Just off the top of my head, Chuck Liddell (Kempo, Koei Kan), GSP (Kyokushin), and Bas Rutten (Kyokushin) all have karate in their backgrounds.
Can they point to something in their individual styles that is truly karate? Yes. Is it "pure" 100% unadulterated karate? No. No-one in MMA does a "pure" style.