Inhibition of pro-inflammatory cytokines by homalolide A and homalomenol A isolated from rhizomes of Homalomena pendula

Inflammation, a natural process of the innate immune system, involves elevated levels of various proinflammatory mediators, such as, nitric oxide (NO) and prostaglandin (PGE2), cytokines such as interleukin 6 (IL-6), interleukin 10 (IL-10) and tumor necrosis factor alpha (TNF-alpha), and enzymes including inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). This study investigated the anti-inflammatory effects of homalolide A (1) and homalomenol A (2), two sesquiterpenoids isolated from the rhizome of Homalomena pendula, on lipopolysaccharide (LPS)- stimulated macrophage cells. The results demonstrated that both 1 and 2 dose-dependently inhibited the production of PGE2, TNF-alpha and IL-6 in RAW 264.7 macrophages. Furthermore, 2 also stimulated IL-10 production in RAW 264.7 cells. Consistent with these findings, these compounds suppressed the LPS-stimulated protein levels of iNOS and COX-2 in RAW 264.7 cells. These results suggested that 1 and 2 could be effective candidates for ameliorating inflammatory-associated complications.