DL-Malic acid is the racemate of the metabolic intermediate L-malic acid.1 It reduces CCL2 and ICAM expression induced by IFN-γ and TNF-α in HaCaT human keratinocytes when used at a concentration of 1 mM.2 Topical administration of DL-malic acid (10 mM) inhibits epidermis and dermis thickening, as well as mast cell and eosinophil dermal infiltration in a mouse model of atopic dermatitis induced by 2,4-dinitrochlorobenzene (DNBC). Formulations containing DL-malic acid have been used as food and cosmetic preservatives and acidity regulators.
1.Ryan, D.G., Murphy, M.P., Frezza, C., et al.Coupling Krebs cycle metabolites to signalling in immunity and cancerNat. Metab.116-33(2019) 2.Lee, B., Heo, J., Hong, S., et al.??-Malic acid as a component of α-hydroxy acids: Effect on 2,4-dinitrochlorobenzene-induced inflammation in atopic dermatitis-like skin lesions in vitro and in vivoImmunopharmacol. Immunotoxicol.41(6)614-621(2019)