New inhibitors of ROS generation and T-cell proliferation from Myrtus communis

The therapeutic value of Myrtus communis L.: an updated review

Myrtus communis L. (Family: Myrtaceae) is naturally found in the western part of Asia, Southern Europe, and North Africa. It has been reportedly applied in pharmaceutical industry, traditional medicine, cosmetics, spices, and food. Pubmed, Google scholar, Web of Science, and Scopus were utilized to seek out relevant content concerning the therapeutic potential of M. communis. Subsequently, we conducted a review to identity noteworthy updates pertaining to M. communis. Myrtle berries, leaves, seeds, and essential oils are natural sources of several nutrients and bioactive compounds with marked health effects. The chemical analysis showed that M. communis contained oils, alkaloids, flavonoids, phenolics, coumarins, saponosides, tannins, quinines, and anthraquinones. A pharmacological investigation revealed that M. communis possessed anti-inflammatory, analgesic, antimicrobial, antiparasitic, antioxidant, antidiabetic, anticancer, antimutagenic, immunomodulatory, dermatological, cardiovascular, central nervous system, and gastrointestinal protective effects, among numerous other biological effects. This current review focused on the biochemical, pharmacological, therapeutic effects, and various biological activities of different parts of M. communis. It signifies that M. communis is a therapeutic plant with numerous applications in medicine and could be used as a drug isolate based on its safety and effectiveness.

Oligomeric phloroglucinols with hAChE inhibitory and antibacterial activities from tropic Rhodomyrtus tomentosa

Alzheimer's diseases (AD) and other infectious diseases caused by drug-resistance bacteria have posed a serious threat to human lives and global health. With the aim to search for human acetylcholinesterase (hAChE) inhibitors and antibacterial agents from medicinal plants, 16 phloroglucinol oligomers, including two new phloroglucinol monomers (1a and 1b), four new phloroglucinol dimers (3a, 3b, 4b, and 5a), six new phloroglucinol trimers (6a, 6b, 7a, 7b, 8a, and 8b), and two naturally occurring phloroglucinol monomers (2a and 2b), along with two known congeners (4a and 5b), were purified from the leaves of tropic Rhodomyrtus tomentosa. The structures and absolute configurations of these new isolates were unequivocally established by comprehensive analyses of their spectroscopic data (NMR and HRESIMS), ECD calculation, and single crystal X-ray diffraction. Structurally, 3a/3b shared a rare C-5' formyl group, whereas 6a/6b possessed a unique C-7' aromatic ring. In addition, 7a/7b and 8a/8b were rare phloroglucinol trimers with a bis-furan and a C-6' hemiketal group. Pharmacologically, the mixture of 3a and 3b showed the most potent human acetylcholinesterase (hAChE) inhibitory activity with an IC50 value of 1.21 ± 0.16 μM. The molecular docking studies of 3a and 3b in the hAChE binding sites were performed, displaying good agreement with the in vitro inhibitory effects. In addition, the mixture of 3a and 3b displayed the most significant anti-MRSA (methicillin-resistant Staphylococcus aureus) with MIC and MBC values of both 0.50 μg/mL, and scanning electron microscope (SEM) studies revealed that they could destroy the biofilm structures of MRSA. The findings provide potential candidates for the further development of anti-AD and anti-bacterial agents.

Antiradical and Antioxidant Activity of Compounds Containing 1,3-Dicarbonyl Moiety: An Overview

Free radicals and oxidants may cause various damages both to the lifeworld and different products. A typical solution for the prophylaxis of oxidation-caused conditions is the usage of various antioxidants. Among them, various classes are found-polyphenols, conjugated polyalkenes, and some sulfur and nitrogen derivatives. Regarding the active site in the molecules, a widely discussed group of compounds are 1,3-dicarbonyl compounds. Among them are natural (e.g., curcumin and pulvinic acids) and synthetic (e.g., 4-hydroxy coumarins, substituted Meldrum's acids) compounds. Herein, information about various compounds containing the 1,3-dicarbonyl moiety is covered, and their antiradical and antioxidant activity, depending on the structure, is discussed.

