Abstract BACKGROUND We studied saffron as an additional intervention to improve clinical manifestations of Ulcerative colitis (UC) patients. METHODS This is a study at Yazd university where 30 UC patients were randomly assigned to placebo (n=9), low (n=9, 25 mg), or high dose saffron (n=12, 50mg), two times a day for 8 weeks. Hemoglobin, platelet levels, CRP, ESR, and fecal calprotectin along with clinical data Simple Clinical Colitis Activity Index (SCCAI), Partial Mayo Score, and Hamilton Depression Anxiety Score (HDRS) were recorded at baseline and completion of treatment. For validation, we recruited 3 UC patients at Howard University who received 50mg of Saffron twice daily for 8 weeks, two underwent a wash-out period and received saffron for a second cycle. Inflammatory markers, CRP, stool calprotectin, and the cytokines from PMA/ionomycin stimulated PBMCs, at baseline and 8 weeks Saffron treatment were compared. 16S rDNA analysis was performed on stool DNA for gut microbiome. RESULTS In Yazd study of 30 patients, all participants completed the study successfully. The high dose group showed significant improvement in HDRS score (p=0.001), SCCAI (p=0.04), Partial Mayo score (p=0.01), fecal calprotectin (p=0.009), and CRP (p=0.001) compared to baseline. The low dose group also improved in HDRS score (p=0.01; Table 1, Fig 1). No adverse events were reported. In HU data, saffron improved Partial Mayo Score, health related quality of life and HDRS. Pro-inflammatory cytokines TNFα, INFγ, IL-6, IL-2, IL-17a decreased while anti-inflammatory IL-10, TGF-β increased. Fecal calprotectin levels of 228 μg/g and 169 μg/g decreased to 63 μg/g and 16 μg/g in two individual patients, respectively. After the wash-out period, fecal calprotectin increased. A second saffron treatment cycle reduced it again further validating the causal relationship. Saffron led to a decrease in gamma Proteobacteria, and enrichment in Ruminococcaceae. CONCLUSION This study demonstrates that saffron led to improvements in clinical response including reduction in partial Mayo scores, HDRS scores, and inflammatory markers such as fecal calprotectin and CRP. These findings suggest that the use of saffron supplements alongside standard treatment protocols may yield beneficial effects for individuals with UC. Table 1. Basic characteristics, clinical variables, and laboratory variables among the study participants in three arms of the clinical trial. Figure 1 Effect of Saffron on quality of life and Inflammatory markers.