From the leaves and stems of Viscum album L., syringenin 4'-O-glucoside (syringin), syringenin 4'-O-apiosyl-l -2-glucoside, syringaresinol 4', 4'-di-O-glucoside (eleutheroside E) and syringaresinolmono-O-glucoside were isolated. The isolated compounds are suitable for the HPLC-fingerprint analysis of alcoholic or aqueous Viscum album extracts. A butanol extract, containing these compounds showed a significant cAMP-phosphodiesterase inhibitory activity.

The newly isolated phenylpropanoids syringin, syringenin-apiosylglucoside, eleutheroside E and the high molecular lectins and viscotoxins were selected for a standardization of mistletoe extracts and drug preparation. The phenylpropanoids found in all alcoholic and aqueous extracts were suitable for an HPLC fingerprint analysis, and for quantitative determination. The lectin content of the drug preparations was determined by single radial immunodiffusion. As shown by the isoelectric focussing method, Iscador® and fermented mistletoe extracts contain only the mistletoe lectins ML II/III, whereas the proteins of the ML I complex are missing. For identification and quantitative determination of viscotoxins, an HPLC method was designed.