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Highly Oxygenated Grayanane Diterpenoids from Flowers of Pieris japonica and Structure–Activity Relationships of Antifeedant Activity against Pieris brassicae

Chen, Xuan-Qin, Gao, Ling-Huan, Li, Yan-Ping, Li, Hong-Mei, Liu, Dan, Liao, Xia-Li, Li, Rong-Tao
Journal of agricultural and food chemistry 2017 v.65 no.22 pp. 4456-4463
Pieris brassicae, Pieris japonica, X-ray diffraction, antifeeding activity, bioassays, diterpenoids, flowers, nuclear magnetic resonance spectroscopy, poisonous plants, structure-activity relationships
Six new highly oxygenated grayanane diterpenoids, neopierisoids G–L, 1–6, together with 10 known related compounds, 7–16, were identified from the flowers of the poisonous plant Pieris japonica. The structures were elucidated on the basis of comprehensive NMR spectroscopy and mass analysis. The relative configurations of 1–6 were elucidated by analysis of ROESY spectra and comparison of NMR data with the analogues. The absolute configurations of 1–6 were established by the X-ray diffraction analysis of 1 and comparison of the CD spectra of 1–6. Compared with the skeleton of the normal grayanane diterpenoids, compounds 1–6 shared an unusual seco A ring moiety. The antifeedant activities of compounds 1–16 against Pieris brassicae were evaluated by using a dual-choice bioassay, and compounds 1–10 with a normal grayanane skeleton showed potent antifeedant activity against P. brassicae. The structure–activity relationships of antifeedant activities of 1–16 against P. brassicae are discussed.