Antimicrobial isopropenyl-dihydrofuranoisoflavones from Crotalaria lachnophora

BBD optimized antioxidants of Crotalaria candicans and its nanoconjugates, exert potent in vivo anti-biofilm effects against MRSA

Crotalaria genus is extensively dispersed in tropical and subtropical provinces, and it is found to harbor antioxidant flavonoids. Response surface methodology-based optimization was carried out for the purpose of efficient extraction involving a suitable solvent which can maximize the yield along with higher total phenolic content and total flavonoid content (TFC). Optimization conditions for extraction of C.candicans flavonoids (CCF) based on variables such as solvent, solid-solvent ratio and extraction temperature were evaluated. The optimized conditions were found as Solvent i.e., Aqueous-ethanol (53.42%), Solid-solvent ratio (1:15.83 w/v) and temperature (44.42 °C) and resulted to obtain the TFC as 176.23 mg QRET/g C. candicans extract with the yield 27.42 mg CCF/g (C. candicans dry weight). LC-MS analysis of CCF, revealed the presence of seven major flavonoids. The antioxidant flavonoids were further used to functionalize the zero-valent silver (ZVAgF) and copper (ZVCuF) nanoparticles. The ZVAgF and ZVCuF were investigated using UV-Vis spectrophotometry, FT-IR spectroscopy and X-ray diffractometry to confirm the presence of the zero valent metals and possible functional groups which capped the elemental metal. Further transmission electron microscopy, dynamic light scattering method and zeta-potential studies were done to understand their respective structural and morphological properties. The efficacy of the as-prepared ZVAgF/ZVCuF as antibiofilm agents on Methicillin-resistant Staphylococcus aureus (MRSA) with the mechanism studies have been explored. The MRSA-colony count from the infection zebrafish (in vivo) model, portrayed a reduction of > 1.9 fold for ZVCuF and > twofold for ZVAgF, with no alteration in liver morphology when treated with ZVAgF, implying that the nanoparticles were safe and biocompatible.

Peroxisome Proliferator Activated Receptor-γ Agonistic Compounds from the Jellyfish-Derived Fungus Cladosporium oxysporum

In our search for peroxisome proliferator-activated receptor (PPAR) agonists, five undescribed compounds, namely two acyclic diterpenes (1 and 2; cladopsol A and cladopsol B), two sesquiterpenes (3 and 4; cladopsol C and cladopsol D), and one C21-ecdysteroid (5; cladopsol E), and 15 known compounds were isolated from the jellyfish-derived fungus - Cladosporium oxysporum. The structures of the undescribed compounds were defined using UV, NMR, HR-ESI-MS, and electronic circular dichroism (ECD) spectroscopy and a modified Mosher's method. Luciferase reporter assay and docking analysis suggested that cladopsol B may function as a PPAR-γ partial agonist with a potential antidiabetic lead which may evade the side effects of full agonists. Moreover, cladopsol B stimulated glucose uptake in HepG2 cells with an efficacy comparable to that of rosiglitazone, but with less side effect induced by lipid accumulation in 3T3-L1 cells. Therefore, cladopsol B could serve as a molecular skeleton in a study of advanced antidiabetic lead with less side effect.

Spectroscopic analysis, kinetic mechanism, computational docking, and molecular dynamics of active metabolites from the aerial parts of Astragalus membranaceusBunge as tyrosinase inhibitors

