Anti-inflammatory effects of novel sinomenine derivatives

Sinomenine is an isoquinoline-type alkaloid found in Sinomenium acutum (Thunb.) Rehd. et Wils and S. acutum (Thunb.) Rehd. et Wils var. cinereum Rehd. et Wils. When used as a medicine, this compound exhibits anti-inflammatory properties; however, sinomenine's use as a medication is limited by side effects, a short half-life, and low efficacy. Owing to these limits, attempts have been made to synthesize sinomenine derivatives with enhanced efficacy. In this study, the anti-inflammatory effects of novel sinomenine derivatives (S1a-S1f) were examined on the basis of lipopolysaccharide-induced inflammatory factor expression in Raw264.7 cells, dimethylbenzene-induced ear oedema, and Evan's blue leakage in mice, and carrageenan-induced paw oedema in rats. Compared with sinomenine, the derivatives significantly inhibited the expression of the inflammatory factors IL-1β and IL-6 at the transcriptional and translational levels. Topical application of 3.250 mg/kg of the derivatives also alleviated ear oedema. Compared with the vehicle, the derivatives significantly inhibited carrageenan-induced rat paw oedema after 6 h. Among the derivatives, S1a exhibited the most potent anti-inflammatory activity. S1a also significantly increased the sinomenine-induced inhibition of Evan's blue leakage. Thus, S1a may elicit the strongest anti-inflammatory effects of the tested compounds. Based on these results, further development of this compound may be warranted.