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.

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.

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.

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.

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.

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.

Two new nor-lignans from Selaginella pulvinata (Hook. & Grev.) Maxim and their antihyperglycemic activities.

Two new nor-lignans, pulvin A (1) and moellenoside C (2), along with two known compounds (3-4) were isolated from the whole plant of Selaginella pulvinate (Hook. & Grev.) Maxim. The structures of the new compounds were established on the basis of spectroscopic data and acid hydrolysis. All the isolates were investigated for their antihyperglycemic activities in 3T3-L1 adipocytes. The results showed that compounds 1 and 2 promoted the glucose consumption prominently in 3T3-L1 adipocytes in a dose-response manner. Compound 1 and 2 induced 1.14-1.73 folds and 1.03-1.55 folds changes relative to the basal level, respectively, in the concentration range of 12.5 µM to 50 µM.

Valtrate as a novel therapeutic agent exhibits potent anti-pancreatic cancer activity by inhibiting Stat3 signaling.

BACKGROUND: Valtrate is a novel epoxy iridoid ester isolated from Chinese herbal medicine Valeriana jatamansi Jones with anti-proliferative activity against various human cancer cell lines. However, its efficacy and molecular mechanisms against pancreatic cancer (PC) cells are largely unclear. PURPOSE: To investigate the anti-cancer effects of valtrate on PC cell lines and its underlying mechanisms. METHODS: MTT assay was first performed to detect the effect of valtrate on cell viability in human PC cell lines and normal pancreatic epithelial cells HPDE. Cell apoptosis and cycle phase assay were detected by flow cytometry. The relative mRNA expressions of Bax, Bcl-2, c-Myc, and CyclinB1 were tested by quantitative PCR (qPCR) assay. The expression of relative proteins was detected by Western blotting (WB). A PANC-1luc cells xenograft mouse model in nu/nu female mice was used to elucidate the effect of valtrate on tumor growth in vivo. RESULTS: Valtrate significantly inhibited the growth of PC cells without affecting the growth of normal pancreatic epithelial cells HPDE, induced significant apoptosis and cell cycle arrest in G2/M phase. Moreover, valtrate inhibited the tumor growth of PC cell PANC-1 in xenograft mice by 61%. Further mechanism study demonstrated that valtrate could increase the expression level of Bax, suppress Bcl-2 as well as c-Myc and Cyclin B1, inhibit the transcriptional activity of Stat3, while valtrate decreased the expression level of Stat3 and phosphated-Stat3 (Tyr705) and induced the high molecular aggregation of Stat3. Molecular docking analysis predicted that valtrate might interact with Cys712 of Stat3 protein. Valtrate could also induce a transient depleted intracellular glutathione (GSH) level and increased reactive oxygen species (ROS). NAC (N-acetylcysteine), a reducer reversed valtrate-induced the depletion of Stat3, p-Stat3, c-Myc, and Cyclin B1. CONCLUSION: Valtrate exerts anti-cancer activity against PC cells by directly targeting Stat3 through a covalent linkage to inhibit Stat3 activity, which causes apoptosis and cell cycle arrest.

Spectral study on inclusion interaction and enantiorecognition of 2-aryl carboxylic acids with hydroxypropyl-ß-cyclodextrin.

