Anti-tick potential and intra-specific chemical variations in Ageratum conyzoides L. collected from Indus plain and Central India

Background: Tick and tick-borne diseases significantly affect the animal husbandry sector worldwide. To overcome this menace, chemically synthesized acaricides are being used. However, these acaricides are toxic to the animals, pose environmental threat and also have led to the development of resistance in ticks. Objectives: Search for safe and efficacious plant-based alternatives to the chemical acaricides and to assess chemical variability among intra-specific germplasms. Materials and Methods: Ageratum conyzoides L. samples were collected from different locations and pharmacognostic analysis was performed. The plant extract was subjected to chromatographic profiling and quantification of three bioactive markers precocene I, precocene II, and caryophyllene oxide followed by in vitro anti-tick activity through the adult immersion test. Results: Precocene I content ranged from 0.001% to 0.019% while precocene II and caryophyllene oxide content varied from 0.003% to 0.11%. In the Indus plain samples, adult tick mortality (%) ranged from 15.0 ± 2.9 to 78.5 ± 4.1, whereas in the Central India, it ranged from 30.0 ± 12.9 to 81.4 ± 7.7 at 8% concentration of plant extract. Precocene II showed weak positive correlation (r = 0.11) with tick mortality. The results indicate that there is considerable variation in the marker compounds content and anti-tick potential of the plant extracts analyzed. There is significant (P < 0.05) variation in marker compound content as well as anti-tick potential of A. conyzoides. Conclusion: The results indicate there apart from the analyzed marker compounds there might be some other phytomolecules playing a role in the tick mortality which needs further investigation.