Isolation and synthesis of a dimeric dihydrochalcone from Agapanthus africanus

A new dimeric dihydrochalcone, rel-(1β,2α)-di-(2,4-dihydroxybenzoyl)-rel-(3β,4α)-di-(4-hydroxyphenyl)-cyclobutane, accompanied by its apparent precursor, the known chalcone isoliquiritigenin, have been isolated from the roots of Agapanthus africanus (Liliaceae). The structure is based on spectroscopic methods including extensive NMR analyses, mass spectrometry and circular dichroism. Conclusions regarding the structure and relative configuration are supported by synthesis of the dimeric dihydrochalcone via a pericyclic [_π2_s + _π2_s] photocyclo-addition of the corresponding chalcone and consideration of the molecular symmetry involved.     

Miscellaneous terpenoid constituents of Abies nephrolepis and their moderate cytotoxic activities

Three monoterpenoids and two triterpenoids were isolated from Abiesnephrolepis together with 53 known terpenoids. The structures of the compounds were established by 1D and 2D NMR spectroscopy. The absolute configuration of 3-hydroxycamphane-2-carboxylic acid was established as (1S,2R,3S,4R) by Cu-Kα X-ray crystallography. All 58 isolates were tested for cytotoxic activity against four tumor cells viz. A549 (human lung adenocarcinoma), Colo205 (colon adenocarcinoma), QGY-7703 (human hepatoma) and THP-1 (human monocytic leukemia). α-Cadinol exhibited the best effects on A549, Colo205 and QGY-7703 with IC₅₀ values of 8.6, 8.1 and 4.6 μg/mL, respectively.     

Dibenzocyclooctadiene lignans from Kadsura philippinensis

Lignans with the dibenzocyclooctadiene skeleton, kadsuphilols I-L, and one C₁₉-homolignan, kadsuphilol M, were isolated by chromatographic fractionation of an ethyl acetate extract of the aerial parts of Kadsura philippinensis. Their structures were elucidated through extensive spectroscopic methods, including HRESIMS and 2D NMR experiments (HMQC, COSY and HMBC). The stereochemistry at the chiral centers and the biphenyl moist, were determined using NOESY, as well as analysis of CD spectra, respectively. The relative configuration of heteroclitin J was confirmed by single crystal X-ray crystallographic analysis. The in vitro radical-scavenging activities of these compounds by using DPPH were evaluated.     

Antibacterial endiandric acid derivatives from Beilschmiedia anacardioides

Three endiandric acid derivatives, beilschmiedic acids A, B and C were isolated from the stem bark of Beilschmiedia anacardioides together with the known β-sitosterol. Their structures were established by means of modern spectroscopic techniques. The relative configuration of compound 1 was determined by single crystal X-ray analysis. The antibacterial activities of compounds A,B,C were evaluated in vitro against five strains of microbes. Compound C showed strong activity against Bacillus subtilis, Micrococcus luteus and Streptococcus faecalis (MICs below 23 μM). This Compound was more active than the reference antibiotic ampicillin against B. subtilis and M. luteus.     

Antimycobacterial dihydronaphthalenone from the endophytic fungus Nodulisporium sp. of Antidesma ghaesembilla

Two new dihydronaphthalenones (1, 2) with four known compounds (3–6) were isolated as secondary metabolites of the endophytic fungus Nodulisporium sp. from Antidesma ghaesembilla. Their chemical structures were established based on 1D and 2D NMR spectroscopic data and HR-ESI–MS analyses. The relative configuration of 2 was confirmed by single crystal X-ray crystallographic analysis. A new isofuranonaphthalenone 2 displayed antimycobacterial and antimalarial activities with IC₅₀ values of 3.125 and 11.3 μg/mL, respectively.     

Withanolides from Withania aristata and their cytotoxic activity

Seven new withanolides (1-7), along with three known ones (8-10), were isolated from the leaves of Withania aristata. Their structures were elucidated on the basis of spectroscopic analysis, including 2D NMR experiments and spectrometric techniques, and the absolute configuration of 1 and 2 was established by CD analysis. In the search for new cytotoxic compounds from Withania species, the isolated compounds 1-9, along with two derivatives, were assayed for their cytotoxicity against HeLa, MCF-7 and A-549 human tumor cell lines. Derivative (4S,20R,22R)-27-acetoxy-4-p-bromobenzoyloxy-1-oxo-witha-2,5,16,24-tetraenolide (13) showed cytotoxicity against all the cell lines assayed with IC₅₀ values ranging from 2.8 to 3.6 μM, and (4S,20R,22R)-4,27-diacetoxy-4-hydroxy-1-oxo-witha-2,5,16,24-tetraenolide (12) exhibited an IC₅₀ value of 5.4 μM on the MCF-7 cell line.     