Recent advances in the synthesis of natural products containing the phloroglucinol motif

Covering: June 2009 to 2021Natural products containing a phloroglucinol motif include simple and oligomeric phloroglucinols, polycyclic polyprenylated acylphloroglucinols, phloroglucinol-terpenes, xanthones, flavonoids, and coumarins. These compounds represent a major class of secondary metabolites which exhibit a wide range of biological activities such as antimicrobial, anti-inflammatory, antioxidant and hypoglycaemic properties. A number of these compounds have been authorized for therapeutic use or are currently being studied in clinical trials. Their structural diversity and utility in both traditional and conventional medicine have made them popular synthetic targets over the years. In this review, we compile and summarise the recent synthetic approaches to the natural products bearing a phloroglucinol motif. Focus has been given on ingenious strategies to functionalize the phloroglucinol moiety at multiple positions. The isolation and bioactivities of the compounds are also provided.

Total syntheses of ericifolione and its analogues via a biomimetic inverse-electron-demand Diels-Alder reaction

Driven by bioinspiration and appreciation of the structure of ericifolione, a biomimetic tautomerization/intermolecular inverse-electron-demand hetero Diels-Alder reaction cascade sequence promoted by sodium acetate to rapidly construct sterically hindered dihydropyran scaffolds was established, which allowed the first straightforward biomimetic total syntheses of ericifolione and its analogues with high simplicity. Moreover, this methodology set the stage for the preparation of relevant natural products or derivatives.

Acylphloroglucinol trimers from Callistemon salignus seeds: Isolation, configurational assignment, hAChE inhibitory effects, and molecular docking studies

Alzheimer's disease (AD) diagnoses are greatly increasing in frequency as the global population ages, highlighting an urgent need for new anti-AD strategies. With the aim to search for human acetylcholinesterase (hAChE) inhibitors from the species of Myrtaceae family, ten acylphloroglucinol trimers (APTs), including eight new APTs, callistemontrimers A-H (1a, 1b, 2a, 2b, 3a, 3b, 4b, and 5b), and two naturally occurring ones (4a and 5a), along with one reported triketone-acylphloroglucinol-monoterpene adduct (6), were obtained and structurally characterized from the hAChE inhibitory acetone extract of Callistemon salignus seeds. The structures and their absolute configurations for new APTs were unequivocally established via the detailed interpretation of extensive spectroscopic data (HRESIMS and NMR), ECD calculations, and single crystal X-ray diffraction, whereas the absolute configurations of known APTs were determined by further chiral separation, and calculated ECD calculations. The results of hAChE inhibitory assay revealed that an enantiomeric mixture of 2a/2b, 2a, and 2b are good hAChE inhibitors with IC₅₀ values of 1.22 ± 0.23, 2.28 ± 0.19, and 4.96 ± 0.39 μM, respectively. Molecular docking was used to uncover the modes of interactions for bioactive compounds with the active site of hAChE. In addition, 2 and 6 displayed moderate neurite outgrowth-promoting effects with differentiation rates of 6.16% and 6.19% at a concentration of 1.0 μM, respectively.

Rhodomentosones A and B: Two Pairs of Enantiomeric Phloroglucinol Trimers from Rhodomyrtus tomentosa and Their Asymmetric Biomimetic Synthesis

Rhodomentosones A and B (1 and 2), two pairs of novel enantiomeric phloroglucinol trimers featuring a unique 6/5/5/6/5/5/6-fused ring system were isolated from Rhodomyrtus tomentosa. Their structures with absolute configurations were elucidated by NMR spectroscopy, X-ray crystallography, and ECD calculation. The bioinspired syntheses of 1 and 2 were achieved in six steps featuring an organocatalytic asymmetric dehydroxylation/Michael addition/Kornblum-DeLaMare rearrangement/ketalization cascade reaction. Compounds 1 and 2 exhibited promising antiviral activities against respiratory syncytial virus (RSV).

