Propionibacterium acnes is a key pathogen involved in acne inflammation. Wild bitter melon (WBM, Momordica charantia L. var. abbreviate Seringe) is consumed as both a vegetable and as folk medicine in Taiwan. We examined the inhibitory activity of the total phenolic extract (TPE) of WBM leaf on P. acnes-induced inflammatory responses in vivo and in vitro. Our data showed that TPE significantly attenuated P. acnes-induced ear swelling in mice along with microabscess. Flow cytometry analysis revealed that TPE treatment significantly decreased the migration of neutrophils and interleukin (IL)-1β⁺ populations in vivo. In P. acnes-stimulated human monocytic THP-1 cells, TPE suppressed the mRNA levels and production of IL-8, IL-1β, and tumor necrosis factor (TNF)-α in vitro. In addition, TPE suppressed P. acnes-induced matrix metalloproteinase-9 levels. TPE blocked nuclear factor-κB (NF-κB) activation and inactivated mitogen-activated protein kinases (MAPK); these actions may partially account for its inhibitory effect on cytokine production. The quantitative HPLC analysis revealed gallic, chlorogenic, caffeic, ferulic, and cinnamic acids, myricetin, quercetin, luteolin, apigenin, and thymol in TPE. All these phenolics significantly suppressed P. acnes-induced IL-8 production in vitro. Our results suggest that WBM leaf extract effectively inhibits P. acnes-induced inflammatory responses and may be useful to relieve the inflammation of acne.

Acne vulgaris (acne) is a common inflammatory skin disorder, and Propionibacterium acnes plays a major role in the development and progression of acne inflammation. Herbs possessing antimicrobial and anti-inflammatory activity have been applied as a medical option for centuries. In this study, we examined the suppressive effect of ethanolic oregano (Origanum vulgare) extract on live P. acnes-induced in vivo and in vitro inflammation. Following ethanol extraction of oregano leaves, four compounds with strong antioxidant activity, including rosmarinic acid, quercetin, apigenin, and carvacrol, were identified by high-performance liquid chromatography. Using the mouse ear edema model, we demonstrated that ethanol oregano extracts (EOE) significantly suppressed P. acnes-induced skin inflammation, as measured by ear thickness (32%) and biopsy weight (37%). In a separate study, using the co-culture of P. acnes and human THP-1 monocytes, EOE reduced the production of interleukin (IL)-8, IL-1β and tumor necrosis factor (TNF)-α up to 40%, 37%, and 18%, respectively, as well as the expression of these three pro-inflammatory mediators at the transcriptional level. Furthermore, EOE inhibited the translocation of nuclear factor-kappa B (NF-κB) into the nucleus possibly by inactivating toll-like receptor-2 (TLR2). The suppressive effect of EOE on live P. acnes-induced inflammatory responses could be due, in part, to the anti-inflammatory and antioxidant properties, but not the anti-microbial effect of EOE.