Zr-Catalyzed Synthesis of Tetrasubstituted 1,3-Diacylpyrroles from N-Acyl α-Aminoaldehydes and 1,3-Dicarbonyls

A Zr-catalyzed synthesis of tetrasubstituted 1,3-diacylpyrroles is reported that employs the direct use of N-acyl α-aminoaldehydes with 1,3-dicarbonyl compounds. The products were formed in up to 88% yield and shown to be hydrolytically and configurationally stable under the reaction conditions (THF/1,4-dioxane and H₂O). The N-acyl α-aminoaldehydes were readily prepared from the corresponding α-amino acids. The reaction tolerates a wide array of substrate types including alkyl-, aryl-, heteroaryl-, and heteroatom-containing groups on the aminoaldehyde side chain. A variety of 1,3-dicarbonyls proved amenable to the reaction along with an aldehyde derived from a l,l-dipeptide, an aldehyde generated in situ, and an N-acylated glucosamine.

Constituents of Aquilaria sinensis Leaves Upregulate the Expression of Matrix Metalloproteases 2 and 9

In this novel study, we isolated 28 compounds from the leaves of Aquilaria sinensis (Lour.) Gilg based on a bioassay-guided procedure and also discovered the possible matrix metalloprotease 2 (MMP-2) and 9 (MMP-9) modulatory effect of pheophorbide A (PA). To evaluate the regulatory activity on MMP-2 and MMP-9, the HT-1080 human fibrosarcoma cells were treated with various concentrations of extracted materials and isolated compounds. PA was extracted by methanol from the leaves of A. sinensis and separated from the fraction of the partitioned ethyl acetate layer. PA is believed to be an active component for MMP expression since it exhibited significant stimulation on MMP-2 and proMMP-9 activity. When treating with 50 μM of PA, the expression of MMP-2 and MMP-9 were increased 1.9-fold and 2.3-fold, respectively. PA also exhibited no cytotoxicity against HT-1080 cells when the cell viability was monitored. Furthermore, no significant MMP activity was observed when five PA analogues were evaluated. This study is the first to demonstrate that C-17 of PA is the deciding factor in determining the bioactivity of the compound. The MMP-2 and proMMP-9 modulatory activity of PA indicate its potential applications for reducing scar formation and comparative medical purposes.

Conversion of Unprotected Aldose Sugars to Polyhydroxyalkyl and C-Glycosyl Furans via Zirconium Catalysis

An efficient, zirconium-catalyzed conversion of unprotected aldose sugars with acetylacetone to polyhydroxyalkyl furans or C-glycosylfurans is reported. The furan products are formed in up to 93% yield using 5-10 mol % ZrCl₄. Pentoses are readily converted at room temperature, while hexoses and their oligosaccharides require mild heating (i.e., 50 °C). Efficient conversions of glycolaldehyde, glyceraldehyde, erythrose, a heptose, and glucosamine are also demonstrated. This approach outpaces each of the previous Lewis acid-catalyzed methods in at least one the following ways: (i) lower catalyst loadings; (ii) reduced reaction temperatures; (iii) shorter reaction times; (iv) equimolar substrate stoichiometry; (v) expanded sugar scope; (vi) higher selectivities; and (vii) the use of an Earth-abundant Zr catalyst.

Hyaluronidase inhibitory saponins and a trypanocidal isoflavonoid from the aerial parts of Oxytropis lanata

A chemical examination of an extract from the aerial part of Oxytropis lanata led to the isolation and identification of 36 compounds, including saponins, isoflavonoids, oxazoles, and glycosides. The three among them were previously unreported oleanane-type saponins. In trypanocidal screening, 5,7,4'-trihydroxyisoflavone showed inhibitory activity against Trypanosoma congolense (IC₅₀ = 10.5 μM), the causative agent of African trypanosomosis in animals; this activity was similar to that of active compounds from the roots of this plant. O. lanata is known to be a traditional medicinal plant in Mongolia for the treatment of inflammatory diseases. The anti-hyaluronidase effect of saponins 3, 5, 8, and 9, (IC₅₀ = 0.15-0.22 mM) was stronger than that of sodium cromoglicate, which was used as a reference drug (IC₅₀ = 0.37 mM). The chemical structures of the new saponins were determined based on HRFABMS, ¹H and ¹³C NMR, ¹H-¹H COSY, HMQC, HMBC, and ROESY spectroscopic data along with chemical procedures.

Identification of potential inflammatory inhibitors from Aster tataricus

Aster tataricus L.f. is a traditional Eastern Asian herbal medicine used for the relief of cough-related illnesses. In this study, 32 known compounds and two novel monoterpene glycosides were isolated from the roots of A. tataricus. With the aid of reported data, elucidation of the root-extract components was carried out using a multitude of spectroscopic techniques. All isolates were investigated for their ability to inhibit nitric oxide (NO) secretion in lipopolysaccharide-activated RAW264.7 cells. Compound 7 remarkably suppressed NO production with an IC₅₀ value of 8.5 µM. In addition, compound 7 exhibited significant inhibitory activity against the production of inflammatory cytokines (prostaglandin E₂, interleukin-6, and interleukin-1 beta) and the expression of inflammatory enzymes (inducible nitric oxide synthase and cyclooxygenase-2) via inhibition of nuclear factor-kappa B activation. Moreover, compound 7 effectively prevented the downstream activation of the mitogen-activated protein kinase signaling pathway by inhibiting phosphorylation of c-Jun N-terminal kinases, extracellular signal-regulated kinases, and p38. These results outline compound 7 as a potential inhibitor for the broad treatment of inflammatory diseases, such as atopic dermatitis, asthma, and various allergies.

