Colletodiol derivatives of the endophytic fungus Trichocladium sp.

The OSMAC (one strain many compounds) concept is a cultivation-based approach to increase the diversity of secondary metabolites in microorganisms. In this study, we applied the OSMAC-approach to the endophytic fungus Trichocladium sp. by supplementation of the cultivation medium with 2.5% phenylalanine. This experiment yielded five new compounds, trichocladiol (1), trichocladic acid (2), colletodiolic acid (3), colletolactone (4) and colletolic acid (5), together with five previously described ones (6-10). The structures were elucidated via comprehensive spectroscopic measurements, and the absolute configurations of compound 1 was elucidated by using TDDFT-ECD calculations. For formation of compounds 3-5, a pathway based on colletodiol biosynthesis is proposed. Compound 6 exhibited strong antibacterial activity against methicillin-resistant Staphylococcus aureus with a minimal inhibitory concentration (MIC) of 0.78 µM as well as a strong cytotoxic effect against the human monocytic cell line THP1 with an IC50 of 0.7 µM. Compound 8 showed moderate antibacterial activity against Mycobacterium tuberculosis with a MIC of 25 µM and a weak cytotoxic effect against THP1 cells with an IC50 of 42 µM.

Azacoccones F-H, new flavipin-derived alkaloids from an endophytic fungus Epicoccum nigrum MK214079.

Three new flavipin-derived alkaloids, azacoccones F-H (1-3), along with six known compounds (4-9) were isolated from the endophytic fungus Epicoccum nigrum MK214079 associated with leaves of Salix sp. The structures of the new compounds were established by analysis of their 1D/2D nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectroscopy (HRESIMS) data. The absolute configuration of azacoccones F-H (1-3) was determined by comparison of experimental electronic circular dichroism (ECD) data with reported ones and biogenetic considerations. Epicocconigrone A (4), epipyrone A (5), and epicoccolide B (6) exhibited moderate antibacterial activity against Staphylococcus aureus ATCC 29213 with minimal inhibitory concentration (MIC) values ranging from 25 to 50 µM. Furthermore, epipyrone A (5) and epicoccamide A (7) displayed mild antifungal activity against Ustilago maydis AB33 with MIC values of 1.6 and 1.8 mM, respectively. Epicorazine A (8) showed pronounced cytotoxicity against the L5178Y mouse lymphoma cell line with an IC50 value of 1.3 µM.

New tricyclic prezizaane sesquiterpenoids from agarwood.

Ten new tricyclic prezizaane types sesquiterpenoids (1-10) were isolated from ethyl ether extract of agarwood originated from Aquilaria sp. Their structures were unambiguously elucidated on the basis of 1D and 2D NMR spectra as well as by HRESIMS data. The absolute configuration of the new prezizaenes 1, 2 and 4 was determined by single-crystal X-ray diffraction, while TDDFT-ECD method was applied for 6. Compounds 4 and 5 displayed significant inhibitory activities toward α-glucosidase with IC50 values of 0.22 and 1.99 mM, respectively.

Indole Diterpenoids from an Endophytic Penicillium sp.

A chemical investigation of the endophyte Penicillium sp. (strain ZO-R1-1), isolated from roots of the medicinal plant Zingiber officinale, yielded nine new indole diterpenoids (1-9), together with 13 known congeners (10-22). The structures of the new compounds were elucidated by 1D and 2D NMR analysis in combination with HRESIMS data. The absolute configuration of the new natural products 1, 3, and 7 was determined using the TDDFT-ECD approach and confirmed for 1 by single-crystal X-ray determination through anomalous dispersion. The isolated compounds were tested for cytotoxicity against L5178Y, A2780, J82, and HEK-293 cell lines. Compound 1 was the most active metabolite toward L5178Y cells, with an IC50 value of 3.6 µM, and an IC50 against A2780 cells of 8.7 µM. Interestingly, 1 features a new type of indole diterpenoid scaffold with a rare 6/5/6/6/6/6/5 heterocyclic system bearing an aromatic ring C, which is suggested to be important for the cytotoxic activity of this natural product against L5278Y and A2780 cells.

Five new epoxy-5,6,7,8-tetrahydro-2-(2-phenylethyl)chromones from Chinese agarwood by artificial holing.

