Synthesis, characterization and biological activity of Rhein-cyclodextrin conjugate

• A series of new Rhein-β-cyclodextrin conjugates have been synthesized through amido linkage in a 1:1 molar ratio.
• The Rhein-β-cyclodextrin conjugates shows improved water solubility which is important for development of drug.
• The Rhein-β-cyclodextrin conjugates shows enhanced biological activity compared with Rhein.

Cyclodextrin conjugate complexation is a useful method to enhance the solubility and absorption of poorly soluble drugs. A series of new Rhein-β-cyclodextrin conjugates (Rh-CD conjugates) have been synthesized and examined. Rhein is covalently linked with the β-CD by amido linkage in a 1:1 molar ratio. The conjugates were characterized by 1H NMR, 13C NMR, HRMS, powder X-ray diffraction (powder XRD) as well as thermogravimetric analysis (TGA). The results reveal that incorporation of β-CD could improve the aqueous solubility of Rhein and the cytotoxicity against hepatocellular carcinoma (HepG2) cell line as well as antibacterial activity against three organisms. The improved biological activity and the satisfactory water solubility of the conjugates will be potentially useful for developing novel drug-cyclodextrin conjugates, such as herbal medicine.

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