The phenolic glucoside salicortin was isolated from a Willow bark extract, and its ability to reduce the TNF-α induced ICAM-1 expression (10 ng/mL, 30 min pretreatment with salicortin) was tested in vitro on human microvascular endothelial cells (HMEC-1). After 24 h, 25 µM salicortin decreased the TNF-α induced ICAM-1 expression to 65.9 % compared to cells which were treated only with TNF-α. In parallel, the stability of 25 µM salicortin under assay conditions was determined by HPLC. Within 24 h, the salicortin concentration decreased to 3.1 µM whereas catechol, a known NF-κB inhibitor, rose as a metabolite. After 8 h the catechol concentration was relatively constant and varied between 8.2 and 10.9 µM. Considering this degradation in the in vitro test system, 10 µM catechol was added 8 h after TNF-α stimulation, and 16 h later the ICAM-1 expression was determined. In this setting, the ICAM-1 expression was reduced to 74.8 %. This is comparable to the effect obtained from 25 µM salicortin and indicates that its activity is related to the generation of catechol, as salicin, saligenin, and salicylic acid are only marginally active or inactive in this test system in a concentration up to 50 µM. These results indicate catechol as an important bioactive metabolite from salicortin.
Key words
Salix
- Salicaceae - salicortin - catechol
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