Four new pregnane steroids, 3β,4β,16β-trihydroxypregna-5,17-diene-10,2-carbolactone (1), 16β-acetoxy-3β,4β-dihydroxypregna-5,17-diene-10,2-carbolactone (2), 12β-acetoxy-3β,4β,16β-trihydroxypregna-5,17-diene-10,2-carbolactone (3), and 12β,16β-diacetoxy-3β,4β-dihydroxypregna-5,17-diene-10,2-carbolactone (4) were isolated from an extract of an Epipolasis sp. marine sponge. The structures of the new compounds were determined by extensive NMR spectroscopic analysis and comparison with data from previously reported compounds.
The extract of an Epipolasis sp. marine sponge collected
in the Republic of Palau provided four new pregnane 10,2 carbolactone
derivatives. The structures of these rare pregnane analogues were fully
elucidated through HRMS measurements and detailed analysis of their one- and
two-dimensional NMR spectroscopic data. Pregnane steroids possessing a
10,2-carbolactone ring have only been reported previously from Hawaiian
collections of Myrmekioderma and Petrosia (Stongylophora)
sponges, so the current results suggest this class of steroid is more widely
distributed in the marine environment than previously recognized.
Intercellular lipids in the stratum corneum protect the living body from invasion by allergens and pathogens, and also suppresses water evaporation within the body. It is important to understand how differences in the microstructure of intercellular lipids arise. This microstructure is affected by lipid composition. Studies using intercellular lipid models have reported the formation of two phases with different short lamellar periodicities. However, the details of the packing structure characteristics of the two phases observed in these intercellular lipid models are unclear. Our previous report revealed that different short periodicity phases coexist in the N-(α-hydroxyoctadecanoyl)-dihydrosphingosine (CER[ADS]), cholesterol (CHOL), and palmitic acid (PA) complex model. In this study, the characteristics of the packing structure of two phases with different short lamellar periodicities, which were observed in the intercellular lipid model (CER[ADS]/CHOL/PA) that we used previously, were adjusted for models with different lipid compositions. The characteristics of the packed and lamellar structures have been determined by temperature-scanning small-angle X-ray scattering and wide-angle X-ray diffraction measurements simultaneously. These differences in lamellar structure were thought to be caused by differences in ceramides (CER) conformation between the hairpin and the V-shape type. The lamellar structure of the V-shaped CER conformation has a low orthorhombic ratio. The above results suggest that an increase in the ratio of CER with the V-shaped structure causes the lamellar structure to have low orthorhombic ratio, thereby contributing to a decrease in the bilayer’s barrier function.
The packing structure of intercellular lipids in the
stratum corneum plays a critical role in the skin’s barrier function. The
mechanism of packing structure disruption is not fully understood. The authors constructed
models for collapsed skin intercellular lipids composed of short-chain free
fatty acids and α-hydroxy
ceramide. To investigate the packing structure’s characteristics, they changed the
lipid composition and used temperature-scanning, simultaneous small-angle and
wide-angle X-ray diffraction to determine resulting structural changes. The results suggest a change in ceramide
conformation into a V-shape structure. The authors discussed the relationship
between the V-shape structure formation and a reduction in the skin’s barrier
function.
This study aimed to investigate the characteristics of acid-activated bentonite by focusing on its capability of improving the quality of tap water used during wire electrical discharge machining. Raw bentonite (RB) was activated using sulfuric acid, nitric acid, and phosphoric acid solutions with concentrations of 1, 5, and 10 mol/L, respectively. Scanning electron microscopy images, specific surface area, pore volume, cation exchange capacity, X-ray diffraction patterns, and binding energy of RB and acid-activated bentonites were also evaluated. The specific surface area and pore volume of acid-activated bentonites exceeded those of RB. Conversely, the cation exchange capacity of acid-activated bentonites exhibited an opposite trend. The electrical conductivity of tap water was decreased significantly due to bentonite activated with sulfuric acid, nitric acid, and phosphoric acid solution (removal percentage of approximately 31–39%), as compared to that due to RB. Therefore, the relationship between electrical conductivity and the removed concentration of anion/cation ions was evaluated; the correlation coefficient was −0.950 for the experimental condition in this study. Additionally, the amount of magnesium, calcium, potassium, and sodium ions were decreased after the treatment. These results indicated that acid-activated bentonite can be produced from RB via acid activation and that it can be used to decrease electrical conductivity of tap water.
