Composition and Protein Precipitation Capacity of Condensed Tannins in Purple Prairie Clover (Dalea purpurea Vent.)

This study aimed to determine the concentration and composition of condensed tannins (CT) in different tissues of purple prairie clover (PPC; Dalea purpurea Vent.) at different maturities and to determine their protein-precipitating capacity. The compositions of CT were elucidated after thiolysis with benzyl mercaptan followed by high-performance liquid-chromatography (HPLC) and 1H–13C heteronuclear single quantum coherence (HSQC) NMR spectroscopy. The results indicated that PPC flowering heads contained the highest CT concentration. Purple prairie clover CT consisted mainly of epicatechin (EC) and epigallocatechin (EGC) subunits. CT in the leaves were composed of more EC and less EGC than CT in stems and flowering heads at both the early flowering (EF) and late flowering (LF) head stages. The mean degree of polymerization was the highest for CT in stems and increased with maturity. CT isolated from PPC leaves at the early flowering head stage exhibited the greatest biological activity in terms of protein precipitation. Overall, the CT in PPC were predominantly procyanidins and the concentration and composition varied among the plant tissues and with maturity.

N-[7-Chloro-4-[4-(phenoxymethyl)-1H-1,2,3-triazol-1-yl] quinoline]-acetamide

The 1,2,3-triazole is a well-known biologically active pharmacophore constructed by the copper-catalyzed azide–alkyne cycloaddition. We herein reported the synthesis of 4-amino-7-chloro-based [1,2,3]-triazole hybrids via Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition of 4-azido-7-chloroquinoline with an alkyne derivative of acetaminophen. The compound was fully characterized by Fourier-transform infrared (FTIR), proton nuclear magnetic resonance (1H-NMR), carbon-13 nuclear magnetic resonance (13C-NMR), heteronuclear single quantum coherence (HSQC), ultraviolet (UV) and high-resolution mass spectroscopies (HRMS). This compound was screened in vitro with different normal and cancer cell lines. The drug likeness of the compound was also investigated by predicting its pharmacokinetic properties.

Effects of Fenton oxidation on structural changes of lignin from steam-exploded poplar

Pretreatment of steam-exploded poplar by Fenton oxidation was used to effectively biodegrade lignin. The structure of lignin samples (LS from steam-exploded poplar and LSF from samples further treated by Fenton oxidation) obtained by enzymatic hydrolysis during pretreatment were characterized and compared. The results showed that the demethoxy reaction occurred in the process of Fenton oxidation. GPC results indicated that the weight average molecular weight (Mw) of LSF did not change significantly, indicating that that there was no significant condensation during Fenton oxidation pretreatment. Heteronuclear single quantum coherence nuclear magnetic resonance (HSQC NMR) results suggested that the proportion of the three-unit basic structural units of poplar (H, G, and S) were significantly changed during Fenton oxidation process, and more lignin S units were removed than lignin G units. The content of β-O-4 linkages was lower in LSF (74.0%, as a fraction of β-O-4 + β-5 + β-β) than in LS (78.2%), which indicated that β-O-4 linkages were destroyed to a certain extent during Fenton oxidation process, and the content of total lignin interunit linkages including β-O-4, β−β, and β-5 linkages over total lignin aromatic subunits (Ar%) in LSF was higher, reaching 49.9%.

Effects of Gamma-Valerolactone Assisted Fractionation of Ball-Milled Pine Wood on Lignin Extraction and Its Characterization as Well as Its Corresponding Cellulose Digestion

Gamma-valerolactone (GVL) was found to be an effective, sustainable alternative in the lignocellulose defragmentation for carbohydrate isolation and, more specifically, for lignin dissolution. In this study, it was adapted as a green pretreatment reagent for milled pinewood biomass. The pretreatment evaluation was performed for temperature (140–180 °C) and reaction time (2–4 h) using 80% aqueous GVL to obtain the highest enzymatic digestibility of 92% and highest lignin yield of 33%. Moreover, the results revealed a positive correlation (R2 = 0.82) between the lignin removal rate and the crystallinity index of the treated biomass. Moreover, under the aforementioned conditions, lignin with varying molecular weights (150–300) was obtained by derivatization followed by reductive cleavage (DFRC). 2D heteronuclear single quantum coherence nuclear magnetic resonance (2D-HSQC-NMR) spectrum analysis and gel permeation chromatography (GPC) also revealed versatile lignin properties with relatively high β-O-4 linkages (23.8%–31.1%) as well as average molecular weights of 2847–4164 with a corresponding polydispersity of 2.54–2.96, indicating this lignin to be a heterogeneous feedstock for value-added applications of biomass. All this suggested that this gamma-valerolactone based pretreatment method, which is distinctively advantageous in terms of its effectiveness and sustainability, can indeed be a competitive option for lignocellulosic biorefineries.

