Characterization of Phytoestrogens in Medicago sativa L. and Grazing Beef Cattle

Abstract

Phytoestrogens are plant-produced bioactive secondary metabolites known to play an integral role in plant defense that frequently accumulate in times of stress and/or microbial infection. Phytoestrogens typically belong to two distinct chemical classes; flavonoids (isoflavones) and non-flavonoids (lignans and coumestans). Upon consumption by livestock, high concentrations of phytoestrogens can cause long-term disruption in reproduction due to structural similarities with mammalian estrogens and their tendency to bind estrogen receptors. Wide variation in phytoestrogen concentration has been reported in pasture legumes and corresponding silage or hay. Lucerne is a common perennial pasture legume in temperate climates, but information on phytoestrogen production or accumulation in grazing livestock is currently limited. Therefore, metabolic profiling using UHPLC-MS-QToF was performed to identify and quantitate key phytoestrogens in both fresh and dried lucerne fodder from replicated field or controlled glasshouse environments. Phytoestrogens were also profiled in the blood plasma of Angus cattle grazing field-grown lucerne. Results revealed that phytoestrogens varied quantitatively and qualitatively among selected lucerne cultivars grown under glasshouse conditions. Fresh lucerne samples contained higher concentrations of coumestans and other phytoestrogenic isoflavones than did dried samples for all cultivars profiled, with several exceeding desirable threshold levels for grazing cattle. Coumestans and isoflavones profiled in plasma of Angus heifers grazing lucerne increased significantly over a 21-day sampling period following experimental initiation. Currently, threshold concentrations for phytoestrogens in plasma are unreported. However, total phytoestrogen concentration exceeded 300 mg·kg−1 in fresh and 180 mg·kg−1 in dried samples of selected cultivars, suggesting that certain genotypes may upregulate phytoestrogen production, while others may prove suitable sources of fodder for grazing livestock.

Cocktails of Mycotoxins, Phytoestrogens, and Other Secondary Metabolites in Diets of Dairy Cows in Austria: Inferences from Diet Composition and Geo-Climatic Factors

“…These metabolites are found primarily in Leguminosae plants, such as soy, but also in clovers ( Trifolium spp.) and alfalfa/lucerne ( Medicago sativa ) [ 9 , 28 , 142 ]. Coumetrans such as coumestrol seem to be more potent in estrogenic activity [ 9 , 31 ].…”

Phytoestrogens: A Review of Their Impacts on Reproductive Physiology and Other Effects upon Grazing Livestock

“…Recently, 3′methoxycoumestrol has been quantified in bovine plasma after a grazing period of 21 days on lucerne (var. Genesis) where concentrations increased significantly over the period [ 15 ].…”

“…In a recent investigation assessing the concentrations of six key phytoestrogens in commercially available lucerne cultivars, concentrations of individual phytoestrogens ranged from 66.5 to 333.8 mg/kg DM [ 15 ]. Currently, producers are recommended to remove or dilute the level of estrogenic feed or forages in the diet of grazing livestock to avoid adverse effects on reproduction [ 16 ].…”

Evaluating the Antioxidant and Antidiabetic Properties of Medicago sativa and Solidago virgaurea Polyphenolic-Rich Extracts

“…Medicago sativa (lucerne; Fabaceae family) contains significant quantities of polyphenols, especially isoflavones known as phytoestrogens [ 20 , 21 ]. M. sativa is one of the most prevalent forage crops, but it also has a long tradition of use in folk medicine for central nervous and digestive system disorders and for curing other ailments, including cancer [ 22 , 23 , 24 , 25 ].…”