Could mesalazine be responsible for causing raynaud's syndrome?

Maybe not: Mesalazine (mesalamine, 5-asa) is the active ingredient of sulfasalazine. Mesalazine is for treating inflammatory bowel disease (ulcerative colitis, Crohn's disease) and does not contain sulfa (avoids the problems of sulfa allergy or sulfonamide side effects). There was a report of raynaud's occurring with sulfasalazine, but I have not seen raynaud's reported with mesalazine.

Not typically: Mesalamine the drug does not commonly cause raynaiud's syndrome. Think if there is a correlation between when you started the drug and when symptoms of raynaud's started, and discuss the possibility of an association with your doctor.