An Evidence-Based Review of Antitussive Herbs Containing Essential Oils in Traditional Persian Medicine

BACKGROUND

Cough is one of the most common medical symptoms for which medical advice is sought. Although cough is a protective reflex responsible for clearing the airways from secretions and foreign bodies, it can be a troublesome symptom that causes discomfort to patients. Due to the increasing interest in herbal remedies in both developed and developing countries, in the current study, we aimed to overview medicinal herbs containing essential oils used as antitussive agents according to Traditional Persian Medicine (TPM) textbooks. We summarized the relevant scientific evidence on their possible pharmacological effects.

METHODS

To collect the evidence for the treatment of cough or "seaal" (cough in ancient books) from TPM sources, five main medicinal Persian manuscripts were studied. The antitussive herbs were listed and their scientific names were identified and authenticated following botanical reference books. ScienceDirect and PubMed online databases were searched for related mechanisms of action of the reported medicinal plants.

RESULTS

Forty-nine herbs containing essential oils have been recommended in TPM for the treatment of cough; 21 of them had at least one known mechanism of action for cough suppression in the scientific literature. According to this review, most of the cited medicinal plants were assessed for either nitric oxide inhibitory or antitussive/expectorant activities.

CONCLUSION

In addition to advantageous effects of antitussive herbs recommended by TPM, the present review highlighted some recent evidence-based data on these promising herbs that could be used as an outline for future research on their medicinal use.

Antibacterial Triketone-Phloroglucinol-Triketone Adducts from Myrtus communis

Myrtucyclitones A-C ((+)- and (-)-1-3), three pairs of new triketone-phloroglucinol-triketone hybrids were isolated from the plant Myrtus communis. Their structures with absolute configurations were established by NMR analysis and chemical calculations. Myrtucyclitones B and C exhibited remarkable antibacterial effect.

Advances in catalytic and protecting-group-free total synthesis of natural products: a recent update

Catalytic processes in protecting-group-free syntheses of natural products are fast emerging towards achieving the goal of efficiency and economy in total synthesis. Present day sustainable development in synthesis of natural products does not permit the luxury of using stoichiometric reagents and protecting groups. Catalysis and step-economy can contribute significantly toward economy and efficiency of synthesis. This feature article details the ingenious efforts by many researchers in the last couple of years toward concise total syntheses, based on catalytic steps and protecting-group-free-strategies. These would again serve as guidelines in future development of reagents and catalysts aimed at achieving higher efficiency and chemoselectivity to the point that catalysis and protecting-group-free synthesis will be an accepted common practice.

Inhibitory Effects of Myrtucommuacetalone 1 (MCA-1) from Myrtus communis on Inflammatory Response in Mouse Macrophages

(1) Introduction: Reactive oxygen species (ROS) and nitric oxide (NO) are key signaling molecules that play important roles in the progression of inflammatory disorders. The objective of this study was to explore the use of myrtucommuacetalone-1 (MCA-1), as a novel compound of natural origin and a potential anti-inflammatory agent. (2) Methodology: The anti-inflammatory potential of MCA-1, which was isolated from Myrthus communis Linn, was determined by assaying superoxide, hydrogen peroxide, and nitric oxide production in macrophages. Furthermore, the effects of the compound were analyzed via phosphorylation and translocation of the transcription factor NF kappa B, which is a key regulator of iNOS activation. The effect of MCA-1 on the inducible nitric oxide synthase (iNOS) enzyme was also examined using in silico docking studies. The anticancer potential for MCA-1 was evaluated with an MTT cytotoxic assay. (3) Results: In stimulated macrophages, MCA-1 inhibited superoxide production by 48%, hydrogen peroxide by 53%, and nitric oxide (NO) with an IC₅₀ of <1 µg/mL. MCA-1 also showed a very strong binding pattern within the active site of the inducible nitric oxide synthase enzyme. Furthermore, 25 µg/mL of MCA-1 inhibited inducible nitric oxide synthase expression and abolished transcription factor (NFκB) phosphorylation and translocation to the nucleus. Cytotoxicity analyses of MCA-1 on 3T3 mouse fibroblasts, CC1 liver cell line, J774.2, macrophages and MDBK bovine kidney epithelial cell, yielded IC₅₀ values of 6.53 ± 1.2, 4.6 ± 0.7, 5 ± 0.8, and 4.6 ± 0.7, µg/mL, respectively. (4) Conclusion: Our results suggest that MCA-1, a major phloroglucinol-type compound, shows strong anti-inflammatory activity and has a potential to be a leading therapeutic agent in the future.

