Potentiometric, UV and1H NMR study on the interaction of penicillin derivatives with Zn(II) in aqueous solution.
The interaction of Zn(II) with ampicillin [(2S,5R,6R)-6-([(2R)-2-amino-2-phenylacetyl]amino)-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2- carboxylic acid] and amoxicillin [(2S,5R,6R)-6-{[(2R)-2-amino-2-(4-hydroxyphenyl)-acetyl]amino}-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-24-carboxylic acid] in NaCl aqueous solution at different ionic strengths and at t=25°C was investigated by potentiometric, UV and1H NMR techniques. Fairly similar speciation models were obtained for the two systems. At I=0.15molL-1, two different sets of measurements, at low and high concentrations, were carried out. For the Zn2+-amoxicillin system, the Zn2L2(OH)2species was obtained in the set of measurements at high concentration. The spectrophotometric and1H NMR results thus obtained are fully consistent with the speciation models found from potentiometric investigations, confirming the formation as well as the relative stability of the complex species. The dependence of the stability constants on the ionic strength was modeled by means of the Debye-Hückel and SIT (Specific ion Interaction Theory) approaches, and the parameter that accounts for the variation of the stability constants with the ionic strength and the specific ion interaction parameters were determined for all the ionic species. The sequestering ability of the ligands towards Zn2+was evaluated by determining the pL0.5parameter at different ionic strengths. It resulted that the sequestering ability of ampicillin is higher of ~0.5 order of magnitude with respect to amoxicillin.
Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, Università di Messina, Viale F. Stagno d'Alcontres 31, 98166 Messina, Italy.
Paola
P
Cardiano
Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, Università di Messina, Viale F. Stagno d'Alcontres 31, 98166 Messina, Italy.
Rosalia Maria
RM
Cigala
Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, Università di Messina, Viale F. Stagno d'Alcontres 31, 98166 Messina, Italy.
Francesco
F
Crea
Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, Università di Messina, Viale F. Stagno d'Alcontres 31, 98166 Messina, Italy.
Concetta
C
De Stefano
Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, Università di Messina, Viale F. Stagno d'Alcontres 31, 98166 Messina, Italy. Electronic address: ogiuffre@unime.it.
Ottavia
O
Giuffrè
Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, Università di Messina, Viale F. Stagno d'Alcontres 31, 98166 Messina, Italy.
Silvio
S
Sammartano
Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, Università di Messina, Viale F. Stagno d'Alcontres 31, 98166 Messina, Italy.
Giuseppina
G
Vianelli
D000658:Amoxicillin / Q000737:chemistry; D000667:Ampicillin / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D009994:Osmolar Concentration; D010406:Penicillins / Q000737:chemistry*; D011199:Potentiometry; D012965:Sodium Chloride; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D014867:Water; D015032:Zinc / Q000737:chemistry*
D010406:Penicillins; D012996:Solutions; D014867:Water; D012965:Sodium Chloride; D000667:Ampicillin; D000658:Amoxicillin; D015032:Zinc
(1)H NMR titrations; Amoxicillin; Ampicillin; Dependence on ionic strength; Potentiometric; Sequestration; Spectrophotometric; Zinc