A Study Of Change In Phytoestrogens During Different Growth Stages Of Alfalfa And White Clover

Phytoestrogens are naturally bioactive substances having estrogenic activities which exist widely in leguminous plants. Phytoestrogens (genistein, coumestrol and formononetin) in alfalfa(Medicago sativa L. )and white clover (Trifolium repens L.) which were widely planted in China during different growth stages were quantitated with reversed phase high performance liquid chromatography (HPLC) , and relationship between phytoestrogens and plant growth characteristics was analyzed.The results showed that kinds and content of phytoestrogens varied among the species, varieties and growth stages. Coumestrol, formononetin and genistein were detected in alfalfa, and coumestrol was the primary phytoestrogens. Total phytoestrogens content in leaf was higher than that in stem, and total phytoestrogens content of Victoria was higher than that of Derby. Formononetin, genistein and coumestrol were detected in white clover, and formononetin was the main phytoestrogens. Total phytoestrogens content of Persistent was higher than that of Haifa, Huia and Rivendal.Growth stages had a significant effect on total phytoestrogens content in alfalfa and white clover. Total phytoestrogens content in alfalfa was remarkably high in the spring, and decreased sharply after bloom, maximal coumestrol content was 267.92 g/g; total phytoestrogens content in white clover increased constantly in the spring and decreased promptly after bloom, maximal formononetin content was 176.51 g/g in early bloom. Total phytoestrogens content in alfalfa and white clover was least at later bloom.With plant height increasing and leaf/stem ratio decreasing, total phytoestrogens content in alfalfa constantly decreased. Total phytoestrogens content in white clover constantly increased with growth of plant height, but tended higher in varieties with smaller leaflet.Nitrogen (N) and phosphorus (P) contents of alfalfa and white clover had no significant change with growth in spring, so there was significant correlationbetween phytoestrogens content and N, P contents of alfalfa and white clover.In spring, phytoestrogens content of alfalfa and white clover was high, when these legumes are applied to animal, the feeding quantum should be limited or used together with other forages to avoid negative effect on livestocks. When extracting phytoestrogens of alfalfa and white clover, proper species or varieties should be selected and reaped before heading bloom in spring.