The review gives an insight into inherent biological properties of bacterial metabolites-low-molecular weight Phenylcarboxylic Acids (PCAs), including Benzoic Acid (BA), p-Hydroxyphenyllactic Acid (HPLA), Phenyllactic Acid (PLA), p-Hydroxyphenylacetic Acid (HPAA), Phenylacetic Acid (PAA), and Phenylpropionic Acid (PPA). It has been demonstrated that bacteria from human microflora-predominantly anaerobes-can metabolize aromatic amino acids into PCAs, and PCAs are capable to suppress the growth and propagation of other bacteria, entering competitive interactions within microbial associations. The authors suggest that in the human colon, where concentrations of microbial metabolites reach biologically active level, PCAs may exert not only local, but also systemic effects, thus any deviation from existing composition of microbial associations may potentially result in the breakdown of habitual PCAs balance and emergence of PCAs with opposite biological properties. Available published data as well as findings from own research allowed us to substantiate a novel approach directed at the development of new therapeutic strategies based on regulation of local and systemic balance of microbial aromatic metabolites in the human body.

Some exometabolites produced by basic representatives of human anaerobic microflora were investigated, detected by gas chromatography - mass spectrometry (GC-MS). In vitro besides lactic acid Bifidobacterium and Lactobacillus generate substantial amounts of phenyllactic and p-hydroxyphenyllactic acids. Clostridium produced 2-hydroxybutyric acid and to a lesser extent lactic and phenyllactic acids. In contrast to С. perfringens, C. sporogenes generates substantial amount of phenylpropionic and p-hydroxyphenylpropionic acids and less p-hydroxyphenyllactic acid. С. perfringens produced minor amounts of 2-hydroxyglutaric acid. Bacteroids are potent producers of succinic and fumaric acids; they also contribute to production of significant portion of lactic acid. E. lentum generate lactic, phenyllactic and succinic acids and form a characteristic only for ones (from studied microorganisms) 2-hydroxyhexanic and 2-hydroxy-3-methylbutyric acids.