Hop Extract Acts as an Antioxidant with Antimicrobial Effects against Propionibacterium Acnes and Staphylococcus Aureus

Abstract

Acne is associated with hyperkeratosis, elevated levels of skin sebum and growth of <i>Propionibacterium acnes</i> (<i>P. acnes</i>) and <i>Staphylococcus aureus</i> (<i>S. aureus</i>). Furthermore, <i>P. acnes</i> promotes inflammation by inducing IL-6 production and oxidative stress. The aim of this study was to assess the antioxidant, anti-inflammatory and antibacterial potential of a hop-CO₂-extract with 50% humulone and lupulone. The susceptibility of <i>P. acnes</i> and <i>S. aureus</i> to the hop extract was tested by using the broth microdilution technique. The minimal inhibitory concentrations (MIC) for <i>P. acnes</i> and <i>S. aureus</i> were 3.1 and 9.4 µg/mL, respectively. In addition, the hop extract showed an antioxidative effect with a half maximal inhibitory concentration (IC₅₀) of 29.43 µg/mL as well as additional anti-inflammatory effects by reducing the IL-6 expression (IC₅₀: 0.8 µg/mL). In addition, a gel formulation with 0.3% hop extract (<i>w</i>/<i>w</i>) had antibacterial activity against <i>P. acnes</i> and <i>S. aureus</i> (inhibition zone value: 5.5 mm and 3 mm, respectively) which was significantly superior to the placebo gel. The positive control (a gel with the antibiotic clindamycin) showed an inhibition zone of 9 mm. Due to its antioxidant, anti-inflammatory and antibacterial effects hop extract might be a treatment option for acne-prone skin.