The effect of salicylic acid on shelf life and bio-active compounds in lettuce (Lactuca sativa L.)

Lettuce (Lactuca sativa L.) is a vital leafy vegetable, primarily consumed as fresh or in salad mixes. It is an excellent source of phytochemicals and is renowned for its functional properties around the globe. Biosynthesis of bioactive compounds can be improved by elicitation with crops to enhance nutraceutical and nutritional quality. Lettuce plants were treated with 100 mg/L Salicylic Acid (SA) on the 35^th, 42^nd, and 49^th days after planting to enhance bioactive compounds and preserve their bioactivity after harvest. Total phenolics, Vitamin C, Antioxidant activity (DPPH), Chlorophyll a, b, and Carotenoid levels were measured immediately after harvest and seven days after storing both at room temperature and 4°C. SA application on the 49^th day (T3) significantly increased Vitamin C content (4.00 ± 0.38 mg/g; P<0.05) and reduced postharvest degradation, with refrigerated storage (4°C). Carotenoid levels remained stable under refrigeration (0.13 ± 0.01 mg/g) but declined at room temperature (P<0.05). Total phenolics (4.01 ± 0.45 mg/g) and antioxidant activity (1.52 ± 0.05 mg/g) peaked in SA-treated at the 49^th day, with refrigeration preserving more of the phenolics and antioxidant activity. The time of the SA application has an important role in enhancing the total phenol content and enhanced antioxidant activity of lettuce. These results suggest that the optimal timing of SA application, particularly on the 49^th day, improves the nutritional quality and stability of bioactive compounds in lettuce during storage. This study reveals that the application of SA as a pre-harvest treatment enhances and stabilizes bioactive compounds in lettuce, improving its functional properties.