Analgesic and Anti-inflammatory properties of RD-A and RD-B extracted from the leaves of Rhododendron dauricum Linn.

To further understand the purpose of the traditional processing method of the leaves of Rhododendron dauricum Linn. (Ericaceae) as well as analgesic and anti-inflammatory activities of RD-A and RD-B extracted from this medicinal plant, various pain and inflammatory models were employed in the present study to investigate their pharmacological profiles. Both RD-A and RD-B revealed significant protective effects against thermal and chemical stimuli in hot plate and writhing test. However, on different phases, they exhibited analgesic activities in formalin test. RD-B showed stronger inhibitory effect than RD-A in carrageenan induced rat-paw oedema, both of them, significantly inhibited the release of prostaglandin E2 in inflammatory tissue, reduced acetic acid-induced vascular permeability and the content of 6-Keto PGF1α in Freund’s complete adjuvant (FCA) induced arthritis rat’s blood plasma, while increase the content of 5-hydroxytryindole-3-acetic acid (5-HIAA), accordingly. These results suggest that central and peripheral mechanism are involved in the pain modulation and anti-inflammatory effects of RD-A and RD-B, biochemical mechanisms of RD-A and RD-B are different.