Hydroxymatairesinol, a novel enterolactone precursor with antitumor properties from coniferous tree (Picea abies)

The potential for the extraction of the plant lignan hydroxymatairesinol (H MR) in large scale from Norway spruce (Picea abies) has given us the opport unity to study the metabolism and biological actions of HMR in animals. HMR , the most abundant single component of spruce lignans, was metabolized to enterolactone (ENL) as the major metabolite in rats after oral administrati on. The amounts of urinary ENL increased with the close of HMR (from 3 to 5 0 mg/kg), and only minor amounts of unmetabolized HMR isomers and other lig nans were found in urine. HMR (15 mg/kg body wt po) given for 51 days decre ased the number of growing tumors and increased the proportion of regressin g and stabilized tumors in the rat dimethylbenz[a]anthracene-induced mammar y tumor model. HMR (50 mg/kg body wt) did not exert estrogenic or antiestro genic activity in the uterine growth test in immature rats. HMR also showed no antiandrogenic responses in the growth of accessory sex glands in adult male rats. Neither ENL nor enterodiol showed estrogenic or antiestrogenic activity via a classical alpha- or beta-type estrogen receptor-mediated pat hway in vitro at <1.0 mu M. HMR was an effective antioxidant in vitro.