Compositional changes induced by UV-B radiation treatment of common bean and soybean seedlings monitored by capillary electrophoresis with diode array detection

In this work, a new CE method with diode array detection (DAD) was developed for the monitoring and quantitation of flavonoids in different beans treated and untreated with UV‐B radiation. Flavonoid concentration was monitored in UV‐B‐treated and untreated sprouts of three common beans (Zolfino ecotype, cv. Verdone, cv. Lingua di Fuoco) and one soybean (cv. Pacific). After acid hydrolysis of extracts, the CE‐DAD method provides reproducible quantitative determinations of daidzein, glycitein, genistein, and kaempferol at ppm level in these natural matrices within a relatively short time (less than 16 min). Total flavonoid content determined by CE‐DAD was 159 ± 8, 26 ± 2, 13 ± 1, and 1.3 ± 0.3 μg/g fresh weight for untreated sprouts of Pacific soybean, Verdone bean, Zolfino bean, and Lingua di Fuoco bean, respectively. UV‐B treatment caused no significant quantitative effect on Pacific soybean sprouts, whereas it enhanced the total isoflavone content by 1.5, 1.8, and 3.2‐fold in Verdone, Zolfino, and Lingua di Fuoco beans, respectively. The proposed method shows (i) the potentialities of bean sprouts as a natural source of bioactive compounds (antioxidants); (ii) the technological role of UV‐B treatment for sprout isoflavone enrichment; and (iii) the good capabilities of CE‐DAD to monitor this process.