Reglucosylation of the Benzoxazinoid DIMBOA with Inversion of Stereochemical Configuration is a Detoxification Strategy in Lepidopteran Herbivores

Benzoxazinoids are chemical defenses against herbivores and are produced by many members of the grass family. These compounds are stored as stable glucosides in plant cells and require the activity of glucosidases to release the corresponding toxic aglucones. In maize leaves, the most abundant benzoxazinoid is (2R)‐DIMBOA‐Glc, which is converted into the toxic DIMBOA upon herbivory. The ways in which three Spodoptera species metabolize this toxin were investigated. (2S)‐DIMBOA‐Glc, an epimer of the initial plant compound, was observed in the insect frass, and the associated glucosyltransferase activity was detected in the insect gut tissue. The epimeric glucoside produced by the insect was found to be no longer reactive towards plant glucosidases and thus cannot be converted into a toxin. Stereoselective reglucosylation thus represents a detoxification strategy in Spodoptera species that might help to explain their success as agricultural pests on benzoxazinoid‐containing crops.     

Isolation and Total Synthesis of Kirkamide,an Aminocyclitol from an Obligate Leaf Nodule Symbiont

The new C₇N aminocyclitol kirkamide ( 1 ) was isolated from leaf nodules of the plant Psychotria kirkii by using a genome‐driven ¹H NMR‐guided fractionation approach. The structure and absolute configuration were elucidated by HRMS, NMR, and single‐crystal X‐ray crystallography. An enantioselective total synthesis was developed, which delivered kirkamide ( 1 ) on a gram scale in 11 steps and features a Ferrier carbocyclization and a Pd‐mediated hydroxymethylation. We propose that kirkamide is synthesized by Candidatus Burkholderia kirkii, the obligate leaf symbiont of Psychotria kirkii. Kirkamide ( 1 ) was shown to be toxic to aquatic arthropods and insects, thus suggesting that bacterial secondary metabolites play a protective role in the Psychotria/Burkholderia leaf nodule symbiosis.     

Polar constituents of <Emphasis Type="Italic">Ligustrum vulgare</Emphasis> L. and their effect on lipoxygenase activity

The present work summarizes results of isolation and identification of polar constituents of the methanolic extract of Ligustrum vulgare L. leaves and of the evaluation of inhibiting activity of selected isolates on rat lung cytosol fraction lipoxygenase. Six different compounds were isolated from the ethylacetate and butanol portions of the methanolic extract (hydroxytyrosol and its glucoside, ligustroflavon, oleuropein, acteoside, echinacoside). The inhibitory activity of oleuropein, echinacoside and the water infusion of Ligustrum vulgare leaves tested on LOX was expressed as IC₅₀. Kinetic parameters (K _M, V _max) and type of inhibition were determined. As the most effective in competitive inhibition of LOX, oleuropein was proved.     

Isolation and Total Synthesis of Kirkamide,an Aminocyclitol from an Obligate Leaf Nodule Symbiont

The new C₇N aminocyclitol kirkamide ( 1 ) was isolated from leaf nodules of the plant Psychotria kirkii by using a genome‐driven ¹H NMR‐guided fractionation approach. The structure and absolute configuration were elucidated by HRMS, NMR, and single‐crystal X‐ray crystallography. An enantioselective total synthesis was developed, which delivered kirkamide ( 1 ) on a gram scale in 11 steps and features a Ferrier carbocyclization and a Pd‐mediated hydroxymethylation. We propose that kirkamide is synthesized by Candidatus Burkholderia kirkii, the obligate leaf symbiont of Psychotria kirkii. Kirkamide ( 1 ) was shown to be toxic to aquatic arthropods and insects, thus suggesting that bacterial secondary metabolites play a protective role in the Psychotria/Burkholderia leaf nodule symbiosis.     

