Coumarins from the roots of Angelica dahurica cause anti-allergic inflammation.

Allergic inflammation is induced by allergens and leads to various allergic diseases, including rhinitis, asthma and conjunctivitis. Histamine is important in the pathogenesis of an immunoglobulin E-dependent allergic reaction and results in the secretion of cytokines associated with inflammation. Angelica dahurica (A. dahurica) is a medicinal plant widely used in China for the treatment of symptoms related to allergic inflammation. The present study investigated the chemical constituents from A. dahurica and evaluated their reductive effect on allergic inflammation. As a result, 15 compounds including 13 coumarins have been identified as isoimperatorin (1), imperatorin (2), oxypeucedanin (3), oxypeucedanin hydrate (4), bergapten (5), byakangelicin (6), phellopterin (7), byakangelicol (8), isopimpinellin (9), xanthotoxol (10), xanthotoxin (11), pimpinellin (12), scopoletin (13), β-sitosterol (14) and daucosterol (15). Compounds 1-13 were able to reduce the release of histamine, with compounds 4-6 exhibiting the most potent activity. Furthermore, compounds 1-12 were able to inhibit the secretion of tumor necrosis factor-α, interleukin (IL)-1β and IL-4, with compounds 5 and 7 exhibiting the strongest inhibitory effects. These compounds implemented the inhibitory effects on the expression of inflammatory cytokine genes through the inhibition of nuclear factor-κB activation. Virtual screening by a docking program indicated that compound 3 is a potent histamine H1 receptor antagonist. Additionally, the calculated physicochemical properties of these compounds support most furanocoumarins to be delivered to binding sites and permeate the cell membrane. The present findings contribute to understanding how A. dahurica attenuates allergic inflammation.