Derivatization of Natural Compound β-Pinene Enhances Its In Vitro Antifungal Activity against Plant Pathogens

Abstract

Some derivatives exhibited moderate or significant antifungal activity due to the fusion of the amide moiety or the acylthiourea moiety with the pinane skeleton. The structure-activity relationship analysis showed that the fluorine atom and the strong electron withdrawing nitro group, or trifluoromethyl group on the benzene ring of the derivatives had a significant effect on the improvement of the antifungal activity against <i>Colletotrichum gloeosporioides</i>, <i>Fusarium proliferatum</i>, <i>Alternaria kikuchiana</i> and <i>Phomopsis</i> sp. Meanwhile, the introduction of an ethyl group at the meta-position on the benzene ring of the derivatives could improve the antifungal activity against <i>Phytophthora capsici</i>. Compounds <b>4e</b>, <b>4h</b>, <b>4q</b>, <b>4r</b> exhibited broad-spectrum antifungal activity against the tested strains. Compound <b>4o</b> had significant antifungal activity against <i>Phytophthora capsici</i> (IC₅₀ = 0.18 μmol/L). These derivatives were expected to be used as precursor molecules for novel pesticide development in further research.