Structural diversity of microbial secondary metabolites based on chemical epigenetic manipulation.

Fungi are microorganisms with biosynthetic potential that are capable of producing a wide range of chemically diverse and biologically interesting small molecules. Chemical epigenetic manipulation has been increasingly explored as a simple and powerful tool to induce the production of additional microbial secondary metabolites in fungi. This review focuses on chemical epigenetic manipulation in fungi and summarizes 379 epigenetic manipulation products discovered from 2008 to 2022 to promote the discovery of their medicinal value.

[Research progress in biosynthesis-related enzymes of coumarin compounds and their bioactivities].

Coumarins are natural products with benzopyran ring as the parent nucleus. Numerous coumarin derivatives exhibit a variety of pharmacological activities, including antibacterial, anti-inflammatory, antitumor, anti-coagulant, anti-osteoporotic, and insecticidal activities. Therefore, they play an important role in both medicine and agriculture. The development and utilization of coumarin derivatives have attracted increasing attention. The advancement of gene sequencing technology and the rapid progress in synthetic bio-logy have led to significant advancement in the biosynthesis of coumarin derivatives, and has received increasing attention from global researchers. This paper presents a comprehensive overview of the key biosynthesis-related enzymes of coumarin derivatives, such as cytochrome P450 enzyme(CYP450), prenyltransferase(PT), UDP-glucosyltransferase(UGT). Additionally, the pharmacological activities of these enzymes, including anti-tumor, anti-inflammatory, antioxidant, and antibacterial activities, are systematically summarized. This review aims to provide a valuable reference for the biosynthesis of coumarin derivatives and further exploration of their medicinal potential.

[Research progress on chemical constituents and pharmacological activities of halogenated sesquiterpenes from natural sources].

Halogenated sesquiterpenes are important derivatives of sesquiterpenes, referring to chemical components of sesquiterpenes that contain halogens such as chlorine, bromine, and iodine. Halogenated sesquiterpenes have attracted attention from researchers in China and abroad because of their diverse structures, unique halogen elements, and extensive pharmacological activities. Studies have shown that halogenated sesquiterpenes exhibit significant antimicrobial, anti-inflammatory, anticancer, insecticidal, hypoglycemic, and enzyme inhibitory activities. In order to better explore the potential pharmaceutical value of halogenated sesquiterpenes, this paper reviewed the structural characteristics and pharmacological activities of halogenated sesquiterpenes in the past two decades, aiming to provide references for further research and development of this class of compounds.

Two New Austocystin Analogs from the Marine-Derived Fungus Aspergillus sp. WHUF05236.

Two new austocystin analogs, austocystin P (1) and austocystin Q (2), along with fourteen known compounds (3-16) were isolated from the fermentation extract of Aspergillus sp. WHUF05236. The planar structures of 1 and 2 were elucidated through 1D, 2D NMR and MS analyses. Their absolute configurations were determined by the time-dependent density functional (TDDFT)-ECD calculation. Compounds 3, 11, and 12 exhibited antimicrobial activities against Helicobacter pylori with MIC values ranging from 20.00 to 43.47 µM. Compounds 3, 6, and 7 showed cytotoxicities against the human colon cancer cell lines Hct-116 with IC50 values of 101.79, 65.46, and 36.72 µM, respectively.

Cinnamic acid derivatives: inhibitory activity against Escherichia coli ß-glucuronidase and structure-activity relationships.

Gut microbial ß-glucuronidase (GUS) is a potential therapeutic target to reduce gastrointestinal toxicity caused by irinotecan. In this study, the inhibitory effects of 17 natural cinnamic acid derivatives on Escherichia coli GUS (EcGUS) were characterised. Seven compounds, including caffeic acid ethyl ester (CAEE), had a stronger inhibitory effect (IC50 = 3.2-22.2 µM) on EcGUS than the positive control, D-glucaric acid-1,4-lactone. Inhibition kinetic analysis revealed that CAEE acted as a competitive inhibitor. The results of molecular docking analysis suggested that CAEE bound to the active site of EcGUS through interactions with Asp163, Tyr468, and Glu504. In addition, structure-activity relationship analysis revealed that the presence of a hydrogen atom at R1 and bulky groups at R9 in cinnamic acid derivatives was essential for EcGUS inhibition. These data are useful to design more potent cinnamic acid-type inhibitors of EcGUS.

