Design, Synthesis, Anti-Oomycete, and Insecticidal Activities of 3β-Acyloxy-18β-Glycyrrhetinic Acid Derivatives

Area of Science:

• Natural Product Chemistry
• Agrochemical Research
• Organic Synthesis

Background:

• 18β-Glycyrrhetinic acid (GA), a triterpenoid from licorice roots, is a potential precursor for novel agrochemicals.
• Development of effective and eco-friendly botanical pesticides is crucial for sustainable agriculture.
• Phytophthora capsici and Mythimna separata are significant agricultural pests causing substantial crop losses.

Purpose of the Study:

• To synthesize novel 3β-acyloxy-18β-glycyrrhetinic acid derivatives.
• To evaluate the synthesized compounds for anti-oomycete activity against Phytophthora capsici.
• To assess the insecticidal potential of the derivatives against Mythimna separata.

Main Methods:

• Twelve 3β-acyloxy-18β-glycyrrhetinic acid derivatives (3a-l) were synthesized.
• Compound structures were confirmed using spectroscopic techniques (¹H NMR, ¹³C NMR, HR-MS).
• Bioassays were conducted to determine anti-oomycete activity (EC₅₀ values) and insecticidal efficacy (mortality rates).

Main Results:

• Six synthesized derivatives (3d, 3e, 3h, 3i, 3j, 3k) displayed notable anti-oomycete activity against Phytophthora capsici, with EC₅₀ values ranging from 20.03 to 29.36 mg/L.
• Six derivatives (3b, 3c, 3f, 3g, 3i, 3l) demonstrated significant insecticidal activity against Mythimna separata, achieving mortality rates between 51.9% and 75.6%.
• The observed bioactivities were found to be closely related to the R-group substituent, indicating its significant impact on efficacy.

Conclusions:

• The synthesized 18β-glycyrrhetinic acid derivatives show potential as novel botanical pesticides.
• Specific derivatives exhibit promising efficacy against both oomycete pathogens and insect pests.
• Further research into structure-activity relationships can optimize these compounds for agricultural applications.