Sequential Baylis-Hillman/RCM protocol for the stereoselective synthesis of (+)-MK7607 and (+)-streptol

Sequential Baylis-Hillman/ring-closing metathesis (RCM) approach toward the total synthesis of (+)-MK7607 and (+)-streptol starting from (R,R)-tartaric acid is reported.     

A new triterpenoid glucoside from Leucas zeylanica

Abstract

A new triterpenoid glucoside, leuctriterpencoside (1), along with two known compounds (2–3) were isolated from Leucas zeylanica. The structure of the new compound was elucidated using comprehensive spectroscopic methods. Compound 1 showed significant inhibitory activity against α-glucosidase (IC₅₀ value of 0.85?±?0.12?μM).     

Antifungal activity of Annona coriacea Mart. ethanol extracts against the aetiological agents of cryptococcosis

Cryptococcosis is an opportunistic disease with a worldwide distribution. This disease is caused by fungi of the genus Cryptococcus, and its treatment is limited to several antifungals. In this study, the antifungal, cytotoxic and mutagenic properties of ethanol extracts from the bark and leaves of Annona coriacea were evaluated against the standard Cryptococcus species and clinical yeast specimens. Both extracts of A. coriacea showed inhibitory activity of 1.5 mg/mL for all of the yeasts tested. The number of viable cells at the lowest tested concentration was 0.187 mg/mL. The extracts that were tested showed inhibitory activity and reduced the fungal growth of the Cryptococcus gattii species and Cryptococcus neoformans species complexes, suggesting that this plant may be an effective alternative treatment for cryptococcosis.     

An Efficient Total Synthesis of (2E,4E,7R)-Farnesa-2,4,10-triene from (R)-(+)-Citronellal

(2E,4E,7R)-farnesa-2,4,10-triene(Caparratriene) ( 1 ), a novel sesquiterpene hydrocarbon with significant growth inhibitory activity against CEM leukemia cells, was first synthesized from (R)-(+)-citronellal ( 2 ) by employing titanium-induced intermolecular carbonyl-coupling as the key step. The absolute configuration of (+)-Caparratriene was determined to be 7R.     

A new β-tetralonyl glucoside from the Santalum album derived endophytic fungus Colletotrichum sp. GDMU-1

A new β-tetralonyl glucoside, methylberchemiaside (1), along with five known compounds (2–6) were isolated from a fungus Colletotrichum sp. GDMU-1 derived from the leaves of Santalum album. Their structures were determined by detailed analysis of spectroscopic data. All compounds were tested for the inhibitory effects on the nitric oxide (NO) production in lipopolysaccharide (LPS)-treated RAW264.7 cells. Among them, compounds 4 and 5 showed moderate anti-inflammatory activity with IC₅₀ value of 30.4 and 8.9 μM, respectively.     

Abeliaside,a new phenolic glucoside from Abelia triflora

A new phenolic glucoside, abeliaside, along with four known compounds, 5,6,7,4′-tetrahydroxy flavones, caffeic acid, 4-O-caffeoylquinic acid and caffeic acid glucoside, was isolated from the leaves of Abelia triflora R. Br. (Caprifoliaceae). The structure of the new compound was elucidated by different spectroscopic techniques. Compounds 1–5 were assayed for their anticancer activities against two cancerous human cell lines, MCF-7 and PC-3 cells, and normal Vero cell line using the crystal violet staining method. From the results it could be seen that caffeic acid possessed the highest anticancer effect against MCF-7 (IC₅₀: 17 μg/mL) and PC-3 (IC₅₀: 20.1 μg/mL) compared to vinblastine sulphate as reference drug (IC₅₀: 4.6, 2.8 μg/mL). The other compounds showed weak anticancer activity on both cell lines.     