Authors evaluate the characteristics of
acid-activated bentonite by focusing on its capability of improving the quality
of tap water used during wire electrical discharge machining. This study shows
that the acid activation of bentonite using sulfuric acid, nitric acid, and
phosphoric acid solutions increases the specific surface area and pore volume. Additionally,
authors revealed that the relationship between the concentrations of the
removed ions and electrical conductivity were negatively correlated (correlation
coefficient: -0.950). Thus, the acid-activated bentonite is useful in
controlling the reduction in the electrical conductivity of tap water.
Quantitative NMR (qNMR) is applied to determine the absolute quantitative value of analytical standards for HPLC-based quantification. We have previously reported the optimal and reproducible sample preparation method for qNMR of hygroscopic reagents, such as saikosaponin a, which is used as an analytical standard in the assay of crude drug section of Japanese Pharmacopoeia (JP). In this study, we examined the absolute purity determination of a hygroscopic substance, indocyanine green (ICG), listed in the Japanese Pharmaceutical Codex 2002, using qNMR for standardization by focusing on the adaptation of ICG to JP. The purity of ICG, as an official non-Pharmacopoeial reference standard (non-PRS), had high variation (86.12 ± 2.70%) when preparing qNMR samples under non-controlled humidity (a conventional method). Additionally, residual ethanol (0.26 ± 0.11%) was observed in the non-PRS ICG. Next, the purity of non-PRS ICG was determined via qNMR when preparing samples under controlled humidity using a saturated sodium bromide solution. The purity was 84.19 ± 0.47% with a lower variation than that under non-controlled humidity. Moreover, ethanol signal almost disappeared. We estimated that residual ethanol in non-PRS ICG was replaced with water under controlled humidity. Subsequently, qNMR analysis was performed when preparing samples under controlled humidity in a constant temperature and humidity box. It showed excellent results with the lowest variation (82.26 ± 0.19%). As the use of a constant temperature and humidity box resulted in the lowest variability, it is recommended to use the control box if the reference ICG standard is needed for JP assays.
Quantitative
NMR (qNMR) has emerged
as a new absolute
quantitation method for
small molecules. Authors examined the absolute purity determination of a hygroscopic substance
indocyanine green (ICG)
using qNMR. The three different humidity conditions yielded comparable purity
means of 86.12 ± 2.70%, 84.19 ± 0.47%, and 82.26 ± 0.19%
under non-controlled humidity, controlled humidity using a saturated NaBr
solution, and using a constant temperature and humidity box, respectively. As
the results using the constant temperature and humidity box showed the lowest
variability, it is recommended to use it if the reference standard of ICG with
its purity value is needed for Japanese Pharmacopoeia assays.
Herein, we describe two counterexamples of the previously reported β/α-selectivity of 96/4 for glycosylation using ethyl 2-O-[2,3,4-tris-O-tert-butyldimethylsilyl (TBS)-α-L-rhamnopyranosyl]-3,4,6-tris-O-TBS-thio-β-D-glucopyranoside as the glycosyl donor. Furthermore, we investigated the effects of protecting group on the rhamnose moieties in the glycosylation with cholestanol and revealed that β-selectivity originated from the two TBS groups at the 3-O and 4-O positions of rhamnose. In contrast, the TBS group at the 2-O position of rhamnose hampered the β-selectivity. Finally, the β/α-selectivity during the glycosylation was enhanced to ≥99/1. The results obtained herein suggest that the protecting groups on the sugar connected to the 2-O of a glycosyl donor with axial-rich conformation can control the stereoselectivity of glycosylation.
Stereoselectivity
in chemical glycosylation frequently varies in reaction substrates. This paper
describes the influence of the protecting groups on rhamnose connected to the
2-O position of a glucosyl donor with axial-rich conformation on stereoselectivity
in its glycosylation with cholestanol. The authors revealed that two bulky
silyl groups existing at the 3-O and 4-O positions of rhamnose synergistically
enhanced β-selectivity. In contrast, the silyl group introduced to the 2-O
position decreased the selectivity. These results suggest that appropriately designing
a protecting-group pattern for another sugar far from the reaction center of a
glycosyl donor can control the stereoselectivity of glycosylation.
Improvement in the Anticancer Activity of 6-Mercaptopurine via Combination with Bismuth(III)
Released: November 01, 2016 | Volume 64 Issue 11 Pages 1539-1545
Yang Yang, Shuang Zhou, Ruizhuo Ouyang, Yaoqin Yang, Huihong Tao, Kai Feng, Xiaoshen Zhang, Fei Xiong, Ning Guo, Tianyu Zong, Penghui Cao, Yuhao Li, Yuqing Miao
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