The inclusion interaction between hydroxypropyl-ß-cyclodextrin (HP-ß-CD) and 21 2-aryl carboxylic acids was investigated by UV (ultraviolet) spectrophotometer. The inclusion constant of each 2-aryl carboxylic acids with HP-ß-CD was determined by Benesi-Hildebrand's equation. According to our previous work, it was found that a high inclusion constant for inclusion complex formed by a racemate and cyclodextrin was always observed with the fact that a high enantioseparation factor was achieved for the racemate in enantioseparation by liquid-liquid chromatography, which suggested that high binding combination between racemate and cyclodextrin is very important for a successful enantioseparation in enantioselective liquid-liquid extraction. Among all the studied subjects, mandelic acid enantiomer, 2,3-diphenylpropionic acid enantiomer, and naproxen enantiomer were selected for the further study. The inclusion constants of enantiomers of these three subjects were determined by UV spectra, which indicated that a necessary difference in inclusion constants between enantiomer and cyclodextrin was also essential. It was found in UV spectra that the absorbance of the analytes with the addition of cyclodextrin would increase or decrease, which was determined by the type of electron excitation. The conformation changes of small molecules can lead to the changes of chromophore valence electron clouds distribution, causing the HOMO-LUMO energy difference decreased. Thus, a red shift of the wavelength of the maximum absorption was produced indicating that the possibility of the molecular interaction of enantiomers with HP-ß-CD exists.

A cyclic peptide and two pairs of norlignan lignanoside epimers from Selaginella pulvinata.

A new cyclopeptide, pulvpeptin A (1), two pairs of norlignan lignanosides, tamariscinosides G and H (2, 3), together with five known compounds (4-8) were isolated from Selaginella pulvinata. The structures were elucidated by spectroscopic data and chemical degradation. The activity of tamariscinoside G (2) was evaluated by stimulating glucose uptake in 3T3-L1 adipocytes. The results showed 1.49-fold increase in glucose uptake in 3T3-L1 cells relative to basal.

Enantioseparation of three isomeric α-(chlorophenyl)propanoic acid by countercurrent chromatography and investigation of chlorine substituent through characterization of inclusion interaction.

The influence of chlorine substituents in chiral separation of three racemic 2-(chlorophenyl)propanoic acids by countercurrent chromatography using hydroxypropyl-ß-cyclodextrin as a chiral additive were mainly investigated in the present paper, including 2-(2-chlorophenyl)propanoic acids, 2-(3-chlorophenyl)propanoic acids and 2-(4-chlorophenyl)propanoic acids. The influences of chromatographic conditions on the retention behavior were studied by enantioselective liquid-liquid extraction experiments using the methodology of response surface It was found that 2-(3-chlorophenyl)propanoic acids could be successfully chiral separated by countercurrent chromatography, while no resolution was achieved for racemic 2-(2-chlorophenyl)propanoic acids and 2-(4-chlorophenyl)propanoic acids under optimized separation conditions. The formation of 1:1 stoichiometric inclusion compounds between 2-(3-chlorophenyl)propanoic acids and HP-ß-CD was determined by UV spectra measurements. The inclusion constants for 2-(3-chlorophenyl)propanoic acids and HP-ß-CD were determined by the Benesi-Hildebrand equation. Meanwhile, the inclusion constants of 2-(3-chlorophenyl)-propanoic acid enantiomer and HP-ß-CD were obtained by the pesudophase retention equation in countercurrent chromatography. Furthermore, the inclusion interactions of the three racemates with HP-ß-CD were also investigated by the molecular docking. The results obtained from UV spectra measurements and molecular docking showed that the racemate with chlorine substituents in meta-position presented the highest enantiorecognition while the racemates with chlorine substituents in ortho-position had the lowest enantiorecognition. The above results further indicated that forming a stable inclusion complex between racemate and chiral selector is a prerequisite for a successful enantioseparation and at the same time, the difference in inclusion capacity between the two enantiomers is also essential for the enantioseparation.

Protective effects and potential underlying mechanisms of sodium copper chlorophyllin against ethanol-induced gastric ulcer in mice.

