A bunch of 'plant steroid' molecules (like ecdysteroids are insect steroids) that are present in relatively high amounts in mustard; still nowhere near enough to get jacked off of mustard. Have not been shown to be effective in humans yet, remains an unexplored research field.
Brassinosteroids is most often used for
Sources and structure
Brassinosteroids are polyhydroxylated compounds related to the structure of 5a-cholestane, a chemical structure similar to many androgenic compounds. The chemical class of brassinosteroids share similar actions of mammalians steroids, but act in plants mostly via genetically mediated factors.
One of the main sources of brassinosteroids is in pollens in order to induce growth. They act in micromolar concentrations, which helps to explain a past yield of 10mg from 230kg pollen. Brassinosteroids can be synthesized in laboratory settings.
Muscle protein synthesis
In does of 20-60mg/kg bodyweight, a brassinosteroid found in mustard (28-Homobrassinolide, or 28-HB) was able to stimulate protein synthesis and concomitantly inhibit breakdown of muscle while increasing strength. The mode of adminstration was oral consumption via Akt phosphorylation, and the results were somewhat confounded with increases in food intake, although the magnitude of which is not causative of the differences seen in lean mass. No binding to the Androgen Receptor (AR) was noted, and no changes in serum testosterone noted.