STRUCTURE ELUCIDATION OF HOP PLANT (HUMULUS-LUPULUS) PHYTOALEXIN ELICITORS BY FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRY

Cell wall material (CWM) derived from hop leaves (Humulus lupulus) was extracted and characterized by fast atom bombardment mass spectrometr y (FABMS). The material consists of monosaccharides, fucose, rhamnose, arabinose, galactose, glucose, and xylose, and galacturonic acid olig omers ranging from trimers to octamers, each with a double bond. The u nsaturated galacturonic acids showed elicitor activity for phytoalexin s in soybean cotyledons. By HPLC analysis it was observed that the pen tagalacturonide is present in 'greatest amount, but the compound with the greatest biological activity is the unsaturated hexagalacturonide. The relative elicitor activity was found to be roughly 3:3:4:10:2 for the trimer, tetramer, pentamer, hexamer, and octamer, respectively. S tructural analyses by FABMS of the peracetylated reductively aminated pentaglacturonide showed that the unsaturated galacturonosyl residue i s located at the nonreducing end of the oligomer with unsaturation ded uced to be at the 4,5-position.