Reference

Molecular structures of ionophore antibiotics

Molecular structures of ionophore antibiotics. Infrared spectra of nigericin and grisorixin in the diluted state and at the phospholipid-water interface. Mellier, Andre; Auge, Odile (Lab. Opt. Mol., Poitiers 86022, Fr.). Colloids Surf., 10, 211-16 (English) 1984. CODEN: COSUD3. ISSN: 0166-6622. DOCUMENT TYPE: Journal CA Section: 63 (Pharmaceuticals) Section cross-reference(s): 22, 26 IR spectra of grisorixin (I, R = H) [31357-58-1] and nigericin (I, R = OH) [28380-24-7] both in soln. and in a multilamellar phospholipid-water system contg. 1,2-L-a-dimyristoylphosphatidylcholine [18194-24-6] show the presence of intramol. hydrogen bonds. The bonds are stronger in the case of nigericin. The chelated structure is unchanged when the ionophores are incorporated into fluid lipid multilamellar systems, but other hydrogen bonds occur between the phosphate group and the polar access region.

Characteristics of drug-phospholipid coprecipitates

Characteristics of drug-phospholipid coprecipitates. I: Physical properties and dissolution behavior of griseofulvin-dimyristoylphosphatidylcholine systems. Venkataram, S.; Rogers, J. A. (Fac. Pharm. Pharm. Sci., Univ. Alberta, Edmonton, AB, Can.). J. Pharm. Sci., 73(6), 757-61 (English) 1984. CODEN: JPMSAE. ISSN: 0022-3549. DOCUMENT TYPE: Journal CA Section: 63 (Pharmaceuticals) Solid dispersions of griseofulvin (I) [126-07-8] and L-a-dimyristoylphosphatidylcholine (lecithin) [18194-24-6] were prepd. as both coppts. and phys. mixts., and their phys. characteristics and dissoln. behavior compared with pure I. The dissoln. of the phys. mixts. was similar to pure drug, but the coppts. yielded a 3.5-fold greater initial dissoln. rate and a limiting concn. after 60 min which was 72% greater at a I-lecithin wt. ratio of . Increasing the lecithin content to 1.5:1 compns. resulted in only a further 50% increase in the initial dissoln. rate and a further 12% increase in the limiting concn. The effect of the pH of the medium on dissoln. was slight, but varied with the compn. of the system. The phase diagram indicated that these systems have no significant eutectic or solid soln. formation. X-ray diffraction spectra further showed that freshly prepd. or aged coppts. contained I crystals, and photomicrographs showed that the crystals essentially retained their characteristic shapes and sizes in all systems. DTA yielded heats of fusion that gave a good linear correlation with the percent of I dissolved from coppts. at all time intervals, but not with phys. mixts. Furthermore, aged coppts. underwent a slower rate of dissoln. compared with fresh samples. The results are interpreted to suggest that I undergoes improved dissoln. from coppts. due to the formation of crystals of lower stability. In addn., the rapid dispersion of lecithin in the aq. medium (as seen microscopically) entraps I in myelinic structures and liposomes and effectively increases the satn. concn. of drug in the diffusion layer during the dissoln. process.