Insecticidal activity and systematic insights of carvacrol against Tribolium castaneum: Acetylcholinesterase inhibition, oxidative stress, and molecular docking"

Carvacrol is a potent insect control agent with significant bioactivity against various agricultural pests. This study aimed to investigate the mode of action of carvacrol, an effective insect control agent, against Tribolium castaneum adults and larvae. The study included assessments of carvacrol toxicity, biochemical alterations, and scanning electron microscopy observations. Additionally, molecular docking studies were performed to predict the insecticidal mechanism of carvacrol. The contact toxicity assay revealed significant mortality rates for both adults and larvae, with LC₅₀ values of 30.95 mg/mL and 8.08 mg/mL, respectively. Carvacrol treatment resulted in a significant decrease in the levels of reduced glutathione (GSH), superoxide dismutases (SODs), and glutathione peroxidase (GPx), while increasing malondialdehyde (MDA) levels. Additionally, carvacrol inhibited acetylcholinesterase (AChE) activity. Scanning electron microscopy revealed morphological abnormalities in treated larvae, including flaccidity, deformation, cuticle shrinkage, and genital papillae deformation. The docking analysis showed that carvacrol has a high affinity for specific proteins within T. castaneum, supporting its insecticidal potential. Notably, Glutathione S-transferase (GST) demonstrated the strongest binding affinity for carvacrol with a binding energy of −6.4 kcal/mol. In contrast, chlorpyrifos showed no affinity for target active sites. Carvacrol exhibited a stronger binding affinity for AChE (−7.1 kcal/mol) compared to chlorpyrifos. However, both compounds displayed equivalent binding affinities for nicotine mononucleotides. Carvacrol showed a binding affinity of −4.3 kcal/mol for microRNA 20b, which was lower than the binding affinity of chlorpyrifos (−5.1 kcal/mol) for microRNA 20b. Carvacrol demonstrated a stronger binding affinity for cytochrome P450 enzymes compared to chlorpyrifos. Notably, both compounds exhibited an identical binding affinity of −5.2 kcal/mol for odorant-binding protein. In conclusion, these findings highlight carvacrol's potential as an effective biocontrol agent against T. castaneum. This potential insecticidal activity is supported by its toxicity, inhibition of GST activity, suppression of cytochrome P450 enzymes, and its ability to inhibit microRNA and AChE activity.