Metabolic Analyses and Evaluation of Antioxidant Activity in Purple Kohlrabi Sprouts after Exposed to UVB Radiation

Abstract

Various metabolites act as plant defense molecules due to their antioxidant abilities. This study aimed to investigate the influence of UVB irradiation on the accumulation of metabolites, including primary metabolites (sugar, sugar alcohols, amino acids, organic acids, and an amine) and secondary metabolites (anthocyanins, fatty acids, and phenolic acids), and its synergistic antioxidant ability, in purple kohlrabi sprouts. Metabolite analyses revealed a total of 92 metabolites in the sprouts. Specifically, the levels of most amino acids increased after 24 h of UVB treatment, and then slightly decreased in the kohlrabi sprouts. The levels of most sugars and sugar alcohols increased after 24 h of UVB treatment and then decreased. The levels of TCA cycle intermediates and phenolic acids gradually increased during the UVB treatment. Furthermore, the levels of some fatty acids gradually increased during the UVB treatment, and the levels of the other fatty acids increased after 6 h of UVB treatment and then decreased. In particular, the levels of most anthocyanins, known to be strong antioxidants, gradually increased after 24 h of UVB treatment. In the in vitro ABTS scavenging assay, UVB-treated purple kohlrabi sprouts showed increased scavenging ability. This may be attributed to the increased accumulation of metabolites acting as antioxidants, in response to UVB treatment. This study confirmed that UVB irradiation induced the alteration of primary and secondary metabolism in the kohlrabi sprouts.

Metabolic Profiling of Primary and Secondary Metabolites in Kohlrabi (Brassica oleracea var. gongylodes) Sprouts Exposed to Different Light-Emitting Diodes

“…Only purple kohlrabi contains anthocyanins and has a higher phenylpropanoid content than green kohlrabi [ 6 ]. Various studies have shown cruciferous vegetables, including kohlrabi, are beneficial for human health, as they contain abundant ascorbic acid, carotenoids, and tocopherol [ 7 , 8 ].…”

Comparative Analysis of Primary and Secondary Metabolites in Different In Vitro Tissues of Narcissus tazetta var. chinensis

“…Analysis of Hydrophilic Compounds by GC-TOFMS. The hydrophilic metabolites were extracted using the methodology outlined in a recent work by Yeo et al 45 with minor modifications. Briefly, 1 mL of water, CHCl 3 , and MeOH in a ratio of 1:1:2.5 (v/v/v) was added to 10 mg of N. tazetta tissues (callus, adventitious root, and stem) generated in vitro, followed by the addition of 60 μL of 0.2 g/L adonitol as an internal standard.…”

Bioavailability and Bioactivity of Plant Antioxidants

“…The cultivation conditions and the type and parameters of the production processes used affect the chemical composition and properties of raw materials as well as semi-finished and finished products. Research into the effect of UVB radiation on changes in the composition of primary and secondary metabolites in plants was conducted by Yeo et al [ 5 ]. Purple kohlrabi sprouts ( Brassica oleracea var.…”

“…The study indicated that UVB irradiation could induce an overall alteration in metabolite composition. Increased levels of secondary metabolites, such as anthocyanins and phenolic acids and ABTS free radical scavenging ability were observed during UVB irradiation [ 5 ].…”