Antimicrobial Properties of Mandelic Acid, Gallic Acid and their Derivatives

Purpose: Alpha-hydroxy acids (AHAs) are one of the classes of hydroxy acids being beneficial for human health. The manuscript summarizes the biological properties of two popular members of AHAs, i.e., Mandelic Acid (MA) and Gallic Acid (GA), with particular emphasis on antimicrobial properties. Moreover, attempts to design new derivatives improving the natural properties of AHAs by using the chemical and physical approach are discussed.

Methods: Antimicrobial properties of MA, an arylalkyl AHA containing phenyl group attached to α- carbon, and GA, an aromatic trihydroxybenzoic acid containing the phenolic ring and carboxylic acid functional group, and their derivatives against common human and plant pathogenic fungi have been reviewed.

Results: The antimicrobial activity of MA and GA is a complex phenomenon strictly correlated with other properties exhibited by these acids, e.g., pro-oxidative activity and hydrophobicity. In most cases, the acids derivatives exhibited higher antimicrobial activity than the acids themselves. This is probably because of the higher lipophilicity of moiety that allows better penetration through the cell membrane.

Conclusion: MA and GA present an excellent health-promoting tool and are valuable starting materials for the design of new compounds such as metal complexes with alkali, or alkali earth metals. The lipophilic, antimicrobial, and pro-oxidative properties act synergistically, supporting the pharmacological and therapeutic effect of acids and their derivatives.