In study, we aimed to determine the mechanisms underlying the gastroprotective effects of sodium copper chlorophyllin (SCC) against ethanol-induced gastric ulcer injury in mice. First, the gastroprotective effects of SCC against gastric ulcer induced by ethanol were assessed. Then, biochemical, histopathological, immunohistochemistry assays, and western blot analysis were conducted to determine the possible mechanisms of action underlying the effects of SCC. Compared to the effects of omeprazole (OME) in a confirmed mouse model of ethanol-induced gastric ulcer injury, treatment with various doses of SCC resulted in up-regulation of Bcl-2 and down-regulation of the pro-apoptotic protein Bax. Significant decreases in the levels of the malondialdehyde (MDA), myeloperoxidase (MPO), and NO in the gastric tissues were observed. Furthermore, inflammatory cytokine analysis revealed that SCC treatment inhibited the expressions of TNF-α and IL-6, greatly reduced the phosphorylation level of IκB, and repressed the nuclear translocation of NF-κB p65, which demonstrated that SCC inhibited the activation of the NF-κB pathway. The present findings suggest that the protective effects of SCC may be beneficial as a potential preventive and therapeutic agent for gastric ulcer through the NF-κB pathway. Taken together, SCC administration significantly decreased the levels of MPO, NO, and MDA in gastric tissue and exerted a powerful anti-inflammatory activity as demonstrated by reduction in the secretions of proinflammatory mediators such as IL-6 and TNF-α in the serum of mice exposed to ethanol.

On-line synergistic stacking in capillary zone electrophoresis featuring field-amplified sample stacking and micelle to cyclodextrin stacking in the determination of two alkaloids in complicated matrix samples.

A novel on-line synergistic proconcentration strategy coupling field-amplified sample stacking and micelle to cyclodextrin stacking for cationic analytes in capillary zone electrophoresis has been proposed and applied for the separation and determination of two alkaloids, matrine, and oxymatrine in complicated matrix samples. The approach was performed by the long injection of sample in a low-conductivity sodium dodecyl benzene sulfonate solution followed by the injection of hydroxypropyl-ß-cyclodextrin solution in higher conductivity. The stacking mechanism of this method has been expounded and parameters affecting stacking effect have been optimized in our study. Under the optimum experimental conditions, 169- and 218-fold sensitivity improvements were achieved for matrine and oxymatrine when compared with normal injection. Analytical indicators including linearity, limits of detection, and reproducibility (intra- and inter-day relative standard deviations) were evaluated. Moreover, sample matrix effect was studied using compound flavescent sophora and salicylic acid powder and spiked urine samples. The developed method is an attempt for the combination of micelle to cyclodextrin stacking with other stacking methods. It could be a good alternative choice for the determination of alkaloids in a complex sample matrix.

The genus Tripterygium: A phytochemistry and pharmacological review.

The genus Tripterygium belongs to the family Celastraceae, and contains three species, i.e. Tripterygium wilfordii Hook. F, Tripterygium hypoglaucum (Levl.) Hutch. and Tripterygium regelii Sprague et Takeda. All three species are reported to have excellent medicinal properties that help to cure rheumatoid arthritis, nephrotic syndrome, systemic lupus erythematosus and widely used as a folk medicine in China. Phytochemical studies have led to discovering more than 500 secondary metabolites in this genus, including five main types: sesquiterpenoids, diterpenes, triterpenoids, flavonoids, lignans. This work provides structurally grouping statistic of 198 secondary metabolites of Tripterygium species published from 2008 to the present, as well as pharmacological knowledges in the past five years. The information will be helpful for developing the new discoveries of medicinal value related to the genus Tripterygium.

Stereoselectiveseparation of racemic trans-paroxol, N-methylparoxetine and paroxetine containing two chiral carbon centres by countercurrent chromatography.

