Immunomodulatory Polyketides from a Phoma-like Fungus Isolated from a Soft Coral

Fourteen new polyketides with a trans-fused decalin ring system, libertalides A-N (3-16), together with two known analogues, aspermytin A and its acetate (1, 2), were isolated from the fermentation extract of a coral-derived Libertasomyces sp. fungus. Their relative configurations were elucidated on the basis of detailed spectroscopic analysis, and the absolute configurations were determined by TDDFT-ECD and optical rotation (OR) calculations. The OR of 1 and 2 were found to have opposite signs in CH₃CN and CHCl₃, which was in agreement with the OR calculations producing alternating signs for the optical rotation depending on the applied conditions. Because the signs of the OR for 1 and 2 showed high solvent dependence, they may not be used alone to correlate the absolute configurations. Compound 16 displayed structural novelty characterized by an α-enol ether bridge conjugated with an aldehyde group. In in vitro immunomodulatory screening, compounds 1, 4, and 10 significantly induced the proliferation of CD3⁺ T cells, while compounds 2, 7, 11, and 14 significantly increased the CD4⁺/CD8⁺ ratio at 3 μM. A preliminary structure-activity analysis revealed a crucial role of Δ⁷ and a terminal OH group in the regulation of CD3⁺ T cell proliferation. This is the first report of immunoregulatory activity for metabolites of this kind.

Lactones from the Sponge-Derived Fungus Talaromyces rugulosus

The marine-derived fungus Talaromyces rugulosus isolated from the Mediterranean sponge Axinella cannabina and cultured on solid rice medium yielded seventeen lactone derivatives including five butenolides (1–5), seven (3S)-resorcylide derivatives (6–12), two butenolide-resorcylide dimers (13 and 14), and three dihydroisocoumarins (15–17). Among them, fourteen compounds (1–3, 6–16) are new natural products. The structures of the isolated compounds were elucidated by 1D and 2D NMR (Nuclear Magnetic Resonance) spectroscopy as well as by ESI-HRMS (ElectroSpray Ionization-High Resolution Mass Spectrometry). TDDFT-ECD (Time-Dependent Density Functional Theory-Electronic Circular Dichroism) calculations were performed to determine the absolute configurations of chiral compounds. The butenolide-resorcylide dimers talarodilactones A and B (13 and 14) exhibited potent cytotoxicity against the L5178Y murine lymphoma cell line with IC₅₀ values of 3.9 and 1.3 µM, respectively.

Glucopyranosylidene-Spiro-Thiazolinones: Synthetic Studies and Determination of Absolute Configuration by TDDFT-ECD Calculations

Reactions of O-peracylated C-(1-bromo-β-d-glucopyranosyl)formamides with thioamides furnished the corresponding glucopyranosylidene-spiro-thiazolin-4-one. While O-debenzoylations under a variety of conditions resulted in decomposition, during O-deacetylations the addition of MeOH to the thiazolinone moiety was observed, and with EtOH and water similar adducts were isolated or detected. The structure and stereochemistry of the new compounds were established by means of NMR and electronic circular dichroism (ECD) data supported by time-dependent density functional theory ECD (TDDFT-ECD) calculations. TDDFT-ECD calculations could efficiently distinguish the proposed epimeric products having different absolute configuration in the spiro heterocyclic ring.

Characterization of Cladosporols from the Marine Algal-Derived Endophytic Fungus Cladosporium cladosporioides EN-399 and Configurational Revision of the Previously Reported Cladosporol Derivatives

Four new cladosporol derivatives, cladosporols F-I (1-4), the known cladosporol C (5), and its new epimer, cladosporol J (6), were isolated and identified from the marine algal-derived endophytic fungus Cladosporium cladosporioides EN-399. Their structures were determined by detailed interpretation of NMR and MS data, and the absolute configurations were established on the basis of TDDFT-ECD and OR calculations. The configurational assignment of cladosporols F (1) and G (2) showed that the previously reported absolute configuration of cladosporol A and all the related cladosporols need to be revised from (4'R) to (4'S). Compounds 1-6 showed antibacterial activity against Escherichia coli, Micrococcus luteus, and Vibrio harveyi with MIC values ranging from 4 to 128 μg/mL. Compound 3 showed significant cytotoxicity against A549, Huh7, and LM3 cell lines with IC₅₀ values of 5.0, 1.0, and 4.1 μM, respectively, and compound 5 showed activity against H446 cell line with IC₅₀ value of 4.0 μM.

