According to Steven Marrocco of MMAjunkie, the two substances that Jon Jones tested positive for and caused him to be pulled from the main event of UFC 200 against Daniel Cormier were revealed by the Nevada Athletic Commission in today's hearing.
So per the NSAC, Jones tested positive for Hydroxy-clomiphene, "an anti-estrogenic agent" & "Letrozole metabolite, an "aromatase inhibitor"— Steven Marrocco (@MMAjunkieSteven) July 18, 2016
As far as Hydroxy-clomiphene is concerned, anti-estrogen agents usually are used by athletes looking for an extra advantage to create an hormonal imbalance in which testosterone is not limited or countered by estrogen as it naturally develops in men. The second substance is commonly used for post'menopausal breast cancer patients in endocrine therapy. Some side effects include nausea, hot flashes, constipation, and bone pain.
No plans on suspension or any action on behalf of UFC management has been announced as of yet, as Jones and his management claim that this was the result of a tainted supplement. They plan to make their case to USADA much like Malki Kawa (Jones' manager) had done for his fellow client Yoel Romero, who had gotten his suspension reduced to only six months after testing positive for a banned substance as well, albeit out of competition.
The NAC has since placed Jones, who was not present at the hearing, under a temporary suspension.