Emerging resistance to insecticides has influenced pharmaceutical research and the search for alternatives to control the common bed bug Cimex lectularius. In this sense, natural products can play a major role. Tagetes patula, popularly known as dwarf marigold, is a plant native to North America with biocide potential. The aim of this work was to evaluate the biological activity of T. patula essential oil (EO) against adult common bed bugs via exposure to dry residues by the Impregnated Paper Disk Test (IPDT) using cypermethrin as a positive control. We selected the enzyme acetylcholinesterase as a target for modeling studies, with the intent of investigating the molecular basis of any biological activity of the EO. Chemical analysis of the EO was performed using gas chromatography coupled to mass spectrometry (GC-MS). Additionally, oral and dermal acute toxicity tests were performed according to Organization for Economic Cooperation and Development (OECD) guidelines. The sulforhodamine B assay (SRB) was performed to verify the cytotoxicity of EO to HaCaT cells. The EO eliminated 100 % of the bed bugs at 100 mg mL with an LC value of 15.85 mg mL. GC-MS analysis identified α-terpinolene, limonene, piperitenone, and piperitone as major components of the mixture. Molecular modeling studies of these major compounds suggested that they are acetylcholinesterase inhibitors with good steric and electronic complementarity. The in vitro cytotoxicity evaluation revealed a LC = 37.06 μg mL and in vivo acute toxicity showed an LC >4000 mg kg, indicating that the EO presents low risk of toxic side effects in humans. The T. patula essential oil components provide a promising strategy for controlling bed bug populations with low mammalian toxicity. These findings pave the way for further in vivo studies aimed at developing a safe and effective insecticide.

The secondary metabolism of plants plays a key role in plant-insect interactions. Among the various classes of metabolites produced, volatile organic compounds (VOCs) play important echophysiological roles, including the attraction of pollinators. This work aimed to develop a method to extract VOCs using headspace (HS) and solid-phase microextraction (SPME), which can be applied in future studies to contribute to the understanding of the role of VOCs in the pollination process. Therefore, a HS-SPME method combined with gas chromatography-mass spectrometry (GC-MS) was developed for the extraction and characterization of VOCs of melon flowers (Cucumis melo L.). The extraction was carried out with the fibers PDMS, DVB/ CAR/PDMS and CAR/PDMS for the times 15, 30, and 45 min. Fifty compounds belonging to the following chemical classes were identified: terpenes, hydrocarbons, esters, ethers, ketones, aldehydes, and alcohols. CAR/PDMS fiber extracted the largest amount of compounds, and was more efficient for the extraction of volatile compounds with lower molecular weight, low boiling point and ideal for analytes in low concentration. Therefore, the evaluated method proved to be a promising tool for the analysis of VOCs of melon flowers, to be applied in new studies of the relationships between chemical composition and the processes of attraction of pollinators.

The cattle tick Rhipicephalus microplus is a great sanitary problem and causes huge losses to livestock, being a vector of important diseases. The aim of this work was to verify the action of plant-derived material obtained from Tagetes patula on the life cycle of R. microplus, as well as to analyze the action of these extracts on ovary cells of engorged females.