Racemic trans-paroxol, trans-N-methylparoxetine and trans-paroxetine containing two chiral centres were stereoselectively separated using countercurrent chromatography with hydroxypropyl-ß-cyclodextrin as the chiral selector. A two-phase solvent system composed of n-butyl acetate and 0.1 mol L-1 sodium carbonate-sodium bicarbonate buffer at pH 9.2 (1:1, v/v) was selected, and 0.10 mol L-1 hydroxypropyl-ß-cyclodextrin was added to the aqueous phase as the chiral selector. Racemic trans-N-methylparoxetine and racemic trans-paroxol (20 mg of each) were stereoselectively separated by countercurrent chromatography in an individual run, yielding 7.1-8.3 mg of enantiomers with a purity of 95-98%, where the recovery of each separated isomer reached approximately 70-83%. Racemic trans-paroxetine (20 mg) was stereoselectively separated by countercurrent chromatography using a recycling elution mode with a biphasic solvent system composed of n-hexane: n-butyl acetate: 0.1 mol L-1 sodium carbonate-sodium bicarbonate buffer at pH 9.2 (9:1:10, v/v/v), and 0.10 mol L-1 hydroxypropyl-ß-cyclodextrin was added to the aqueous phase as the chiral selector, yielding 5.0-5.6 mg of enantiomer with a high purity of over 98-99%.

CDC Reaction and Subsequent Cyclization for the Synthesis of 2-Hydroxy-3-alkyl-1,4-naphthoquinones and Pyranonaphthoquinones.

The metal-free cross-dehydrogenative coupling (CDC) reaction and subsequent cyclization of 2-hydroxy-1,4-naphthoquinone (lawsone) and 1,3-diarylpropene promoted by DDQ has been developed. 2-Hydroxy-3-alkyl-1,4-naphthoquinones and pyranonaphthoquinones with potential pharmaceutical applications are obtained in moderate to good yields. The reaction is also compatible for 4-hydroxycoumarins.

neo-Clerodane diterpenoids from the aerial parts of Teucrium fruticans cultivated in China.

Seven neo-clerodane diterpenes, teufruintins A-G (1-7), together with eight known compounds (8-15) were isolated from the CHCl3-soluble fraction of the aerial parts of Teucrium fruticans cultivated in China. The chemical structures of the isolated compounds were elucidated using different spectroscopic methods. All of the isolated diterpenes were evaluated for their cytotoxic activities on three human cancer cell lines, and for their ability to inhibit LPS-induced nitric oxide production in RAW 264.7 macrophages. None of the compounds displayed cytotoxic activities on the cancer cell lines, and only 15 showed weak NO inhibitory activity.

Two new ß-carboline alkaloids from the roots of Gypsophila oldhamiana.

Phytochemical investigation of the roots of Gypsophila oldhamiana afforded two new ß-carboline alkaloids, oldhamiaines A and B (1 and 2), along with a known analogue (3). Their structures were elucidated by using spectroscopic and chemical methods. This is the first report of ß-carboline alkaloids in the genus Gypsophila.

Teucvisins A-E, five new neo-clerodane diterpenes from Teucrium viscidum.

Two new neo-clerodane diterpenoids, teucvisins A and B (1, 2), and three new 19-nor-neoclerodane diterpenoids, teucvisins C-E (3-5), together with ten known constituents (6-15) were isolated from the whole plants of Teucrium viscidum. All the isolates were evaluated for their inhibitory activities of lipopolysaccharide (LPS)-induced nitric oxide production in RAW264.7 macrophages. The results indicated that compounds 11 and 15 showed moderate inhibition with an IC50 value of 21.9 and 22.4 µM, respectively.

Antihyperglycemic glucosylated coumaroyltyramine derivatives from Teucrium viscidum.

Eight new glucosylated coumaroyltyramine derivatives, teuvissides A-H (1-8), were isolated from whole plants of Teucrium viscidum. Their structures were elucidated using spectroscopic data and chemical methods. The antihyperglycemic activities of these compounds were evaluated in HepG2 cells and 3T3-L1 adipocytes, and all of the isolates elicited different levels of glucose consumption at a concentration of 2.0 µM. Teuvissides A (1), B (2), and F (6) induced 2.2-, 2.1-, and 2.2-fold changes, respectively, in the levels of glucose consumption in HepG2 cells and 2.5-, 2.1-, and 2.3-fold changes, respectively, in 3T3-L1 adipocytes relative to the basal levels.