Phenolic, antioxidant capacity, and antinutritional compounds in different Australian Acacia seeds

Abstract

The polyphenols, antioxidant activities, and antinutrients in Acacia seeds of different species, growing locations, and harvest years were characterised in this study. The main phenolic compounds were 6-hydroxy-2-methylindole and 2,2-methylenebis(6-tert-butyl-methylphenol). The total phenolic and total flavonoid contents of the free polyphenol fractions were positively correlated, while the total phenolic content and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), 2,2-diphenyl-1-picrylhydrazyl, and oxygen radical absorbance capacity of the bound fractions were negatively correlated. There were no differences in trypsin and chymotrypsin inhibition activities across all seed batches. The lowest phytate (11.1038 ± 0.006 mg/g) and tannin contents (2.0323 ± 0.7462%) were found in Acacia retinodes Amphitheatre 2020 and A. retinodes Firgrove 2022, respectively. The highest saponin (45.4578 ± 12.2990%) and oxalate contents (4.2396 ± 0.7949%) were found in A. retinodes Grampians 2020 and A. retinodes Firgrove 2020, respectively. The results of this study showed differences in antioxidant activities and antinutrients content which implies that compositional values should not be extrapolated between different species and harvest years.