Some physicochemical properties of 4-amino-3,5-dinitrobenzoic acid (ADBA).

Some physicochemical properties of the aromatic amino acid 4-amino-3,5-dinitrobenzoic acid (ADBA) were determined. This provides, for the first time, quantitative data about this chemical of current pharmaceutical and biomedical interest. The analytical reagent grade of ADBA has 100% purity, determined by potentiometry. The ionization constant (pKa) is 4.00 +/- 0.04. The specific absorbance of ADBA [A(1%, 1 cm)] was determined as 389.42 +/- 51.33 and 381.67 +/- 38.99 (p = 0.05) in water (435 nm) and octanol (415 nm), respectively. The lipophilicity of ADBA is described by its octanol/water partition coefficient (Log P) of -1.50. An analogous parameter descriptive of lipophilicity, the chromatographic hydrophobicity index (Rm), was determined as -0.84 on reversed phase thin layer chromatography (RPTLC). ADBA is more acidic thanp-amino benzoic acid (PABA), the prototype aromatic amino acid of which ADBA is an analogue. It is also about thirty-two times more water soluble than in n-octanol. These findings have a predictive value with respect to absorption and distribution of this compound in living organisms.