Dietary myricetin intake is inversely associated with the prevalence of type 2 diabetes mellitus in a Chinese population

Myricetin is a natural plant-derived inhibitor for α-glucosidase and α-amylase and possesses strong antioxidant activity. Myricetin is reported to be effective in treating many symptoms that are associated with type 2 diabetes mellitus (T2DM), therefore, we hypothesized that myricetin plays a preventive role in the development of T2DM. To test this hypothesis, we designed a cross-sectional population study, which included 24 138 subjects, with 1357 of them diagnosed with T2DM. A validated 100-item food frequency questionnaire was used to collect dietary information. Daily intakes of myricetin and nutrients were calculated, based on the Chinese food composition tables. Multiple logistic regression analysis models were used to analyze the relationship between the quartiles of myricetin intake and the prevalence of T2DM. We found that, in this Chinese population, the daily intake of myricetin was 120.5 ± 95.7 mg, with apple, peach, orange, pineapple, and sweet potato being the main food sources. Significant inverse trends were observed between intakes of myricetin and prevalence of T2DM in multivariable models (all p-trend <0.0001). The odds ratios (95% CI) for T2DM across the ascending quartiles of myricetin intake were: 1.00 (reference), 0.73 (0.61, 0.87), 0.61 (0.50, 0.75), and 0.51 (0.40, 0.64). This study showed that myricetin intake was inversely related to the prevalence of T2DM in this Chinese population, suggesting a protective effect of myricetin in the development of T2DM.

Fe(III)-Catalyzed Diastereoselective Friedel-Crafts Alkylation-Hemiketalization-Lactonization Cascade for the Synthesis of Polycyclic Bridged 2-Chromanol Lactones

An unprecedented Fe(III)-catalyzed Friedel-Crafts alkylation-hemiketalization-lactonization cascade of electron-rich hydroxy arenes and distinctively functionalized unsaturated 4-keto esters is developed for the construction of polycyclic bridged 2-chromanol lactones. Following this simple and facile protocol, a broad range of products was prepared in good to excellent yields as a single diastereomer. An unusual conglomerate (enantiomerically pure polymorph) of 3ac is reported along with the absolute stereochemistry, and the remaining products were rigorously confirmed by single-crystal X-ray analysis and analogy.

A new antibacterial dibenzofuran-type phloroglucinol from myrtus communis linn

Our continuation on the bio-assay guided isolation from Myrtus communis Linn. led to the discovery of a new dibezofuran type phloroglucinol 1,1'-(1,3,7,9-tetrahydroxydibenzo[b,d]furan-2,8-diyl)bis(ethan-1-one) 1. The structure was established through detailed spectroscopic studies including one and two dimensional NMR spectroscopy and electrospray ionization high resolution mass spectrometer (ESI-HRMS). The crude acetone extract from M. communis (AMA), dichloromethane fraction (DCM), and the isolated pure compound 1 were tested against pathogenic bacteria. Compound 1 displayed higher antibacterial activity against the Gram-positive and Gram-negative Staphlocococus aureus and Escherichia coli respectively as compared to the crude extract and fractions.

