Four New Insect Antifeedant neo-Clerodane Diterpenoids, Ajugacumbins A, B, C and D, from Ajuga decumbens

Abstract

From the ethanol extract of whole herbs of Ajuga decumbens (Labiatae), four new neo-clerodane diterpenoids, named ajugacumbins A, B, C and D (1-4), were isolated. The configuration of 1 was determined to be 6α-acetoxy-4, 17-epoxy-18-tigloyloxy-neo-cleroda-13-en-15, 16-olide by X-ray analysis. THe other structures were also determined by spectroscopic analysis to be 4, 17-epoxy-6α-hydroxy-18-tigloyloxy-neo-cleroda-13-en-15, 16-olide (2), 1α, 3β, 6α-triacetoxy-4, 17-epoxy-18-tigloyloxy-neo-cleroda-13-en-15, 16-olide (3) and 6α-acetoxy-4, 17-epoxy-3β-hydroxy-18-tigloyloxy-neo-cleroda-13-en-15, 16-olide (4). These compounds displayed insect antifeedant activity.