Abstract ▼ AI-Helper

Peppermint (Mentha piperita L.) is a medicinal plant that belongs to the family Labiate. It was very famous to various biological function such as antifungal, antimicrobial, antioxidant and anti-pain activities. However, few research about anti-mite function was reported. In this study, it was to ev...

Peppermint (Mentha piperita L.) is a medicinal plant that belongs to the family Labiate. It was very famous to various biological function such as antifungal, antimicrobial, antioxidant and anti-pain activities. However, few research about anti-mite function was reported. In this study, it was to evaluate acaricidal toxicities of bioactive constituent isolated from M. piperita leaves and its analogues against pyroglyphid mites, Dermatophagoides farinae and D. pteronyssinus. The essential oil of M. piperita leaves were extracted by steam distillation extraction. It was analyzed the compound by GC/MS. The acaricidal activities of peppermint oil against Dermatophagoides spp. were estimated using the fumigant and contact bioassays. To compared the activities of M. piperita oil, it was using the commercial acaricides (DEET). In this fumigant bioassay, the LD50 values of M. piperita oil were 1.00 and 1.50 ㎍/㎤ against D. farinae and D. pteronyssinus, respectively. Similarly, in this contact bioassay, the LD50 values of M. piperita essential oil were 4.35 and 5.21 ㎍/㎠ against D. farinae and D. pteronyssinus, respectively.
The active compound of M. piperita oil was isolated by the silica gel column chromatography and prep HPLC. On the analyses of various spectroscopies technique, the active compound was identified as (±)-menthol (2-isopropyl-5-methylcyclohexanol). The acaricidal activities of menthol and its structural analogues were evaluated against Dermatophagoides spp. by fumigant and contact bioassays. In the fumigant bioassay, the acaricidal activity of (-)-menthol (0.19 and 0.12 ㎍/㎤) showed strongest activity against D. farinae and D. pteronyssinus, followed by (±)-menthol (0.23 and 0.21 ㎍/㎤), (+)-menthol (0.29 and 0.23 ㎍/㎤), (+)-neomenthol (0.32 and 0.26 ㎍/㎤), (+)-isomenthol (0.34 and 0.29 ㎍/㎤), 4-methylcyclohexanol (5.45 and 4.76 ㎍/㎤), 2-methylcyclohexanol (7.64 and 5.67 ㎍/㎤), and 1-methylcyclohexanol (9.82 and 8.56 ㎍/㎤). In this contact bioassay, (-)-menthol (0.31 and 0.27 ㎍/㎠) showed potent activities against D. farinae and D. pteronyssinus, followed by (±)-menthol (0.40 and 0.34 ㎍/㎠), (+)-menthol (0.45 and 0.39 ㎍/㎠), (+)-neomenthol (0.52 and 0.45 ㎍/㎠), (+)-isomenthol (0.58 and 0.51 ㎍/㎠), 4-methylcyclohexanol (6.69 and 5.55 ㎍/㎠), 2-methylcyclohexanol (8.68 and 7.50 ㎍/㎠), and 1-methylcyclohexanol (10.96 and 9.98 ㎍/㎠). However, 1-bromo-4-methylcyclohexane, 1,1-difluoro-2-methylcyclohexane and methylcyclohexane showed no activity against Dermatophagoides spp. in the fumigant and contact methods. In terms of structure relationships between acaricidal activities and functional groups (hydroxyl and isopropyl) on the cyclohexane skeleton, a isopropyl group (menthol isomers such as (+)-menthol, (-)-menthol, (+)-isomenthol and (+)-neomenthol) on the cyclohexane skeleton was more toxic than the other compound. This study indicates that M. piperita oil and menthol structural analogues could be valuable for development as safety acaricide for controlling of Dermatophagoides spp.

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