Abstract
Ultraviolet lamps irradiation has been extensively used in water treatment, surface disinfection, and as a germicidal agent. Yet, activation of some essential reactions in fruits and vegetables occurs at low doses of irradiation, which in turn leads to an improvement of their shelf-life or bioactive compounds. In this study, postharvest effects of ultraviolet irradiation at different wavelengths were investigated on antioxidants properties, nutritional and vitamin D contents of six leafy vegetables. The six vegetables were each subjected to UV-A, B, and C lamps irradiation at wavelengths of 400, 315, and 230 nm respectively in irradiation chambers. The results revealed that ultraviolet irradiation increased the phenolic and flavonoid contents with a better-reducing power ability and antioxidant capacity in tested vegetables. More also, the essential amino acid contents were significantly (P ≤ 0.05) increased. In UV-A treatment, increased nutritional and antioxidant properties were significant (P ≤ 0.05) in M. oleifera leaf extract. On the other hand, a significant (P ≤ 0.05) increase in the level of vitamin D2 and D3 synthesis in the leaves of all the vegetables was observed under UV-B treatment. The results revealed that M. oleifera leaf responds more positively to ultraviolet irradiation than other treated vegetables. Therefore, this study shows that postharvest treatments with UV-A and B lamps may be a useful biological strategy for enhancing the antioxidant and nutritional quality of vegetables. Keywords: Antioxidant activity, UV-radiation, Vegetables, Bioactive compounds, Vitamin D. DOI: 10.7176/ALST/88-04 Publication date: July 31 st 2021
Highlights
Free radical’s generation is not far-fetched in organisms’ natural processes of metabolism
Plant samples The fresh leaves of A. hybridus, B. oleracea, H. sabdariffa, L. capensis, M. oleifera, and S. melongena, were collected from the Bodija market, Ibadan, the authentication was done at the Department of Botany Herbarium, University of Ibadan, where the voucher numbers were deposited (UIH-21131, UIH-22213, UIH-21213, UIH22712, UIH-22913, UIH-22913 respectively)
The increased phenolic and flavonoid contents observed in M. oleiferaand A. hybidus when treated with UV-A and B respectively might be a result of the phenylalanine ammonia-lyase activation, which is responsible for the synthesis of bioactive compounds in plants tissues (Papoutsis et al 2016)
Summary
Free radical’s generation is not far-fetched in organisms’ natural processes of metabolism. The endogenous antioxidant enzymes in an organism scavenge these free radicals. Any derangement in the antioxidant functions of an organism results to the accumulation of free radicals in the body, which causes damage to biomolecules and in turn brings about various diseases like cardiovascular disease, atherosclerosis, hormonal disorder, and other related diseases (Li et al 2013). The most common causes of chronic kidney disease (CKD) in the developed world are diabetes mellitus and hypertension, whereas, in sub-Saharan Africa, the commonest causes are hypertension and chronic glomerulonephritis (Rashad & Barsoum, 2006). A potential source of natural antioxidants can be derived from plant products. The use of plants for ethnomedicine is fast gaining recognition and publicity in Africa and the rest of the world, because of their affordability and availability and they are relatively cheap (Choi et al 2012)
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