Abstract
High-speed counter-current chromatography (HSCCC) was successively applied to the separation of three sulfur-containing diketopiperazines (DKPs) (including two new compounds cladosporin A (1) and cladosporin B (3), and a known compound haematocin (2)) from a marine fungus Cladosporium sp. The two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water at (1:1:1:1, v/v) and (2:1:2:1, v/v), in stepwise elution mode, was used for HSCCC. The preparative HSCCC separation was performed on 300 mg of crude sample yielding 26.7 mg of compound 3 at a purity of over 95%, 53.6 mg of a mixture of compounds 1 and 2, which was further separated by preparative-HPLC yielding 14.3 mg of compound 1 and 25.4 mg of compound 2 each at a purity of over 95%. Their structures were established by spectroscopic methods. The sulfur-containing DKPs suppressed the proliferation of hepatocellular carcinoma cell line HepG2. The present work represents the first application of HSCCC in the efficient preparation of marine fungal natural products.
Highlights
The oceans are special environments with harsh conditions, such as high salinity, low-luminance, low temperature, high pressure, oligotrophic, etc
The two-phase solvent system was selected according to the KD values of each target compound
Dr Ito has demonstrated the golden rules in selecting optimum conditions for High-speed counter-current chromatography (HSCCC)
Summary
The oceans are special environments with harsh conditions, such as high salinity, low-luminance, low temperature, high pressure, oligotrophic, etc. Diketopiperazines (DKPs) constitute a large class of natural products that exhibit various biological properties. They were first discovered in 1880 and later studied by Emil Fischer [4]. High-speed counter-current chromatography (HSCCC), being a support-free liquid-liquid partition method, eliminates irreversible adsorption of sample on to the solid support [9,10]. Because of these advantages, HSCCC has been widely used in the preparative separation of natural products [11]. We can acquire compounds with high purity through one-step separation, while in other studies enrichment of sample were achieved
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