Enzymic and non-enzymic liberation of tulipalin A (α-methylene butyrolactone) in extracts of tulip

Abstract

Extracts of pistils, white bulb skins and outer bulb scales of tulip were prepared using methanol, acetone and buffers of various pH values. Except for the pH 7·5 extract, all extracts of the tulip cultivars under study contained a precursor of the fungitoxic substance tulipalin A. The precursor is not toxic to Fusarium oxysporum, and is relatively stable below a pH of about 5·4 and relatively unstable above pH 6·5 in extracts or in a fungal culture medium. Buffered extracts of bulb tissues contain enzymes that liberate tulipalin A very rapidly at pH values above 5. The present findings demonstrate that, in vitro, the precursor must be split chemically or enzymically to yield the fungitoxic tulipalin A.