Multistalides A and B, two novel sesquiterpenoid dimers from Chloranthus multistachys

Two novel sesquiterpenoid dimers, multistalides A and B (1-2), were isolated from the whole plant of Chloranthus multistachys. Their structures were established on the basis of spectroscopic analysis, and the absolute configuration of 1-2 was determined by CD exciton chirality method.     

Swiemahogins A and B, two novel limonoids from Swietenia mahogani

Two novel limonoids, swiemahogins A (1) and B (2) isolated from the twigs and leaves of Swietenia mahogany, are the first examples of andirobin and phragmalin types of limonoids, of which the D-ring δ-lactone is demolished and a rare γ-lactone is fused to the C-ring at C-8 and C-14. Their structures were elucidated by extensive spectroscopic means, and that of 1 was confirmed by single-crystal X-ray diffraction.     

Briaexcavatins A and B, novel briaranes from the octocoral Briareum excavatum

Two novel briaranoidal derivatives, designated as briaexcavatins A (1) and B (2), along with two known metabolites, excavatolides B and C (3 and 4), were isolated from the octocoral Briareum excavatum. Both compounds 1 and 2 possess unprecedented 5,6-epoxy moiety in the 10-membered ring. Diterpenoid 1 possesses a novel pentacyclic skeleton with a ε-lactone. The structures of diterpenoids 1 and 2 were elucidated by interpretation of spectral data and the absolute stereochemistry was established by application of modified Mosher’s method on 3.     

Dilospiranes A and B: diterpenes featuring novel carbocyclic units from the brown alga Dilophus spiralis

Dilospiranes A and B (1 and 2), two diterpenes featuring unprecedented carbocycles, were isolated from the organic extract of the brown alga Dilophus spiralis, collected from the coast of Elafonissos Island, Greece. The structures and the relative configurations of the isolated natural products were determined on the basis of extensive analyses of their spectroscopic data.     

Two novel tetracycles,cassibiphenols A and B from the flowers of Cassia siamea

Chemical investigation of the flowers of Cassia siamea (Leguminosae), resulted in the isolation of two novel tetracycles connecting 5-(2-hydroxypropyl)benzene-1,3-diol, cassibiphenols A (1) and B (2). The structures were elucidated by analysis of the 1D, 2D NMR, and HRMS spectra. Synthesis of a tetracyclic core of 1 and 2 led to determine the absolute configuration of 1 and C-12 of 2.     

Schilancidilactones A and B: two novel tetranortriterpenoids with an unprecedented skeleton from Schisandra lancifolia

Schilancidilactones A (1) and B (2), two novel tetranortriterpenoids possessing an unprecedented skeleton, have been isolated from the stems of Schisandra lancifolia. Their structures were elucidated on the basis of extensive spectroscopic analysis. The relative configurations of 1 were further determined by single-crystal X-ray crystallography. Compounds 1 and 2 were tested for their cytotoxicity against four tumor cell lines NB4, A549, SH-SY5Y, and PC-3, and compound 1 was further tested for its anti-HIV-1 activity.     

Sequence and three-dimensional structure of cycloreticulins A and B, new cyclooctapeptides from the seeds of Annona reticulata

Two cyclooctapeptides, cycloreticulin A, cyclo(Pro¹-Gly²-Asp³-Ile⁴-Ser⁵-Ile⁶-Tyr⁷-Tyr⁸) (1) and cycloreticulin B, cyclo(Pro¹-Mso²-Tyr³-Gly⁴-Thr⁵-Val⁶-Ala⁷-Val⁸) (2), have been isolated from the methanol extract of the seeds of Annona reticulata L. The sequences were elucidated on the basis of the MS/MS fragmentation using a QTOF mass spectrometer equipped with an ESI source, chemical degradation and extensive 2D-NMR. The solid state conformation of cycloreticulin A, carried out by X-ray study, is characterised by the presence of two β-turns (types II and III) and an inversed γ-turn. Its solution structure appeared quite similar to the crystal one. The cyclic backbone solution structure of cycloreticulin B, close to that of the cyclooctapeptide squamin A, from which its sequence only differs by a Val⁸/Ile⁸ substitution, involves three β-turns, two of type I and one of type III, being similar to the crystal structure of squamin A.     

Rubiyunnanins A and B, two novel cyclic hexapeptides from Rubia yunnanensis

Two novel cyclic hexapeptides, named rubiyunnanins A (1) and B (2), were isolated from the roots of Rubia yunnanensis (Franch.) Diels. Their structures were elucidated extensively by spectroscopic analysis and theoretical computation. Possible biosynthetic pathways for RAs, 1, and 2 were proposed. Compound 2 showed moderate cytotoxicities against 11 cancer cell lines and inhibited nitric oxide (NO) production in LPS and IFN-γ-induced RAW 264.7 murine macrophages.     

