Abstract: Nimbya alternantherae is a leaf spot fungus isolated from Alternanthera philoxeroides. It could produce phytotoxin to Alternanthera philoxeroides in several kinds of liquid media, especially in modified Fries. The filtrate of the pathogen was chromatographed on a DM-130 colophony column eluting with methanol, and evaporation of the solvent gave a brown mush. The crude product was then extracted with ethyl acetate. The toxin could be purified as white needles by re-crystallizing from benzene and acetone(volume ratio is 1:1) and silica gel chromatograph. The results of elemental analysis, MS, IR and NMR indicate that molecular weight of the toxin was 240, formula was C₁₁H₁₂O₆, and its chemical name was 2-acetyl-3,4-dihydroxy-5-methoxyphenyl-acetic acid(Vulculic acid ).

Key words: Nimbya alternantherae, Phytotoxin, Separation and purification, Structural identification, 2-Acetyl-3,4-dihydroxy-5-methoxyphenyl-acetic acid