Five optically active epoxy-5,6,7,8-tetrahydro-2-(2-phenylethyl)chromone derivatives (1-5) with four chirality centers in the condensed cyclohexene ring were isolated from artificial holing agarwood originating from Aquilaria sinensis (Lour.) Gilg. Their structures were elucidated by spectroscopic techniques (UV, IR, 1D and 2D NMR) and MS analyses. The absolute configuration of 2 was elucidated by TDDFT-ECD calculations and ECD spectra of 1, 3-5 allowed their configurational assignment as well. All of the new compounds contained a condensed oxirane ring, and compound 1 was the only 6,7-epoxy-2-(2-phenylethyl)-5,6,7,8-tetrahydrochromone derivative that has ever been found in agarwood. AChE inhibitory activity was tested for the first time of these new compounds by using modified Ellman's colorimetric method. Compounds 3 and 5 exhibited inhibitory activity against AChE with IC50 value of 441.6, and 155.6 µM, respectively.

Induction of Secondary Metabolites from the Marine-Derived Fungus Aspergillus versicolor through Co-cultivation with Bacillus subtilis.

A new cyclic pentapeptide, cotteslosin C (1: ), a new aflaquinolone, 22-epi-aflaquinolone B (3: ), and two new anthraquinones (9: and 10: ), along with thirty known compounds (2, 4:  - 8, 11:  - 34: ) were isolated from a co-culture of the sponge-associated fungus Aspergillus versicolor with Bacillus subtilis. The new metabolites were only detected in the co-culture extract, but not when the fungus was grown under axenic conditions. Furthermore, the co-culture extract exhibited an enhanced accumulation of the known constituents versicolorin B (14: ), averufin (16: ), and sterigmatocyctin (19: ) by factors of 1.5, 2.0, and 4.7, respectively, compared to the axenic fungal culture. The structures of the isolated compounds were elucidated on the basis of 1D and 2D NMR spectra and mass spectrometry as well as by comparison with literature data. The absolute configuration of compounds 3, 9: , and 10: was determined by ECD (electronic circular dichroism) analysis aided by TDDFT-ECD (time-dependent density functional theory electronic circular dichroism) calculations. Compounds 15, 18:  - 21: , and 26: exhibited strong to moderate cytotoxic activity against the mouse lymphoma cell line L5178Y, with IC50 values ranging from 2.0 to 21.2 µM, while compounds 14, 16, 31, 32: , and 33: displayed moderate inhibitory activities against several gram-positive bacteria, with MIC values ranging from 12.5 to 50 µM.

Pyrone derivatives from Helichrysum italicum.

Chemical investigation of aerial parts of Helichrysum italicum yielded two new pyrone derivatives (1 and 2) along with ten known compounds. The structures of the new compounds were established by 1D and 2D NMR spectra as well as by HRESIMS data. Compound 1 represented a rare dimer of substituted α- and γ-pyrone units. DFT-NMR and TDDFT-ECD calculations were carried out to determine the absolute configuration of 1 but failed, representing the limitation of TDDFT-ECD calculation for the configurational assignment. All compounds were measured for their antibacterial and cytotoxic activity but proved to be inactive.

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-ß-d-glucopyranosyl-(1→2)-ß-d-glucopyranoside-7-O-α-l-rhamnopyranoside (13), and daidzein 7-O-ß-d-glucopyranosyl-(1→2)-ß-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.

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.

Isolation, Stereochemical Study, and Antioxidant Activity of Benzofuranone Derivatives from a Mangrove-derived Fungus Eurotium rubrum MA-150.

Enantiomers of a 2-benzofuran-1(3H)-one derivative [(-)- and (+)-] and four known analogs () were isolated and identified from the culture extract of Eurotium rubrum MA-150, a fungus obtained from the mangrove-derived rizospheric soil. Their structures were established by detailed interpretation of nuclear magnetic resonance (NMR) data and the structure of (±)- was confirmed by single-crystal X-ray diffraction analysis. The absolute configuration of the enantiomers (-)- and (+)- was determined by means of online high-performance liquid chromatography - electronic circular dichroism (HPLC-ECD) measurements and time-dependent Density Functional Theory - electronic circular dichroism (TDDFT-ECD) calculations. Compounds (±)- as well as and exhibited potent DPPH radical scavenging activities with IC50 values of 1.23, 2.26, and 3.99 µg/mL, respectively. Chirality 28:581-584, 2016. © 2016 Wiley Periodicals, Inc.

