ABSTRACT
Oxalicine B ( 1) is an α-pyrone meroterpenoid with a unique bispirocyclic ring system derived from Penicillium oxalicum. The biosynthetic pathway of 15-deoxyoxalicine B ( 4) was preliminarily reported in Penicillium canescens, however, the genetic base and biochemical characterization of tailoring reactions for oxalicine B ( 1) has remained enigmatic. In this study, we characterized three oxygenases from the metabolic pathway of oxalicine B ( 1), including a cytochrome P450 hydroxylase OxaL, a hydroxylating Fe(II)/α-KG-dependent dioxygenase OxaK, and a multifunctional cytochrome P450 OxaB. Intriguingly, OxaK can catalyze various multicyclic intermediates or shunt products of oxalicines with impressive substrate promiscuity. OxaB was further proven via biochemical assays to have the ability to convert 15-hydroxdecaturin A ( 3) to 1 with a spiro-lactone core skeleton through oxidative rearrangement. We also solved the mystery of OxaL that controls C-15 hydroxylation. Chemical investigation of the wild-type strain and deletants enabled us to identify 10 metabolites including three new compounds, and the isolated compounds displayed potent anti-influenza A virus bioactivities exhibiting IC50 values in the range of 4.0-19.9 μmol/L. Our studies have allowed us to propose a late-stage biosynthetic pathway for oxalicine B ( 1) and create downstream derivatizations of oxalicines by employing enzymatic strategies.
ABSTRACT
italic>Psidium guajava Linn. is an evergreen shrub or small tree of Psidium Linnaeus in the Myrtaceae family. One new glycoside (1) together with 3 known meroterpenoids (2-4) and 9 known glycosides (5-13) were isolated from the fruits of Psidium guajava Linn.. The structure of the new compound was elucidated by the spectroscopic data analysis of HR-ESIMS, 1D- and 2D-NMR, and it was named psiguaoside A (1). The known compounds were identified as guajadial (2), 4,5-diepipsidial A (3), psidial A (4), chrysin-8-C-β-D-glucoside (5), 2,6-dihydroxy-3,5-dimethyl-4-O-β-D-glucopyranosyl-benzophenone (6), quercetin-3-O-β-D-glucopyranoside (7), quercetin-3-O-xyloside (8), guaijaverin (9), avicularin (10), guavinoside E (11), guavinoside B (12), guajaphenone A (13). In the bioactivity assay, compound 3 exhibited significant inhibitory activitiy of U87 with IC50 values of 8.379 μmol·L-1.
ABSTRACT
Twenty-six compounds, including sixteen meroterpenoids(1-16), a triterpenoid(17), four terpenoid derivatives(18-21), and five aromatic compounds(22-26), were isolated from the leaves of Psidium guajava. Their structures were identified by spectroscopic analyses including NMR and MS. Compounds 21-26 were obtained from plants of Psidium for the first time. Based on the structure,(R)-2-ethylhexyl 2H-1,2,3-triazole-4-carboxylate(24 a), an α-glucosidase inhibitor recently isolated from Paramignya trimera, should be revised as compound 24. Meroterpenoids 1-16 were evaluated for their antitumor and antifungal activities. Meroterpenoids psiguajadial D(4), guapsidial A(5), 4,5-diepipsidial A(7), guadial A(14), and guadial B(15) showed cytotoxicities against five human tumor cell lines(HL-60, A-549, SMMC-7721, MCF-7, and SW-480), among which 5 was the most effective with an IC_(50) of 3.21-9.94 μmol·L~(-1).
Subject(s)
Humans , Antifungal Agents/pharmacology , Magnetic Resonance Spectroscopy , Plant Extracts , Plant Leaves , Psidium , TerpenesABSTRACT
Phytochemical investigation of the aerial parts of Baeckea frutescens resulted in the isolation of three new mono- or sesquiterpene-based meroterpenoids, frutescones S-U (1-3), and one pair of new (±)-5,7-dihydroxy-8-isobutyryl-6-methyldihydroflavonol (4). Their structures and absolute configurations were established by HR-ESI-MS, 1D and 2D NMR, and quantum chemical ECD calculation. Compound 1 exhibited inhibitory effect on NO production in LPS-activated RAW 264.7 macrophages with an IC value being 0.81 μmol·L.
ABSTRACT
Five pairs of optically pure meroterpenoid enantiomers (1a/1b-5a/5b) and two known compounds (6 and 7) were isolated from Rhododendron fastigiatum. Compounds 1a/1b-5a/5b were resolved from naturally scalemic mixtures by chiral HPLC. Their structures were elucidated by spectroscopic methods, X-ray crystallographic experiments, and ECD analyses. Compounds 1a/1b, 2a/2b, 3b, 4a/4b, and 5a/5b were new meroterpenoids with different polycyclic systems. Two enantiomeric pairs (2a/2b and 3a/3b), 6, and 7 exhibited inhibitory effects on protein tyrosine phosphatase 1B (PTP1B) in vitro.
ABSTRACT
Objective: For the purpose of finding new agents, the chemical study on Ganoderma resinaceum was carried out. Methods: The chemical constituents from the dried fruiting bodies of G. resinaceum were isolated by column chromatographic methods of silica gel, MCI-Gel resin, and high performance liquid chromatography. The structures were elucidated by spectroscopic methods, including extensive 1D and 2D NMR techniques. Results: Four compounds including one new meroterpenoid were isolated from this fungus. Their structures were identified as ganoresinains F (1), 3β,7β,15β-trihydroxy-11,23-dioxo-lanost-8,16-dien-26-oic acid (2), ganoderic acid XL2 (3) and 2,3-dihydro-4(1H)-quinolone (4). Conclusion: Compound 1 is a new compound and named as ganoresinains F (1).
ABSTRACT
Fungal genomes carry many gene clusters seemingly capable of natural products biosynthesis, yet most clusters remain cryptic or down-regulated. Genome mining revealed an unconventional paraherquonin-like meroterpenoid biosynthetic gene cluster in the chromosome of . The cryptic or down-regulated pathway was activated by constitutive expression of pathway-specific regulator gene encoded within biosynthetic gene cluster. Chemical analysis of mutant -OE: extracts enabled the isolation of four berkeleyacetal congeners, in which two of them are new. On the basis of careful bioinformatic analysis of the coding enzymes in the gene cluster, the biosynthetic pathway of berkeleyacetals was proposed. These results indicate that this approach would be valuable for discovery of novel natural products and will accelerate the exploitation of prodigious natural products in filamentous fungi.
ABSTRACT
Objective: To study the chemical constituents of the fungus Ganoderma cochlear. Methods: The compounds were isolated by using MCI gel CHP 20P, Sephadex LH-20, RP-18 column chromatography, and preparative TLC. The structures were identified by means of spectroscopic methods. Results: Two phenolic normeroterpenoid and meroterpenoid, cochlearols C and D (1 and 2), together with six benzene derivatives, 3-methoxy-4-hydroxy-phenylethanol (3), 4-hydroxyacetophenone (4), p-hydroxycinnamic methyl ester (5), 2-methoxy-4-hydroxybenzaldehyde (6), 4-hydroxy-3-methoxy benzoic acid (7), and 2-hydroxy-5-ethoxybenzoic acid (8), were isolated from the fruiting bodies of Ganoderma cochlear. Conclusion: Compounds 1 and 2 are new phenolic normeroterpenoid and meroterpenoid, respectively.