Natural preservative ingredient from marine alga Ulva lactuca L.

Summary The contents of total chlorophyll (T‐Chl), carotenoids and phenolics compounds were quantified in the biomasses of Ulva lactuca grown either in normal or artificial sea water under indoor conditions. The antioxidant and antibacterial activities of U. lactuca crude organic extracts ( Ulva‐ COEs) were determined. Thirty‐four compounds in Ulva‐ COEs were characterised by thin layer chromatography and high‐performance liquid chromatography. The major compounds were chlorophyll a (Chl a ) (15.60–30.90%) and b (Chl b ) (12.20–14.89%) , 9‐cis β‐carotene (13.12–14.47%), α‐carotene (11.44–11.47%) and all‐trans β‐carotene (6.16–29.70%, of total carotenoids).The Ulva‐ COEs exhibited remarkable antioxidant activity, with an IC 50 (concentration which causes a 50% of DPPH radical scavenging activity) values ranged from 16.5 and 18.7 μg mL −1 , which could be compared with the synthetic antioxidants: α‐tocopherol (14.4 μg mL −1 ), butylated hydroxyanisol (13.1 μg mL −1 ) and butylated hydroxyltoluene (13.1 μg mL −1 ). Also, Ulva‐ COEs exhibited great potential antibacterial activities against six bacterial strains, with minimal inhibitory concentration values ranged from 0.40 to 0.35 mg mL −1 .