Growth Inhibitory Properties of Scaevola spinescens R.Br. Leaf Extracts against the Acne Vulgaris causing Bacterium Cutibacterium acnes

Introduction: Acne vulgaris is a skin conditions that affects most adolescents and may also afflict adults. Medicinal plant extracts may provide leads for the development of new topical and/or oral therapies for acnes vulgaris, yet many traditional medicine plants are yet to be screened for growth inhibitory activity against Cutibacterium acnes (the major bacterial cause of acne). Materials and Methods: Methanolic and aqueous Scaevola spinescens R.Br. leaf extracts were investigated by disc diffusion and liquid dilution MIC assays against Cutibacterium acnes (a significant bacterial cause of acne). Toxicity was determined using Artemia franciscana nauplii bioassays. Results: Methanolic and aqueous S. spinescens leaf extracts displayed noteworthy bacterial growth inhibitory activity against C. acnes growth. The aqueous S. spinescens leaf extract had particularly good antibacterial effects against C. acnes, with an LD MIC value of 344 μg/mL. Similar, albeit slightly higher LD MIC values were noted for the aqueous methanolic S. spinescens leaf extract against C. acnes (LD MIC = 875 μg/mL). The methanolic and aqueous S. spinescens leaf extracts were nontoxic in the Artemia fransiscana bioassay, with LC50 values substantially >1000 μg/mL. Conclusion: The lack of toxicity of the methanolic and aqueous S. spinescens leaf extracts and their noteworthy growth inhibition of C. acnes indicate their potential as treatments to alleviate acne vulgaris. Further studies are warranted to isolate and identify the active components and to determine their antibacterial mechanism.