Anti-inflammatory properties of phenolic compounds and crude extract from Porphyra dentata

Porphyra dentata, a red edible seaweed, has long been used worldwide in folk medicine for the treatment of inflammatory diseases such as hypersensitivity, lymphadenitis, bronchitis.

To clarify the anti-inflammatory role of Porphyra dentata crude extract and its identified phenolic compounds by investigating their effect on the nitric oxide (NO)/inducible nitric oxide synthase (iNOS) transcription pathway in macrophage RAW 264.7 cells.

Porphyra dentata crude extract was prepared with methanol. High performance liquid chromatography (HPLC) hyphenated to electrospray ionization mass spectrometry (ESI-MS) and UV detection were utilized to analyze the extract fingerprints. Nitrite measurement, iNOS promoter activity and nuclear factor-kappaB (NF-kappaB) enhancer activity were used to assess the anti-inflammatory effect in lipopolysaccharide (LPS) challenged mouse RAW 264.7 cell line.

Phenolic compounds (catechol, rutin and hesperidin) were identified in the crude extract of Porphyra dentata. The crude extract and the phenolic compounds inhibited the production of NO in LPS-stimulated RAW 264.7 cells. Catechol was a more potent suppressor of the up-regulation of iNOS promoter and NF-kappaB enhancer than rutin and yet, hesperidin alone failed to inhibit either activity.

Our results indicate that catechol and rutin, but not hesperidin, are primary bioactive phenolic compounds in the crude extract to suppress NO production in LPS-stimulated macrophages via NF-kappaB-dependent iNOS gene transcription. The data also explain the anti-inflammatory use and possible mechanism of Porphyra dentata in iNOS implicated diseases.