Jung-Ho Kwak

Chemical Composition and Antioxidant Activity in Different Tissues of Brassica Vegetables

This research was conducted to evaluate glucosinolate profiles, vitamin C, total phenol, total flavonoid, and free sugar (glucose, fructose, and sucrose) content, fatty acid composition, and antioxidant activity in floret and leaf of six cauliflower and broccoli cultivars. The level of chemical constituents as well as antioxidants significantly varied among crop types, cultivars, and their different parts, in that phytochemicals such as glucosinolate were statistically higher in florets compared with leaves in both broccoli and cauliflower cultivars. In contrast, total flavonoid and free sugar were found at higher levels in the leaf parts. The Asia purple cultivar exhibited statistically higher vitamin C (649.7 mg·100 g−1), total phenol (1345.2 mg·GAE 100 g−1), and total flavonoid (632.7 mg·CE 100 g−1) contents and consequently had the highest antioxidant activity (1.12 mg·mL−1) in its florets, while Baeridom and Bridal had the highest total glucosinolate (9.66 µmol·g−1) and free sugar (318.6 mg·g−1) contents, respectively compared with other cultivars. Likewise, the major fatty acids were palmitic (23.52%–38.42%), linoleic (13.09%–18.97%), and linolenic (26.32%–51.80%) acids, which comprised the highest compositional ratio (more than 50%) of polyunsaturated fatty acids (PUFAs) in most cultivars. Among the antioxidants, total phenol exhibited the most significant positive correlation (r = 0.698 **) with antioxidant activity, followed by vitamin C (r = 0.522 **) and total flavonoid (r = 0.494 **), indicating their significant contributions to total antioxidant activity.

Seasonal variation in phytochemicals and antioxidant activities in different tissues of various Broccoli cultivars

Florets, leaves, and stems of twelve commercial broccoli cultivars grown in the spring and fall seasons at the National Institute of Horticultural and Herbal Science (NIHHS), Rural Development Administration (RDA), Suwon, South Korea were evaluated for glucosinolates, vitamin C, total phenol, and total flavonoid contents and antioxidant activity. The levels of all phytochemicals and antioxidant activity were significantly influenced by cultivar (C), plant part (P), and growing season (S). Among the glucosinolates, glucoraphanin and glucobrassicin were the major constituents. The highest total glucosinolate content was found in the florets of plants grown in both seasons. Phenols and flavonoids were highest levels in leaves, while vitamin C was highest in stems, suggesting that broccoli leaves and stems may be good sources of such phytochemicals. The levels of all phytochemicals were generally higher in florets in the spring than in the fall, but were higher in leaves and stems during the fall than the spring. Furthermore, higher cultivar-dependent and tissue-dependent variation was observed in the spring than in the fall. Total phenol content exhibited a strong positive correlation (r = 0.674**) with antioxidant activity, followed by total flavonoid content (r = 0.497**), indicating their significant contribution to total antioxidant activity. Key words: Antioxidant activity, broccoli, glucosinolate, seasonal variation, total phenol, vitamin C.

Contents of Phytochemical Constituents and Antioxidant Activity of 19 Garlic (Allium sativum L.) Parental Lines and Cultivars

Phytochemical constituents, such as alliin, vitamin C, total phenol and total flavonoid, content of free sugars, and antioxidant activity of 19 garlic lines and cultivars [six parental lines, three controlled cultivars, five cultivars for regional adaptation test (RAT cultivars), and five new cultivars, released by NIHHS for commercialization] cultivated at the experimental field in the NIHHS, RDA in Suwon were evaluated. Average contents of alliin, vitamin C, total phenol and total flavonoid per 100 g dry weight, respectively, were 1,938.4 mg, 9.3 mg, 97.0 mg gallic acid equivalent (GAE) and 16.1 mg catechin hydrate equivalent (CE), and antioxidant activity was 27.5%. Among the three free sugars analyzed, sucrose was present in the greatest quantity (3.48%), followed by fructose (1.05%) and glucose (0.54%). The RAT cultivars, R-01, R-04 and R-05, and new cultivars released for commercialization, NC-02, NC-03 and NC-04, exhibited statistically greater contents of phytochemicals, and consequently possessed higher antioxidant activities as compared to the parental lines and control cultivars. Total flavonoid content showed the highest positive correlations with antioxidant activity (r = 0.908**), followed by total phenol and vitamin C contents.