GC–MS and GC-FID analyses, antimicrobial and insecticidal activities of Origanum glandulosum essential oil and their effect on biochemical content of CX pipiens larvae

Abstract

In this study the chemical composition of the essential oil extracted by hydrodistillation from Origanum glandulosum was analysed by GC-FID and GC–MS. Moreover, antibacterial and insecticidal activities and their effects on main biochemical constituents (proteins, carbohydrates, lipids and nucleic acids DNA/RNA) were evaluated against the fourth instar larvae of Culex pipiens. The essential oil yield calculated was 1.69 ± 0.01%. Twenty compounds in essential oil were distinguished. The chemical composition of the oil was largely dominated by oxygenated monoterpene with carvacrol (78.4%) as a major component. The antibacterial activity of the essential oil was determined against three standard bacteria Escherichia coli ATCC 25,922, Staphylococcus aureus ATCC 29,213 and Pseudomenas aeruginosa ATCC 27,853. The results proved that essential oil was highly active against Escherichia coli ATCC 25,922 and Staphylococcus aureus ATCC 29,213 by inhibition diameters varying between 30 and 40 mm respectively. In contrast, Origanum glandulosum essential oil did not inhibit the growth of Pseudomenas aeruginosa (≤ 6 mm). Moreover, the essential oil was found to exhibit a larvicidal activity, the LC50 and LC90 values against fourth instar larvae were 13.70 and 36.98 ppm, respectively. Lastly, biochemical bioassays revealed that the essential oil affected the energy reserves with a marked effect on lipids of larvae. In addition, a decrease of DNA and RNA were recorded after treatment of larvae with essential oil. Conclusively, insecticidal and antibacterial properties of the essential oil were also described in this work, in attempt to contribute to the use of Origanum glandulosum essential oil as an alternative to control microbial and insect-borne diseases.