Wild bitter melon (Momordica charantia Linn. var. abbreviata Ser.) extract and its bioactive components suppress Propionibacterium acnes-induced inflammation

► Wild bitter melon extract suppresses Propionibacterium acnes-induced inflammation. ► Saponifiable and nonsaponifiable fractions of extract reduced pro-inflammatory cytokines in P. acnes-stimulated THP-1 cells. ► The bioactive components of extract possessed PPARα and PPARγ agonistic activities. In this study, we aimed to evaluate the inhibitory effect of wild bitter melons (WBM; Momordica charantia Linn. var. abbreviata Ser.) on Propionibacterium acnes-induced inflammation and to identify the bioactive components. Our results showed that ethyl acetate (EA) extract of WBM fruit in vitro potently suppressed pro-inflammatory cytokine and matrix metalloproteinase (MMP)-9 levels in P. acnes-stimulated THP-1 cells. Furthermore, concomitant intradermal injection of WBM EA extract in mice effectively attenuated P. acnes-induced ear swelling and granulomatous inflammation. To further investigate the bioactive components, we found that both saponifiable (S) and nonsaponifiable (NS) fractions of WBM EA extract significantly suppressed pro-inflammatory cytokine and MMP-9 levels. Phytol and lutein, identified in the NS fraction, also inhibited cytokine production. Moreover, S and NS fractions of EA extract, phytol and lutein, activated peroxisome proliferator-activated receptor (PPAR) α and β in the transactivation assay. Our results suggested that PPARα or PPARγ signalling may contribute, at least in part, to the anti-inflammatory activity of WBM.