Polycyclic polyprenylated acylphloroglucinol and phenolic metabolites from the aerial parts of Hypericum elatoides and their neuroprotective and anti-neuroinflammatory activities

A phytochemical study on the aerial parts of Hypericum elatoides led to the isolation of a previously undescribed polycyclic polyprenylated acylphloroglucinol derivative, hyperelatone A, seven previously undescribed phenolic metabolites, hyperelatones B-H, along with ten known analogues. The structures of hyperelatones A-H were elucidated by 1D and 2D NMR spectroscopy, HRESIMS experiment, single-crystal X-ray diffraction and comparison of experimental and calculated ECD spectra, as well as chemical derivatization. All compounds were evaluated for their neuroprotective activity against hydrogen peroxide (H₂O₂)-induced cell injury in rat pheochromocytoma PC-12 cells and inhibitory effects on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in BV-2 microglial cells. Hyperelatones B-D and H, cinchonain Ib, and tenuiside A showed noticeable neuroprotection at concentrations of 1.0-100.0 μM. Hyperelatones D, G, and H, (-)-epicatechin, tenuiside A, and (Z)-3-hexenyl-β-D-glucopyranoside exhibited significant anti-neuroinflammatory activity with IC₅₀ values ranging from 0.75 ± 0.02 to 5.83 ± 0.23 μM.

A new phenylpropanoid and an alkylglycoside from Piper retrofractum leaves with their antioxidant and α-glucosidase inhibitory activity

Two new compounds, piperoside (1) and isoheptanol 2(S)-O-β-D-xylopyranosyl (1→6)-O-β-D-glucopyranoside (11), along with 10 known compounds 3,4-dihydroxyallylbenzene (2), 1,2-di-O-β-D-glucopyranosyl-4-allylbenzene (3), tachioside (4), benzyl-O-β-D-glucopyranoside (5), icariside F2 (6), dihydrovomifoliol-3'-O-β-D-glucopyranoside (7), isopropyl O-β-D-glucopyranoside (8), isopropyl primeveroside (9), n-butyl O-β-D-glucopyranoside (10), isoheptanol 2(S)-O-β-D-apiofuranosyl-(1→6)-O-β-D-glucopyranoside (12), were isolated from the leaves of Piper retrofractum. Their structures were determined from 1D-NMR, 2D-NMR, and HR-ESI-MS spectral, a modified Mosher's method, and comparisons with previous reports. All of the isolated compounds showed modest α-glucosidase inhibitory (4.60±1.74% to 11.97±3.30%) and antioxidant activities under the tested conditions.

Chemical Components of Ardisia splendens Leaves and Their Activity against Coxsackie A16 Viruses

Using a combination of chromatographic methods, one new flavonol glycoside, myricetin 3,7-di-O-α-L-rhamnopyranoside (1), and nine known compounds myricitrin (2), quercetin 3,7-di-O-α-L-rhamnopyranoside (3), quercitrin (4), desmanthin-1 (5), myricetin 3-O -(3″-O-galloyl)-α-L-rhamnopyranoside (6), (+)-catechin (7), benzyl O-β-D-glucopyranoside (8), 2-phenylethyl O-β-D-glucopyranoside (9), and corilagin (10) were isolated from the leaves of Ardisia splendens Pit. Based on an in vitro test against Coxsackie viruses A16 by SRB assay, only compounds 2, 5, and 10 exhibited activity against Coxsackie viruses A16 with IC50 values of 40.1, 32.2, and 30.5 μM, respectively. This result suggested that compounds 2, 5, and 10 might be potential agents for treating hand, foot and mouth diseases.

Chemical Constituents from the Aerial Parts of Gynura Bicolor

Gynura bicolor (Willd.) DC., is used in folk recipes for the treatment of diabetes mellitus in Jiangsu, Zhejiang and Sichuan province in the south of China. A previous pharmacological study proved that the plant showed significant hypoglycemic activity on normal and alloxan-diabetic mice. In this study, two terpenes, four megastigmane-type norisoprenoids and two glycosides were isolated from the aqueous ethanolic extract of the aerial parts of Gynura bicolor and characterized mainly by NMR spectroscopy and mass spectrometry. These compounds were isolated for the first time from this plant, and no evidence could be found for the previous reported presence of megastigmane-type norisoprenoids in the genus Gynura.

Three new glycosides from Hylocereus undatus

Three new glycosides, undatusides A-C (1-3), and 11 known compounds (4-14) were isolated from the flowers of Hylocereus undatus. Their structures were elucidated on the basis of spectroscopic data and chemical method.

Chemo-enzymatic synthesis of the carbohydrate antigen N-glycolylneuraminic acid from glucose

N-Glycolylneuraminic acid (Neu5Gc) is a non-human sialic acid, which may play a significant role in human pathologies, such as cancer and vascular disease. Further studies into the role of Neu5Gc in human disease are hindered by limited sources of this carbohydrate. Using a chemo-enzymatic approach, Neu5Gc was accessed in six steps from glucose. The synthesis allows access to gram-scale quantities quickly and economically and produces Neu5Gc in superior quality to commercial sources. Finally, we demonstrate that the synthesized Neu5Gc can be incorporated into the cell glycocalyx of human cells, which do not naturally synthesize this sugar. The synthesis produces Neu5Gc suitable for in vitro or in vivo use.