Novel Nitric Oxide-Releasing Derivatives of Brusatol as Anti-Inflammatory Agents: Design, Synthesis, Biological Evaluation, and Nitric Oxide Release Studies

Brusatol, a biologically active natural product, was modified in four distinct positions through the covalent attachment of a furoxan moiety, which acts as a nitric oxide (NO) donor. Forty derivatives were synthesized and evaluated for their inhibitory effects on excess NO biosynthesis in activated macrophages. Among them, compound 75 demonstrated inhibition (IC50 = 0.067 μM) comparable to that of brusatol but were less cytotoxic. More importantly, even at very low doses (2 μmol/kg/day), compound 75 also showed substantial inhibitory efficacy against chronic obstructive pulmonary disease (COPD)-like inflammation in the mouse model induced by cigarette smoke (CS) and lipopolysaccharide (LPS). Particularly, this compound was over 100-fold less toxic (LD50 > 3852 μmol/kg) than brusatol and could be a promising lead for further studies. Notably, the improved properties of this derivative are associated with its NO-releasing capability.