Structure-activity studies on analogues of 4-methylguaiacol, a cattle anal odour constituent repellent to the brown ear tick (Rhipicephalus appendiculatus)

Abstract

Previously, 4-methylguaiacol, a major constituent of cattle anal odour, was found to have a high repellence on Rhipicephalus appendiculatus. In the present study, 10 structural analogues of the phenol were tested for repellence against R. appendiculatus in order to assess the effects of (i) absence or presence of the 4-alkyl group of varying length, (ii) inclusion of a double bond in the 4-alkyl chain, (iii) linking the two phenolic oxygen in a methylenedioxy bridge, (iv) replacement of the OCH 3 with CH 3 and inclusion of another CH 3 at position 6, and (v) presence of an additional OCH 3 group at position 6. The analogues comprised of 2-methoxyphenol (guaiacol), 4-ethyl-2methoxyphenol, 4-propyl-2-methoxyphenol, 4-allyl-2-methoxyphenol (eugenol), 3,4-methylenedioxytoluene, 2,4dimethylphenol, 4-ethyl-2-methylphenol, 2,4,6-trimethylphenol, 4-propyl-2,6-dimethoxy-phenol and 4-allyl-2,6dimethoxyphenol, which were compared at different doses in a two-choice climbing assay set up. Each analogue showed either increased or reduced repellence compared with 4-methylguaiacol. The structural feature that was associated with the highest repellence was 4-propyl moiety in the guaiacol unit (RD 75 = 0.031 for 4-propyl-2methoxyphenol; that of 4-methylguaiacol = 0.564). Effects of blending selected analogues with high repellence were also compared. However, none of the blends showed incremental increase in repellence compared with that of 4propyl-2-methoxyphenol. We are currently evaluating the effects of controlled release of the compound at different sites on cattle on the behavior and success of R. appendiculatus to locate their predilection feeding site.

Nanoencapsulation of 4-Propylguaiacol in β-Cyclodextrin, Ethyl Cellulose, and Polyvinylpyrrolidone

“…PVP ligand interacts with Pd NPs through O-atom of the pyrrolidone ring [16]. Structural activity studies carried out previously on analogues of 4-methylguaiacol [21]. e objective of this study was to develop controlled release formulations of nanocapsules of 4propylguaiacol in different polymers.…”