Changes in phytochemical content and antioxidant activity during inflorescence development in broccoli
ABSTRACT This study was performed to monitor glucosinolate (GSL) profile, total phenol, ascorbic acid, total flavonoid contents, and antioxidant activity in florets of six broccoli (Brassica oleracea L. var. italica Plenck) genotypes at three different inflorescence developmental stages. The level of phytochemicals and antioxidant activities varied significantly among genotypes and developmental stages. Out of the eight GSLs identified in this study, only five were present in all genotypes and their respective developmental stages. Glucoraphanin (GRA), a major GSL, was significantly increased towards the later stages of development (1.41 μg g-1 in immature stage of ‘Koyoshi’ to 10.57 μg g-1 in commercial stage of ‘09FA- M295’), whereas glucobrassicin (BRA) showed a reverse accumulation pattern with the highest value at the immature stage (5.10-7.97 μg g-1). Other minor GSLs varied depending on the genotype. Total phenolic and ascorbic acid content increased significantly as maturity progressed in all the genotypes with a relatively higher increment observed in ascorbic acid (65.8%-100.9%) than phenolic content (10.2%-31.2%). Flavonoid content, on the other hand, showed a cultivar- dependent accumulation pattern throughout the developmental stages. However, although antioxidant activity increased with inflorescence development, the increment was higher and lower than in total phenol and ascorbic acid content, respectively. The highest value for GRA (10.57 μg g-1), ascorbic acid (502.3 mg 100 g-1), total phenol (523.7 mg 100 g-1) and antioxidant activities was obtained for ‘09FA-M295’ at the commercial stage. Taken together, these results indicate that phytochemicals in broccoli have a differential accumulation pattern during inflorescence development. Regardless of genotypes and inflorescence developmental stage, total phenolic content showed the highest correlation with antioxidant activity (r = 0.779**), followed by ascorbic acid (r = 0.674**) and flavonoid content (r = 0.602**), whereas total GSLs showed a nonsignificant correlation with antioxidant activity.