Stabilization of Ampicillin Analogs in Aqueous Solution. VI. Kinetic Analysis of the Stabilization Mechanism of Bacampicillin with Benzaldehyde in Aqueous Solution

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It was proved that bacampicillin hydrochloride (BAPC) is degraded according to a parallelconsecutive reaction scheme consisting of the direct deactivation reaction of β-lactam cleavage and the process through ampicillin (ABPC) in aqueous solution. In particular, the degradation of the 3-carboxylate of BAPC was faster than that of the β-lactam, and BAPC was transformed quite easily to ABPC in the alkaline region (pH 7.00-9.00). However, the degradation of the β-lactam and that of the ester moiety of BAPC were inhibited due to adduct formation upon addition of benzaldehyde at this pH region. On the other hand, such a stabilization was not observed in the acidic region (pH<6.00) because no adduct formation developed. The formation constant of the adduct increased with increase of pH. On the basis of the above results and infrared and mass spectra of the freeze-dried product prepared from an alkaline solution containing BAPC and benzaldehyde, the adduct was concluded to be the Schiff's base formed between the α-amino group of BAPC and benzaldehyde ; a similar adduct is formed by ABPC.
社団法人日本薬学会の論文
1985-03-25