Days before UFC 200, interim champion Jon Jones was pulled from his main event title fight after it was revealed he violated the promotion’s anti-doping policy.

Jones was scheduled to fight a unification bout with champion Daniel Cormier, who instead faced Anderson in a non-title fight.

At the time, the banned substances Jones tested positive was not revealed, but today the Nevada commission revealed that Jones failed his drug test due to the detection of estrogen blockers:

The Nevada State Athletic Commission today confirmed the substances for which Jon Jones tested positive prior to his ill-fated title unifier with light heavyweight champ Daniel Cormier at UFC 200.

Jones came back positive for hydroxy-clomiphene, an anti-estrogenic agent and letrozole metabolite, an aromatase inhibitor, NSAC attorney Caroline Bateman said today during a hearing in Las Vegas. The substances, which are both banned year-round by the World Anti-Doping Agency, are consistent with the type named by Jones’ ex-training partner and opponent, Rashad Evans, who first claimed the interim champ tested positive for estrogen blockers.

Estrogen blockers can potentially act in tandem with performance-enhancers by helping to mitigate their side effects, and are also thought to restart natural testosterone production.

source: mmajunkie.com