Detoxification of Plant Aromatic Abietanoids via Cleavage of the Benzene Ring into 11,12-Seco-diterpene Polyenes by a Specialist Insect of Leucosceptrum canum.

Leaves of Leucosceptrum canum harbor abundant toxic aromatic abietanoids, and they are rarely attacked by insect herbivores, except for the larvae of Nacna malachitis. The excrements of the insect that fed on L. canum leaves were investigated, leading to the isolation and identification of two unprecedented 11,12-seco-abietane diterpene polyenes: nacnabietanins A (1) and B (2). This discovery heralds a unique detoxification mechanism of plant aromatic abietanoids by insects through enzymatic cleavage of stable benzene rings into more easily degraded polyenes.