New cardenolide glycosides from the defence glands of chrysolinina beetles (coleoptera: Chrysomelidae)

Abstract

The composition of the defence secretions of s i x species of chrysomelid b e e t l e s (Chrysolina PO Eta, C. americana, C. grossa, C . herbacea, C. fastuosa, and Oreina gloriosal belonging t o the sub-tribe Chrysolinina has been investigated. Two known cardenolide aglycones, sarmentogenin ( I ) and oleandrigenin ( 2 3 ) , and fourteen new cardiac glycosides (7-20) have been i s o l a t e d %d t h e i r s t r u c t u r e e s t a b l i s h e d by s p e c t r a l and chemical methods. Three of the glycosides (18, 19, and 20) a r e based on a new cardenolide aglycone, namely A"-digitoxigenin. ribose, a l l o s e ) which are r a r e l y encountered i n s e c o n d a r y metabolites. Ethanolamine was shown t o be present in the s e c r e t i o n s of t h e s i x species examined, a s well a s i n C. hyperici and i n C . coeruZans. In the l a t t e r , ethanolamine i s accompanied by i t s N-(y-glutamyl) derivative. A l l tG new g l y c o x d e s but 1 7 contain monosaccharides (e.g. lyxose,

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“…Tyrosine-betaine was found in the secretion of adult Oreina gloriosa (Chrysomelinae). [43,44] The biogenesis of isoxazolinone derivatives released by several adult Chrysomelinae species is also known to be based on amino acids, in this case aspartic acid. [45] Interestingly, the defensive glandular secretions of several adult Chrysomelinae species also contain cardenolides or pyrrolizidine alkaloids in addition to amino acid derivatives, [10,46] but we did not detect any of these compounds in the investigated fluid.…”

“…[42] A further glutamic acid derivative, gl-glutamyl-ethanolamine (25), was detected in defensive secretions of the adult Chrysomelinae Labidomera trimaculata, Zygogramma suturalis, and Chrysolina coerulans. [41,43] These compounds are structurally closely related to 1, because each contains a g-conjugated glutamic acid unit.…”