Acaricidal activities of the essential oil from Rhododendron nivale Hook. f. and its main compund, δ-cadinene against Psoroptes cuniculi

In this paper, the acaricidal activities of Rhododendron nivale Hook. f. and its main compound, delta-cadinene were investigated, and the chemical composition of the essential oil was analyzed. The results showed that among aqueous, 70% ethanols, acetic ether, chloroform, petroleum ether and essential oil extracts from the shoots and leaves, the essential oil showed the best in vitro acaricidal activity against adult P. cuniculi, which occurred in a concentration- and time-dependent manner. The median lethal time (LT50) values of four concentrations (33.33-4.17 mg/ml) of the essential oil ranged from 1.476 to 25.900 h, respectively. After the treatment of P. cuniculi with the essential oil and ivermectin, infected rabbits were free of scabs or secretions in the ear canal by day 20. Then, the percent yield of essential oil from the leaves and shoots was 2.45% (w/w), which includes 50 compounds. The primary component identified was terpenes, and among of compounds identified from the essential oil of R. nivale the highest relative content was delta-cadinene, which also presented the marked acaricidal activity against Psoroptes cuniculi in vitro. These findings provide evidence for the use of acaricides as a traditional medicine and indicate that the essential oil and delta-cadinene could be used to control mites in livestock. (C) 2017 Elsevier B.V. All rights reserved.