Structures and Bioactive Properties of Myrtucommulones and Related Acylphloroglucinols from Myrtaceae

Myrtaceae are a group of plants that include a number of renowned species used in ethnomedicine in many areas worldwide. Their valuable therapeutic properties have stimulated a fruitful research activity addressed to the identification of the bioactive components of their extracts yielding a great diversity of terpenes; polyphenols; and other exclusive products. Among the latter, starting with the discovery of myrtucommulone A from myrtle (Myrtus communis), a series of structurally-related acylphloroglucinol compounds have been characterized from several species that represent the basic active principles to be considered in view of possible drug development. Aspects concerning chemical and biological properties of these products are reviewed in the present paper.

Applications of Friedel-Crafts reactions in total synthesis of natural products

Over the years, Friedel-Crafts (FC) reactions have been acknowledged as the most useful and powerful synthetic tools for the construction of a special kind of carbon-carbon bond involving an aromatic moiety. Its stoichiometric and, more recently, its catalytic procedures have extensively been studied. This reaction in recent years has frequently been used as a key step (steps) in the total synthesis of natural products and targeted complex bioactive molecules. In this review, we try to underscore the applications of intermolecular and intramolecular FC reactions in the total syntheses of natural products and complex molecules, exhibiting diverse biological properties.

Antioxidant Activity of Myrtus communis L. and Myrtus nivellei Batt. & Trab. Extracts: A Brief Review

Myrtus communis L. (myrtle) and Myrtus nivellei Batt. & Trab. (Saharan myrtle) have been used in folk medicine for alleviating some ailments. M. communis is largely distributed in the Mediterranean Basin, whereas M. nivellei is confined in specific zones of the central Saharan mountains. The chemical composition and antioxidant activity of berry and leaf extracts isolated from myrtle are deeply documented, whereas those isolated from Saharan myrtle extracts are less studied. In both species, the major groups of constituents include gallic acid derivatives, flavonols, flavonol derivatives, and hydroxybenzoic acids. In coloured berries, anthocyanins are also present. In M. nivellei extracts are reported for some compounds not described in M. communis so far: 2-hydroxy-1,8-cineole-β-d-glucopyranoside, 2-hydroxy-1,8-cineole 2-O-α-l-arabinofuranosyl (1→6)-β-d-glucopyranoside, rugosin A, and rugosin B. Berries and leaves extracts of both species had antioxidant activity. Comparative studies of the antioxidant activity between leaf and berry myrtle extracts revealed that leaf extracts are best antioxidants, which can be assigned to the galloyl derivatives, flavonols, and flavonols derivatives, although the ratio of these groups of compounds might also have an important role in the antioxidant activity. The anthocyanins present in myrtle berries seem to possess weak antioxidant activity. The antioxidant activity of sample extracts depended on various factors: harvesting time, storage, extraction solvent, extraction type, and plant part used, among other factors. Leaf extracts of myrtle revealed to possess anti-inflammatory activity in several models used. This property has been attributed either to the flavonoids and/or hydrolysable tannins, nevertheless nonprenylated acylphloroglucinols (e.g., myrtucommulone and semimyrtucommulone) have also revealed a remarkable role in that activity. The biological activities of myrtle extracts found so far may direct its use towards for stabilizing complex lipid systems, as prebiotic in food formulations, and as novel therapeutic for the management of inflammation.

Antiplasmodial β-Triketone-Flavanone Hybrids from the Flowers of the Australian Tree Corymbia torelliana

The methanol extract of the flowers of the Australian eucalypt tree Corymbia torelliana yielded six new β-triketone-flavanone hybrids, torellianones A-F (1-6), the tetrahydroxycyclohexane torellianol A (7), and known β-triketones (4 S)-ficifolidione (8) and (4 R)-ficifolidione (9), and β-triketone-flavanones kunzeanone A (10) and kunzeanone B (11). Torellianones A and B, C and D, and E and F were each isolated as inseparable diastereomeric mixtures. Exchange correlations observed in a ROESY spectrum indicated that 5 and 6 also interconverted between stable conformers. The structures of 1-7 were elucidated from the analysis of 1D/2D NMR and MS data. Relative configurations of torellianones C-F and torrellianol A were determined from analysis of ROESY data. Compounds 1-10 were tested for antiplasmodial activity against a drug-sensitive (3D7) strain of Plasmodium falciparum, with 3-6 and 8-10 showing limited antiplasmodial activity, with IC₅₀ values ranging from 3.2 to 16.6 μM.

