• Journal of Microbiology and Biotechnology
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• v.18 no.2
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• pp.314-321
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• 2008

Acaricidal effects of materials derived from Diospyros kaki roots against Dermatophagoides farinae and D. pteronyssinus were assessed using impregnated fabric disk bioassay and compared with that of the commercial benzyl benzoate. The observed responses varied according to dosage and mite species. The $LD_{50}$ values of the chloroform extract of Diospyros kaki roots were 1.66 and $0.96{\mu}g/cm^2$ against D. farinae and D. pteronyssinus. The chloroform extract of Diospyros kaki roots was approximately 15.2 more toxic than benzyl benzoate against D. farinae, and 7.6 times more toxic against D. pteronyssinus. Purification of the biologically active constituent from D. kaki roots was done by using silica gel chromatography and high-performance liquid chromatography. The structure of the acaricidal component was analyzed by GC-MS, $^1H-NMR,\;^{13}C-NMR,\;^1H-^{13}C$ COSY-NMR, and DEPT-NMR spectra, and identified as plumbagin. The acaricidal activity of plumbagin and its derivatives (naphthazarin, dichlon, 2,3-dibromo-1,4-naphthoquinone, and 2-bromo-1,4-naphthoquinone) was examined. On the basis of $LD_{50}$ values, the most toxic compound against D. farinae was naphthazarin $(0.011{\mu}g/cm^2)$ followed by plumbagin $(0.019{\mu}g/cm^2),$ 2-bromo-1,4-naphthoquinone $(0.079{\mu}g/cm^2)$, dichlon $(0.422{\mu}g/cm^2)$, and benzyl benzoate $(9.14{\mu}g/cm^2)$. Additionally, the skin color of the dust mites was changed from colorless-transparent to dark brown-black by the treatment of plumbagin. Similar results have been exhibited in its derivatives (naphthazarin, dichlon, and 2-bromo-1,4-naphthoquinone). In contrast, little or no discoloration was observed for benzyl benzoate. From this point of view, plumbagin and its derivatives can be very useful for the potential control agents, lead compounds, and indicator of house dust mites.

• Journal of Microbiology and Biotechnology
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• v.16 no.10
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• pp.1591-1596
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• 2006

Acaricidal effects of materials derived from Caesalpinia sappan heartwoods against Dermatophagoides farinae and D. pteronyssinus were assessed and compared with those evidenced by commercial benzyl benzoate and DEET. The observed responses varied according to dosage and mite species. The $LD_{50}$ values of the methanol extracts derived from C. sappan heartwoods were 6.13 and $5.44{\mu}g/cm^3$ against D. farinae and D. pteronyssinus, respectively. Furthermore, the ethyl acetate fraction derived from the methanol extract was approximately 8.71 more toxic than DEET against D. farinae, and 4.73 times more toxic against D. pteronyssinus. The biologically active constituent from the ethyl acetate fraction of C. sappan heartwood extract was purified via silica gel chromatography and high-performance liquid chromatography. The structure of the acaricidal component was analyzed by $GC-MS,\;^1H-NMR,\;^{13}C-NMR,\;^1H-^{13}C\;COSY-NMR$, and DEPT-NMR spectroscopy, and identified as juglone (5-hydroxy-l,4-naphthoquinone). Based on the $LD_{50}$ values of juglone and its derivatives, the most toxic compound against D. farinae was juglone ($0.076{\mu}g/cm^3$), followed by benzyl benzoate ($9.143{\mu}g/cm^3$) and 2methyl-l,4-naphthoquinone ($40.0{\mu}g/cm^3$). These results indicate that the acaricidal activity of C. sappan heartwoods is likely to be the result of the effects of juglone. Additionally, juglone treatment was shown to effect a change in the color of the cuticles of house dust mites, from colorless-transparent to dark brownish-black. Accordingly, as a naturally occurring acaricidal agent, C. sappan heartwood-derived juglone should prove to be quite 'useful as a potential control agent, lead compound, and house dust mite indicator.

• Journal of Microbiology and Biotechnology
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• v.17 no.8
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• pp.1394-1398
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• 2007

Acaricidal activity of the active constituent derived from Pyrus ussuriensis fruits against Dermatophagoides farinae and D. pteronyssinus was examined and compared with that of the commercial benzyl benzoate. The $LD_{50}$ value of the ethyl acetate fraction obtained from the aqueous extract of P. ussuriensis fruits was 9.51 and $8.59{\mu}g/cm^3$ against D. farinae and D. pteronyssinus, respectively. The active constituent was identified as quinone by spectroscopic analyses. On the basis of $LD_{50}$ values with quinone and its congeners, the compound most toxic against D. farinae was quinone ($1.19{\mu}g/cm^3$), followed by quinaldine (1.46), benzyl benzoate (9.32), 4-quinolinol (86.55), quinine (89.16), and 2-quinolinol (91.13). Against D. pteronyssinus, these were quinone ($1.02{\mu}g/cm^3$), followed by quinaldine (1.29), benzyl benzoate (8.54), 4-quinolinol (78.63), quinine (82.33), and 2-quinolinol (86.24). These results indicate that the acaricidal activity of the aqueous extracts can be mostly attributed to quinone. Quinone was about 7.8 and 8.4 times more toxic than benzyl benzoate against D. farinae and D. pteronyssinus. Additionally, quinaldine was about 6.4 and 6.6 times more toxic than benzyl benzoate against D. farinae and D. pteronyssinus, respectively. Furthermore, the skin color of the dust mites was changed from colorless-transparent to dark brown-black by the treatment of quinone. These results indicate that quinone can be very useful as potential control agents, lead compounds, or the indicator of house dust mites.