Inclusion Criteria:

1. Male and female patients, between 18 and 70 years of age.
2. Patients with a confirmed diagnosis of ulcerative colitis in treatment with fixed-dose of oral mesalazine or other 5-ASA derivatives for at least 4 weeks with a high clinical suspicion of active disease, confirmed by sigmoidoscopy at enrolment in the study .
3. Presence of ulcerative colitis located at left side of the colon, from splenic flexure of the colon to the rectum (up to 15 cm proximal to the anus).
4. Patients with mild to moderate active ulcerative colitis, as defined by the DAI ≥ 4 and ≤ 10, and CAI ≥ 5 and ≤ 12.
5. Women with negative serum test for pregnancy.
6. Women of childbearing potential provided they use adequate contraceptive precautions during the treatment period. Adequate contraceptive methods are defined as those with a failure rate <1% per year when correctly used, and include implants, injectables, combined oral pills, some IUDs or a vasectomised partner in a stable relationship.
7. Ability to understand and willing to sign the Informed Consent Form, and other documents required to be read or signed by the subject.

Exclusion Criteria:

1. Presence of other clinically significant medical condition as determined by the Investigator.
2. History of hypersensitivity or idiosyncratic reaction to heparins.
3. History of hemorrhages, excluding intestinal bleeding due to ulcerative colitis, hemocoagulative disorders, or platelet dysfunction.
4. Presence of arterial hypertension (SAP ≥ 160 mm Hg; DAP ≥ 95 mm Hg).
5. Receipt of any investigational agent within 90 days of starting treatment.
6. Use of rectal 5-ASAs or rectal corticosteroids within 2 weeks before the starting the study.
7. Use of anti-TNF agents or immunosuppressive drugs such as azothioprine, 6-mercaptopurine or cyclosporine A in the last 3 months.
8. Patients with ulcerative colitis of severe entity (DAI > 10 or CAI > 12), or with limited distal ulcerative proctitis, or with infectious colitis confirmed by microbiological assessment in stool.
9. Patients with severe intestinal bleeding, or with Hb < 9 g/dL.
10. Presence of significant hepatic impairment (AST, ALT > 2 ULN).
11. Presence of significant renal impairment (creatinine > 2 ULN).
12. Women who are pregnant or who are breast feeding.
13. Intestinal obstruction.
14. Presence of type 1 or type 2 diabetes.
15. Concomitant oral antibiotic treatment, within 2 weeks before starting the study.