**3. Materials and Methods**

#### *3.1. DSS-Induced Experimental Colitis Mice Modeling and Monitoring*

All experiments were approved by and followed the regulations of the Institute of Laboratory Animals Resources (PNU-2018-2034, Pusan National University). Experimental colitis was induced in mice by the addition of 3% (wt/vol) DSS (MP Biochemicals, Solon, OH, USA) in drinking water for 7 days as previously described [31]. Four groups were designed as positive (DSS, n = 6) or negative (no DSS, n = 6) controls and a low-dose (1 mg/kg, n = 6) and a high dose (10 mg/kg, n = 6) of Ech A treated group. Ech A was administrated at day 1 via i.v injection, while a vehicle (0.1% DMSO in PBS) was given to negative control mice instead. Total 12 day-long daily monitoring for body weight and survival rate was conducted. On day 12, the disease activity index of surviving animals was scored by assessing stool consistency, rectal bleeding and coat roughness (grade from 0 to 4), general activity and bedding contamination with stool and blood (graded from 0 to 2). All subjects were then sacrificed for the evaluation of gross pathologic severity (measuring colon length) and further histological analysis using H&E staining.