A new isoflavane derivative (2), a new natural isoflavane (6), four new oleanane-type triterpenoid saponins (23, 25, 28, and 29), and twenty three known secondary metabolites (1, 3-5, 7-22, 24, 26, and 27) were isolated from the aerial parts of Astragalus membranaceus Bunge. The chemical structures of these compounds were elucidated through spectroscopic analysis and compared with those identified in previous studies. Tyrosinase inhibition ability of isolated compounds (1-29) was evaluated. Of these, compounds 3, 4, 6, and 14 exhibited inhibitory effects, with IC₅₀ values ranging from 24.6 to 59.2 μM. According to kinetic analysis, compounds 3 and 4 were non-competitive inhibitors of tyrosinase, whereas compounds 6 and 14 inhibited tyrosinase in uncompetitive and competitive modes, respectively. Molecular docking analysis identified that compounds 3, 4, and 6 could bind to allosteric sites and compound 14 could bind to the catalytic site of tyrosinase, which is consistent with the results of kinetic studies. Molecular dynamics behaviors of the active compounds in complex with tyrosinase were investigated via 60 ns simulation which demonstrated their high stability. These findings indicate that the aerial parts of A. membranaceus are a potential source of natural tyrosinase inhibitors.

Competitive CatSper Activators of Progesterone from Rhynchosia volubilis

The root Rhynchosia volubilis was widely used for contraception in folk medicine, although its molecular mechanism on antifertility has not yet been revealed. In human sperm, it was reported that the cation channel of sperm, an indispensable cation channel for the fertilization process, could be regulated by various steroid-like compounds in plants. Interestingly, these nonphysiological ligands would also disturb the activation of the cation channel of sperm induced by progesterone. Therefore, this study aimed to explore whether the compounds in R. volubilis affect the physiological regulation of the cation channel of sperm. The bioguided isolation of the whole herb of R. volubilis has resulted in the novel discovery of five new prenylated isoflavonoids, rhynchones A - E (1:  - 5: ), a new natural product, 5'-O-methylphaseolinisoflavan (6: ) (¹H and ¹³C NMR data, Supporting Information), together with twelve known compounds (7:  - 18: ). Their structures were established by extensive spectroscopic analyses and drawing a comparison with literature data, while their absolute configurations were determined by electronic circular dichroism calculations. The experiments of intracellular Ca²⁺ signals and patch clamping recordings showed that rhynchone A (1: ) significantly reduced cation channel of sperm activation by competing with progesterone. In conclusion, our findings indicat that rhynchone A might act as a contraceptive compound by impairing the activation of the cation channel of sperm and thus prevent fertilization.

Semisynthesis of prunetin, a bioactive O-methylated isoflavone from naringenin, by the sequential deacetylation of chalcone intermediates and oxidative rearrangement

Prunetin (4',5-dihydroxy-7-methoxyisoflavone) was semisynthesized in 8 steps from readily available naringenin in 26% total yield. The key reaction was chemoenzymatic sequential deacetylation to 6'-acetoxy-2',4″-dihydroxy-4'-methoxychalcone, the in situ-formed precursor for thallium(III) nitrate-mediated oxidative rearrangement.

Crotalaria spectabilis as a source of pyrrolizidine alkaloids and phenolic compounds: HPLC-MS/MS dereplication and monocrotaline quantification of seed and leaf extracts

INTRODUCTION

Crotalaria spectabilis is an important species used as a pre-plant cover for soybean crops to control the proliferation of endoparasitic nematodes. Species from the Crotalaria genus are known for presenting pyrrolizidine alkaloids (PAs) in their composition, however, C. spectabilis is still considered chemically under-explored.

OBJECTIVE

The goal of this manuscript is the development and validation of a method for PAs and flavonoids identification and quantification of C. spectabilis seeds and leaves, a toxic plant used for nematode proliferation control in soil, especially in soybean crops.

MATERIALS AND METHODS

Seeds and leaves extracts were analysed by high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) for the identification of the compounds.

RESULTS

PAs and phenolic compounds could be identified in both samples based on the MS/MS fragmentation pattern. Molecular formulas of the annotated compounds were confirmed by ultra-high-performace liquid chromatography-quadrupole time-of-flight (UHPLC-QToF), and monocrotaline could also be confirmed by standard comparison. The quantification of monocrotaline was performed by HPLC-MS/MS, resulting in 123 times higher monocrotaline content in seeds than in the leaves, which could explain its efficiency in combating nematode proliferation in soil.