Cytisine-Pterocarpan-Derived Compounds: Biomimetic Synthesis and Apoptosis-Inducing Activity in Human Breast Cancer Cells.

Cytisine-pterocarpan-derived compounds were biomimetically synthesized with (-)-cytisine and (-)-maackiain via a N,N-4-dimethyl-4-aminopyridine (DMAP)-mediated synthetic strategy in a mild manner. In the present study, tonkinensine B (4) was elaborated in good and high yields with the optimized reaction conditions. The in vitro cytotoxicity of compound 4 was evaluated against breast cancer cell lines and showed that 4 had a better cytotoxicity against MDA-MB-231 cells (IC50 = 19.2 µM). Depending on the research on cytotoxicities of 4 against RAW 264.7 and BV2 cells, it was suggested that 4 produced low cytotoxic effects on the central nervous system. Further study indicated that 4 demonstrated cytotoxic activity against MDA-MB-231 cells and the cytotoxic activity was induced by apoptosis. The results implied that the apoptosis might be induced by mitochondrion-mediated apoptosis via regulating the ratio of Bax/Bcl-2 and promoting the release of cytochrome c from the mitochondrion to the cytoplasm in MDA-MB-231 cells.

pH-zone-refining elution-extrusion countercurrent chromatography: Separation of hydroxyanthraquinones from Cassiae semen.

Seven hydroxyanthraquinones were successfully separated from the traditional Chinese medicinal herb Cassiae semen by conventional and pH-zone-refining countercurrent chromatography with an environmentally friendly biphasic solvent system, in which elution-extrusion mode was investigated for pH-zone-refining countercurrent chromatography for the first time. A two-phase solvent system composed of n-hexane/ethyl acetate/ethanol/water (5:3:4:4, v/v/v/v) was used for the conventional countercurrent chromatography while the same system with a different volume ratio n-hexane/ethyl acetate/ethanol/water (3:5:2:6, v/v/v/v) was used for pH-zone-refining countercurrent chromatography, in which 20 mmol/L of trifluoroacetic acid was added in the organic phase as a retainer and 15 mmol/L of ammonia was added to the aqueous phase as an eluter. A 400 mg crude sample could be well separated by pH-zone-refining countercurrent chromatography, yielding 53 mg of aurantio-obtusin, 40 mg of chryso-obtusin, 18 mg of obtusin, 24 mg of obtusifolin, 10 mg of emodin, and 105 mg of the mixture of chrysophanol and physcion with a purity of over 95.8, 95.7, 96.9, 93.5, 97.4, 77.1, and 19.8%, as determined by high-performance liquid chromatography. Furthermore, the difference in elution sequence between conventional and pH-zone-refining mode was observed and discussed.

Application of a computer-assisted structure elucidation program for the structural determination of a new terpenoid aldehyde with an unusual skeleton.

The structure of a novel compound from Adansonia digitata has been elucidated, and its 1 H and 13 C NMR spectra have been assigned employing a variety of one-dimensional and two-dimensional NMR techniques without degradative chemistry. The Advanced Chemistry Development ACD/Structure Elucidator software was important for determining part of this structure that contained a fused bicyclic system with very few hydrogen atoms, which in turn, exhibited essentially no discriminating HMBC connectivities throughout that portion of the molecule. Copyright © 2016 John Wiley & Sons, Ltd.

Elution-extrusion counter-current chromatography for the separation of two pairs of isomeric monoterpenes from Paeoniae Alba Radix.

