Assessment of GC-MS and antioxidant properties of seaweed extracts as a new larvicidal agent targeting Culexquinquefasciatus.

Mosquito-borne illnesses present a major public health issue, requiring the development of sustainable and environmentally friendly approaches to control vectors. The present study explores the larvicidal potential of seaweed extracts and the antioxidant activities of Codium fragile and Turbinaria conoides-derived bioactive substances as a natural alternative to synthetic insecticides. The phytochemical analysis indicated that both C. fragile and T. conoides ethanolic extracts contained a total of fourteen compounds, which is greater than the other extracts. The GC-MS analysis performed on the ethanolic extract of C. fragile and T. conoides revealed the presence of twenty distinct compounds. C. fragile was found to have hexadecanoic acid (27.79 %), 4-methanocycloocta[d]pyridaz (7.39 %), 1,1-dimethoxy-2-hepten-7-al (7.04 %), and octadecanoic acid (5.9 %). For T. conoides, the main compounds discovered were dibutyl phthalate (69.56 %), 1,2-benzenedicarboxylic acid (14.01 %), and phthalic acid (2.58 %), all of which exhibited the highest area percentages. The ethanolic extract of T. conoides demonstrated the highest antioxidant activity, with DPPH at 81.48 ± 1.0 %, ABTS at 88.29 ± 1.0 %, and hydroxyl radical scavenging at 86.51 ± 1.0 %, followed by other extracts. The antioxidant exhibited IC50 values of 22.50 ± 1 μg mL-1, 34.86 ± 0.9 μg mL-1, and 40.69 ± 1.1 μg mL-1 for DPPH, ABTS, and hydroxyl radical scavenging activities, respectively. The findings suggest that the compound acts as a powerful antioxidant, with lower IC50 values indicating a greater antioxidant potential. Chloroform extracts from C. fragile and T. conoides demonstrated significant effects on Cx. quinquefasciatus larvae. Consequently, the bioactive compounds derived from the ethanolic extracts could be utilized as alternatives for both antioxidant and larvicidal applications, potentially reducing the negative environmental impacts associated with synthetic insecticides. Seaweed presents a promising option for controlling mosquitoes due to its larvicidal characteristics.