Browsing by Author "Wu, Danni"

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Magnesium and calcium reveal different chelating effects in a steroid compound: A model study of prednisolone using NMR spectroscopy
(2019-10-01)
Carillo, Kathleen D.
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Wu, Danni
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Lin, Su-Ching
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Tsai, Shen-Long
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Shie, Jiun-Jie
In this work, we used high resolution NMR spectroscopy to investigate metal cation chelation by the steroidal drug 1,4-pregnadiene-11 beta,17 alpha,21-triol-3,20-dione (Prednisolone; abbreviated as Prd). Prd/MgCl2 and Prd/CaCl2 mixtures were prepared at eight different molar ratios. Using two-dimensional H-1/C-13 heteronuclear correlation spectroscopy, we were able to resolve most of the H-1 signals, except those at 1.4-1.55 ppm, where signals for H15 beta, H16 alpha and Me-19 are superimposed. The chelation sites were determined by the cation concentration-dependent C-13 signals. Both ring A and ring D of Prd were found to be involved in Mg2+ chelation, whereas only ring A was involved in Ca2+ chelation. The dihedral angles deduced from the (3)J(H)(-H) coupling constants indicated that ring D of Prd might undergo rather small, but different, distortions in the presence of Mg2+ and Ca2+. Additionally, using the continuous variation method, we deduced that the stoichiometric ratios of the Prd/Mg2+ and Prd/Ca2+ complexes were 1:1 and 2:1, respectively. All of the evidence led us to conclude that the Prd/Mg2+ and Prd/Ca2+ complexes are mediated by different chelating mechanisms.
Solid-state nuclear magnetic resonance investigation of neurosteroid compounds and magnesium interactions
(2019-10-01)
Wu, Danni
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Carillo, Kathleen Joyce D.
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Tsai, Shen-Long
;
Shie, Jiun-Jie
;
Tzou, Der-Lii M.
The neurosteroid trans-dehydroandrosterone (DHEA) and its analogs with slightly different modifications in the side chain attached to C17, that is, (3S)-acetoxypregn-5-en-20-one (1) and (3S,20R)-acetoxypregn-5-en-20-ol (2), have been synthesized to investigate DHEA-cation interactions. In this study, we applied solid-state H-1/C-13 cross-polarization/magic-angle spinning (CP/MAS) nuclear magnetic resonance (NMR) spectroscopy to a series of DHEA analog/Mg2+ mixtures at different Mg2+ concentrations. The high-resolution C-13 NMR spectra of 1/Mg2+ mixtures exhibit two distinct C-13 spectral patterns, one attributable to 1 free from Mg2+, and the other attributable to 1 with bound Mg2+. For 2, the C-13 NMR spectra exhibit three distinct spectral patterns; besides that of the free form, the other two can be assigned to Mg2+-bound forms. Based on the analysis of the chemical shift deviations (CSDs), we conclude that both 1 and 2 might be subject to a cation-pi interaction via the C5-C6 double bond, in contrast to that observed previously for DHEA. As demonstrated, DHEA possesses two Mg2+ binding sites, that is, C17-O and C5-C6 double bond, in which the binding affinity of the former is at least three times stronger than that of the latter. The solid-state C-13 NMR investigation allows better understanding of the underlying cation binding effects of neurosteroid molecules in vitro.