14 J. Cosmet. Sci., 74, 14–30 (January/February 2023) Address all correspondence to Mehzat Altun, mehzataltun@comu.edu.tr Chemical Characterization, Antibacterial, Antioxidant, and Cytotoxic Activity of Some Essential Oils Against Strains Causing Acne MEHZAT ALTUN, NURAY YILDIRIM AND BINNUR M. YAPICI Canakkale Onsekiz Mart University, Canakkale, Turkey (M.A., N.Y., B.M.Y.) Accepted for publication May 24, 2023. Synopsis The potential of essential oils (EOs) as alternatives to antibiotics for the treatment of acne vulgaris is an area of growing interest due to increasing antibacterial resistance. This study aimed to determine antimicrobial efficacy, chemical profile, and the antioxidant and cytotoxic potential of EOs. Antimicrobial activity was assessed using disc diffusion and minimum inhibitory concentration (MIC) assays against Staphylococcus epidermidis ATCC 12228 and Cutibacterium acnes ATCC 6919. The phytochemical content of oils was determined by gas chromatography/mass spectrometry. The 2,2-diphenyl-1-picrylhydrazyl and the 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide methods were used to detect antioxidant properties and cell viability, respectively. Limonene, p-cymene, linalool, 1.8-cineole, β-santalol, cinnamaldehyde, carvacrol, and eucalyptol were the major components of lemon, tea tree, lavender, laurel, sandalwood, cinnamon, oregano, and eucalyptus EOs, respectively. The MIC/minimum bactericidal concentration values were between 0.03125% and 32% (v/v). Binary combinations of cinnamon/lavender and cinnamon/sandalwood exhibited synergism against both bacteria. The Cinnamomum verum showed the greatest antioxidant activity (IC50: 35.08 µg/ml). The cytotoxic activity of EOs at concentrations between 2% and 0.0625% was evaluated against a mouse fibroblast (NIH 3T3) cell line. In vitro test results revealed that antibacterial effective EOs may be used in development of topical acne therapy after in vivo and clinical trials are carried out. INTRODUCTION Acne vulgaris involving the pilosebaceous units (hair follicle and sebaceous glands) is a chronic inflammatory skin disease that affects approximately 650 million people worldwide (1,2). Acne is seen in about 80% of the 11–30 age group and 20% of adults over the age of 30. Individuals with acne are negatively affected socially and mentally (3–5). Increasing sebum production, cornification of sebaceous glands and excretory ducts releasing inflammatory mediators, and enlargement of the bacterial flora in the skin constitute the pathogenesis of patients with acne vulgaris (3). Cutibacterium acnes, formerly Propionibacterium acnes, and Staphylococcus epidermidis are members of normal human skin microbiota and are named acne-associated pathogens (6).

15 CHARACTERIZATION AND ACTIVITY OF ESSENTIAL OILS Acne lesions have been treated by topical and systemic (oral) antibiotics for more than 40 years. Macrolides such as erythromycin and clindamycin are frequently found in topical formulations of liquid, gel, lotion, and ointment (7). Current treatments are used to reduce sebum production and inflammation, inhibit bacterial growth, and normalize keratinization. Oral therapy is mostly successful but shows some side effects. Isotretinoin is known to be a powerful anti-acne agent but causes serious ailments such as headaches, muscle pain, and suicidal tendencies. Topical therapy like benzoyl peroxide, retinoids, antibiotics, and salicylic acid that reduce the effects of acne pathogens are preferred but cause skin irritation (8–13). Inappropriate and excessive use of antibiotics causes resistant bacteria (14). Complementary and alternative medicine treatments have less toxicity and side effects and are frequently preferred, especially in dermatology (15,16). Essential oils (EOs) are the secondary metabolites of plants, showing antioxidant, antifungal, and antibacterial activities due to their different phytochemical constituents such as flavonoids, alkaloids, phenol and phenolic compounds, phenylpropanoid glycosides, and bisnaphthicione derivatives (17,18). Plant-derived antioxidants accelerate the wound healing process (19). EOs are often used in combination to increase their therapeutic efficacy (20). In this study, we aimed to determine antibacterial properties of different EOs both alone and in combination with S epidermidis ATCC 12228 and C acnes ATCC 6919 microbial strains, and to investigate the chemical components, antioxidant potential, total phenolic content (TPC) of effective EOs, and their cytotoxicity against NIH 3T3 cell line by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. MATERIALS AND METHODS ESSENTIAL OILS EOs extracted from oregano leaves (Origanum vulgare, lot 1110), garlic bulb (Allium sativum, lot 2512), cinnamon trunk bark (Cinnamomum verum, lot 00018), orange peels (Citrus aurantium, lot 1708), laurel leaves (Laurus nobilis, lot 03112022), lavender flowers and leaves (Lavandula officinalis, lot 1510), rosemary leaves (Rosmarinus officinalis, lot 10112022), tea tree leaves and twigs (Melaleuca alternifolia, lot 1510), sage leaves and twigs (Salvia officinalis, lot 02022021), eucalyptus leaves (Eucalyptus globulus, lot 2810), clove oil flower buds (Eugenia caryophyllus, lot 2510), lemon peels (Citrus limon, lot 0402), and coconut seeds (Cocos nucifera, lot 211010318) were acquired commercially produced by Naturoil, Turkey. Ginger rhizome (Zingiber officinale, lot 19680) and chamomile flowers (Matricaria recutita, lot 20549) were purchased from Arifoglu (Turkey), and sandalwood trunk bark (Santalum album, lot SM48A) was purchased from Misbahce, Turkey. All EOs were obtained by steam distillation method and stored in the dark at room temperature before the test. Each EO was dissolved in 0.5% Tween 80 (Sigma-Aldrich, St. Louis, MO, USA) and sterilized using a syringe filter. GAS CHROMATOGRAPHY/MASS SPECTROMETRY ANALYSIS—CHEMICAL COMPOSITION Separation and characterization of chemical constituents of EOs were performed via Agilent 6890N GC system coupled with a 5973 inert mass selective detector and equipped