Inhibition of Inducible Nitric Oxide Synthase and Cyclooxygenase‐2 Expression by Phenolic Compounds from Roots of Rhododendron mucronulatum

Abstract

The roots of Rhododendron mucronulatum Turzaninov have been used in Oriental traditional medicine for the treatment of dysuria, fever, increase of digestive activity and tonics in China and Korea. Activity guided isolation of the roots of Rhododendron mucronulatum Turzaninov has led to the isolation of three flavonoids, one flavan 3-ol and one proanthocyanidin. Chemical investigation of the 80% Me2 CO extract from the roots of Rhododendron mucronulatum led to the isolation and identification of five compounds: taxifolin (1), taxifolin 3-O-β-D-glucopyranoside (2), quercetin 3-O-α-L-arabinofuranoside (3), (-)-epicatechin (4), procyanidin B-3 (5). To investigate the antioxidative and antiinflammatory effects of these compounds, their 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities and the protein levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in LPS-stimulated HaCaT cells were also quantified by western blotting and their end products, nitric oxide (NO) and prostaglandin E2 (PGE2 ), respectively. Compounds (1-5) showed potent DPPH radical scavenging compared with positive controls (L-ascorbic acid). Also, compounds 1 and 2 dose-dependently inhibited the expressions of inflammatory mediators, NO and PGE2 , suggesting they are promising candidates as antiinflammatory agents.

The antioxidative potential of farrerol occurs via the activation of Nrf2 mediated HO-1 signaling in RAW 264.7 cells

“…Some flavonoids isolated from the roots of Rhododendron mucronulatum Turzaninov were reported to be potential anti-inflammatory agents based on the results of their dose-dependent inhibition of the expression of inflammatory mediators, NO and PGE2 [19]. Farrerol, a new type of 2,3-dihydro-flavonoid, has also been isolated from rhododendron, a traditional Chinese herbal medicine [20]. Accumulating evidence suggests that farrerol possesses many biological properties, including antitussive, antibacterial, anti-inflammatory effects, with also an inhibitory effect on vascular smooth muscle cells (VSMCs) proliferation [21,22].…”

Metabolomics approach based on ultra‐high‐performance liquid chromatography coupled with quadrupole‐time‐of‐flight mass spectrometry to identify the chemical constituents of the Traditional Chinese Er‐Zhi‐Pill

“…However, such isomers could not be further distinguished due to the intrinsic limitations of MS. The analogous fragmentation patterns were applied to further verify other oleanane‐type triterpenoids, and compounds 35 , 37 – 45 , 48 – 56 , 59 , 61 , and 63 – 65 were identified as such .…”

“…Compound 16 was consequently identified as luteoloside . Similarly, compounds 6 , 8 , 9 , 14 , 27 , 28 , and 33 were tentatively identified by comparing their molecular weights and MS spectral data with the literature .…”

Different Effects of Farrerol on an OVA-Induced Allergic Asthma and LPS-induced Acute Lung Injury

“…Farrerol (structure shown in Fig. 1 ), a new kind of 2,3-dihydro-flavonoid drug, is also isolated from rhododendron, which belongs to a traditional Chinese herbal medicine [16] . It has been shown to have the anti-bacterial activity, but no details on the anti-inflammatory activity [17] .…”