Verbascum cheiranthifolium var. cheiranthifolium is a traditional remedy utilized in Eastern Anatolia, Turkey to cure a number of conditions, including rheumatism and inflammation. Lyophilized hydrophilic extract of V. cheiranthifolium leaf contained phenolic compounds and reducing sugars with luteolin hexoside as the dominating phytochemical and traces of apigenin, apigenin glucoside, chlorogenic acid, rosmarinic acid and quercetin glycosides. The extract, applied at non-toxic concentrations, suppressed the accumulation of nitric oxide (NO) in lipopolysaccharide (LPS)-activated murine macrophages (RAW 264.7) and hepatocellular carcinoma (HepG2) cells. The result suggests that V. cheiranthifolium phytochemicals downregulate the activity of the pro-inflammatory enzyme, inducible nitric oxide synthase (iNOS), which results in a decrease of NO production. These findings warrant future research towards an understanding of the mechanism of anti-inflammatory action of V. cheiranthifolium. Crown Copyright (C) 2014 Published by Elsevier GmbH. All rights reserved.