-kernelled Sclerocarya birrea seeds.

Abstract

Marula (Sclerocarya birrea) is an indigenous African fruit-bearing tree with many commercial uses; however, de-kernelled seeds generated from marula fruit-processing are wasted. The phytochemical constituents of de-kernelled marula seeds have not been investigated previously and its extract/tea may potentially serve as a promising source of antioxidants and phytochemicals. This study aimed to investigate the effect of different extraction methods (maceration and decoction) on the recovery of phenolic compounds, sugars, organic acids, and antioxidants from de-kernelled marula seeds. Extracts produced from decoction for 30 min contained the highest phenolic content (2253.93 ± 25.72 mg gallic acid equivalent kg-1 extract), flavonoid content (1020.99 ± 23.90 mg rutin equivalent kg-1 extract), as well as combined sugars and organic acids (1884.03 mg kg-1 extract). Fourier-transform infrared spectroscopy analysis confirmed the presence of functional groups typically present in phenolic compounds, sugars, and organic acids in the extracts obtained from decoction. The characterization revealed that decoction extraction increased solubility, variety, and yield of phytochemical and antioxidant compounds recovered from de-kernelled marula seeds. The highest concentrations of phytochemicals were obtained using the decoction method. This study may therefore pave the way for extract composition and future utilization of de-kernelled marula seeds in the food industry. © 2023 Society of Chemical Industry.