Bio-Insecticide of Thymus vulgaris and Ocimum basilicum Extract from Cell Suspensions and Their Inhibitory Effect against Serine, Cysteine, and Metalloproteinases of the Red Palm Weevil ( Rhynchophorus ferrugineus ).

The current study was designed to investigate the insecticide role of volatile constituents produced from cell suspensions of T. vulgaris and O. basilicum against R. ferrugineus . Constituents were extracted from cell suspension after 40 days. Growth kinetics were measured with an inoculation of Verticillium dahliae and identified by GC-MS. Total volatile phenolic constituents were measured. Insecticidal activity against R. ferrugineus (adult) and proteolytic enzyme activity in larvae were assessed. GC-MS showed that the T. vulgaris extract has higher amounts of thymol, p -cymene, γ-terpinene, β-caryophyllene, and linalool in comparison to the O. basilicum extract, which is rich in estragole, β-terpineol, ( E )-β-ocimene, 1,8-cineole, germacrene D, and eugenol. The T. vulgaris extract showed an LC ₅₀ of 1032 µg/mL, followed by O. basilicum with an LC ₅₀ of 1246 µg/mL. The IC ₅₀ values against the total proteases were 110.8 and 119.4 µg/mL for T.   vulgaris and O.   basilicum , respectively. The IC _{5 0} for the trypsin-like serine proteinase assessment was 81.6 and 91 µg/mL for T.   vulgaris and O.   basilicum , respectively. Cysteine, chymotrypsin, and metalloproteinase assessment showed an IC ₅₀ above 5000 µg/mL for both extracts. The study is proposed as a potential approach to use T. vulgaris and O. basilicum extract as a bio-insecticide against R. ferrugineus using an accessible and efficient cell suspension technique.