Solubility, spectroscopic properties and photostability of Rhein/cyclodextrin inclusion complex.
The host-guest interaction between Rhein (Rh)--an anthraquinonic drug characterized by low water solubility and recently considered for its potential antidiabetic and antitumoral activities other than for the well-established anti-inflammatory properties--with cyclodextrins (CDs) was investigated using phase-solubility diagrams. The typical A(L) phase-solubility profiles suggest the formation of the 1:1 inclusion complexes between Rh and the two CDs investigated, namely beta-cyclodextrin and 2-hydroxypropyl-beta-cyclodextrin and the resulting constant values of complex formation, K(c), were estimated. Due to the higher K(c) value, complex of Rhein with 2-hydroxypropyl-beta-cyclodextrin was chosen for further investigation. Characterization in solution of 2-hydroxypropyl-beta-cyclodextrin/Rhein complex was achieved both by fluorescence and visible spectroscopic techniques. These results confirm the formation of inclusion complexes in solution and the 1:1 stoichiometry of the binary system. With respect to Rhein aqueous solution behavior, the inclusion complex appears to be able: (i) to enhance Rhein solubility; (ii) to control its neutral/anionic equilibrium; (iii) to affect both its electronic absorption and fluorescence spectra. Finally, the photostability of Rhein in the presence of cyclodextrins was evaluated.
Dipartimento di Chimica e Tecnologie del Farmaco, Sapienza-Università di Roma, Piazzale Aldo Moro, 5-00185 Rome, Italy.
Stefania
S
Petralito
Iacopo
I
Zanardi
Adriana
A
Memoli
Maria Cristina
MC
Annesini
Valter
V
Travagli
D000073738:2-Hydroxypropyl-beta-cyclodextrin; D000042:Absorption; D000880:Anthraquinones / Q000737:chemistry*; D002021:Buffers; D006863:Hydrogen-Ion Concentration; D008027:Light; D012995:Solubility; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013997:Time Factors; D047392:beta-Cyclodextrins / Q000737:chemistry*
D000880:Anthraquinones; D002021:Buffers; D047392:beta-Cyclodextrins; D000073738:2-Hydroxypropyl-beta-cyclodextrin; C020491:rhein