Methyl palmitate, an acaricidal compound occurring in green walnut husks

Area of Science:

• Agricultural Science
• Organic Chemistry
• Entomology

Background:

• Walnut (Juglans regia L.) exhibits known insecticidal properties against various pests.
• Exploring natural compounds from walnut offers a sustainable route for novel pesticide development.

Purpose of the Study:

• To investigate the acaricidal potential of walnut green husk extracts.
• To isolate and identify bioactive compounds responsible for the observed activity.

Main Methods:

• Bioassay-guided fractionation of petroleum-ether extracts from walnut green husks.
• Structure characterization of the isolated compound using infrared spectroscopy and NMR.
• High-performance liquid chromatography (HPLC) for compound identification.
• Slide dip bioassays to determine acaricidal activity against Tetranychus cinnabarinus.

Main Results:

• Methyl palmitate (MP), a fatty acid ester, was identified as the active compound.
• MP demonstrated strong acaricidal activity, causing 97.9% mortality in adult Tetranychus cinnabarinus at 10 mg/ml.
• Significant mortality (62.8%) was observed at 1 mg/ml within 24 hours.
• Lower efficacy was noted against mite eggs (57.2% mortality).

Conclusions:

• Methyl palmitate isolated from walnut green husks possesses potent acaricidal properties against adult carmine spider mites.
• MP represents a promising natural product for the development of environmentally friendly pesticides.