Compositacins A-K: Bioactive chamigrane-type halosesquiterpenoids from the red alga Laurencia composita Yamada

Eleven highly halogenated chamigrane sesquiterpenoids, compositacins A-K, including one unusual rearranged chamigrane sesquiterpenoid, compositacin A, were isolated from the red alga Laurencia composita Yamada, along with seven known structural analogues. Compositacins B and D are the first examples of chamigranes bearing an ether bridge involving C-5/C-9 and C-3/C-5, respectively, while compositacins B and C represent the first chamigranes with a C-10 carbonyl group. Their structures were elucidated on the basis of extensive spectroscopic analysis. The absolute configuration of compositacin B was determined by ECD calculation, whereas the absolute configurations of compositacins A and C-L were proposed on biosynthetic grounds by comparison to compositacin B and the related known sesquiterpenoids johnstonol and yicterpene A. We also suggest that the structure of the previously reported sesquiterpenoid laurokamin A should be revised. Cytotoxicity and antifungal activity of these isolates were also investigated. The results showed that compositacin G exhibited good antifungal activity against Microsporum gypseum (Cmccfmza) with a MIC₈₀ value of 4 μg/mL relative to positive controls. Four of the chamigrane halosesquiterpenoids showed marginal cytotoxicity against the A-549 human lung adenocarcinoma cell line with IC₅₀ values ranging from 48.6 to 85.2 μM.

Structural and Stereochemical Studies of Laurokamurols A-C, Uncommon Bis-sesquiterpenoids from the Chinese Red Alga Laurencia okamurai Yamada

Three novel heterodimeric laurane-type sesquiterpenoids, laurokamurols A-C (1-3), along with eight known related monomeric ones (4-11) were isolated from the East China Sea red alga Laurencia okamurai Yamada. The absolute configurations of the new bis-sesquitepenoids, especially their axial chirality, were determined by extensive spectroscopic analyses and TDDFT-ECD method. All of the new compounds showed promising PTP1B inhibitory activities with IC₅₀ values comparable to the positive control, indicating them as potential food additives or pharmaceutical drug leads toward obesity or diabetes.

Antibacterial and Cytotoxic Phenolic Metabolites from the Fruits of Amorpha fruticosa

Fourteen new natural products, namely, 2-[(Z)-styryl]-5-geranylresorcin-1-carboxylic acid (1), amorfrutin D (2), 4-O-demethylamorfrutin D (3), 8-geranyl-3,5,7-trihydroxyflavanone (4), 8-geranyl-5,7,3'-trihydroxy-4'-methoxyisoflavone (5), 6-geranyl-5,7,3'-trihydroxy-4'-methoxyisoflavone (6), 8-geranyl-7,3'-dihydroxy-4'-methoxyisoflavone (7), 3-O-demethyldalbinol (8), 6a,12a-dehydro-3-O-demethylamorphigenin (9), (6aR,12aR,5'R)-amorphigenin (10), amorphispironones B and C (11 and 12), resokaempferol 3-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside-7-O-α-l-rhamnopyranoside (13), and daidzein 7-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside (14), together with 40 known compounds, were isolated from the fruits of Amorpha fruticosa. The structures of the new compounds were elucidated by 1D and 2D NMR spectroscopic analysis as well as from the mass spectrometry data. ECD calculations were performed to determine the absolute configurations of 11 and 15. Compounds 1, 4-6, and 16-23 showed potent to moderate antibacterial activities against several Gram-positive bacteria with MIC values ranging from 3.1 to 100 μM. In addition, compounds 11 and 24-33 were significantly cytotoxic against the L5178Y mouse lymphoma cell line and exhibited IC₅₀ values from 0.2 to 10.2 μM.

Hydroquinone derivatives from the marine-derived fungus Gliomastix sp

A novel cytotoxic quinone/hydroquinone dimer from the marine-derived fungus Gliomastix sp.

Daldinone derivatives from the mangrove-derived endophytic fungus Annulohypoxylon sp

Three new benzo[j]fluoranthene metabolites, including an isolation artefact which induces intrinsic apoptosis and blocks autophagy, were isolated fromAnnulohypoxylonsp.

