Characterization of Antioxidant Potential and Variability Among Green Lettuce Lines

Lettuce (Lactuca sativa L.) is widely consumed for its flavor, nutritional value, and bioactive compounds such as chlorophyll and phenolics, which act as antioxidants and contribute to the prevention of chronic diseases. Chlorophyll also supports metabolic health and exhibits anti-inflammatory and anticancer properties. This study aimed to evaluate instrumental color, antioxidant capacity, chlorophyll content, and total phenolic compounds in green lettuce samples, considering different typologies and their respective lines. A total of twenty-four experimental green lettuce lines were analyzed, including sixteen belonging to the ‘Lisa’ typology (0204-1-4, 0204-2-3, 2030-1, 2031-2, 114671, 11471-2, 11573, 11661, 11694, 11739-1, 252G-3, Regina, Regiane Mill, Patrona, Janine, and Biof01) and eight to the ‘Mimosa’ typology (2000-2, 2001, 2012, 2015, Kirobalt, Nataly, Tango Verde, and Maraisa). Color was assessed using a Konica Minolta CM-25d spectrophotometer with D65 illuminant and a 10° observation angle, measuring lightness (L*), chromaticity (Chroma), and hue angle (°Hue). Antioxidant capacity was determined using the DPPH and ABTS methods, with results expressed in μmol Trolox per gram of sample. Chlorophyll content (mg/g) was measured by spectrophotometry at absorbances of 646.8 and 663.2 nm. Total phenolic compounds (TPC) were quantified by the Folin–Ciocalteu method and expressed in mg gallic acid equivalent per mL of sample. Data were subjected to Principal Component Analysis (PCA) using SAS software version 9.4. The first two principal components explained 84.6% of the total variance, with the first component associated with phenolic compounds and antioxidant capacity, and the second with the color parameters Chroma and °Hue. A positive correlation was observed among TPC, ABTS, and DPPH, and between chlorophyll and °Hue, while chlorophyll and lightness were negatively correlated. Lines such as 0204_1_4, Janine, and 11573 stood out due to their high antioxidant and phenolic content, as well as higher chlorophyll levels and a yellowish-green hue. Line 2030_1 exhibited more intense coloration (higher Chroma), while Kirobalt, Nataly, and 11467_1 were associated with greater lightness. In contrast, Tango Verde and Patrona showed higher °Hue and chlorophyll content. A clearer clustering of ‘Lisa’ lines was observed, associated with higher antioxidant capacity and bioactive content, whereas ‘Mimosa’ lines were more related to color traits such as lightness and chromaticity, with lower functional performance. The analysis revealed variation among green lettuce lines, with 0204_1_4, 11573, JANINE, and 252G_3 standing out for their high antioxidant, phenolic, and chlorophyll levels, indicating their potential for developing nutritionally superior lettuce varieties.