In Vitro and In Silico Protocols for the Assessment of Anti-Tick Compounds from Pinus roxburghii against Rhipicephalus (Boophilus) microplus Ticks

SIMPLE SUMMARY: Rhipicephalus (Boophilus) microplus, commonly known as the cattle tick, is an ectoparasite that affects all terrestrial vertebrates, including livestock. As animal husbandry is the backbone of Pakistan’s economy, tick infestation results in significant economic losses for farmers annually. Given the reported resistance of various tick species to chemical acaricides, a recent study investigated the effectiveness of Pinus roxburghii plant extract in controlling tick populations. This study observed that the plant extract showed high efficacy in vitro against different tick stages in adult immersion test and larval packet test. Additionally, the in silico approach confirmed the in vitro results. This revealed a strong binding interaction between the plant’s phytochemicals, particularly catechin and myricetin, and the GABA tick protein in a molecular docking study with a docking score of −7.7 and −7.6 kcal/mL, respectively. As a result, this study suggests the use of P. roxburghii as a promising anti-tick agent. ABSTRACT: Pinus roxburghii, also known by the name “Himalayan chir pine,” belongs to the Pinaceae family. Rhipicephalus (Boophilus) microplus tick is one of the most significant bovine ectoparasites, making it a major vector of economically important tick-borne diseases. The researchers conducted adult immersion tests (AIT) and larval packet tests (LPT) to investigate the acaricidal effect of P. roxburghii plant extract on R. (B.) microplus and its potential modulatory function when used with cypermethrin. Eggs were also assessed for their weight, egg-laying index (IE), hatchability rate, and control rate. After exposure to essential extract concentrations ranging from 2.5 to 40 mg/mL for 48 h, adult female ticks’ oviposition inhibition and unfed R. (B.) microplus larvae’s mortality rates were analyzed. Engorged females exposed to P. roxburghii at 40 mg/mL had reduced biological activity (oviposition, IE) compared to positive and negative controls. A concentration of 40 mg/mL of P. roxburghii caused 90% mortality in R. (B.) microplus larvae, whereas cypermethrin (the positive control) caused 98.3% mortality in LPT. In AIT, cypermethrin inhibited 81% of oviposition, compared to the 40 mg/mL concentration of P. roxburghii, which inhibited 40% of the ticks’ oviposition. Moreover, this study assessed the binding capacity of selected phytocompounds with the targeted protein. Three servers (SWISS-MODEL, RoseTTAFold, and TrRosetta) recreated the target protein RmGABACl’s 3D structure. The modeled 3D structure was validated using the online servers PROCHECK, ERRAT, and Prosa. Molecular docking using Auto Dock VINA predicted the binding mechanisms of 20 drug-like compounds against the target protein. Catechin and myricetin showed significant interactions with active site residues of the target protein, with docking scores of −7.7 kcal/mol and −7.6 kcal/mol, respectively. In conclusion, this study demonstrated the acaricidal activity of P. roxburghii extract, suggesting its potential as an alternative natural acaricide for controlling R. (B.) microplus.