Diterpenoids From <i>Erythroxylum sinense</i> : Bidirectional Behavioral Regulation of Root‐Knot Nematode <i>Meloidogyne incognita</i>

Root-knot nematodes (RKNs) (e.g., Meloidogyne incognita) pose a major threat to global agriculture, driving the need for sustainable control of nematodes. Current strategies mainly rely on synthetic nematicides, but their applications were limited by concerns over environmental toxicity and public health risks. In this study, two new diterpenoids, sinensins A‒B (1‒2), together with eight analogues (3‒10), were isolated from the endemic Chinese plant Erythroxylum sinense Y. C. Wu. Four selected compounds (4, 6, 7, and 10) were evaluated for their chemotaxis of M. incognita second-stage larvae (J2s) and their nematicidal activity. Among them, compound 10 with a cyclopropyl moiety exhibited a bidirectional regulation of J2s parasitic behavior: it attracted J2s at lower doses (10‒100 µg/mL), while repelled J2s at higher doses (160 and 200 µg/mL). These results highlighted that diterpenoid 10 from E. sinense represents a promising candidate for an eco-friendly "attract-kill" microsphere system to control nematodes.