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 -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 -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.