Research of the (E/Z)-isomerization of carotenoids in Pécs since the 1970s

Geometrical configuration of the polyene chain of approximately 40 mono- and di-cis carotenoids was determined from 1970 through 1990. Subsequently, the kinetic, equilibrium and thermodynamic parameters (k, K, A, E_A, ΔH^#, ΔG^#, ΔS^#) of the reversible thermal isomerization of several symmetrical and unsymmetrical carotenoids were calculated. The rate of the iodine-catalyzed photoisomerization of (all-E)-, (9Z)- and (13Z)-zeaxanthin was compared and the ‘specific rate’ (per unit light energy at given wavelengths) of the iodine-catalyzed photoisomerization for several (13Z)-carotenoids was investigated. As the missing links of the biosynthetic pathway of paprika-carotenoids, carotenoids containing new end groups were isolated; their sterically unhindered mono-cis isomers were also prepared and their geometrical configuration was determined. The investigation concentrated on the substrate specificity of the enzyme violaxanthin-deepoxidase, the light-induced formation of (13Z)-violaxanthin in green leaves, the binding of xanthophylls to the bulk light-harvesting complex (LHC) of photosystem II in higher plants, the biochemical basis of color as an aesthetic quality in Citrus-fruits and the (9Z)-epoxycarotenoid cleavage enzyme activity for ABA biosynthesis. Recently (9Z)-capsanthin-5,6-epoxide and capsoneoxanthin, two novel carotenoids have been isolated from natural sources.     

Lanostane-triterpenoids from the fungus Phellinus gilvus

Triterpenoids gilvsins A-D (1-4), with oxygenated lanostane skeletons, were isolated from the fruiting body of Phellinus gilvus, together with two known compounds, 24-methylenelanost-8-ene-3β, 22-diol and 5α-ergosta-7,22-diene-3-one. The structures of 1-4 were deduced from analysis of spectroscopic data. The absolute configuration at C-22 of 1 was determined by the modified Mosher’s method and the structure of 1 was confirmed by X-ray analysis. The hypoglycemic activities of the crude extract of P. gilvus and the isolated compounds were also evaluated, but were not promising for further investigation.     

Iridoids from leaves of Gelsemium elegans

Six iridoids, geleganoids, designated A-F, and five iridoid glycosides, geleganosides A and B together with three previously reported compounds, were isolated from leaves of Gelsemium elegans. Their structures were elucidated by spectroscopic and chemical analyses. The relative configuration of geleganoid A was confirmed by X-ray crystallographic diffraction analysis, and the absolute configuration of geleganoid B was determined by a modified Mosher’s method. Selected compounds were evaluated for PC12 cell neurite outgrowth activity, but they were inactive.     

Two pairs of new dihydrobenzophenanthridine alkaloid isolated from the root of Macleaya cordata

Two pairs of dihydrobenzophenanthridine alkaloid, named (±)(S)-6-((R)-1-hydroxyethy) dihydrochelerythrine (1a, 1b) and (±)(S)-6-((R)-1-hydroxyethyl)dihydro-sangunarine (2a, 2b) were isolated from the root of Macleaya cordata. Their chemical structures were elucidated by analysis of the spectroscopic data including one-dimensional (1D) and two-dimensional (2D) NMR spectra, and were further confirmed by X-ray crystallographic analysis.     

Isochroman and isocoumarin derivatives from hypersaline lake sediment-derived fungus Penicillium sp.

Chromatographic analysis of the ethyl acetate extract of the fungus Penicillium sp., which was isolated from the sediment of the hyper saline lake Wadi El-Natrun in Egypt, afforded two new isochromans (1 and 2) and a new isocoumarin derivative (3), along with six known compounds (4–9). The planar structures of new compounds were unequivocally elucidated on the basis of extensive 1D- and 2D-NMR spectroscopy as well as HRESIMS. The relative configurations of the new compounds were established by analysis of the coupling constants as well as through ROESY experiments, while the absolute configurations were determined by comparison of the [α]_D values and by plausible biosynthetic considerations. Compounds (1–6) were found to share (3S) configuration. All compounds demonstrated a weak to moderate cytotoxic activity against the murine lymphoma L5178Y cell line.     