CONCLUSION

This was the first report of phenolic compounds in C. spectabilis. The current study highlights the importance of C. spectabilis for nematode control due to the presence of toxic PAs, and the employment of analytical techniques for identification and quantification of compounds present in the extracts.

A New Prenylated Isoflavonoid From Limonium leptophyllum

Phytochemical investigation of methanolic extract of Limonium leptophyllum (Plumbaginaceae), led to the isolation of 1 new isoflavonoid with a rare 5-membered dihydrofuran ring (1, leptoisoflavone A) and 8 known compounds. The known isolated compounds were identified as euchrenone b9 (2), auriculasin (3), kaempferol (4), avicularoside (5), myricetin-3-arabinoside (6), trans-N-feruloyltyramine (7), trans-N-caffeoyltyramine (8), and β-sitosterol (9). The crude methanolic extract exhibited moderate activity toward endocannabinoid receptors. Auriculasin (3) showed activity toward cannabinoid receptor type 1 (86.7% displacement with IC50 8.92 μM).

Isolation of a New Homomonoterpene from Madhuca Pasquieri and Effect of Isolated Compounds on NO Production

A new homomonoterpene, l,3,3-trimethyl-7-oxabicyclo[3.1.1]hexa-9-en-10-oic acid, named madhusic acid A (1), together with ten known compounds (2-11) were isolated from the methanolic extract of the dried leaves of Madhuca pasquieri (Dubard) H. J. Lam. The structure of the new compound was elucidated on the basis of ID, 2D NMR (COSY, HMQC, and HMBC) and mass spectral analyses. We examined the effects of the isolated compounds against LPS-induced NO production in macrophage RAW264.7 cells and compound 2 showed effective activity with an IC50 value of 14.5 μM.

Eriosema (Fabaceae) Species Represent a Rich Source of Flavonoids with Interesting Pharmacological Activities

Many flavonoids have so far been isolated as main secondary metabolites in plant species of the genus Eriosema (Fabaceae), which contains approximately 160 species. A total of 52 flavonoids including isoflavones, dihydroflavonols, flavonols, flavanones, dihydrochalcones, isoflavanone and their pyrano or glucoside derivatives were isolated and characterized from the five species of this genus investigated to date. Total synthesis and semi-synthesis (acetylation, methylation, hydrogenation, and cyclization) of some isolated flavonoids were reported. Due to several significant pharmacological properties (antimicrobial, cytotoxicity, anti-mycobacterial, antioxidant, antiviral, erectile-dysfunction, vasodilatory and hypoglycemic) of the isolated flavonoids and derivatives, more scientists should be interested in investigating Eriosema species. The present review is the first to document all flavonoids that have been reported from the genus Eriosema to date together with their synthetic and semi-synthetic derivatives, and their pharmacological properties. Dihydrochalcones, which are precursors of other classes of flavonoids, are very rare in natural sources and their isolation from Eriosema species may explain the large number of flavonoids found in this genus. It appears that isoflavone could be a marker for species in this genus. The 83 flavonoids (1–83) documented include 52 isolates, 31 semi-synthetic and 3 totally synthetic derivatives. Data were obtained from Google scholar, Pubmed, Scifinder, Sciencedirect, and Scopus. With 52 different flavonoids isolated from only 5 of the approximately 160 species it shows the remarkable chemical diversity of this genus. This compilation of the biological activities and chemical composition may renew the interest of pharmacologists and phytochemists in this genus.

Crocetenone, a New Rotenoid with an Unusual trans-fused Ring System from Iris crocea

Crocetenone, a new rotenoid (1), along with five known compounds apocyanin (2), tectorigenin (3), 5,2′,3′-trihydroxy-7-methoxy flavanone (4), tectoridin (5) and tectoridin glycoside (6), were isolated from the methanolic extract of the root of Iris crocea. The structure of compounds was elucidated on the basis of 1D- and 2D-NMR spectroscopic and MS analysis. Antibacterial and antioxidant activities of compounds 1-6 were evaluated. Crocetenone (1) showed a prominent antibacterial activity.