Stereochemistry of a Rhododaurichromanic Acid Derivative.

A rhododaurichromanic acid A derivative was synthesized from the naturally occurring daurichromenic acid in enantiomeric pure form. Its absolute configuration was elucidated by applying VCD, ECD and DFT calculations.

Four phragmalin orthoesters from the Chinese mangrove Xylocarpus granatum.

Four new 8,9,30-phragmalin orthoesters (1-4), along with six related known compounds, namely xyloccensins O-S (5-9) and V (10), were isolated and characterized from the twigs and leaves of the Chinese mangrove Xylocarpus granatum. The structures of the new compounds were determined on the basis of extensive spectroscopic analysis and by comparison with those of related known compounds in the literature. The absolute configuration of xyloccensin Q (7) was revised as its enantiomer by X-ray diffraction analysis employing graphite monochromated Cu Kα radiation (λ=1.54178 Å) with a Flack parameter of -0.04 and was further secured by a time-dependent density functional theory electronic circular dichroism (TDDFT ECD) calculation. Consequently, the absolute configurations of xyloccensins O (5), P (6), R (8), S (9), and V (10) were all corrected as their corresponding enantiomers, respectively. Xyloccensin S (9) exhibited inhibitory activity against protein tyrosine phosphatase 1B, a potential drug target for the treatment of type II diabetes and obesity, with an IC50 value of 8.72 µg/mL.

Design, synthesis, and structure-activity relationships of 3,4,5-trisubstituted 4,5-dihydro-1,2,4-oxadiazoles as TGR5 agonists.

Given its role in the mediation of energy and glucose homeostasis, the G-protein-coupled bile acid receptor 1 (TGR5) is considered a potential target for the treatment of type 2 diabetes mellitus and other metabolic disorders. By thorough analysis of diverse structures of published TGR5 agonists, a hypothetical ligand-based pharmacophore model was built, and a new class of potent TGR5 agonists, based on the novel 3,4,5-trisubstituted 4,5-dihydro-1,2,4-oxadiazole core, was discovered by rational design. Three distinct synthetic methods for constructing 4,5-dihydro-1,2,4-oxadiazoles and extensive structure-activity relationship studies are reported herein. Compound (R)-54 n, the structure of which was determined by single-crystal X-ray diffraction and quantum chemical solid-state TDDFT-ECD calculations, showed the best potency, with an EC50 value of 1.4 nM toward hTGR5. Its favorable properties in vitro warrant further investigation.

Protolimonoids and norlimonoids from the stem bark of Toona ciliata var. pubescens.

Six new tirucallane protolimonoids, toonapubesins A-F (1-6), one new rearranged tirucallane protolimonoid, toonapubesin G (7), and two new 21,22,23-trinorapotirucallane limonoids, toonapubesic acids A (8) and B (9), possessing an unprecedented carbon skeleton, along with five known tirucallane protolimonoids (10-14) and one known apotirucallane limonoid (15), were isolated from the stem bark of Toona ciliata var. pubescens. Their structures and relative configurations were determined by detailed spectroscopic analysis and by chemical methods. The proposed structures of 8 and 11 were confirmed by X-ray diffraction analysis of their respective derivatives (8a and 11a). The absolute configuration of 8 was determined by a novel solid-state TDDFT ECD approach on its derivative 8a while the absolute configuration of 10 was determined by the modified Mosher's method. In addition, the structures of dyvariabilin H (10c) proposed by Sticher et al. and cneorin-NP(36) (11b) by Mondon et al. were corrected as 10 and 11, respectively. Toonapubesin G (7) showed promising inhibitory activity against CDC25B with an IC(50) value of 2.1 µM, while compound 8a showed significant cell protecting activity against H(2)O(2)-induced SH-SY5Y cell damage with 11.5% increase in cell viability.

Sibiralactone: a new monoterpene from Sibiraea angustata.

Sibiralactone (1), a new monoterpene derivative, was isolated from the leaves of Sibiraea angustata. The structure was determined by the analysis of its NMR data and the absolute configuration was established by TDDFT ECD calculation of the solution conformers.