In this work, a simple and efficient protocol for the rapid separation of two pairs of isomeric monoterpenes from Paeoniae Alba Radix was developed by combining macroporous resin and elution-extrusion counter-current chromatography. The crude extract was firstly subjected to a D101 macroporous resin column eluted with water and a series of different concentrations of ethanol. Then, effluents of 30 and 95% ethanol were collected as sample 1 and sample 2 for further counter-current chromatography purification. Finally, a pair of isomers, 96 mg of compound 1 and 48 mg of compound 2 with purities of 91.1 and 96.2%, respectively, was isolated from 200 mg of sample 1. The other pair of isomers, 14 mg of compound 3 and 8 mg of compound 4 with purities of 93.6 and 88.9%, respectively, was isolated from 48 mg of sample 2. Their purities were analyzed by high-performance liquid chromatography, and their chemical structures were identified by mass spectrometry and (1) H NMR spectroscopy. Compared to a normal counter-current chromatography separation, the separation time and solvent consumption of elution-extrusion counter-current chromatography were reduced while the resolutions were still good. The established protocol is promising for the separation of natural products with great disparity of content in herbal medicines.

Anti-proliferative and apoptosis-inducing effects of camptothecin-20(s)-O-(2-pyrazolyl-1)acetic ester in human breast tumor MCF-7 cells.

Camptothecin-20(s)-O-(2-pyrazolyl-1)acetic ester (CPT6) is a novel semi-synthetic analog of camptothecin. In a previous report, CPT6 possessed higher cytotoxic activity in vitro towards human breast tumor MCF-7 cells than topotecan. In this study, the antitumor activity of CPT6 on the human breast tumor MCF-7 cell line was analyzed using the MTT method. The underlying mechanism of CPT6 action was investigated by analyzing the cell cycle distribution, apoptotic proportion, changes in mitochondrial membrane potential, and intracellular Ca2+ concentration using flow cytometry. Nuclear and mitochondrial morphologies were also observed by laser scanning confocal and transmission electron microscopy. DNA damage was observed in MCF-7 cells treated with CPT6. Low-dose CPT6 had a significant cytotoxic effect and could inhibit proliferation and induce apoptosis in MCF-7 cells, possibly through cell nucleus fragmentation and DNA damage. CPT6 thus appears to display potent antitumor activity against human breast tumor MCF-7 cells via the induction of apoptosis, and may be a useful alternative drug for breast cancer therapy.

Synthesis and biological activity of some bile acid-based camptothecin analogues.

In an effort to decrease the toxicity of camptothecin (CPT) and improve selectivity for hepatoma and colon cancer cells, bile acid groups were introduced into the CPT 20 or 10 positions, resulting in the preparation of sixteen novel CPT-bile acid analogues. The compounds in which a bile acid group was introduced at the 20-hydroxyl group of CPT showed better cytotoxic selectivity for human hepatoma and colon cancer cells than for human breast cancer cells. Fluorescence microscopy analysis demonstrated that one compound (E2) entered human hepatoma cells more effectively than it did human breast cancer cells. Compound G4 exhibited the best anti-tumour activity in vivo. These results suggested that introduction of a bile acid group at the 20-position of CPT could decrease toxicity in vivo and improve selectivity for hepatoma cells.

Coumarins from Edgeworthia chrysantha.

A new coumarin, edgeworic acid (1), was isolated from the flower buds of Edgeworthia chrysantha, together with the five known coumarins umbelliferone (2), 5,7-dimethoxycoumarin (3), daphnoretin (4), edgeworoside C (5), and edgeworoside A (6). Their structures were established on the basis of spectral data, particularly by the use of 1D NMR and several 2D shift-correlated NMR pulse sequences (1H-1H COSY, HSQC and HMBC), in combination with acetylation reactions.

An efficient strategy for the extraction and purification of lignans from Schisandra chinensis by a combination of supercritical fluid extraction and high-speed counter-current chromatography.

