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 antiinflammatory
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 antiinflammatory
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.