Vernonia patula (Dryand.) Merr. and Leucas chinensis (Retz.) R. Brown exert anti-inflammatory activities and relieve oxidative stress via Nrf2 activation

Ethnopharmacological relevance: Vernonia patula (Dryand.) Merr. and Leucas chinensis (Retz.) R. Brown have anti-inflammatory properties and are popularly used as complementary and alternative medicine in Asia.

Aim of the study: To investigate the underlying molecular mechanism and active chemicals in the ethanol extracts of V. patula (VP) and L. chinensis (LC).

Materials and methods: The inhibitory activities of VP and LC on lipopolysaccharide (LPS)-stimulated nitric oxide (NO) and interleukin-6 (IL-6) production were investigated in RAW264.7 macrophages and BV2 microglia. Downregulation of pro-inflammatory genes and upregulation of Nrf2 (NF-E2 p45-related factor 2)-ARE (antioxidant response element) pathway were investigated using RT-Q-PCR and Western blotting. Direct antioxidant capacities were measured using free radical scavenging and Folin-Ciocalteu assays. The flavonoids and triterpenes in VP and LC were identified by HPLC-ESI-MS.

Results: VP and LC inhibited NO and IL-6 production and suppressed iNOS, IL-6, IL-1β and CCL2 gene expression. VP and LC were potent direct antioxidants and effective indirect antioxidants assayed by Nrf2 activation and induction of heme oxygenase (HO)-1, glutamate-cysteine ligase modifier subunit (GCLM) and NAD(P)H quinone oxidoreductase 1 (NQO1). Three flavonoids including apigenin (1), luteolin (2) and chryseriol (3), and one triterpene betulinic acid (4) were found in VP; while compounds 1-4 and oleanolic acid (5) were in LC.

Conclusion: Anti-inflammatory and antioxidant activities of VP and LC may be in great part attributed to the identified Nrf2 activating compounds, which induce expression of Phase II enzymes and attenuate the upregulation of pro-inflammatory genes.

Keywords: HO-1; HPLC-MS; Leucas chinensis; Nrf2; Vernonia patula; apigenin; betulinic acid; luteolin.