Effects of pre‐harvest synthetic chemicals on post‐harvest bioactive profile and phytoconstituents of white cultivar of Vigna unguiculata grains

Abstract

In this study, the impact of pre-harvest synthetic chemical treatments on the post-harvest bioactive compounds, phyto-constituents, and thermal properties of white cultivar of V. unguiculata was investigated. The results showed that organic V. unguiculata grains (white cultivar) contained 36.02 g bioactive compounds/100 g grain, whereas nonorganic (control) recorded 22.94 g bioactive compounds/100 g grains. Among the bioactive compounds in the organic grains were [3-(2-hydroxy-6-methylphenyl)-4(3H)-quinazolinone (10.25 g/100 g grain)]; [methaqualone (13.94 g/100 g grain)]; [pyrazole-3-carboxylic acid, 4-iodo-1-methyl- (5.78 g/100 g grain)]; and [cinnamic acid, p-(trimethylsiloxy)-, methyl ester (4.43 g/100 g grain)]. The identified bioactive compounds have health-promoting potentials. Organic grains had peak viscosity of 114.02 RVU, final viscosity (135.81RVU), and pasting temperature (76.15°C), whereas nonorganic grains recorded peak viscosity of 84.89RVU, final viscosity (92.98 RVU), and pasting temperature (77.08°C). Organic grains had L*, a*, and b* of 84.31, 0.42, and 13.01, respectively. The nonorganic grains had 88.98, 0.33, and 15.09 for L*, a*, and b*, respectively. The enthalpies of the organic and nonorganic were 2.98 J/g and 2.94 J/g, respectively. Organic grains showed significant (p < .05) superiority in bioactive compounds, phytochemicals, and antioxidants over nonorganic grains. Flavonoids, alkaloids, total phenolic, DPPH, and FRAP contents of the organic grains were 13.45 mgRE/100 g, 1.90 mg/100 g, 1,350 mgGAE/100 g, 2,700 µmolTEAC/100 g, and 19 mmol Fe2+/100 g, respectively, whereas nonorganic grains had flavonoids (8.11 mgRE/100 g), alkaloids (1.20 mg/100 g), total phenolic (978 mgGAE/100 g), DPPH (1802 µmolTEAC/100 g), and FRAP (8.04 mmol Fe2+/100 g). Phenolic compounds profile showed that organic grains were richer in epicatechin, gallic acid, ferulic acid, chlorogenic acid, 4-hydroxy benzoic acid, and catechin. Good pasting properties of the organic grains showed that it could function as a food thickener. Organic V. unguiculata grains (white cultivar) are rich in health-promoting compounds and could, therefore, be used as an ingredient in the development of functional foods. Practical applications Bioactive compounds and their bioactivity have become invaluable in human health due to the occurrence of diverse cardiovascular diseases. The consumption of plant foods that are rich in bioactive compounds is imperial for healthy living. The white cultivar of Vigna unguiculata is consumed in many homes in Africa with limited industrial applications at present. However, the organic V. unguiculata grains are rich in health-promoting compounds. Consequently, organic V. unguiculata grain has potential application as an active ingredient in the development of functional foods that could serve as anti-inflammatory, immune-stimulating, neuroprotective, anti-apoptotic, anti-cancer, antioxidant, anti-mutagenic, and cardioprotective.