Cytotoxic activity of acetogenins and styryl lactones isolated from Goniothalamus undulatus Ridl. root extracts against a lung cancer cell line (COR-L23)

An investigation of the chemical constituents in a dichloromethnae extract of Goniothalamus undulatus root led to the isolation of three known styryl lactones (5-acetoxyisogoniothalamin oxide, O-acetylaltholactone and altholactone), and four known annonaceous acetogenins (annonacin, cis-annonacin, goniothalamicin and cis-goniothalamicin). These compounds were subjected to a sulphorhodamine B (SRB) cytotoxicity assay against human large cell lung carcinoma (COR-L23), and normal human fetal fibroblast (MRC-5), cell lines. The isolated acetogenins showed higher cytotoxic activity against COR-L23 compared to the styryl lactones, with IC₅₀ values in the range of 0.5-1.7 μM and 7.4-15.4 μM, respectively. A similar pattern of cytotoxicity was also observed against the other cell line (MRC-5); acetogenins IC₅₀ values were in the range of 11.8-31.4 μM, and those for styryl lactones were in the range of 48.7-102.8 μM. This is the first report of a bioassay-guided isolation of chemical constituents from G. undulatus and on cytotoxic studies of the isolated compounds using these particular lung cancer cell lines.     

Molecular cloning and biochemical characterization of a myotoxin inhibitor from Bothrops alternatus snake plasma

Phospholipases A₂ (PLA₂s) are important components of Bothrops snake venoms, that can induce several effects on envenomations such as myotoxicity, inhibition or induction of platelet aggregation and edema. It is known that venomous and non-venomous snakes present PLA₂ inhibitory proteins (PLIs) in their blood plasma. An inhibitory protein that neutralizes the enzymatic and toxic activities of several PLA₂s from Bothrops venoms was isolated from Bothrops alternatus snake plasma by affinity chromatography using the immobilized myotoxin BthTX-I on CNBr-activated Sepharose. Biochemical characterization of this inhibitory protein, denominated αBaltMIP, showed it to be a glycoprotein with Mr of ∼24,000 for the monomeric subunit. CD spectra of the PLA₂/inhibitor complexes are considerably different from those corresponding to the individual proteins and data deconvolution suggests that the complexes had a relative gain of helical structure elements in comparison to the individual protomers, which may indicate a more compact structure upon complexation. Theoretical and experimental structural studies performed in order to obtain insights into the structural features of αBaltMIP indicated that this molecule may potentially trimerize in solution, thus strengthening the hypothesis previously raised by other authors about snake PLIs oligomerization.     

Nitrification expanded: discovery,physiology and genomics of a nitrite-oxidizing bacterium from the phylum Chloroflexi

Nitrite-oxidizing bacteria (NOB) catalyze the second step of nitrification, a major process of the biogeochemical nitrogen cycle, but the recognized diversity of this guild is surprisingly low and only two bacterial phyla contain known NOB. Here, we report on the discovery of a chemolithoautotrophic nitrite oxidizer that belongs to the widespread phylum Chloroflexi not previously known to contain any nitrifying organism. This organism, named Nitrolancetus hollandicus, was isolated from a nitrifying reactor. Its tolerance to a broad temperature range (25–63 °C) and low affinity for nitrite (K_s=1 mℳ), a complex layered cell envelope that stains Gram positive, and uncommon membrane lipids composed of 1,2-diols distinguish N. hollandicus from all other known nitrite oxidizers. N. hollandicus grows on nitrite and CO₂, and is able to use formate as a source of energy and carbon. Genome sequencing and analysis of N. hollandicus revealed the presence of all genes required for CO₂ fixation by the Calvin cycle and a nitrite oxidoreductase (NXR) similar to the NXR forms of the proteobacterial nitrite oxidizers, Nitrobacter and Nitrococcus. Comparative genomic analysis of the nxr loci unexpectedly indicated functionally important lateral gene transfer events between Nitrolancetus and other NOB carrying a cytoplasmic NXR, suggesting that horizontal transfer of the NXR module was a major driver for the spread of the capability to gain energy from nitrite oxidation during bacterial evolution. The surprising discovery of N. hollandicus significantly extends the known diversity of nitrifying organisms and likely will have implications for future research on nitrification in natural and engineered ecosystems.     

