Studies on the effects of cucurbit (n = 7) uril on the physicohemical properties and anticancer activity of 10-hydroxycamptothecin

Abstract

The changes in the physicochemical properties and the anticancer activity of 10-Hydroxycamptothecin (HCPT) in the presence of Cucurbit (n = 7) uril(Q[7]) were studied by using UV absorption spectroscopy, fluorescence spectroscopy and phase solubility method. The results revealed that in the acid solution (pH 2), the absorption band of the guest HCPT exhibited a progressively lower absorbance at λ265 nm, while a progressively higher absorbance at λ425 nm as the ratio of N(Q[7])/N(HCPT) was increased. A sharp isosbestic point at λ387 nm was consistent with a simple interaction between Q[7] and HCPT. The emission spectra of the guest HCPT also exhibited a progressive decrease in fluorescence intensity at λ558 nm with a violet shift when the ratio of N(Q[7])/N(HCPT) was increased. The measured data from both absorption spectrophotometric and fluorescence spectroscopy analysis fitted to a 2 : 1 host:guest complexation, yielded a calculated stable constants (β) of 1.549 x 10(13) L2 x mol(-2) and 0.907 x 10(13) L2 x mol(-2) respectively through Reactlab EQULLIBRIA software. The effect of Q[7] on the solubility of HCPT was investigated by using phase solubility method. Upon the addition of Q[7] concentration, the solubility of HCPT was enhanced step by step at the value of pH 2 and an about 250 times advance was attained when the concentration of Q[7] was 1 x 10(-3) mol x L(-1), while the Q[7]-HCPT inclusion complex made by total evaporation method can increase about 1 170 times compared to the pure HCPT. At the end, the mixtures of Q[7] and HCPT were tested in terms of cytotoxicity on the human lung cancer cell line A549 and human leukemia cell line K562 to compare their reactivity with the free HCPT and the comparative cytotoxic activity was got for A549 and K562.