Insecticidal and growth inhibitory effects of some thymol derivatives on the beet armyworm,Spodoptera exigua(Lepidoptera: Noctuidae) and their impact on detoxification enzymes

Abstract

BACKGROUND: Thymol is a known natural product with insecticidal activity against several insect species. A recent study on structural modifications of thymol to thymyl esters and their efficacy against Spodoptera litura suggested that such an approach could develop generalized novel insecticides/insect growth inhibitors and requires further studies to establish the efficacy against lepidopterans.RESULTS: Thymol and structurally modified eight esters were evaluated against beet armyworm, Spodoptera exigua using the topical application. Thymyl butanoate was the most toxic compound with a median lethal dose (LD 50 ) of 2.33 and 1.62 ∼g/larva after 24 and 48 h posttreatment, respectively. All thymyl esters were potentially better than the parent compound thymol, except thymyl dibromoacetate, in their efficacy against Spodoptera exigua. Essentially, there were three levels of activity visà-vis the compounds used, that is, with the LD 50 range of 1.5 to 5.0, 7.0 to 15.0, and > 20 ∼g/larva, respectively. Ovicidal activity and reduction in larval growth were also determined by treating third instars at sub-lethal doses, that is, LD 50 doses of second instars. Thymyl butanoate treated larvae inhibited glutathione S-transferase, carboxylesterase, and acetylcholinesterase activities, whereas the other thymyl esters induced these enzymes. CONCLUSION: Thymyl butanoate exhibited higher toxicity against Spodoptera exigua and is the first to report about > 15.5× more toxicity than thymol and > 6.5× than thymyl cinnamate, which suggests that the efficacy was species-specific versus the chemical structural variation of the esters.

Biological Activity of Hybrid Molecules Based on Major Constituents of Cinnammomun verum and Thymus vulgaris Essential Oils

“…In the present study, we proposed to develop reliable chemical methods for the industrial scaling-up of six bioactive hybrid molecules based on major constituents of Cinnamomun verum and Thymus vulgaris EOs. Some recent works have demonstrated the possibility of obtaining, by other chemical methods, a few of these hybrid molecules, namely, 2-Isopropyl-5-methylphenyl benzoate ( 1 ), 4-Allyl-2-methoxyphenyl benzoate ( 3 ), and 2-Isopropyl-5-methylphenyl cinnamate ( 4 ), and their potential bioactivity as antileishmanial and insecticidal compounds has been tested [ 43 , 44 ]. For the first time, we have demonstrated further biological activities in the form of antifungal effects against two different modes of action, and their cytotoxicity results allowed us to propose industry-targeted applications for EO-based hybrid molecules.…”

Antifungal activity of Ligusticum chuanxiong essential oil and its active composition butylidenephthalide against Sclerotium rolfsii

“…[14][15][16][17] More importantly, numerous active compounds derived from plants have the potential to serve as lead compounds for the synthesis and development of novel fungicides. [18][19][20] For example, fungicides Yinguo (2-allyl phenol) and Yintai (4-butanoyl phenol), flumorph and Xiangcaoliusuobingmi were created based on ginkgo phenol, cinnamic acid and vanillin as lead compound, respectively. [21][22][23][24] It is worth noting that the chemical structures modified on the lead compounds and the functional groups attached to them also can affect the bioactivity.…”

“…This makes it difficult for pathogens to develop resistance, aligning with sustainable development strategies for disease management 14–17 . More importantly, numerous active compounds derived from plants have the potential to serve as lead compounds for the synthesis and development of novel fungicides 18–20 . For example, fungicides Yinguo (2‐allyl phenol) and Yintai (4‐butanoyl phenol), flumorph and Xiangcaoliusuobingmi were created based on ginkgo phenol, cinnamic acid and vanillin as lead compound, respectively 21–24 .…”

Repellency of Carvacrol, Thymol, and Their Acetates against Imported Fire Ants

“…Additionally, carvacrol acetate, a naturally occurring compound found in thyme oil [19], has shown superior repellency against unfed Rhipicephalus sanguineus sensu lato ticks compared to carvacrol [20]. Thymol acetate, a minor compound naturally found in thyme oil [21], has exhibited a higher toxicity against the beet armyworm than thymol [22]. To the best of our knowledge, there are no reports on the behavioral effects of carvacrol and thymol, as well as their acetates, against imported fire ants.…”