In brewing beer, the phenylethylamine alkaloid hornenine is found in barley (Hordeum vulgare), which has now made its way into supplements, recently removed from the FDA advisory list. Chemically, it is like bitter orange stimulants, notably synepherine HCL. Some algae, cacti, and grass species also contain this ingredient, thus making certain the claim that it occurs naturally.
In addition to helping athletes perform better, hordenine can help people lose weight. The chemical has been shown to have antibiotic properties in some studies and to be a biomarker for estimating how much beer someone has consumed.
Research indicates that hordenine stimulates the central nervous system, raises blood pressure, heart rate, and breathing rate but the effects are still being studied. It appears that these effects are short-lived and require relatively high doses. This is commonly why you see this ingredient in pre workout and fat burning supplements. Hordenine contains, Adenosine, which is adrenergic, meaning that it releases the neurotransmitters norepinephrine (noradrenaline) and epinephrine (adrenaline) in the brain. As part of the fight-or-flight response, these neurotransmitters increase energy and focus.
It is technically possible to use Hordenine as a stimulant and fat burner due to its association with tyramine and noradrenaline, but there is not enough evidence currently to support its use as a nutritional supplement. However, this ingredient has been now granted NDI status and can be used as a dietary supplement it appears.