Growth Inhibitory Activity of Callicarpa americana Leaf Extracts Against Cutibacterium acnes

Abstract

Acne vulgaris is a common skin disease affecting adolescents and young adults of all ethnic groups, negatively impacting self-esteem, self-confidence, and social life. The Gram-positive bacteria <i>Cutibacterium acnes</i> colonizes the sebum-rich follicle and contributes to inflammation of the pilosebaceous gland. Long-term antibiotic therapies targeting <i>C. acnes</i> lead to the development of antimicrobial resistance, and novel acne vulgaris therapies are needed. This study investigated the <i>C. acnes</i> inhibitory activity of <i>Callicarpa americana</i> leaves, a native Southeastern United States shrub historically used by Native Americans to treat fever, stomachache, and pruritis. Flash chromatography fractions of the ethyl acetate-soluble <i>C. americana</i> ethanol leaf extract (649C-F9 and 649C-F13) exhibited MICs ranging from 16 to 32 µg ml^-1 and IC₅₀ range of 4-32 μg ml^-1 against a panel of 10 distinct <i>C. acnes</i> isolates. Cytotoxicity against an immortalized human keratinocyte cell line (HaCaTs) skin was detected at more than eight times the dose required for growth inhibitory activity (IC₅₀ of 256 μg ml^-1 for 649C-F9 and IC₅₀ of >512 μg ml^-1 for 649C-F13). This work highlights the potential of <i>C. americana</i> leaf extracts as a cosmeceutical ingredient for the management of acne vulgaris. Further research is necessary to assess its mechanism of action and <i>in vivo</i> efficacy.