Antibacterial chromene and chromane stilbenoids from Hymenocardia acida

Enhanced Anticancer Activity of Hymenocardia acida Stem Bark Extract Loaded into PLGA Nanoparticles

Hymenocardia acida (H. acida) is an African well-known shrub recognized for numerous medicinal properties, including its cancer management potential. The advent of nanotechnology in delivering bioactive medicinal plant extract with poor solubility has improved the drug delivery system, for a better therapeutic value of several drugs from natural origins. This study aimed to evaluate the anticancer properties of H. acida using human lung (H460), breast (MCF-7), and colon (HCT 116) cancer cell lines as well as the production, characterization, and cytotoxicity study of H. acida loaded into PLGA nanoparticles. Benchtop models of Saccharomyces cerevisiae and Raniceps ranninus were used for preliminary toxicity evaluation. Notable cytotoxic activity in benchtop models and human cancer cell lines was observed for H. acida crude extract. The PLGA nanoparticles loading H. acida had a size of about 200 nm and an association efficiency of above 60%, making them suitable to be delivered by different routes. The outcomes from this research showed that H. acida has anticancer activity as claimed from an ethnomedical point of view; however, a loss in activity was noted upon encapsulation, due to the sustained release of the drug.

Naturally occurring prenylated stilbenoids: food sources, biosynthesis, applications and health benefits

Prenylated stilbenoids are a unique class of natural phenolic compounds consisting of C6-C2-C6 skeleton with prenyl substitution. They are potential nutraceuticals and dietary supplements presented in some edible plants. Prenylated stilbenoids demonstrate promising health benefits, including antioxidant, anti-cancer, anti-inflammatory, anti-microbial activities. This review reports the structure, bioactivity and potential application of prenylated stilbeniods in food industry. Edible sources of these compounds are compiled and summarized. Structure-activity relationship of prenylated stilbenoids are also highlighted. The biosynthesis strategies of prenylated stilbenoids are reviewed. The findings of these compounds as food preservative, nutraceuticals and food additive are discussed. This paper combines the up-to-date information and gives a full image of prenylated stilbenoids.

Critical Review on the Chemical Aspects of Cannabidiol (CBD) and Harmonization of Computational Bioactivity Data

Cannabidiol (CBD) is a non-psychotropic phytocannabinoid which represents one of the constituents of the "phytocomplex" of Cannabis sativa. This natural compound is attracting growing interest since when CBD-based remedies and commercial products were marketed. This review aims to exhaustively address the extractive and analytical approaches that have been developed for the isolation and quantification of CBD. Recent updates on cutting-edge technologies were critically examined in terms of yield, sensitivity, flexibility and performances in general, and are reviewed alongside original representative results. As an add-on to currently available contributions in the literature, the evolution of the novel, efficient synthetic approaches for the preparation of CBD, a procedure which is appealing for the pharmaceutical industry, is also discussed. Moreover, with the increasing interest on the therapeutic potential of CBD and the limited understanding of the undergoing biochemical pathways, the reader will be updated about recent in silico studies on the molecular interactions of CBD towards several different targets attempting to fill this gap. Computational data retrieved from the literature have been integrated with novel in silico experiments, critically discussed to provide a comprehensive and updated overview on the undebatable potential of CBD and its therapeutic profile.

Computational insight into the mechanism and origin of high regioselectivity in the ring-opening cyclization of spirocyclopropanes with stabilized sulfonium ylides by the DFT

Chromanes with high bioactivity play an important role in nature, and cyclization reactions of cyclopropanes with sulfonium ylides to form chromane skeletons have attracted great attention of scientists. The mechanism as well as origins of regioselectivity and stereoselectivity for the ring-opening/cyclization reactions between cyclohexane-1,3-dione-2-spirocyclopropanes and stabilized sulfonium ylides in CH₂Cl₂ were investigated by using the density functional theory (DFT) M06-2X/6-311+G(d,p)//M06-2X/6-31G(d,p) method combined with the SMD model. The calculated results revealed that the reaction process involved two key steps: the ring-opening step and the cyclization step, with the former being the rate-determining and stereoselectivity-determining step. The regioselectivity of the ring-opening step of spirocyclopropane indicated that the tertiary carbon was more preferential than the secondary one when sulfonium ylide attacked spirocyclopropane. The theoretical results confirmed that the stereoselectivity of the reaction to form the trans-isomer product is more favorable than the cis-isomer, and the calculated trans/cis ratio is in accordance with the experiment. Moreover, the conceptual density functional theory reactivity indices suggest that the electronic effect controls the regioselectivity. What is more, the stereoselectivity analyzed by weak non-covalent interaction also shows the importance of electronic effect. Graphical Abstract.

