Food protective effects of Periploca sepium oil and its active component against stored food mites.

The aim of this study was to examine the acaricidal activity of Periploca sepium oil and its active component against Tyrophagus putrescentiae. Based on its 50% lethal dose (LD(50) ) value, P. sepium oil (8.45 μg/cm(2)) was highly active against T. putrescentiae. The active constituent of P. sepium was isolated by chromatographic techniques and identified as 2-hydroxy-4-methoxybenzaldehyde. In the comparison with synthetic acaricides, the acaricidal activity of 2-hydroxy-4-methoxybenzaldehyde (0.94 μg/cm(2)) against T. putrescentiae was 12.2- and 31.2-fold greater than those of benzyl benzoate (11.45 μg/cm(2)) and N,N-diethyl-m-toluamide (29.33 μg/cm(2)), respectively. To establish structure-activity relationships, the acaricidal activities of 2-hydroxy-4-methoxybenzaldehyde and its derivatives against T. putrescentiae were determined by using an impregnated fabric disk bioassay. On the basis of LD(50) values, 4-methoxybenzaldehyde (0.48 μg/cm(2)) was the most effective against T. putrescentiae, followed by 3-methoxybenzaldehyde (0.82 μg/cm(2)), 2-hydroxy-5-methoxybenzaldehyde (0.92 μg/cm(2)), 2-methoxybenzaldehyde (0.95 μg/cm(2)), 2-hydroxybenzaldehyde (0.97 μg/cm(2)), and 2-hydroxy-3-methoxybenzaldehyde (2.35 μg/cm(2)). These results indicate that the introduction of a hydroxyl and/or methoxy group into the benzaldehyde skeleton increased the acaricidal activity. Therefore, 2-hydroxy-4-methoxybenzaldehyde and its derivatives could potentially be used as potent mite control agents.