Insect toxins from spruce endophytes

Abstract

Extracts of fermentation cultures of a fungal endophyte (DAOM 221611) from spruce needles have afforded the known macrocyclic antibiotic vermiculin (1), 7α,8β,11-trihydroxydrimane (2), and eight novel 13-carbon γ-lactones, namely trans-3-methyldodec-cis-6-en-4-olide (3), trans-8-hydroxy-3-methyldodec-cis-6-en-4-olide (4), trans-8-acetoxy-3-methyldodec-cis-6-en-4-olide (5), trans-9-hydroxy-3-methyl-8-oxo-dodec-trans-6-en-4-olide (6), trans-8,9-dihydroxy-3-methyldodec-cis-6-en-4-olide (7), trans-9-hydroxy-8-oxo-3-methyldodecan-4-olide (8), trans-7,9-dihydroxy-3-methyl-8-oxo-dodecan-4-olide (9), and trans-6-hydroxymethyl-3-methyl-7-oxo-undecan-4-olide (10). A known JH III metabolism product, 10,11-dihydroxyfarnesenic acid (11), was also isolated and synthesized from farnesol. Other endophyte cultures from black spruce and white spruce afforded the novel 6,7-dihydroxy-2-propyl-2,4-octadien-4-olide (16), 5,6,8-trihydroxy-4-(1'-hydroxyethyl) isocoumarin (17) plus the known sescandelin (18), sescandelin B (19), and 4-hydroxy-2-methoxyacetanilide (20). Several of the γ-lactones showed toxicity to spruce budworm (Choristoneura fumiferana Clem.) larvae and vermiculin 1 and compound 16 were toxic to spruce budworm cells.Key words: toxigenic endophytes, insect toxins, γ-lactones, isocoumarins.