Stilbenoids: A Natural Arsenal against Bacterial Pathogens

The escalating emergence of resistant bacterial strains is one of the most important threats to human health. With the increasing incidence of multi-drugs infections, there is an urgent need to restock our antibiotic arsenal. Natural products are an invaluable source of inspiration in drug design and development. One of the most widely distributed groups of natural products in the plant kingdom is represented by stilbenoids. Stilbenoids are synthesised by plants as means of protection against pathogens, whereby the potential antimicrobial activity of this class of natural compounds has attracted great interest in the last years. The purpose of this review is to provide an overview of recent achievements in the study of stilbenoids as antimicrobial agents, with particular emphasis on the sources, chemical structures, and the mechanism of action of the most promising natural compounds. Attention has been paid to the main structure modifications on the stilbenoid core that have expanded the antimicrobial activity with respect to the parent natural compounds, opening the possibility of their further development. The collected results highlight the therapeutic versatility of natural and synthetic resveratrol derivatives and provide a prospective insight into their potential development as antimicrobial agents.

Cannabimimetic plants: are they new cannabinoidergic modulators?

Phytochemicals and secondary metabolites able to interact with the endocannabinoid system (Cannabimimetics) have been recently described in a broad range of plants and fruits. These findings can open new alternative avenues to explore for the development of novel therapeutic compounds. The cannabinoids regulate many physiological and pathological functions in both animals and plants. Cannabis sativa is the main plant that produces phytocannabinoids inside resins capable to defend the plant from the aggression of parasites and herbivores. Animals produce anandamide and 2-arachidonoyl glycerol, which thanks to binding with main receptors such as type-1 cannabinoid receptor (CB1R) and the type-2 cannabinoid receptor (CB2R) are involved in inflammation processes and several brain functions. Endogenous cannabinoids, enzymes for synthesis and degradation of cannabinoids, and CB1R and CB2R constitute the endocannabinoid system (ECS). Other plants can produce cannabinoid-like molecules such as perrottetinene extracted from Radula perrottetii, or anandamide and 2-arachidonoyl glycerol extracted from some bryophytes. Moreover, several other secondary metabolites can also interact with the ECS of animals and take the name of cannabimimetics. These phytoextracts not derived from Cannabis sativa can act as receptor agonists or antagonist, or enzyme inhibitors of ECS and can be involved in the inflammation, oxidative stress, cancer, and neuroprotection. Finally, given the evolutionary heterogeneity of the cannabimimetic plants, some authors speculated on the fascinating thesis of the evolutionary convergence between plants and animals regarding biological functions of ECS. The review aims to provide a critical and complete assessment of the botanical, chemical and therapeutic aspects of cannabimimetic plants to evaluate their spread in the world and medicinal potentiality.

Diastereo- and Enantioselective Syntheses of Trisubstituted Benzopyrans by Cascade Reactions Catalyzed by Monomeric and Polymeric Recoverable Bifunctional Thioureas and Squaramides

4-Vinylphenyl-substituted squaramides have been tested as organocatalysts for the diastereo- and enantioselective synthesis of trisubstituted benzopyrans via an oxa-Michael intramolecular nitro-Michael cascade reaction. Both the enantio- and diastereoselection were good to moderate, depending on the nature of the chiral scaffold in the catalyst. The diastereoselection is better for the most active catalyst because the final products epimerize at C-3 along the time. Supported squaramide sq-9 prepared by copolymerization of sq-4 with styrene and divinylbenzene is also effective in promoting the cascade reaction, and it is recoverable and reusable for five cycles maintaining the activity.

Asymmetric synthesis of polysubstituted chiral chromans via an organocatalytic oxa-Michael-nitro-Michael domino reaction

A catalytic asymmetric method for the synthesis of polysubstituted chromans via an oxa-Michael-nitro-Michael reaction has been developed. The squaramide-catalyzed domino reaction of 2-hydroxynitrostyrenes with trans-β-nitroolefins produced chiral chromans with excellent enantioselectivities (up to 99% ee), diastereoselectivities (up to >20 : 1 dr), and moderate to good yields (up to 82%).

