In vitro and in vivo studies of natural anti- acne treatments from pomegranate pericarp extract and essential oils of bitter orange, sweet marjoram, and tea tree

Abstract Background Acne vulgaris is a prevalent inflammatory skin disorder marked by excessive oil production (seborrhea), follicular hyperkeratinization, bacterial proliferation (notably Cutibacterium acnes and Staphylococcus epidermidis ), and inflammatory responses. Current treatments, including antibiotics, are increasingly challenged by rising resistance and adverse effects, emphasizing the need for safer, natural alternatives. The purpose of this study was to evaluate the antibacterial and anti-acne properties of pomegranate pericarp extract (PPE) and essential oils (EOs) of bitter orange, sweet marjoram, and tea tree. Results The chemical compositions of PPE and EOs were confirmed using advanced mass spectrometry techniques. Bitter orange oil, sweet marjoram oil, and PPE demonstrated superior antibacterial activity, as evidenced by larger zones of inhibition compared to reference antibiotics (clindamycin, erythromycin, and vancomycin). The minimum inhibitory concentrations (MICs) against C. acnes were 0.21 mg/mL for bitter orange oil, 0.44 mg/mL for sweet marjoram oil and tea tree oil, and 1.95 mg/mL for PPE. Against S. epidermidis , the MICs were 0.10, 1.75, 13.90, and 1.95 mg/mL, respectively. Synergistic antibacterial activity was observed when combining PPE with either bitter orange or sweet marjoram oil against C. acnes . Hence, two formulations with bitter orange oil (1.65 mg/g) and PPE (1.95 mg/g) were developed: regular gel (BOP) and nano-cubosomal gel (nBOP). Similarly, sweet marjoram oil (3.50 mg/g) and PPE (3.90 mg/g) were combined to create regular gel (MP) and nano-cubosomal gel (nMP). These formulations were tested in a C. acnes -induced inflammatory acne animal model to simulate the complex microbial, immune, and inflammatory interactions of acne pathogenesis. All developed herbal formulations exhibited in vivo anti-acne activities, demonstrated by the restoration of the normal histology of the mice ear tissue and a significant reduction in bacterial load, inflammation percent, and the inflammatory markers relative to the untreated group. However, nBOP showed the highest anti-inflammatory efficacy, followed by BOP; the difference in inflammation inhibition per cent between them (8.2%) was insignificant, suggesting that the regular gel may offer a cost-effective alternative without significantly compromising efficacy. Conclusion The study highlights the potential of combining bitter orange oil and pomegranate pericarp extract in a regular gel as a safe, natural, and affordable alternative for acne treatment.