A Move Toward Green Agriculture: Discovery of Novel Environmental-Friendly Insecticidal “ulvan’’ from the Renewable Bioresource Ulva lactuca; Effect of the Extraction Processes on the Chemical–Physical, and Insecticidal Properties

The research of effective insecticidal agents is important challenging to limit the insecticide resistance of many larvae insect populations. This study aimed not only, to discover the insecticidal efficiency of the sulphated polysaccharide ‘ulvan’ from the green seaweed Ulva lactuca, as a novel environmental-friendly insecticidal agent; but also, to investigate an alternative strategy for insecticide productions and to improve the effective control of Spodoptera littoralis larvae. This aim reached by the investigation of the enzymatic chemical extraction and acid extractions effects on physical properties and insecticidal activities of ulvan extract; for further, feasible and optimal application of ulvans, as insecticidal agent. The study demonstrated that ulvans were characterized by anionic stable structure and molecular weight distribution; varied between 1.77 and 7.21 (× 10² kDa), as well as, special particle size, which were affected by extraction processes. Ulvan will be a precious candidate due to their bioactivity and environmental safety. The extraction procedure effects were observed in chemical composition, molecular weight, particle size, surface charge and insecticidal activities of ulvans. At high concentrations, the enzymatic-chemical (EE) and acidic (CA1) extraction processes can successfully produce ulvans with the greatest insecticidal activities against S. littoralis larvae. The mortality rate of larvaes after treatments with concentration at 100 (mg/ml), achieved 75% of larvae’s mortality. LC 30, LC50 and LC 90 evidenced the expected outcome of the insecticidal ability of ulvans. The insecticidal efficiency of ulvans with a dose-dependent manner promote their use as novel eco- friendly bio-insecticidal agent suitable for the agriculture systems needs and technology trends. This strategy of (EE) and (CA1) extraction processes can considerably improve the economic and environmental benefits.