They have been suggested to have anticarcinogenic potential (Boccardo et al, 2006). Plant lignans are currently being widely studied for their potential benefits for human health as their consumption has been correlated with lower risks for developing chronic diseases, such as breast cancer and coronary heart disease. However, studies of some classes of lignans, in particular the furofurans, are hampered by the lack of suitable standards to allow accurate analysis (Haajanen and Botting, 2006).
A study investigating the association between lignan intake and breast cancer in the early 1980s included small groups of women who were classified as vegetarian, or meat-eating. Over the course of 1 year, the concentrations of lignans excreted in their urine were compared with those of breast cancer patients who had had small breast tumours removed by surgery. The women with breast-cancer had a tendency to excrete smaller concentrations of lignans than vegetarians (Lamartiniere, 2000).
Isoflavonoids and lignans are diet constituents with chemo-preventive properties. They occur in certain vegetables as their glycosides from which they are released by the bacterial micro-flora in the gut. The mechanisms by which these agents interfere with the process of carcinogenesis are only poorly understood.
Although many epidemiological studies have shown that a phytoestrogen-rich diet, in which isoflavones and lignans are both found, is protective against breast cancer development (Lamartiniere, 2000) the use of soy and its isoflavone GEN by postmenopausal breast cancer patients is controversial (Duncan et al, 2003).
The mammalian phytoestrogens enterodiol (END) and enterolactone (ENL) are produced in the colon by the action of bacteria on the plant precursors matairesinol (MAT), secoisolariciresinol (SECO), their glycosides, and other precursors in the diet. Both END and ENL have been shown to possess weakly estrogenic and antiestrogenic activities, and it has been suggested that the high production of these antiestrogenic mammalian lignans in the gut may serve to protect against breast cancer in women and prostate cancer in men. Various in vitro experiments suggested END and ENL significantly inhibited the growth of human colon tumor cells, and the E2-induced proliferation of MCF-7 breast cancer cells was inhibited by ENL (Wang, 2002).
Till now, the evidence for a cancer-protective role of dietary nutrients, particularly those with antioxidant properties, has been based on women without any known genetic pre-disposition and it is important to identify and evaluate dietary factors which may modify the risk of cancer in BRCA carriers. Diet modification may modulate the risk of hereditary breast cancer by decreasing DNA damage (possibly linked to estrogen exposure) or by enhancing DNA repair. The prevention of hereditary breast cancer through diet is an attractive complement to current management strategies and deserves exploration (Kotsopoulos and Narod, 2005).
In a recent study by Lambert et al six lignans, including the cyclolignan 3,4-dihydroxy-3,4-dimethoxy-6,7 cyclolignan, were isolated from the flowering tops of Larrea tridentata. Furthermore the flavanone, (S)-4, 5-dihydroxy-7-methoxyflavanone, was isolated