1,720,971 research outputs found
The acetonation of methyl 5-C-methoxy-beta-D-galactopyranoside with 2,2-dimethoxypropane
No full textThe acetonation of methyl 5-C-methoxy-beta-beta-d-galactopyranoside (1a), masked bis-glycoside form
of L-arabino-hexos-5-ulose, with a large excess of 2,2-dimethoxypropane and catalytic amounts of
p-toluenesulfonic acid gives a mixture of five acetonides. The most abundant isolated product was
the mixed acetal methyl 6-O-(1-methoxy-1-methylethyl)-3,4-O-isopropylidene-5-C-methoxy-beta-d-
galactopyranoside (44% yield)
Vesicles and micelles: two versatile vectors for the delivery of natural products
No full textNatural plant-based extracts and isolated constituents have been widely used around the world since ancient times for both treatment and prevention of human diseases. Currently, the importance of natural products in clinical practice is highlighted by the number of herbal medicinal products on the market. However, formulation development of many active constituents of plant extracts is often hampered by their limited bioavailability due to several issues among which low water solubility, poor absorption and degradation are the most frequent. To overcome these issues, several research studies proposed to combine herbal medicinal products with nanocarriers widely used as drug delivery systems. The nanotechnology approach is especially attractive because colloidal carriers can modify the payload pharmacokinetic and biodistribution, as well as increase solubility, stability, and efficacy. Moreover, nanoencapsulation may decrease toxicity and modulate drug release. In recent years, delivery systems such as micelles and vesicles, obtained by the self-assembly of biocompatible surfactants, have attracted increasing attention as carriers for various herbal products. Thus, the aim of this paper is to review the main investigations developed by Italian research groups on formulations of natural products, including isolated compounds, extracts and essential oils, using micelles and vesicles as carrier
Polar Constituents from the Aerial Parts of Origanum vulgare L. Ssp. hirtum Growing Wild in Greece
No full textFrom the polar extracts of Origanum vulgare L. ssp. hirtum 19 compounds have been isolated. The structures and relative stereochemistry have been elucidated by spectroscopic analysis and determined as apigenin, luteolin, chrysoeriol, diosmetin, quercetin, eriodictyol, cosmoside, vicenin-2, caffeic acid, p-menth-3-ene-1,2-diol 1-O-â-glucopyranoside, thymoquinol 2-O-â-glucopyranoside, thymoquinol 5-O-ß-glucopyranoside, thymoquinol 2,5-O-ß-diglucopyranoside, 12-hydroxyjasmonic acid, 12-hydroxyjasmonic acid 12-O-â-glucopyranoside, lithospermic acid B, rosmarinic acid, 10-epi-lithospermic acid, and epi-lithospermic acid B. The three latter products display unusual stereochemistry of the 3,4-hydroxyphenyllactic acid unit(s), which to the authors’ best knowledge has never been reported before in similar compounds. Moreover, lithospermic acid B (and its stereoisomers), p-menth-3-ene-1,2-diol 1-O-ß-glucopyranoside, 12-hydroxyjasmonic acid, and 12-hydroxyjasmonic acid 12-O-ß-glucopyranoside were isolated for the first time from Origanum species
Cyclodextrins as carriers for kavalactones in aqueous media: Spectroscopic characterization of (S)-7,8-dihydrokavain and ß-cyclodextrin inclusion complex
No full textKavalactones represent the active constituents of kava–kava (Piper methysticum G. Forster),endowed with sedative and anaesthetic properties. Kavalactones are polar constituents, but poorly soluble in water with a low bioavailability. In this study, the formation of inclusion complexes of one of the most representative avalactone isolated from kava–kava extract, (S)-7,8-dihydrokavain (DHK), with beta-cyclodextrin (beta-CyD) was investigated mainly by spectroscopic methods. NMR experiments were extensively used for the complete characterization of the complex and included 1H NMR complexation shifts analysis, 1H NMR diffusion measurements (DOSY), and ROESY experiments. In particular DOSY experiments demonstrated that in the presence of beta-CyD the translational diffusion of kavalactone is sizably slowed down (2.5×10−10m2/s) with respect to the free drug (4.4×10−10m2/s) according to the inclusion of DHK in the cavity of beta-CyD. ROESY experiments confirmed the inclusion