Mekongenines A and B, two new alkaloids from Bousigonia mekongensis

Mekongenine A (1) possessing an unprecedented structure constituted from the union of a rare 2,7-seco eburnamine half and an aspidospermine alkaloid, together with a new bisindole alkaloid, mekongenine B (2), consisting of an eburnamine-aspidospermine type skeleton, was isolated from Bousigonia mekongensis. Their structures were elucidated by means of spectroscopic methods and those of 2 were further confirmed by X-ray diffraction. The absolute configurations of 1 and 2 were determined by comparison of quantum chemical TDDFT calculated and experimental ECD spectra. Mekongenines A (1) and B (2) exhibited cell growth inhibitory activities against various human cancer cell lines.     

Neoverataline A and B, two antifungal alkaloids with a novel carbon skeleton from Veratrum taliense

Bioassay-guided fractionation of the ethanol extract of the roots and rhizomes of Veratrum taliense yielded two new and thirteen known steroidal alkaloids. The structures of the two new compounds, neoverataline A and B, were established by extensive spectroscopic analyses to be 3,4-secocevane-4,9-olid-14,15,16,20-tetra-ol-3-oic acid and 3,4-secocevane-4,9-olid-7,14,15,16,20-penta-ol-3-oic acid, respectively, and are a novel carbon skelton. All of the fifteen alkaloids were subjected to in vitro antifungal assays, which showed that the verazine- (veramitaline, stenophylline B, stenophylline B-3-O-β-d-glucopyranoside, veramiline-3-O-β-d-glucopyranoside) and jerveratrum-type (jervine, jervine-3-O-β-d-glucopyranoside) alkaloids exhibited strong antifungal activities against the phytopathogenic fungus Phytophthora capisis with MICs of 160, 120, 160, 80, 80 and 120 μg·L⁻¹, respectively. Furthermore, the verazine-type alkaloids stenophylline B, stenophylline B 3-O-β-d-glucopyranoside and veramiline 3-O-β-d-glucopyranoside were shown to also inhibit the growth of another fungal phytopathogen Rhizoctonia cerealis with MICs of 160, 120 and 120 μg mL⁻¹. The MICs of triadimefon (an antifungal agrochemical used herein as a positive control) against P. capisis and R. cerealis were 120 and 80 μg mL⁻¹, respectively. A preliminary structure-activity relationship regarding these alkaloids has been formulated.     

Novel alkaloids, paxdaphnines A and B with unprecedented skeletons from the seeds of Daphniphyllum paxianum

Two novel Daphniphyllum alkaloids with unprecedented skeletons, namely paxdaphnines A (1) and B (2), have been isolated from the seeds of Daphniphyllum paxianum. Paxdaphnine A (1) is a 19-nor-Daphniphyllum alkaloid with highly caged skeleton, and paxdaphnine B (2) is the first 1,19-bisnor-Daphniphyllum alkaloid. The relative structures of 1 and 2 were elucidated by spectral methods, and their unique biosynthetic pathway postulated. The absolute structure of 1 was determined by X-ray diffraction of the iodide derivative (1a) of 1, and the absolute stereochemistry of 2 was proposed by correlation with the biosynthetic pathway for 1.     

Ligustolide A and B, two novel sesquiterpenes with rare skeletons and three 1,10-seco-guaianolide derivatives from Achillea ligustica

Achillea ligustica afforded two novel sesquiterpene lactones with rare 5/6/5 skeletons, three 1,10-seco-guaianolides and a chlorine-containing sesquiterpene lactone as well as six known compounds, including two monoterpenes, two guaianolides, one eudesmane and one secocaryophyllene derivative. The structures of the compounds were elucidated by extensive application of one- and two-dimensional NMR spectroscopy.     

Trigonoines A and B, two novel alkaloids from the leaves of Trigonostemon lii

Two novel alkaloids, trigonoine A containing a 2,8-diazabicyclo[3.3.1]nonane ring system and trigonoine B formed by a combination of a 2,3-dihydroquinolin-4-one and 3H-pyrrolo[2,3-c]quinoline rearranged from β-carboline skeleton were isolated from the leaves of Trigonostemon lii. Their structures were elucidated by 1D and 2D NMR spectroscopic methods.     