An efficient strategy for extracting and separating five lignans from Schisandra chinensis (Turcz.) Baill has been developed using supercritical fluid extraction (SFE) and high-speed counter-current chromatography (HSCCC) in the present study. First, the extraction was performed by a preparative SFE system under 15 MPa of pressure at 36°C for 4 h. Then, the SFE extract was successfully separated and purified by HSCCC with a two-phase solvent system composed of n-hexane/ethyl acetate/methanol/water (6:4:5:5, 6:4:6:4, 6:4:8:2, v/v) in a stepwise elution mode. The fractions were analyzed by HPLC, and the chemical structures of the products were identified by ESI-MS and 1H NMR spectroscopy. As a result, a total of 12.5 mg of schisandrin at 98.0% purity, 7.1 mg of gomisin A at 98.1% purity, 1.8 mg of schisantherin B at 93.3% purity, 4.4 mg of deoxyschisandrin at 92.9% purity, and 6.8 mg of γ-schisandrin at 89.1% purity were obtained from 300 mg crude extract in a one-step purification.

Preparative enantioseparation of propafenone by counter-current chromatography using di-n-butyl L-tartrate combined with boric acid as the chiral selector.

This paper extends the research of the utilization of borate coordination complexes in chiral separation by counter-current chromatography (CCC). Racemic propafenone was successfully enantioseparated by CCC with di-n-butyl l-tartrate combined with boric acid as the chiral selector. The two-phase solvent system was composed of chloroform/ 0.05 mol/L acetate buffer pH 3.4 containing 0.10 mol/L boric acid (1:1, v/v), in which 0.10 mol/L di-n-butyl l-tartrate was added in the organic phase. The influence of factors in the enantioseparation of propafenone were investigated and optimized. A total of 92 mg of racemic propafenone was completely enantioseparated using high-speed CCC in a single run, yielding 40-42 mg of (R)- and (S)-propafenone enantiomers with an HPLC purity over 90-95%. The recovery for propafenone enantiomers from fractions of CCC was in the range of 85-90%.

A new efficient multi-stage strategy based on the complementarity of ultrafiltration and high resolution biochromatogram for the screening of skin-whitening candidates from the fibrous root of Bletilla striata.

Ultrafiltration-high performance liquid chromatography (UF-HPLC) and high resolution biochromatogram (HR-biochromatogram), have been proven to be effective methods for the rapid discovery of enzyme inhibitors in natural medicines. In attempt to conquer false-positive and false- negative screening results, a new multi-stage strategy based on the complementarity of UF-HPLC and HR-biochromatogram has been proposed for the fast screening of tyrosinase inhibitory components using the fibrous root of Bletilla striata as a case study. For the first two stages, UF- HPLC and HR-biochromatogram, were applied individually for the screening of high-affinity tyrosinase ligands and tyrosinase inhibitors. After that, the inconsistent results, which yielded two potential active fractions, indicated a third stage screening. Thus, a "strengthen" biochromatogram was established to microfractionate the concentrated extract and further evaluate the tyrosinase inhibitors. The complementarity nature of two different screening methods was firstly explored to distinguish tyrosinase inhibitors from the fibrous root of Bletilla striata. As a result, four compounds were screened, isolated and characterized as new potent tyrosinase inhibitors. The screening results were verified by tyrosinase inhibition assays, melanin inhibitory in zebrafish and molecular docking. All compounds possessed much higher tyrosinase inhibition than α-arbutin, especially, 1-(4- Hydroxybenzyl)-4-methoxy-9,10-dihydrophenanthrene-2,7-diol demonstrated stronger tyrosinase inhibition than kojic acid. This study presented a new screening strategy which had a great potential in rapidly and efficiently exploring tyrosinase inhibitors in complex mixtures. Moreover, it is the first time to reveal the skin-whitening nature of the fibrous root of B. striata, which indicating the promising prospect in the full utilization of B. striata plant.

Secondary metabolites from Aspergillus terreus F6-3, a marine fungus associated with Johnius belengerii.

