<i>In vitro</i> bio-activity of <i>Rosa rubiginosa</i> L. (sweet briar) rosehip fixed oil combined with essential oils for acne vulgaris

<i>Cutibacterium acnes</i>, <i>Staphylococcus epidermidis</i>, and <i>Staphylococcus aureus</i> proliferate within accumulated sebum and produce localised inflammation thereby inducing acne vulgaris. Essential oils are one of the leading natural products used for acne and are diluted in fixed oils to reduce irritation and toxicity. This study investigated the <i>in vitro</i> antimicrobial, anti-inflammatory, cytotoxicity, and skin retention properties of <i>Rosa rubiginosa</i> rosehip fixed oil in combination with essential oils having activity against acne vulgaris. The broth microdilution assay was used to determine the minimum inhibitory concentration (MIC), and the sum of the fractional inhibitory concentration index (ΣFIC) was calculated for the interactions. The lipopolysaccharide (LPS) induced inflammatory pathway in RAW 264.7 macrophages was used to assess anti-inflammatory activity. A dual-staining method in A549 epithelial cells was used to assess cytotoxicity. Qualitative Fourier Transform Infrared spectroscopy analysis was used for initial skin retention determination. <i>Rosa rubiginosa</i> oil combined with <i>Cinnamomum zeylanicum</i> essential oil displayed antimicrobial synergy (MIC = 0.42 mg/ mL; ΣFIC = 0.45) against three acne-inducing strains. <i>Rosa rubiginosa</i> fixed oil combined with <i>Styrax benzoin</i> essential oil suppressed LPS-induced nitrite production by 33.80%. <i>Rosa rubiginosa</i> oil combined with <i>Melaleuca quinquenervia</i> essential oil exhibited the lowest cytotoxicity (84.32% cell viability). <i>Rosa rubiginosa</i> oil combined with either <i>C. zeylanicum</i>, <i>Eugenia caryophyllata</i>, <i>Rosa damascena</i> or <i>S. benzoin</i> essential oil was retained within the porcine skin. <i>Rosa rubiginosa</i> fixed oil serves as an ideal carrier oil that can potentiate selected essential oils for the treatment of acne vulgaris.