Gilberto Ramirez promised that Roamer Alexis Angulo would be the first to taste defeat - when the two undefeated fighters collided in Oklahoma on Saturday night.

Ramirez unanimously outpointed Angulo to retain the WBO super middleweight championship, winning 120-108 on one judge's card and 119-109 on the other two.

Angulo tagged Ramirez early on, and the Mexican fighter decides to box instead of slug it out - which made some of the ringside fans frustrated during the contest.

"He was a tough fighter, it was a tough fight for me and I learned a lot," Ramirez said. "I am really happy because I keep my belt and stay undefeated too, and he has a loss now, like I promised in the press conference —- he had no losses but he does now."

The 27-year-old Ramirez, from Mexico, improved to 38-0. He landed powerful punches in the fifth and eighth rounds.

The 34-year-old Angulo, from Colombia, fell to 23-1.

Angulo had flurries of punches in both the seventh and the 11th rounds, but neither fighter ever appeared to hurt the other. Ramirez sustained a cut under his left eye in the fifth, but his corner attended to it after the round and it never bled again.

"He was an undefeated fighter. He came with a lot of hunger to try to take away my world title. I'm not happy with my performance, but I got the job done. I'm still a world champion. I want to go back to the gym to start training and evolve as a fighter. I want to unify titles and I want to be one of the top pound for pound fighters in the world," Ramirez said.