The effects of glutathione (GSH) depletion on the in vivo formation of cyclic 1,N2- propanodexoxyguanosine adducts (AdG and CdG) as background lesions in the liver DNA of F344 rats were investigated. A group of 5 male F344 rats were given drinking water containing 30 mM L-buthionine (S,R)-sulfoximine (BSO) for 21 days, and another group of 8 rats were given only drinking water as controls. The BSO-treated rats had significantly lower weight gain than control rats. The hepatic GSH levels in the BSO-treated group were reduced by 84% as compared with the control group, from 4.43 to 0.72 mumol/g of tissue. The isomeric AdG3, CdG1, and CdG2 were detected by the 32P-postlabeling/HPLC method in the liver DNA of rats without carcinogen treatment, as we reported previously [Nath, R. G., and Chung, F.-L. (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 7491-7495. Nath, R. G., et al. (1996) Cancer Res. 56, 452-456]. The mean levels (mumol/mol of guanine) for AdG3, CdG1, and CdG2 were 0.57 +/- 0.25, 0.15 +/- 0.18, and 0.16 +/- 0.22 for the control group and 1.18 +/- 1.03, 3.16 +/- 3.26, and 2.50 +/- 2.59 for the BSO group, respectively. These increases correspond to approximately 2-fold for AdG and 15-21-fold for CdG adducts. The dramatic increase in the cyclic adduct levels in rat liver DNA could have resulted mainly from GSH depletion as a result of the BSO treatment, even though other unknown effects due to the toxicity of BSO cannot be ruled out. These results suggest that GSH plays an important role in protecting the liver against cyclic propano DNA adduction and provide further support for the endogenous origin of these adducts.

Fluorescein isothiocyanate-labeled insulin (FITC-insulin) has been widely used for bioanalytical applications. Due to the high cost of commercial FITC-insulin and tedious labeling procedures described in the literature, there is still a need to develop a cost effective, reliable and quick labeling method for insulin. The purpose of the present work was to develop a quick and affordable method for FITC labeling of human insulin and to determine the effect of different conjugations of FITC to human insulin on its permeability through the MDCK cell monolayer. FITC labeling of insulin gives mono-, di- or tri-conjugates depending on the reaction time and the molar ratio of FITC:insulin. Mono-conjugate with unlabeled insulin, mixture of di- and tri-conjugate, and tri-conjugate with very little amount of di-conjugate were synthesized in less than 4 h. Degree of conjugation had an effect on the permeability of insulin through the MDCK cell monolayer. Mono-conjugate had higher permeability than the unlabeled insulin due to increase in partition coefficient. However, tri-conjugate showed lower permeability than the unlabeled insulin due to the increase in molecular weight.

Betulinic acid (BA), a novel natural product with antimelanoma activity, has poor aqueous solubility (<0.1 μg/mL) and therefore exhibits poor bioavailability. The purpose of this study was to explore the feasibility of preparing BA solid dispersions (BA-SDs) with hydrophilic polymers to enhance the aqueous solubility of BA. Melt-quenched solid dispersions (MQ-SDs) of BA were prepared at various ratios with the hydrophilic polymers including Soluplus, HPMCAS-HF, Kollidon VA64, Kollidon K90, and Eudragit RLPO. BA was found to be miscible in all polymers at a 1:4 (w/w) ratio by modulated differential scanning calorimetry (MDSC). BA/Soluplus MQ-SD exhibited the highest solubility in simulated body fluids followed by BA/Kollidon VA64 MQ-SD. The MQ-SDs of BA/Soluplus, BA/HPMCAS-HF, and BA/Kollidon VA64 were found to be amorphous as indicated by X-ray powder diffraction (XRPD) studies. Fourier transform infra-red (FT-IR) studies indicated molecular interactions between BA and Soluplus. Our preliminary screening of polymers indicates that Soluplus and Kollidon VA64 exhibit the greatest potential to form BA-SDs.

A voltammetric study of a series of alkyl and aryl S-glucosides unveiled the reactivity patterns of alkyl S-glucosides toward anodic oxidation and found noteworthy differences with the trends followed by aryl derivatives. The oxidation potential of alkyl S-glucosides, estimated herein from square-wave voltammetry peak potentials (E p), depends on the steric properties of the aglycone. Glucosides substituted with bulky groups exhibit E p values at voltages more positive than the values of those carrying small aglycones. This relationship, observed in all analyzed alkyl series, is evidenced by good linear correlations between E p and Taft’s steric parameters (E S) of the respective alkyl substituents. Moreover, the role of the aglycone’s steric properties as a primary reactivity modulator is backed by poor correlations between E p and the radical stabilization energies (RSEs) of the aglycone-derived thiyl radicals (RS•). In contrast, aryl glucosides’ E p values exhibit excellent correlations with the aryl substituents’ Hammett parameters (σ+) and the ArS• RSEs, evidencing the inherent stability of the reactive radical intermediate as the primary factor controlling aryl glucoside’s electrochemical reactivity. The reactivity differences between alkyl and aryl S-glucosides also extend to the protective group’s effect on E p. Alkyl S-glucosides’ reactivity proved to be more sensitive to protective group exchange.