Cell Wall-Bound Phenolics from Norway Spruce (Picea abies) Needles

Secondary products, such as phenolics, accumulate predominantly in the form of hydrophilic conjugates in the vacuoles (intraprotoplasmic storage) of plants [1—3]. Also there are many reports on their extraprotoplasmic location, e.g. as exudates [4] or cell wall components. The latter include the polymer lignin [5], as well as monomeric hydrolyzable phenolics, which are mainly hydroxycinnamic acids (HCAs; ferulic, diferulic, andp-coumaric acids) linked to polysaccharides [6—11] and/or lignin [12—14], In contrast, the most widespread flavonoids have rarely been found to be associated with cell walls. Markham [15] isolated a flavone polysaccharide from Monoclea forsten which was possibly cell wall bound, while Ibrahim et al. [16] showed, with the aid of immunological methods, that a methylated flavonol glycoside was probably located in the cell walls of Chrysosplenium americanum. In the course of an investigation of the phenolics in Norway spruce (Picea abies [L.] KARST.) needles we observed both HCAand flavonoid-like insoluble hydrolyzable compounds. We report here their identification and localization and present evidence for cell wall-bound astragalin (kaempferol 3-O-ß-