Eriosema chinense: a rich source of antimicrobial and antioxidant flavonoids

Six prenylated flavonoids, (2R,3S)-3,5,4'-trihydroxy-6″-6″dimethylpyrano(2″,3″:7,6)-8-(3″', 3″'-dimethylallyl)flavanone, (2R,3S)-3,5,2'-trihydroxy-4'-methoxy-6″,6″-dimethylpyrano(2″,3″:7,6)-8-(3″',3″'-dimethylallyl)flavanone, (2R,3R)-3,5,2',4'-tetrahydroxy-6″,6″-dimethylpyrano(2″,3″:7,6)-8-(3″',3″'-dimethylallyl)flavanone, 3,5,2',4'-tetrahydroxy-6″,6″-dimethylpyrano(2″,3″:7,6)-8-(3″',3″'-dimethylallyl)flavone, (2R,3R,2″'R)-3,5,2″'-trihydroxy-4'-methoxy-6″,6″-dimethylpyrano(2″,3″:7,6)-8-(3″'-methylbut-3″'-enyl)flavanone, (2R,3R)-3,5-dihydroxy-4'-methoxy-6″,6″-dimethylpyrano(2″,3″:7,6)-8-(2″',3″'-epoxy-3″'-methyl butyl)flavanone, an isoflavone, 6,7-dimethoxy-5,2',4'-trihydroxyisoflavone, and octaeicosanyl-trans-p-coumarate together with 12 known compounds, were isolated from roots of Eriosema chinense. This structural elucidation was determined by spectroscopic methods. Several isolates and derivatives were evaluated for their antimicrobial and antioxidant activities. Results obtained provide additional evidence showing that the presence of both the free phenolic OH and the lipophilic prenyl groups are crucial for potent antimicrobial activity against yeast, gram positive and gram negative bacteria, whereas the presence of free phenolic OH group is required for strong radical scavenging property.

Antimicrobial activity and cytotoxicity of the ethanol extract, fractions and eight compounds isolated from Eriosema robustum (Fabaceae)

BACKGROUND

The aim of this study was to evaluate the antimicrobial activity and the cytotoxicity of the ethanol crude extract, fractions and isolated compounds from the twigs of Eriosema robustum, a plant used for the treatment of coughs and skin diseases.

METHODS

Column chromatographic and spectroscopic techniques were used to isolate and identify eight compounds, robusflavones A (1) and B (2), orostachyscerebroside A (3), stigmasterol (4), 1-O-heptatriacontanoyl glycerol (5), eicosanoic acid (6), 3-O-β-D-glucopyranoside of sitosterol (7) and 6-prenylpinocembrin (8), from E. robustum. A two-fold serial microdilution method was used to determine the minimum inhibitory concentration (MIC) against fungi and bacteria, and the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide reduction assay was used to evaluate the cytotoxicity.

RESULTS

Fraction B had significant antimicrobial activity against Aspergillus fumigatus and Cryptoccocus neoformans (MIC 0.08 mg/ml), whilst the crude extract and fraction A had moderate activity against A. fumigatus and Candida albicans (MIC 0.16 mg/ml). Fraction A however had excellent activity against Staphylococcus aureus (MIC 0.02 mg/ml), Enterococcus faecalis and Escherichia coli (MIC 0.04 mg/ml). The crude extract had significant activity against S. aureus, E. faecalis and E. coli. Fraction B had good activity against E. faecalis and E. coli (MIC 0.08 mg/ml). All the isolated compounds had a relatively weak antimicrobial activity. An MIC of 65 μg/ml was obtained with robusflavones A (1) and B (2) against C. albicans and A. fumigatus, orostachyscerebroside A (3) against A. fumigatus, and robusflavone B (2) against C. neoformans. Compound 8 had the best activity against bacteria (average MIC 55 μg/ml). The 3 fractions and isolated compounds had LC50 values between 13.20 to > 100 μg/ml against Vero cells yielding selectivity indices between 0.01 and 1.58.

