Buch was born on in Hamburg, Germany. Her birth name is Alexandra Sanchez, and her earlier fights were all under that name. Later she fought as Buch-Sanchez or just Buch.
Buch started training in martial artsin 1999, training in Muay Thai. She moved to Berlin in search for a new gym and it was there that she started training in grappling and MMA.
Buch debuted on at MMA Berlin's event Turnier #15 "The Rematch", defeating fellow countrywoman Tanja Hoffmann by rear naked chokesubmission. Buch next participated in the first round of Jewels Rough Stone GP 2009 –60 kg, facing the favorite and more experienced Japanese star Shizuka Sugiyama, whom Buch controlled during the bout using her reach advantage to defeat her by unanimous decision at Jewels 5th Ring on. In her next bout, Buch was defeated via submission by Sheila Gaff at MMA Berlin Turnier #16 on. Rebounding from her loss, Buch defeated Katharina Schlosser by TKO at MMA Berlin Turnier #17 on. In the Rough Stone GP 2009 –60 kg final, Buch submitted Japanese fighter Tomoko Morii with an armbar in the first round, winning the tournament. After returning to Wuppertal and joining Alligator Rodeo Team, Buch competed on at Respect Fighting Championship 4, where she faced Dutch fighter Melissa Lan, defeating Lan by majority decision after dominating the first two rounds and enduring a triangle choke in the third round. Alexandra Buch returned to MMA at MMAB - MMA Bundesliga in Herne, North Rhine-Westphalia, Germany to compete against Dutch Jorina Baars. She lost the fight in Round one by Submission. At Respect.FC 9 in Dormagen, Germany on April 13 Alexandra Buch faced Dutch Megan van Houtum. She won the fight by TKO due to a cut at the nose of van Houtum. at No Compromises 2 in Hamburg, Germany Buch fought within a 4-women tournament. In the semi-final she defeated Jessy Schwarz by Unanimous decision. She won the final fight vs Anne Merkt via heelhook. Alexandra Buch lost her next fight on November 7, 2013 against Danish Maria Hougaard-Djursaa at European MMA 7 in Aarhus, Denmark. At Superior Challenge 12 in Malmö, Sweden on May 16, 2015 she was defeated by Swede Lina Akhtar Länsberg by TKO due to ground and pound. The fight was for the Bantamweight title of the promotion.