Agariblazeispirols A and B, an unprecedented skeleton from the cultured mycelia of the fungus, Agaricus blazei

Agariblazeispirols A and B, which have a unique steroidal skeleton, have been isolated from the cultured mycelia of Agaricus blazei (Agaricaceae). The absolute structure of Agariblazeispirol A was established to be (20S,22R,23R,24S)-13β,22:22,25-diepoxy-5-methoxy-14β-methyl-18-nor-des-A-ergosta-5,7,9,11-tetraen-23-ol by extensive 1D and 2D NMR spectral data, and X-ray analysis. The structure of Agariblazeispirol B was elucidated to be a stereoisomer of agariblazeispirol A at its carbon 22, (20S,22S,23R,24S)-13β,22:22,25-diepoxy-5-methoxy-14β-methyl-18-nor-des-A-ergosta-5,7,9,11-tetraen-23-ol by comparison of extensive 1D and 2D NMR spectral data with those of agariblazeispirol A. Both compounds showed a moderate circumvention of drug resistance on mouse leukemia P388/VCR cells.     

Saikachinoside A, a novel 3-prenylated isoguanine glucoside from seeds of Gleditsia japonica

A new isoguanine glucoside designated saikachinoside A has been isolated from the seeds of Gleditsia japonica. The structure was determined as 7-β-d-glucopyranosyl-3-[(Z)-4-hydroxy-3-methyl-2-butenyl]isoguanine by interpretation of the spectroscopic data and was confirmed by X-ray crystallographic analysis. Saikachinoside A accelerated acetylcholinesterase activity.     

Two novel diterpenoids from Isodon rubescens var. lushanensis

Two novel diterpenoids, luanchunins A (1) and B (2), along with their precursor, kamebakaurin (3), had been isolated from the stems and leaves of Isodon rubescens var. lushanensis. Their structures were elucidated on the basis of extensive spectroscopic analyses. Compounds 1 and 2 showed potent cytotoxic activity against HL-60 with IC₅₀ values of 4.81 μM and 3.52 μM, respectively. Plausible pathways for the biosynthesis of 1 and 2 were also postulated.     

Rapulasides A and B: two novel intermolecular rearranged biiridoid glucosides from the roots of Heracleum rapula

Two novel intermolecular rearranged biiridoid glucosides, rapulasides A and B (1 and 2), have been isolated from the roots of Heracleum rapula. Their structures were identified by extensive spectral analysis especially different NMR techniques. NOESY experiment, with the help of Dreiding molecular model, was used to elucidate their relative stereochemistry. Both compounds were tested for their inhibitory effects on rabbit platelet aggregation induced by PAF, ADP, or AA, respectively. Only trends of inhibition were observed for them.     

Hupermine A,a novel C16N2-type Lycopodium alkaloid from Huperzia phlegmaria

A novel C₁₆N₂-type Lycopodium alkaloid consisting of a quinolizidine with a 6-dimethylaminohexyl side chain, hupermine A (1), was isolated from the club moss of Huperzia phlegmaria, and the structure and relative stereochemistry were elucidated on the basis of spectroscopic data.     

Gloriosaols A and B, two novel phenolics from Yucca gloriosa: structural characterization and configurational assignment by a combined NMR-quantum mechanical strategy

Gloriosaols A (1) and B (2), two novel phenolic derivatives characterized by unusual spirostructures made up of two C₁₅ units linked via a γ-lactone to a central stilbenic portion were isolated from the roots of Yucca gloriosa. On the basis of an extensive NMR analysis, the same basic structure was established for the two compounds but no further information about their structural difference could be deduced. Thus two hypotheses were formulated: (1) gloriosaols A and B could be atropisomers caused by a restriction of the free rotation around the double bond due to a steric congestion of the bulky phenolic portions; (2) gloriosaols A and B could be two configurational isomers, indicating, in this case, a nonstereoselective biogenetic formation of the stereogenic center C-2. Semi-empirical calculations of the potential energy surfaces on gloriosaols A and B, together with the ¹H NMR spectra recorded at various temperatures, allowed us to unambiguously exclude the hypothesis of two restricted rotational conformers of a single configurational isomer. Finally, quantum mechanical calculations of the geometries and of the ¹H chemical shifts on the gloriasols A and B in combination with the analysis of the ROE data allowed us to deduce a diastereomeric relation between the two compounds and to assess the relative configuration of the two diastereomers.     

Panaxfuraynes A and B, two new tetrahydrofuranic polyacetylene glycosides from Panax ginseng C. A. Meyer

Panaxfurayne A (1), a tetrahydrofuranic polyacetylene glycoside, was isolated from the roots of Panax ginseng C. A. Meyer (Araliaceae) together with panaxfurayne B (2) as a geometric isomer of 1. The chemical structures of these two compounds were ascertained by UV, Mass, 1D, and 2D NMR experiments. During these experiments, these tetrahydrofuranic polyacetylene compounds proved to be of biogenetically novel type.