Aki H, Yamamoto K, Sawai N, Yamamoto M
Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Fukuoka University, Japan.
Drug Des Deliv. 1990 Dec;7(1):59-63.
Ampicillin polymerizes in aqueous solution to produce antigenic polymers; the polymers were separated by anion-exchange chromatography and shown to consist of a dimer, trimer, tetramer and pentamer of ampicillin by the masses found in fast atom bombardment mass spectroscopy. The presence of an intact beta-lactam ring in each of the polymers was revealed by the characteristic positive Cotton effect near 230 nm in their circular dichroism spectra. beta-Cyclodextrin was found to inhibit this polymerization by complex formation involving equimolar quantities of the constituents. Formation of this complex was complete in 10% aqueous solution within 6 hr at 24 degrees C. The positive Cotton effect arising from the beta-lactam ring decreased as the degree of polymerization increased, but was unchanged by the complex formation with beta-cyclodextrin.
氨苄西林在水溶液中聚合产生抗原性聚合物；这些聚合物通过阴离子交换色谱法分离，并通过快速原子轰击质谱法测定的质量表明由氨苄西林的二聚体、三聚体、四聚体和五聚体组成。它们的圆二色光谱在230nm附近有特征性的正科顿效应，表明每种聚合物中均存在完整的β-内酰胺环。发现β-环糊精通过涉及等摩尔量成分的复合物形成来抑制这种聚合。在24℃下，这种复合物在10%水溶液中6小时内形成完全。随着聚合度增加，β-内酰胺环产生的正科顿效应降低，但与β-环糊精形成复合物后该效应未改变。