Two new terrein derivatives asperterreinones A-B (1-2), one new octahydrocoumarin derivative (±)-asperterreinin A (6), along with seventeen known compounds, were isolated from Aspergillus terreus F6-3, a marine fungus associated with Johnius belengerii. The structures of 1, 2, and 6 were established on the basis of 1D and 2D NMR, mass spectroscopy, comparative electronic circular dichroism (ECD) spectra analysis, density functional theory calculation of 13C NMR, and DP4+ probability analysis. Among all the isolates, eurylene (7), a constituent of the Malaysian medicinal plant Eurycoma longifolia, was obtained from a microbial source for first time. In the in vitro bioassay, 11 and 13 showed potent inhibitory activity against the Escherichia coli ß-glucuronidase (EcGUS) with IC50 values of 27.75 ± 0.73 and 17.73 ± 0.81 µM, respectively. It was the first time that questinol (11) and (±)-aspertertone B (13) were reported as potent EcGUS inhibitors.

Cucurbitane-type triterpenoids from the fruits of Citrullus colocynthis.

A phytochemical investigation of the fruits of Citrullus colocynthis resulted in the isolation of 21 structurally diverse cucurbitane triterpenoids, including 9 previously undescribed ones, colocynins A-I (1-9). Their absolute configurations were elucidated by means of quantum chemical electronic circular dichroism (ECD) calculations, CD exciton chirality method, and single-crystal X-ray crystallography. Colocynins A-C (1-3) represent the first examples of nonanorcucurbitane-type triterpenoids. An anti-acetylcholinesterase activity assay showed that 6, 10, 13, 18, and 20 exhibited inhibitory activities, with IC50 values ranging from 5.0 to 21.7 µM. In addition, 18 and 21 showed significant cytotoxicity against PACA, A431, and HepG2 cells, with IC50 values ranging from 0.042 to 0.60 and 3.6-14.4 µM, respectively.

Polyketides with potential bioactivities from the mangrove-derived fungus Talaromyces sp. WHUF0362.

Metabolites of microorganisms have long been considered as potential sources for drug discovery. In this study, five new depsidone derivatives, talaronins A-E (1-5) and three new xanthone derivatives, talaronins F-H (6-8), together with 16 known compounds (9-24), were isolated from the ethyl acetate extract of the mangrove-derived fungus Talaromyces species WHUF0362. The structures were elucidated by analysis of spectroscopic data and chemical methods including alkaline hydrolysis and Mosher's method. Compounds 1 and 2 each attached a dimethyl acetal group at the aromatic ring. A putative biogenetic relationship of the isolated metabolites was presented and suggested that the depsidones and the xanthones probably had the same biosynthetic precursors such as chrysophanol or rheochrysidin. The antimicrobial activity assay indicated that compounds 5, 9, 10, and 14 showed potent activity against Helicobacter pylori with minimum inhibitory concentration (MIC) values in the range of 2.42-36.04 µmol/L. While secalonic acid D (19) demonstrated significant antimicrobial activity against four strains of H. pylori with MIC values in the range of 0.20 to 1.57 µmol/L. Furthermore, secalonic acid D (19) exhibited cytotoxicity against cancer cell lines Bel-7402 and HCT-116 with IC50 values of 0.15 and 0.19 µmol/L, respectively. The structure-activity relationship of depsidone derivatives revealed that the presence of the lactone ring and the hydroxyl at C-10 was crucial to the antimicrobial activity against H. pylori. The depsidone derivatives are promising leads to inhibit H. pylori and provide an avenue for further development of novel antibiotics. Supplementary Information: The online version contains supplementary material available at 10.1007/s42995-023-00170-5.

Phytochemistry and pharmacology of natural prenylated flavonoids.

Prenylated flavonoids are a special kind of flavonoid derivative possessing one or more prenyl groups in the parent nucleus of the flavonoid. The presence of the prenyl side chain enriched the structural diversity of flavonoids and increased their bioactivity and bioavailability. Prenylated flavonoids show a wide range of biological activities, such as anti-cancer, anti-inflammatory, neuroprotective, anti-diabetic, anti-obesity, cardioprotective effects, and anti-osteoclastogenic activities. In recent years, many compounds with significant activity have been discovered with the continuous excavation of the medicinal value of prenylated flavonoids, and have attracted the extensive attention of pharmacologists. This review summarizes recent progress on research into natural active prenylated flavonoids to promote new discoveries of their medicinal value.