Purification and characterization of two grandiuvarones from Desmos chinensis leaves and their antimicrobial activities

Abstract

A novel aromatic compound, grandiuvarone B (5-acetoxy-3-benzoyloxymethyl-5H-oxepin-4-one), along with a known compound grandiuvarone A (5-acetoxy-6-benzoyloxymethyl-5H-oxepin-4-one) were isolated from methanol extracts of Desmos chinensis leaves. Their structures were determined by various spectroscopic techniques including nuclear magnetic resonance (NMR), high-resolution electrospray ionisation mass spectrometry (HR-ESI-MS) and circular dichroism (CD). Grandiuvarone A and grandiuvarone B are isomers and the S configuration of grandiuvarone B was reported for the first time. We then determined their antifungal activity against Aspergillus flavus. Results revealed that grandiuvarone B exhibited better antifungal activity against A. flavus, with MIC values of 0.01?mg/mL compared to grandiuvarone A (MIC values of 0.02?mg/mL). In the presence of each active compound at 160?μg/g of aquafeed, A. flavus growth was completely inhibited. Grandiuvarone B also showed antibacterial activity against the plant pathogen Ralstonia solanacearum.     

Antimicrobial activities,toxicity and phenolic composition of Asphodeline anatolica E. Tuzlaci leaf extracts from Turkey

The antimicrobial activity of acetone, methanol and aqueous extracts of Asphodeline anatolica E. Tuzlaci leaves was evaluated against American type culture collection, food and clinical isolates (Listeria monocytogenes and Staphylococcus aureus including methicillin-resistant strains-MRSA). Biofilm formation, toxicity and characterisation of the polyphenolic content were analysed. The acetone extract demonstrated a higher antibacterial activity against S. aureus including MRSA strains, L. monocytogenes and Pseudomonas aeruginosa than against other extracts. No effect was observed in biofilm formation. The extracts resulted non-toxic against Artemia salina Leach. The phytochemical screening of extracts indicated that they mainly contained six polyphenols identified as catechin 3-O-gallate, protocatechuic acid, diosmin, rutin, cirsimaritin and kaempferol glucoside. This study is the first report on antimicrobial activity and phenolic content of A. anatolica and contributes to enrich the literature data on the biological properties of this plant. A. anatolica leaves have a potential as source of natural antimicrobial compounds.     

A new bibenzyl derivative with nuclear factor-kappaB inhibitory activity from Schefflera arboricola (Araliaceae)

A new bibenzyl derivative (1), 4-acetoxy-3,5,3′,4′-tetramethoxybibenzyl, along with eight known compounds (2–9), was isolated from the twigs and leaves of Schefflera arboricola (Araliaceae). The isolated compounds were elucidated mainly by means of one-dimensional, two-dimensional NMR and MS, and by comparison with the literature data. Compounds 2–5 and 7–9 are first reported from this plant. In the in vitro assays, compound 1 displayed moderate nuclear factor-kappaB inhibitory activity.     

Isolation and structure elucidation of secoiridoid glucosides from <Emphasis Type="Italic">Fraxinus rhynchophylla</Emphasis> leaves

A new secoiridoid glucoside, oleuropein-4″-methyl ether, was isolated, together with two known secoiridoid glucosides, ligstroside and oleuropein, from the leaves of Fraxinus rhynchophylla Hance by repeated column chromatography over Sephadex LH-20. The structure of the new compound has been characterized on the basis of spectroscopic evidence.     

(+)‐N‐Formylnorglaucine Rotamers from Unonopsis stipitata Diels

(+)‐N‐formylnorglaucine ( 1 ), an aporphine alkaloid containing a formyl group linked to the heterocyclic nitrogen, was isolated from the leaves of Unonopsis stipitata, an Amazon medicinal plant. The chemical structure was characterized based on 1D‐ and 2D‐NMR spectroscopy and HR‐ESI‐MS. NMR spectra revealed that 1 is composed of two rotamers ( 1a and 1b ) in a ratio of approximately 2:1. In addition, the fragmentation behavior of 1 displayed an unusual fragmentation pattern compared to regular aporphine alkaloids. Thus, this compound is reported for the first time as a natural product in this study.     

