Bioactive Composition and Free Radical Scavenging Activity of Fresh Orange Maize Hybrids: Impacts of Genotype, Maturity Stages, and Processing Methods.

Emmanuel Oladeji Alamu,Abebe Menkir,Olorunfemi Olaofe,Bussie Maziya-Dixon,Emmanuel Anyachukwu Irondi

doi:10.3389/fnut.2021.640563

Abstract

Bioactive compounds in foods are responsible for their biological activities, but biotic and abiotic factors may influence their levels. This study evaluated the impact of three genotypes (designated 4, 5, and 7), maturity stages (20, 27, and 34 days after pollination) and processing methods (hydrothermal and dry-heating) on the bioactive constituents (carotenoids, phytate, tannins, vitamin C) and 2,2-diphenyl-2-picrylhydrazyl radical (DPPH*) scavenging activity of fresh orange maize hybrids. Freshly harvested maize cobs of each genotype were subjected to hydrothermal processing at 100°C and dry-heating with husks and without husks. Carotenoids (lutein, zeaxanthin, β-cryptoxanthin, α-carotene, and total β-carotene) contents of fresh and processed samples were analyzed using HPLC; other bioactive constituents and DPPH* scavenging ability were determined using spectrophotometric methods. Genotype had a significant effect on the levels of carotenoids (p < 0.001) and vitamin C (p < 0.05), while genotype (p < 0.001), and processing methods (p < 0.001) had significant effects on DPPH* SC50. Maturity stages, processing methods and their interaction also had significant effects (p < 0.001) on the levels of all the bioactive constituents. A positive moderate to strong correlation was observed between (p < 0.001) α-carotene and the following: lutein (r = 0.57), β-cryptoxanthin (r = 0.69), total β-carotene (r = 0.62). However, the relationship between α-carotene and zeaxanthin was positive but weak (r = 0.39). A positive moderate correlation (p < 0.001) was observed between lutein and the following: β-cryptoxanthin (r = 0.57), total β-carotene (r = 0.58), and zeaxanthin (r = 0.52). A positive strong correlation (p < 0.001) was observed between β-cryptoxanthin and each of total β-carotene (r = 0.92) and zeaxanthin (r = 0.63); total β-carotene and zeaxanthin (r = 0.65); while the association between vitamin C and DPPH* SC50 was negative and weak (r = −0.38). Generally, genotype 4 and harvesting at 34 days after pollination had the best combination of bioactive constituents and DPPH* scavenging ability.

Highlights

Pigmented maize (Zea mays L.) grains are rich dietary sources of bioactive compounds, such as anthocyanins, carotenoids, polyphenolic compounds, vitamin C, and phytate [1, 2]
Genotype 4 had a better combination of antioxidant constituents and free radicals scavenging ability than genotypes 5 and 7
Orange maize hybrids harvested at 34 days after pollination contained higher concentrations of carotenoids, tannins and vitamin C, and stronger DPPH∗ scavenging ability than those harvested at 20 and 27 days after pollination

Summary

Introduction

Pigmented maize (Zea mays L.) grains are rich dietary sources of bioactive compounds, such as anthocyanins, carotenoids, polyphenolic compounds, vitamin C, and phytate [1, 2]. One of the approaches to boost the antioxidant status of the body is by increasing the intake of whole cereal grains and many other dietary sources of antioxidant compounds This is because dietary antioxidants can end the chain reactions of free radicals through proton donation. In this context, orange maize has been reported to exhibit antioxidant activity, a property attributed to its bioactive compounds [2]

Methods

Results

Conclusion