Teff (Eragrostis spp.) hay is a palatable forage for horses that is low in soluble sugars, which potentially reduces risk for metabolic disease. Teff has also been reported to contain high levels of synephrine, which is listed as a specified or banned substance by many regulatory authorities. The disposition of synephrine in the horse following the consumption of teff has not been fully investigated which, if available, would provide data to inform sound regulatory decisions for handling detections of this substance in equine athletes.
The goals of this project were two-fold. First, we examined levels of synephrine in >80 samples of growing teff, sampled at different stages of plant development from locations across California, as well as samples of marketed hay. Forage extracts were prepared with methanol/water after sonication and heating, then analyzed using LC-MS/MS. The concentration of synephrine in teff varied considerably, with the majority of samples containing synephrine at levels between 20 and 1000 ug/g. Our findings also revealed that agronomic conditions significantly influenced synephrine concentrations.
Second, we determined the concentration of synephrine in urine and serum of horses (n=6) maintained on orchard grass that were fed teff hay (2% of BW) for just 10 days. Blood and urine samples were collected before, during, and after teff was fed. Samples were extracted using a weak cation exchange SPE cartridge and analyzed using LC-MS/MS. Our data shows that synephrine is readily detectable in hydrolyzed urine following consumption of teff hay, and decreases slowly after teff is withdrawn. In serum, free synephrine was detectable at ~100-1000 times lower concentrations as compared to total synephrine in urine, with the majority of synephrine eliminated 48 hours after ceasing consumption. These data provide important baseline values to address detection of synephrine in regulatory samples.