Analgesic alkaloids from Urticae Fissae Herba

Objective To investigate the analgesic substances in the aerial part of Urtica fissa (Urticae Fissae Herba), commonly used for rheumatoid and rheumatism arthritis. Methods The analgesic constituents were isolated with the active guidance of hot plate and acetic acid writhing models, and identified by comprehensive spectroscopic analysis. Results Thirteen alkaloids (1–13), two lignans (14, 15), and three amides (16–18) were isolated from the active fractions. Among them, compound 1 was a new alkaloid, and compound 6 was a new natural product. The activity evaluation in vivo indicated that various pyrrole alkaloids (1, 3, 6, and 12) possessed significant analgesic activities, they could significantly inhibit the mice pain response induced by acetic acid and hot plate at the dosage of 2 mg/kg BW. Conclusion The study revealed that the pyrrole alkaloids played important roles in the analgesic activities of Urticae Fissae Herba.