Isolation of an isoflavonoid and a terpenoid from the heartwood of Baphia nitida Lodd. (camwood)

Chromatographic separation of methanolic extract of Baphia nitida heartwood gave two crystalline solids characterized as 3,9-dimethoxy-6aR,11aR-dihydro-6H-benzofuro(3,2-C)[1]benzopyran (also known as homopterocarpin) with molecular formula C17H16O4 (1.57% yield) and 2,4-dimethoxybenzaldehyde C9H10O3 (2.27% yield). Each of the isolated compounds showed a single spot on developed thin layer chromatographic plate under ultra-violet light (254 nm) and spray reagent (10% sulfuric acid in methanol solution). Structural elucidation was achieved using Fourier transform infrared (FT-IR) spectroscopy, one and two-dimension nuclear magnetic resonance (NMR) techniques. Distortionless enhancement by polarization transfer-edited-heteronuclear single quantum coherence (DEPT-ed-HSQC) was also a useful tool that aided the characterization of the two secondary metabolites isolated from Baphia nitida heartwood.

Tyrosinase Inhibition Activity of Monoterpene Glucosides From Brugmansia arborea Flowers

Three monoterpene glucosides were isolated from the flowers of Brugmansia arborea L. using repeated silica gel and octadecyl SiO2 column chromatography. Based on spectroscopic data including 1d-NMR (1H, 13C, and distortionless enhancement by polarization transfer (DEPT)), 2D-NMR (gradient correlation spectroscopy (gCOSY), gradient heteronuclear single quantum coherence (gHSQC), and gradient heteronuclear multiple bond coherence (gHMBC)), Infrared Spectroscophy, and Mass Spectroscophy, the glucosides were identified as citronellol O- β-D-glucopyranoside (1), jasminoside N (2), and jasminoside P (3). The EtOAc ( Brugmansia arborea Flowers ethyl acetate fraction [BAFE]) and n-BuOH ( Brugmansia arborea Flowers n-butanol fraction [BAFB]) fractions showed high inhibition of tyrosinase activity (BAFE: IC50 = 68.0 and BAFB: IC50 = 59.3 μg/mL), and all isolated monoterpenes inhibited tyrosinase activity (1: IC50 = 156.5, 2: IC50 = 198.2, and 3: IC50 = 191.0 μM).

Oxidative Depolymerization of Cellulolytic Enzyme Lignin over Silicotungvanadium Polyoxometalates

The aim of this study was to explore the catalytic performance of the oxidative depolymerization of enzymatic hydrolysis lignin from cellulosic ethanol fermentation residue by different vanadium substituted Keggin-type polyoxometalates (K5[SiVW11O40], K6[SiV2W10O40], and K6H[SiV3W9O40]). Depolymerized products were analyzed by gel permeation chromatography (GPC), gas chromatography–mass spectrometer (GC/MS), and two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance (2D HSQC NMR) analysis. All catalysts showed an effective catalytic activity. The best result, concerning the lignin conversion and lignin oil production, was obtained by K6[SiV2W10O40], and the highest yield of oxidative depolymerization products of 53 wt % was achieved and the main products were monomer aromatic compounds. The HSQC demonstrated that the catalysts were very effective in breaking the β-O-4 structure, the dominant linkage in lignin, and the GPC analysis demonstrated that the molecular of lignin was declined significantly. These results demonstrate the vanadium substituted silicotungstic polyoxometalates were of highly active and stable catalysts for lignin conversion, and this strategy has the potential to be applicable for production of value-added chemicals from biorefinery lignin.