CONCLUSION

The isolated compounds generally had a much lower activity than expected based on the activity of the fractions from which they were isolated. This may be the result of synergism between different compounds in the complex extracts or fractions. The results support the traditional use of E. robustum to treat infections. The crude extract had a good activity and low preparation cost, and may be useful in topical applications to combat microbial infections.

Antibacterial and antiplasmodial constituents of Beilschmiedia cryptocaryoides

Four new beilschmiedic acid derivatives, cryptobeilic acids A-D (1-4), and tsangibeilin B (5) have been isolated from the bark of Beilschmiedia cryptocaryoides collected from Madagascar. Their structures were elucidated using detailed spectroscopic and spectrometric methods. Cryptobeilic acid A (1) and tsangibeilin B (5) structures were confirmed by single-crystal X-ray diffraction analysis. Compounds 1-5 displayed moderate antibacterial activity against Escherichia coli 6r3, Acinetobacter calcoaceticus DSM 586, and Pseudonamas stutzeri A1501, with the minimum inhibitory concentrations ranging from 10 to 50 μM, respectively. In addition, the compounds exhibited antiplasmodial activity against erythrocytic stages of chloroquine-resistant Plasmodium falciparum strain NF54 and weak cytotoxicity against L6 cell lines.

On the Biosynthetic Pathway of Papaverine via (S)-Reticuline – Theoretical vs. Experimental Study

The electronic structures, optical properties and molecular structures of a series of isoquinoline alkaloids resulting in the formation of papaverine, through a proposed biosynthetic pathway via S(+)-reticuline were elucidated. The mechanism of papaverine synthesis was studied by electronic absorption, diffuse reflectance, fluorescence and CD spectroscopy, as well as ESI and MALDI Orbitrap imaging mass spectrometry. Quantum chemical DFT calculations in the gas phase and solution were performed with a view to study the electronic transitions of the interacting species, corresponding proposed intermediates, and the expected mass spectrometric fragments. The complete study and understanding of the mechanism of the biosynthetic pathway in the poppy plants appears important for the functional oriented drug-design and synthesis of corresponding structurally related alkaloids.

Physical Properties and Molecular Conformations of Indole Alkaloids and Model Protein Interactions – Theoretical vs. Experimental Study

The physical properties and molecular structure of five natural indole alkaloids (IAs) and their interaction with protein targets have been studied, experimentally and theoretically. Electronic absorption (EAs) and CD spectroscopy, electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS), as well as imaging mass spectrometric techniques (IMS) were used, analyzing the isolated alkaloids and corresponding IAs/protein molecular complexes. Theoretical quantum chemical DFT calculations were also applied. The mechanism of their biological activity and structure-activity relationship as potential neurologically active compounds were studied, using the model interactions with 5HT2A receptors. The gas-phase stable molecular fragments of the IAs are discussed comparing the experimental mass spectrometric data and theoretical quantum chemical DFT calculations of the different molecular fragments of the IAs.

Prenylated Isoflavonoids from Rhynchosia edulis

Four new prenylated isoflavones, rhynedulins A-C (1-3) and rhynedulinal (4), were isolated by bioassay-guided fractionation of the dichloromethane bark extract of Rhynchosia edulis. Five previously described compounds, scandenal, ulexin B, cajanone, cajanin, and cyclochandalone, were also isolated. These isoflavonoids showed weak inhibitory activity towards rhodesain, the major cathepsin-L like protease in Trypanosoma brucei. They also have weak antiproliferative activity towards MCF-7 cells.