Zearalenone is a natural estrogen, a mycotoxin from resorcylic acid lactone group. 

Zearalenone is a non-steroidal estrogenic mycotoxin produced by    several  Fusarium spp. It has been implicated in numerous    mycotoxicoses in farm animals, especially in pigs. Zearalenone is    heat-stable and is found worldwide in a number of cereal crops, such    as maize, barley, oats, wheat, rice, and sorghum (Kuiper-Goodman et    al., 1987; Tanaka et al., 1988a) and also in bread (Aziz et al.,    1997). Zearalenone was shown to be produced on corn by  Fusarium    isolates from Australia, Europe, and North America (Vesonder et al.,    1991) and in New Zealand (diMenna et al., 1997), the Philippines,    Thailand, and Indonesia (Yamashita et al., 1995). The occurrence of    zearalenone in food and feed was also demonstrated in South America    (Dalcero et al., 1997; Molto et al., 1997), Africa (Doko et al.,    1996), China and the former USSR (Ueno et al., 1986).  Fusarium    isolates from bananas can also produce zearalenone