[Lignan: an important natural estrogen from plants].

Lignan is an important phytoestrogen with weakly estrogenic and anti-estrogenic properties, and possesses diverse bioactivities, including antioxidation, antitumor and antivirus etc. In particular, it may prevent hormone-dependent diseases, such as breast cancer, prostate cancer and benign prostatic hyperplasia. However, many important scientific problems have not been constrained, whether do the metabolites of lignans from foods have their potential genic toxicity? What are the anticancer mechanisms of lignans? What is the dosage of lignans to achieve the desired biological effect? In this paper, the references on lignans have systematically been reviewed in the following aspects: classification, distribution, metabolism, pharmacological activities and analytical methods, and a prospective of future studies on lignans is also elucidated.