Oligolignans in the wood of Picea obovata Ledeb.
We studied the chemical composition of the phenolic complex and the structure of oligomeric lignans in Siberian spruce (Picea obovata Ledeb.). We used the wood of Siberian spruce collected near the city of Irkutsk. The extractives were isolated from ground wood (particle size: 10–15 mm; humidity: 5.9%) by three-stage acetone extraction. The extract was separated by consecutive treatment with the solvents with increasing polarity: hexane, ethyl acetate and n-butanol. The main amount of phenolic compounds (lignans) was concentrated in the ethyl acetate fraction and it was 0.7% in absolutely dry wood (adw).The ethyl acetate fraction of spruce wood extract was separated by silica gel column; a chloroform-acetone mixture was used as the eluent (the concentration of acetone in the mixture was increased from 0 to 100%). Monomeric lignans (~60–65% of the ethyl acetate fraction of spruce wood extract), oligomeric lignans (~20–25%), and polymer lignans (~12–15%) were isolated.We also obtained 13C nuclear magnetic resonance (NMR) spectra for the main monomeric, oligomeric and polymeric lignan compounds of phenolic complexes. It was found that oligomeric and polymeric fractions contain monomeric lignan units with the butyrolactone cycle, primarily, the fragments with hydroxymatairesinol structure. Oligomeric lignans contain the fragments with a pinoresinol and lariciresinol structure. All the monomeric structural units are characterized by the guaiacyl substitution type of the aromatic cycles.A preliminary study has been performed on the antiviral and antioxidant activity of the ethyl acetate fraction of acetone extract of Siberian spruce wood. It was found that the lignan complex is active against Coxsackie B4 virus in cell culture and in the pancreatitis model in white mice, reducing the activity of enteroviruses in the cell culture approximately 100 times. The antioxidant activity rate of polyphenol complex of Siberian spruce wood is comparable to that of a known antioxidant dihydroquercetin.
Chemical constituents from Tsuga longibracteata and its chemotaxonomic study
Abstract Phytochemical investigation into the bark of Tsuga longibracteata led to the isolation of three lignans (1–3), two triterpenoids (4, 5), nine flavonoids (6−14), three sterols (15–17) and five phenolic acids (18–22). Their structures were determined by spectroscopic analysis of their spectral data with those reported in literature. Among them, compounds 1–3, 6–22 were obtained from this species for the first time. The chemotaxonomic significance of the isolated compounds is discussed.
Effects of the mineral phase and valence of vanadium on vanadium extraction from stone coal
The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 mol/L H2SO4 at 90°C for 2 h. After the sample is roasted at 900°C for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the content of V(V) increases with the rise of roasting temperature from 600 to 900°C, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000°C. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.