The Chemical Structure of the Intermediate Metabolites of Catechin I–IV

Abstract

Examinations were made on two intermediate metabolites excreted after administration of (+)-catechin to the rabbit. From the infrared and ultraviolet spectra of these two substances (C₁₁H₁₂O₃ and C₁₁H₁₂O₄) and chemical properties of their various derivatives, they were identified as 3-hydroxyphenyl lactone and 3, 4-dihydroxyphenyl lactone. However, it still remains unknown whether they are δ- or γ-lactone.

Abstract

In order to confirm the chemical structures of 3-hydroxyphenyl lactone and 3, 4-dihydroxyphenyl lactone assumed for the intermediate metabolites G and H, respectively, oxidation of the methyl derivatives of G and H with potassium permanganate was carried out. The products of oxidation obtained from G were 3-methoxybenzoic, succinic, and malonic acids, which indicated the structure of G to be δ-(3-hydroxyphenyl)-γ-valerolactone, and further the structure of H was similarly revealed to be δ-(3, 4-dihydroxyphenyl)-γ-valerolactone.

Abstract

Structures δ-(3-hydroxyphenyl)-γ-valerolactone and δ-(3, 4-dihydroxyphenyl)-γ-valerolactone were assigned respectively to the intermediate metabolites from (+)-catechin, G and H, according to experimental results reported in the preceding two papers. In the present series of work, dl-δ- (3- methoxyphenyl) and dl-δ-(3, 4-dimethoxyphenyl)-γ-valerolactones were synthesized and the infrared absorption spectra measured in carbon tetrachloride resulted to be entirely identical with the corresponding methyl derivatives of G and H. Racemic compounds of G and H were prepared by demethylation of these methyl derivatives.

Abstract

It has been reported that three neutral substances (F, G and H) are excreted into the urine after the oral administration of (+)-catechin to the rabbit, and also that substances G and H are respectively determined as δ-(3-hydroxyphenyl) and δ-(3, 4-dihydroxyphenyl)-γ-valerolactones. considering the structures of G and H and the metabolic mechanism of phenols, the structure of F was assumed to be δ-(3-methoxy-4-hydroxyphenyl)-γ-valerolactone and this compound was synthesized. Comparison of the natural and synthesized substances by paper partition chromatography established their identity and the structure of F was thereby confirmed.