Cyanogenic and non-cyanogenic pyridone glucosides from Acalypha indica (Euphorbiaceae)

Seven cyanopyridone derivatives and one corresponding seco compound have been isolated from a methanolic extract of the inflorescences and leaves of Acalypha indica L. (Euphorbiaceae). The absolute configuration of the main cyanogenic glucoside acalyphin, (−)-(5R,6S)-5-cyano-5-β-d-glucopyranosyloxy-6-hydroxy-4-methoxy-1-methyl-2(5,6-dihydro)-pyridone, was deduced from an X-ray crystallographic study. In addition, the 6R-epimer of acalyphin, epiacalyphin, and the corresponding pair of N-demethyl derivatives were isolated. The corresponding amide of acalyphin and a 1′,2′-glucosyl-fused epiacalyphin amide were isolated from air-dried material. Structural elucidation was performed by means of ¹H and ¹³C NMR-spectra, chiroptical methods such as CD-spectroscopy and optical rotation. Two further corresponding derivatives, an aromatized compound and an open-chain structure, were isolated from the aqueous phase.     

Twelve pregnane glycosides from Cynanchum atratum

Eleven new 14,15-seco-pregnane-type steroidal glycosides, cynanosides P₁-P₅, Q₁-Q₃, R₁-R₃, and a novel 12,13-seco-14,18-nor-pregnane-type steroidal glycoside, cynanoside S, were isolated from the roots of Cynanchum atratum, together with four known compounds, atratoside C, sublanceoside E₃, chekiangensoside C and cynatroside B. Their structures were determined on the basis of spectroscopic analysis and chemical evidence.     

Antibacterial activity of halogenated sesquiterpenes from Malaysian Laurencia spp

During our studies on Malaysian Laurencia species, brominated metabolites, tiomanene, acetylmajapolene B, and acetylmajapolene A were isolated from an unrecorded species collected at Pulau Tioman, Pahang along with known majapolene B and majapolene A. Acetylmajapolene A was a mixture of diastereomers as in the case of majapolene A. Tiomanene may be a plausible precursor for acetylmajapolenes B and A. In addition, three known halogenated sesquiterpenes and two known halogenated C₁₅ acetogenins were found from other two unrecorded species collected at Pulau Karah, Terengganu and Pulau Nyireh, Terengganu, respectively. Some of these halogenated metabolites showed moderate antibacterial activity against some marine bacteria.     

Grevillosides A-F: glucosides of 5-alkylresorcinol derivatives from leaves of Grevillea robusta

From a MeOH extract of leaves of Grevillea robusta, seven compounds (1-7) were isolated. One known compound (7) was identified with a benzyl glucoside, icariside F₂. The structures of the six of these, named grevillosides A-F (1-6), were elucidated on detailed inspection of one- and two-dimensional NMR spectroscopic data as glucosides of 5-alkylresorcinols.     

Isolation of n-paraffins and sec-alcohols from Isotachis japonica

Two homologous series of n-paraffins and sec-alcohols from C₂₀ to C₃₄ or C₃₅ were isolated a wax constituents of a liverwort, Isotachis japonica. In both series, odd-members were predominant compared with even-members: the ratio of the total amount of odd- to total amounts of even-members was 3·9 in the n-paraffin homologues, and 16·5 in the sec-alcohol homologues.     

Cytotoxic metabolites from the leaves of the mangrove Rhizophora apiculata

One new 8,4’-oxyneolignan (1) and one new 7,8-dihydrobenzofuranone (2), together with twenty-one known compounds (3‒23) were isolated from the methanol extract of Rhizophora apiculata leaves. The structures of new compounds, as well as their absolute configuration, were determined by a combination of spectroscopic methods and quantum chemical calculations of NMR and ECD data. All isolated compounds were evaluated for their cytotoxicity, and only 2,6-dimethoxy-1,4-benzoquinone (8) exhibited inhibitory effects against SK-LU-1, HepG2, and MCF7 cells with IC₅₀ values in the range of 8.33–14.82 μM.