High-pressure liquid chromatography Sephadex

Isolation of potential anticancer compounds from bioactive extracts involves bioactivity-guided fractionation. The DNA-damaging natural products encountered in our studies were extracted by MEK and/or methanol, and the general methodology which we have employed in our bioassay-directed fractionation of these extracts is schematically presented in Fig. 7. These fractionations involved solvent-solvent partition, Sephadex LH-20 gel filtration, normal phase and reversed-phase (RP) column, preparative thin-layer and high pressure liquid chromatography (HPLC). Silica gel chromatography was employed only if bioactive compounds were found to be stable under these mildly acidic conditions. 

High-pressure liquid chromatography (Hites and Biemann, 1972 Klimisch, 1973 Loheac et al., 1973 Simoneit et al., 1973b Dong et al., 1976 Hunt et al., 1977) and gel permeation chromatography on Sephadex LH 20 (Giger and Blumer, 1974 Giger and Schaffner, 1977) are now commonly used to isolate and to analyse for aromatic hydrocarbons. 

Polymerization of benzylpenicillin has been described by several authors (Batchelor et al. 1967 Stewart 1967 a de Weck et al. 1968 Butcher and Stewart 1969, 1970 Dewdney et al. 1971 Smith et al. 1971 Smith and Marshall 1971 Bungaard and Larsen 1977). Polymerization probably involves hydrolysis of the beta-lactam ring to form penicilloic acid, followed by acylation of the exposed thiazolidine nitrogen by another intact penicillin molecule or a benzyl-penicillenic acid derivative (Stewart 1973 Smith and Marshall 1971 Schneider and de Weck, 1970) (Fig. 8) Such polymers have been isolated by Sephadex gel chromatography (Smith et al. 1971) or by high-pressure liquid chromatography (Bundgaard 1977 b). Polymers have been isolated also from other semisynthetic penicillins such as hetacillin and carbenicillin (Smith et al. 1971), methicillin and pheneticillin (Butcher and Stewart 1970). 

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