Antibacterial and toxicological evaluation of ß-lactams synthesized by immobilized ß-lactamase-free penicillin amidase produced by <i style="">Alcaligenes</i> sp.

Abstract

Search for anti-ß-lactamase and synthesis of newer penicillin were suggested to overcome resistance to penicillin in chemotherapy. It was found that clavulanic acid, an ant-ß-lactamase was ineffective due to its structural modification by bacteria. Thus, there is a need for the synthesis of newer pencillins. Retro-synthesis was inspired by the success of forward reaction <i style="">i.e</i>.conversion of penicillin G to 6-aminopenicillanic acid (6-APA) by biological process. In the present study a better enzymatic method of synthesis of newer pencillin by a ß-lactamase-free penicillin amidase produced by <i style="">Alcaligenes</i> sp. is attempted. Antibacterial and toxicological evaluation of the enzymatically synthesized ß-lactams are reported. Condensation of 6-APA with acyl donor was found to be effective when the reaction is run in dimethyl formamide (DMF 50% v/v) in acetate buffer (25 m<i style="">M</i> <i style="">p</i>H 5.0) at 37°C. Periplasm entrapped in calcium alginate exihibited the highest yield (~34%) in synthesis. The minimum inhibitory concentration of the synthetic products against <i style="">Staphylococcus aureus </i>and <i style="">Salmonella typhi </i>varied between 20–80 µg/ml. Some of the products exhibited antibacterial activity against enteric pathogens. It was interesting to note that product A was potent like penicillin G. LD₅₀ value of three products (product A, B and C) was more than 12mg/kg. Furthermore, these synthetic ß-lactams did not exihibit any adverse effect on house keeping enzymes viz., serum glutamate oxalacetate-<i style="">trans</i>-aminase, serum glutamate pyruvate -<i style="">trans</i>-aminase, acid phosphatase, alkaline phosphatase of the test animals. The hematological profile (RBC and WBC) of the test animals also remained unaffected.