Cyclopeptide Alkaloids from Hymenocardia acida

Four cyclopeptide alkaloids (1-4) were isolated from the root bark of Hymenocardia acida by means of semipreparative HPLC with DAD and ESIMS detection and conventional separation methods. Structure elucidation was performed by spectroscopic means. In addition to the known compound hymenocardine (1), three other alkaloids were isolated for the first time from a natural source. These included a hymenocardine derivative with a hydroxy group instead of a carbonyl group that was named hymenocardinol (2), as well as hymenocardine N-oxide (3) and a new cyclopeptide alkaloid containing an unusual histidine moiety named hymenocardine-H (4). The isolated cyclopeptide alkaloids were tested for their antiplasmodial activity and cytotoxicity. All four compounds showed moderate antiplasmodial activity, with IC50 values ranging from 12.2 to 27.9 μM, the most active one being hymenocardine N-oxide (3), with an IC50 value of 12.2 ± 6.6 μM. Compounds 2-4 were found not to be cytotoxic against MRC-5 cells (IC50 > 64.0 μM), but hymenocardine (1) showed some cytotoxicity, with an IC50 value of 51.1 ± 17.2 μM.

Novel domino procedures for the synthesis of chromene derivatives and their isomerization

Novel tricyclic keto diesters have been synthesized by a one-pot three-component procedure via DABCO-catalyzed domino Knoevenagel-Michael addition reactions. Also, an efficient four-component reaction for the synthesis of another new group of tricyclic keto diesters has been developed via domino Knoevenagel-intramolecular oxo-Diels-Alder reactions. A selective thermal isomerization of the synthesized chromenes to fumarates is also described. X-ray analyses confirm unambiguously the structures of the products.

Phytocannabinoids: a unified critical inventory

Cannabis sativaL. is a prolific, but not exclusive, producer of a diverse group of isoprenylated resorcinyl polyketides collectively known as phytocannabinoids.

Highly Enantioselective Cascade Reaction Catalyzed by Squaramides: the Synthesis of CF3-Containing Chromanes

A catalytic asymmetric method for the synthesis of 2-CF3 chromanes has been described. Generally, the squaramide-catalyzed cascade reaction of 2-hydroxychalcones with β-CF3-nitroalkenes gave the CF3-containing heterocyclic compounds bearing three contiguous stereogenic centers in excellent yields, diastereoselectivities, and enantioselectivities.

Crystal structure of 1-(8-methoxy-2H-chromen-3-yl)ethanone

In the structure of the title compound, C12H12O3, the dihydropyran ring is fused with the benzene ring. The dihydropyran ring is in a half-chair conformation, with the ring O and methylene C atoms positioned 1.367 (3) and 1.504 (4) Å, respectively, on either side of the mean plane formed by the other four atoms. The methoxy group is coplanar with the benzene ring to which it is connected [Cb—Cb—Om—Cmtorsion angle = −0.2 (4)°; b = benzene and m = methoxy], and similarly the aldehyde is coplanar with respect to the double bond of the dihydropyran ring [Cdh—Cdh—Ca—Oa= −178.1 (3)°; dh = dihydropyran and a = aldehyde]. In the crystal, molecules are linked by weak methyl–methoxy C—H...O hydrogen bonds into supramolecular chains along thea-axis direction.

Characterization of antiproliferative activity constituents from Artocarpus heterophyllus

Artocarpus heterophyllus is an evergreen fruit tree cultivated in many tropical regions. Previous studies have shown that some of its compositions exhibited potential tyrosinase inhibition activities. This study indentified 8 new phenolic compounds, artoheterophyllins E-J (1-6), 4-geranyl-2',3,4',5-tetrahydroxy-cis-stilbene (7), and 5-methoxymorican M (8) and 2 new natural compounds (9 and 10), 2,3-dihydro-5,7-dihydroxy-2-(2-hydroxy-4-methoxyphenyl)-4H-benzopyran-4-one and 6-[(1S,2S)-1,2-dihydroxy-3-methylbutyl]-2-(2,4-dihydroxyphenyl)-5-hydroxy-7-methoxy-3-(3-methyl-2-buten-1-yl)-4H-1-benzopyran-4-one, together with 23 known compounds (11-33), from the ethanol extract of the wood of A. heterophyllus. The structures of the eight new compounds (1-8) and two new natural compounds were established by extensive 1D- and 2D-NMR experiments. The anticancer effects of the isolated compounds were examined in MCF-7, H460, and SMMC-7721 human cancer cell lines by MTT assay. Compounds 5, 11, 12, and 30 significantly reduced the cell viabilities of these cell lines. Especially, compounds 11 and 30 resulted in more potent cytotoxicity than the positive control, 5-fluorouracil (5-Fu), in SMMC-7721 cell line, with IC50 values of 15.85 and 12.06 μM, whereas compound 30 exhibited more potent cytotoxicity than 5-Fu in NCI-H460 cell line, with an IC50 value of 5.19 μM. In addition, this study suggests that compounds 11 and 30 from the wood of A. heterophyllus have anticancer potential via MAPK pathways.