Screening of Luzula species native to the Carpathian Basin for anti-inflammatory activity and bioactivity-guided isolation of compounds from Luzula luzuloides (Lam.) Dandy & Wilmott

The present study focused on the anti-inflammatory screening of Luzula species native to the Carpathian Basin and bioactivity-guided isolation of compounds of Luzula luzuloides (Lam.) Dandy & Wilmott. The anti-inflammatory properties of extracts with different polarity prepared from Luzula species were determined. Among them, the CH₂Cl₂-soluble fraction of L. luzuloides possessed strong inhibitory effects on superoxide anion generation (99.39±0.37%) and elastase release (114.22±3.13%) in fMLP/CB-induced human neutrophils at concentration of 10μg/mL. From this fraction, six compounds (1-6) were isolated by the combination of different chromatographic methods. The structures of the compounds were determined by means of MS, 1D and 2D NMR spectroscopy. The results allowed the identification of the new 1,6-dihydroxy-2-keto-1,7-dimethyl-8-vinyl-1,2-dihydrophenanthrene (1) from the plant, named luzulin A. Chiral HPLC and HPLC-ECD analysis revealed that 1 possesses low enantiomeric excess and TDDFT-ECD calculations afforded the configurational assignment of the separated enantiomers. Three known phenanthrenes [juncuenin B (2), dehydrojuncuenin B (3) and juncusol (4)] and two flavonoids [apigenin (5) and luteolin (6)] were also isolated. The anti-inflammatory activity of the isolated compounds was tested and IC₅₀ values were determined. This was the first time that phenanthrenes were detected in a Luzula species. The oxidative transformation of juncuenin B (3) led to the isolation of its possible biometabolites, namely luzulin A (1), dehydrojuncuenin B (4), and juncuenin D (7). The isolated compounds (1-4) confirm that besides flavonoids, phenanthrenes could also serve as chemotaxonomic markers for Luzula species and prove the close relationship of Juncus and Luzula genus.

Biomimetic synthesis and HPLC-ECD analysis of the isomers of dracocephins A and B

Starting from racemic naringenin ((±)-1), a mixture of dracocephin A stereoisomers 6-(2”-pyrrolidinone-5”-yl)naringenin (±)-2a–d and its regioisomer, dracocephin B 8-(2”-pyrrolidinone-5”-yl)naringenin (±)-3a–d originally isolated from Dracocephalum rupestre, have been synthesized in a one-pot reaction. The separation of 2a–d and 3a–d was achieved by preparative HPLC. The four stereoisomers of each natural product were separated by analytical chiral HPLC and their absolute configuration was studied by the combination of HPLC–ECD measurements and TDDFT–ECD calculations. The synthesized flavonoid alkaloids were further characterized by physicochemical and in vitro pharmacological studies.

Phenanthrenes from Juncus inflexus with Antimicrobial Activity against Methicillin-Resistant Staphylococcus aureus

The present study has focused on an investigation of the antibacterial effects of Juncus inflexus and the isolation and identification of its active compounds. Eleven phenanthrenes were isolated from a methanolic extract of the roots. Four compounds (jinflexins A-D, 1-4) are new natural products, while seven phenanthrenes [juncuenins A (5), B (6), and D (8), juncusol (7), dehydrojuncuenins A (9) and B (11), and dehydrojuncusol (10)] were isolated for the first time from the plant. Jinflexin D (4) is a dimer with an unprecedented heptacyclic ring system. The absolute configurations of the new compounds were determined by TDDFT-ECD calculations, and their enantiomeric purity was checked by chiral HPLC analysis. Extracts of different polarity (n-hexane, dichloromethane, and ethyl acetate) were evaluated for their antimicrobial effects against methicillin-resistant Staphylococcus aureus, extended-spectrum β-lactamase (ESBL)-producing Citrobacter freundii, Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, multiresistant Acinetobacter baumannii, and Pseudomonas aeruginosa. The MIC values of the isolated compounds were determined by a microdilution method. Jinflexin B (2), juncusol (7), juncuenin D (8), and dehydrojuncuenin B (11) showed significant activity (MIC value range 12.5-100 μg/mL) against MRSA strains.

Bissubvilides A and B, Cembrane-Capnosane Heterodimers from the Soft Coral Sarcophyton subviride

Two new biscembranoid-like compounds, bissubvilides A (1) and B (2), were isolated together with sarsolilide B (3), the proposed biogenetic precursor to 1, from the soft coral Sarcophyton subviride. The structures and absolute configurations were solved by spectroscopic analysis and TDDFT/ECD and DFT/NMR calculations. The bissubvilides represent a novel biscembranoid-like skeleton presumed to derive from a cembrane-type diene and a capnosane-type dienophile via a Diels-Alder reaction. These two molecules exerted no cytotoxicity against MG-63 or A549 tumor cells or HuH7 tumor stem cells.