Anti‐acne activity of carnitine salicylate and magnolol through the regulation of exfoliation, lipogenesis, bacterial growth and inflammation

BACKGROUND: Salicylic acid has been used as an anti‐acne agent with its comedolytic property and antimicrobial activity. However, there is a limit to use for leave‐on cosmetics because of the transient skin irritation and low efficacy at neutral pH condition. We prepared a salicylic acid‐based ionic pair with (L)‐carnitine (we named, IP‐BHA) overcoming the limitation of salicylic acid. We examined the effect of IP‐BHA as well as the combination effect with magnolol, a bioactive organic lignan, in order to clarify their efficacy as anti‐acne agents. METHODS: After verifying the structure of IP‐BHA, we confirmed anti‐acne activities including the regulation of exfoliation, lipogenesis, bacterial growth, and inflammation with IP‐BHA and/or magnolol. RESULTS: The antibacterial activity of IP‐BHA and magnolol was evaluated by determining the minimum antibacterial inhibitory concentration. Magnolol showed strong activity against Cutibacterium acnes, which was better than a medical antibiotic acne drug, clindamycin. The combined application with IP‐BHA was more effective in antibacterial activity by 2.5 times. It was confirmed that testosterone‐induced lipogenesis was significantly inhibited by treatment with IP‐BHA and magnolol, while single treatment had no significant inhibitory effect. Interestingly, MMP‐1 and VEGF were induced by C. acnes lysate in human keratinocytes. We found that these inflammatory molecules were completely inhibited by combined application of IP‐BHA and magnolol. Through ex vivo test, the dose‐dependent exfoliation effect of IP‐BHA was confirmed at pH 5.5, and the synergic exfoliation effect was shown in the combined application of IP‐BHA and magnolol. When topically applied, the emulsion containing IP‐BHA and magnolol relieved the sodium dodecyl sulfate‐induced erythema and improved inflamed acne with papule and pustule. CONCLUSION: Our data demonstrate that the ionic paired salicylic acid with (L)‐carnitine can overcome the limitations of salicylic acid at low concentration and natural skin pH. Based on the dual administration effects, we suggest that IP‐BHA and magnolol may be the potential agent for acne by improving inflammatory skin condition.