The former world 100 metres record holder is facing a two-year ban if found guilty of a doping violation, after testing positive for the banned substance oxilophrine during the national championships last June.
According to Powell - who testified before a three-member Jamaica Anti-Doping Disciplinary panel during a hearing which lasted for over three hours - the supplements provided by a new trainer were foreign to him and he researched them for six hours before using them.
"I could not remember their names," said the 31-year-old, one of five Jamaicans to test positive at the national championships.
Powell's former training partner, Sherone Simpson, was also among those to return positive tests for the banned substance and appeared before a disciplinary panel last week. Her hearing resumes on February 4.
Both sprinters have blamed Canadian trainer, Chris Xuereb, for supplying them with the supplements. Those included Epiphany D1, which has since been found to contain oxilophrine, although Xuereb has since denied that he provided them with performance-enhancing drugs and insisted the sprinters should take responsibility for their failed dope tests.
Powell held the 100m world record from 2005 until compatriot Usain Bolt broke it in 2008. He claimed that he did not consult his coaches about the supplements, with further statements as his hearing continues today.