Records of Natural Products

Three new chromone glycosides, named 2-methyl-5-hydroxyl-4-chromone-7-O-β-D-glucuronide (1), 2-ethyl-5-hydroxyl-4-chromone-7-O-β-D-glucuronide (2) and 1-acetyl-3-C-β-D-glucopyranosyl-5-methyl-phloroglucinyl-6-O-β-D-glucopyranoside (6), together with eight known compounds were isolated from the water extract of Dryopteris crassirhizoma Nakai，and the water extract preparation process is consistent with Lianhua Qingwen capsule. All the chemical structures of new compounds were characterized by 1D and 2D NMR spectra as well as high resolution mass and IR spectra. The chemical structures of known compounds were characterized by NMR spectra along with comparison of their spectroscopic data with those reported in the literature. The binding ability of these compounds to 3CL hydrolase of SARS-COV-2 was evaluated by molecular docking. The results showed that the chromone glycosides with glucuronic acid fragment had good docking effect with 3CL hydrolase and this indicated the chromone glucuronides could be further studied as potential antiviral compounds.

A new (1) and five known (2-6) bromophenols were isolated from the organic extract of the marine red alga Symphyocladia latiuscula.  Their structures were assigned by interpretation of NMR and MS data, and these compounds were determined as 2,3,5′-tribromo-3′,4,4′,5-tetrahydroxy-diphenylmethane (1), 2-methoxy-3-bromo-5-hydroxymethylphenol (2), 5-(2,3-dihydroxybenzyl)-3,4-dibromobenzene-1,2-diol (3), 5-(2-bromo-3,4-dihydroxy-6-(methoxymethyl)benzyl)-3,4-dibromobenzene-1,2-diol(4), methyl 2-(3,5-dibromo-4-hydroxybenyl) acetate (5), and 3,4-dibromo-5-(methoxymethyl)benzene-1,2-diol (6). All these compounds were evaluated for DPPH radical scavenging activity, and they displayed potent antioxidant activity with IC50 values ranging from 9.6 to 31.5 μM. These compounds also showed moderate ABTS radical scavenging activity with TEAC value ranging from 2.1 to 3.0 mM. The results suggested that these bromophenols or the marine red alga S. latiuscula may have potential application in food as natural antioxidants.

Oxidative stress is one of the leading causes that contribute to the pathogenesis of chronic diseases based on the imbalance between free radicals and the antioxidant defense system. Here, Syzygium jambos (L.) Aston, a traditional herb used to treat various diseases, was evaluated using RAW264.7 macrophages with lipopolysaccharide (LPS)-stimulation to demonstrate its effects and find a new therapy for oxidative stress. This study proved that Syzygium jambos leaf extract exerted its ability to protect cells against oxidative stress via activating the nuclear factor erythroid 2-related factor 2/heme oxygenase-1 (Nrf2/HO-1) pathway to suppress reactive oxygen species (ROS) production. Moreover, the extract also attenuated the nitric oxide (NO) production and the nitric oxide synthase (iNOS) expression, suggesting an anti-inflammatory response. In addition, four active compounds, including gallic acid, quercetin, myricetin, and caffeic acid, were isolated from ethyl acetate fraction using column chromatography. The structure of compounds was analyzed based on one-dimensional nuclear magnetic resonance (1D-NMR) and compared to literature data. Their biological activity was confirmed by promoting the induction of HO-1. Hence, this study provides the initial evidence of Syzygium jambos leaves protective effects and highlights its potential as an antioxidant agent.

A new isobenzofuranone derivative, (R)-3-acetyl-[5,7]-dimethoxy-3H-isobenzofuran-l-one (1), together with six known compounds, (R)-3-acetyl-7-hydroxy-5-methoxy-3H-isobenzofuran-l-one (2), banksialactone D (3), (3R,4S)-3,8-dihydroxy-3-hydroxymethyl-6-methoxy-4,5-dimethyl-isochroman-1-one (4), 1-O-[α-L-rhamnopyranosyl]-2,5-dimethyl-3-phenol (5), p-hydroxybenzaldehyde (6), 2-(4-hydroxyphenyl) ethanol (7), were isolated from Arctic fungus Gyoerffyella sp. CPCC 401434. Their structures and absolute configurations were elucidated by the analysis of spectroscopic data, electronic circular dichroism, and comparison with reported literature data. Herein, all compounds were reported for the first time from the genus Gyoerffyella and their cytotoxic and antibacterial activities.