Effect of acute ingestion of fresh and stored lettuce (Lactuca sativa) on plasma total antioxidant capacity and antioxidant levels in human subjects

Abstract

The present study investigated whether storage under modified-atmosphere packaging (MAP) affected the antioxidant properties of fresh lettuce (Lactuca sativa). Eleven healthy volunteers (six men, five women) consumed 250 g fresh lettuce, and blood was sampled before (0 h) and 2, 3 and 6 h after consumption. The protocol was repeated 3 d later with the same lettuce stored at 5°C under MAP conditions (O2–N2(5:95, v/v)). Results showed that after ingestion of fresh lettuce, plasma total radical-trapping antioxidant potential (TRAP), measured as area under the curve, was significantly higher (1·3 (SEM 0·3) MMOL/L PER 6 H;P<0·05) THAN THE VALUE OBTAINED WITH MAP-STORED LETTUCE (0·1 (sem 0·2) mmol/l per 6 h). Plasma TRAP, quercetin andp-coumaric acid were significantly different from baseline values (P≤0·05) 2 and 3 h after fresh lettuce ingestion. Caffeic acid increased significantly at 3 h (P<0·05). Plasma β-carotene levels increased significantly at 6 h (P<0·05). Vitamin C concentrations (mg/l) rose from 10·9 (sem 2·0) to 12·7 (sem 3·0) (P<0·001), 12·7 (sem 2·0) (P<0·01) and 12·9 (sem 3·0) (P<0·05) at 0, 2, 3 and 6 h respectively. No changes were observed after ingestion of MAP-stored lettuce for all the measured markers. Our present results showed that ingestion of MAP-stored lettuce does not modify plasma redox status in healthy subjects. Further research is needed to develop post-harvesting techniques able to preserve the bioactive molecule content of plant food.