Antioxidant activity and correlation analysis of phenolic compounds in novel varieties of <i>Lactuca sativa L.</i>

Purpose: To determine the antioxidant efficacy of three lettuce (Lactuca sativa L. Asteraceae) varieties: Cheongchima JLS201206-12 (a traditional variety), and two newly bred varieties, Cheongharang Ⅰ and Cheongharang Ⅱ. Method: Extraction was done with 100 mL of water and ethanol at various concentrations (20, 40, 60, 80, and 100 %) using a reflux extractor at 100 °C for 60 min. Total polyphenol content (TPC) and total flavonoid contents (TFC) were determined. Antioxidant activity of the lettuce extracts was evaluated in vitro using DPPH, ABTS, PMA, and FRAP assays with ascorbic acid and trolox as positive controls at 5and 800 μg/mL, respectively. Results: At 60 % ethanol, Cheongchima I also showed significantly higher phenolic (14.33 ± 0.00 mg GAE/g) and flavonoid (16.81 ± 0.00 mg CE/g) contents compared to Cheongchima, Cheongharang Ⅱ, and the standard controls (p < 0.05). Furthermore, Cheongharang Ⅰ exhibited significantly higher antioxidant activity compared to the traditional variety Cheongchima in DPPH, ABTS, PMA, and FRAPassays (p < 0.05). Conclusion: Aqueous and ethanol extracts of Cheongharang Ⅰ demonstrate significantly higher antioxidant effects than other varieties, suggesting its strong potential as a natural source of antioxidants used in functional foods.