Biotransformation of monoterpenoids in common cutworm larvae (Spodoptera litura fabficius)

Abstract

Biotransformation is a useful way to produce biologically active terpenoids. This chapter explores the biotransformation of terpenoids in mammals and by microorganisms, and demonstrates the biotransformation of terpenoids, attempted by the larvae of common cutworm (Spodoptera liturd). The reasons for using the larvae of S. litura as a biological catalyst are: Lepidopteran larvae feed on plants containing terpenoids as their diet and therefore possess a high level of enzymatic activity against terpenoids; the worm consumes a large amount of plants, making it possible to obtain more metabolites; and the worm is easy to rear on a laboratory scale. α-Terpinene is mixed in an artificial diet at a concentration of 10 mg/g of diet, and the diet is fed to the last instar larvae of common cutworm (Spodoptera litura). Metabolites are recovered from frass and analyzed spectroscopically. The α-terpinene is transformed mainly to 4-isopropyl-l,3-cyclohexadienoic acid and cumic acid. Similarly, (+)-limonene is transformed mainly to (+)-ρ-menth-l-ene-8,9-diol (uroterpenol) and (+)- ρ-mentiia-l,8-dien-7-oic acid (perillic acid), (-)-limonene is transformed mainly to (-)- ρ-menth-l-ene-8,9-diol (uroterpenol) and (-)- /7-mentha-l,8-dien-7-oic acid (perillic acid). On the other hand, γ-terpinene is transformed mainly to ρ-mentha-l,4-dien-7-oic acid and ρ-cymen-7-oic acid (cumic acid) by the same way. The results indicate that the intestinal bacteria probably participate in the metabolism of a-terpinene. The aerobically active intestinal bacteria transform α-terpinene to 4-isopropyl-l,3-cyclohexadienemethanol, and the anaerobically active intestinal bacteria transformed a-terpinene to ρ-cymene.