Unusual sesquiterpene glucosides from Amaranthus retroflexus

Implementing the phytochemical study of the weed Amaranthus retroflexus, four new sesquiterpene glucosides were isolated from the methanolic extract of the plant. The structures of these metabolites are determined on the basis of the mass spectrometry, and 1D and 2D NMR spectroscopies (DQ-COSY, TOCSY, HSQC, HSQC-TOCSY, HMBC, and NOESY). Two compounds are characterized by a new aglycone and differed from the site of glucosylation. The other two compounds are dimeric diastereoisomers.All the glucoside sesquiterpenes were tested on the wild species Taraxacum officinale to evaluate the role of this weed in the habitat and on the seed of A. retroflexus to verify the potential autotoxic effect of the plant.     

Enzymatic Synthesis of Novel Bavachinin Glucoside by UDP‐glycosyltransferase

Bavachinin, a member of the flavanone subclass of flavonoids, has long been considered to have various biological activities. Here, the synthesis of novel bavachinin glucoside by the in vitro glycosylation reaction was successfully achieved using a UDP‐glucosyltransferase YjiC, from Bacillus licheniformis DSM‐13. The chemical structure of bavachinin glucoside was characterized based on spectroscopic techniques as bavachinin‐4′‐O‐ß‐D‐glucopyranoside ( 1 ). The water‐solubility of bavachinin‐4′‐O‐ß‐D‐glucopyranoside was found to be 9.96 μM, about 10 times higher than bavachinin. In addition, compound 1 showed moderate anti‐proliferative activity against four human tumor cell lines, with IC₅₀ values ranging from 48.5 to 61.4 μM.     

Structure of Globularidin: An Unusual Iridoid Glucoside from Globularia alypumL.

A novel iridoid glucoside, named globularidin, lacking the typical double bond between C(3) and C(4), has been isolated from the whole plant of Globularia alypum by the combination of open column- and high-performance liquid chromatography. The structure of this compound was established by chemical transformation and spectral data.     

Inhibition of Beta-Lactamase by 1,4-Naphthalenedione from the Plant <Emphasis Type="Italic">Holoptelea integrifolia</Emphasis>

The most important mechanism of the beta-lactam antibiotic resistance is the destruction of the antibiotics by the enzyme beta-lactamase. Use of beta-lactamase inhibitors in combination with antibiotics is one of the successful antibacterial strategies. The inhibitory effect of a phytochemical, 1,4-naphthalenedione, isolated from the plant Holoptelea integrifolia on beta-lactamase is reported here. This compound was found to have a synergistic effect with the antibiotic amoxicillin against a resistant strain of Staphylococcus aureus. The enzyme was purified from the organism and incubated with the compound. An assay showed that the compound can inhibit the enzymatic activity of beta-lactamase. Modeling and molecular docking studies indicated that the compound can fit into the active site of beta-lactamase. Hence, the compound can serve as a potential lead compound for the development of effective beta-lactamase inhibitor that can be used against beta-lactam-resistant microbial strains.     

Improved synthesis,X-ray structure,and antifungal activity of a sugar-psoralen conjugate: 4,4′-Dimethylxanthotoxol 2,3,4,6-tetra-O-Acetyl-β-D-glucoside

An improved synthesis for 4,4′-dimethylxanthotoxol 2,3,4,6-tetra-O-acetyl-β-D-glucoside (1) starting from resorcinol was developed. Crystallographic analysis of glucoside 1 indicated that the dihedral angles between the mean planes of the tricyclic ring system of adjacent molecules was 54.820(22)° probably due to the steric hindrance caused by the bulky O-glucoside moiety, which prevents the molecules from packing via π···π stacking between the tricyclic cores. The antifungal screening data revealed that glucoside 1 had higher inhibition than its parent compound 4,4′-dimethylxanthotoxol and azoxystrobin against Rhizoctonia solani, Pyricularia grisea, and Alternaria alternate Japanese pear pathotype, with the inhibitory rates of 75.4, 65.7 and 70.1%, respectively, at the 50?µg/mL concentration.