Acaricidal activity of Paeonia suffruticosa root bark-derived compounds against Dermatophagoides farinae and Dermatophagoides pteronyssinus (Acari: Pyroglyphidae).

The acaricidal activities of materials derived from the root bark of Paeonia suffruticosa against adults of Dermatophagoides farinae and Dermatophagoides pteronyssinus were examined using direct contact and fumigation bioassays and compared with those of benzyl benzoate, dibutyl phthalate, and N,N-diethyl-m-toluamide (deet), widely used acaricides. The active constituents of Paeonia root bark were identified as paeonol and benzoic acid by spectroscopic analyses. On the basis of 24-h LD50 values, the acaricidal activities of paeonol (7.82 microg/cm3) and benzoic acid (6.58 microg/cm3) against adult D. farinae were comparable to that of benzyl benzoate (7.72 microg/cm3) but higher than those of deet (36.34 microg/cm3) and dibutyl phthalate (33.92 microg/cm3). Against adult D. pteronyssinus, the acaricidal activities of paeonol (7.08 microg/cm3) and benzyl benzoate (7.22 microg/cm3) were comparable to that of benzyl benzoate (7.14 microg/cm3). Deet and dibutyl phthalate were less effective. In fumigation tests with both mite species, paeonol and benzoic acid were much more effective in closed containers than open ones, indicating that the effect of these compounds was largely a result of action in the vapor phase. Neither benzyl benzoate, deet, nor dibutyl phthalate exhibited fumigant toxicity. Paeonia root bark-derived materials, particularly paeonol and benzoic acid, merit further study as potential acaricides or lead compounds for the control of D. farinae and D. pteronyssinus.