Screening and isolation of antinematodal metabolites against Bursaphelenchus xylophilus produced by fungi

Abstract

Sixty crude cultural filtrates of thirty fresh water fungi individually grown in both Potato Dextrose broth and GPC broth were assayed in vitro for antinematodal activity against Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle using immersion test. Filtrates from Camposporium quercicola YMF1.01300, Periconia digitata YMF1.00948, Caryospora callicarpa YMF1.01026 grown in both PDB and GPC broth, and the cultural filtrate of Melanospora zamiae YMF1.00948 grown in PDB were found to be pathogenic to the tested nematodes. The degree of activity varied with the fungal species, length of exposure time, and media composition. From a nematicidal cultural extract of Caryospora callicarpa YMF1.01026, four known naphthalenones were isolated and identified as 4,8-dihydroxy-3,4-dihydronaphthalen-1(2H)-one (1), 4,6-dihydroxy - 3,4-dihydronaphthalen- 1(2H)-one (2), 4,6,8-trihydroxy-3,4-dihydronaphthalen- 1(2H)-one) (3), 3,4,6,8-tetrahydroxy-3,4-dihydronaphthalen-1(2H)-one (cis-4-hydroxyscytalone) (4) by NMR and MS analysis. All four metabolites showed noticeable biological activity against B. xylophilus nematode. This is the first published report of these compounds affecting plant-parasitic nematodes.