of DHK in the hydrophobic pocket of beta-CyD through the primary hydroxyl rim, being the most relevant interactions between the H3' of beta-CyD and the ortho protons on the phenyl ring of the DHK, and between H5' of beta-CyD and the meta/para protons of DHK phenyl ring. The inclusion of the phenyl ring of DHK, leaving the lactone moiety outside of CyD was also confirmed by the induced CD effects. The binary solution DHK/beta-CyD shows a 50% intensity increase of the negative band of the pi–pi* transitions of the phenyl ring with respect to the absorption observed with DHK alone. Molecular dynamics simulations results corroborated and further clarify observed spectroscopic data. It was found that the phenylethyl substituent at C6 has a preferential equatorial position in the free state, and an axial one in the complex, justifying the large downfield shift experienced by H6 of DHK upon binding. Finally the influence of beta-CyD on water solubility of DHK was investigated by phase-solubility studies. In the range 2–4mM of host, solubility of DHK was increased only two-fold, but being beta-CyD also a penetration enhancer, in vivo studies will be performed to clarify a possible role of the complex on the bioavailability of DHK
Studies on the interactions between some flavonols and cyclodextrins
No full textThe interactions of some natural flavonols with alpha, beta- and gamma-Cds have been investigated. Guest molecules were galangin, kaempferol and quercetin. Inclusion complexes were prepared by kneading and freeze-drying. The complexes were characterized using different physico-chemical methods based on differential scanning calorimetry (DSC), infrared spectroscopy (IR) and NMR spectroscopy. In the proton and carbon spectra the effects of complexation on the chemical shifts of the internal and external protons of Us in the presence of each flavonoid were observed. Moreover, the water-solubility of the flavonols in the presence of Us was also evaluated. The increased solubility of quercetin and kaempferol in the presence beta-Cd was evidenced. For all three guests, multidimensional NMR experiments in DMSO and water are consistent with dynamic binding processes, dominated by insertion of the B ring into the wider rim of the Cd cavity
The first synthesis of a ribo-hexos-5-ulose: the L-enantioform
No full textThe title compound, previously unreported in either enantioform, and its 2,6-di-O-benzyl derivative have been synthesized through a stereocontrolled epimerization at C-2 of 6-O-protected methyl 3,4-O-isopropylidene-5-C-methoxy-beta-D-galactopyranosides. The epimerization, performed through a high yielding sequence of oxidation-reduction owing to the cooperative role of the equatorial C-1 aglycon and the steric hindrance of the isopropylidene group, turned out to be completely diastereoselective. Whereas the unprotected L-ribo-hexos-5-ulose exists, as proved by NMR in D2O, in five main tautomeric forms in a ratio of about 4:2:2:1:1, only two anomeric 1,4-furanosic forms are present at equilibrium in its 2,6-di-O-benzyl derivative, in ratios ranging from 10:1 to 7:3, depending on the prevalence of D2O or CD3CN in the solvent mixture
Preparazione di acetonuri del metil 5-C-metossi-BETA-D-galattopiranoside, utili intermedi per la sintesi stereoselettiva dell’L-ribo-esos-5-ulosio.
No full textEsteri glicidici di acidi carbossilici ramificati in grado di indurre il differenziamento eritroide
No full textPreparation of glucidic esters of branched carboxylic acids capable of inducing erythroid cellular differentiation
No full textThe present invention provides compds. which are esters of a carbohydrate, constituted by a carbohydrate unit or a glycoside derived therefrom, having at least one alc. group esterified with a branched chain carboxylic acid and having the remaining alc. groups in part protected with a protector group, such as an isopropylidene group, and partly in the form of free hydroxyls. These carbohydrate esters being provided with a significant biol. activity as erythroid cellular differentiation inducers can be utilized for the prepn. of a medicament for the therapeutic treatment of beta-talaxemia or tumors. Thus, Me 6-O-pivaloyl-3,1-O-isopropylidene- beta-D-galactopyranoside was prepd. and tested in the human cell line K562 for inducing erythroid cellular differentiation (65%)
- …