Phloroglucinol Derivatives with Unusual Skeletons from Cleistocalyx operculatus and Their in Vitro Antiviral Activity

Four novel phloroglucinol derivatives (1-4) featuring a 2,4-dimethyl-cinnamyl-phloroglucinol moiety, along with their putative biosynthetic precursors 5 and 6, were isolated from the leaves of Cleistocalyx operculatus. Compounds 1 and 2 are two pairs of new enantiomeric phloroglucinol dimers possessing an unprecedented polycyclic skeleton with a highly functionalized dihydropyrano[3,2- d]xanthene tetracyclic core. Compounds 3 and 4 are two new phloroglucinol-terpene adducts (PTAs) with a novel carbon skeleton. The structures of 1-4 including their absolute configurations were unambiguously accomplished by combination of extensive spectroscopic analyses, X-ray crystallography, and quantum chemical ECD calculations. A hypothetical biosynthetic pathway for 1-4 was also proposed. Compound 1 exhibited a promising in vitro antiherpes simplex virus type-1 (HSV-1) effect.

Catalytic asymmetric total syntheses of myrtucommuacetalone, myrtucommuacetalone B, and callistrilones A, C, D and E

Herein, we describe a concise catalytic approach to the first asymmetric total syntheses of myrtucommuacetalone, myrtucommuacetalone B, and callistrilones A, C, D and E. The syntheses proceed in only 5-7 steps from the readily available compound 11, without the need for protecting groups. Key features of the syntheses include a unique organocatalytic asymmetric Friedel-Crafts-type Michael addition with high enantioselectivity and a broad substrate scope, a novel Michael-ketalization-annulation cascade reaction, and an oxidative [3 + 2] cycloaddition. Furthermore, the new compound 7 exhibited potent antibacterial activities against several multidrug-resistant strains (MRSA, VISA and VRE), and showed greater potency than vancomycin.

Asymmetric total syntheses of callistrilones B, G and J

A highly concise approach for the first asymmetric and gram-scale total syntheses of callistrilones B, G and J is reported.

Meroterpenoids with New Skeletons from Myrtus communis and Structure Revision of Myrtucommulone K

Five sesquiterpene-based meroterpenoids with three kinds of new skeletons [1, 2, 3, (+)-4, and (-)-4] were isolated from the leaves of Myrtus communis. Compound 1 featured a new carbon skeleton with an unprecedented octahydrospiro[bicyclo[7.2.0]undecane-2,2'-chromene] tetracyclic ring system, which possessed two preferred conformations detected by variable-temperature NMR spectroscopy experiments. In addition, the structure of reported myrtucommulone K was revised to be compound 3. The plausible biosynthetic pathways of these meroterpenoids and their cytotoxicities are discussed.

Callistrilones A and B, Triketone-Phloroglucinol-Monoterpene Hybrids with a New Skeleton from Callistemon rigidus

The first triketone-phloroglucinol-monoterpene hybrids, callistrilones A and B (1 and 2), along with a postulated biosynthetic intermediate (3) were isolated from the leaves of Callistemon rigidus. Compounds 1 and 2 featured a new carbon skeleton with an unprecedented [1]benzofuro[2,3-a]xanthene or [1]benzofuro[3,2-b]xanthene pentacyclic ring system composed of three kinds of building blocks. Their structures and absolute configurations were elucidated by spectroscopic analysis, X-ray diffraction, and electronic circular dichroism (ECD) calculations. A plausible biogenetic pathway for the new compounds is also proposed. Compound 1 exhibited moderate antibacterial activity against Gram-positive bacteria including multiresistant strains.

Studies with Myrtus communis L.: Anticancer properties

Myrtus communis (MC) L. is a well-known Mediterranean plant with important cultural significance in this region. In ancient times, MC was accepted as a symbol of immortality. Maybe due to this belief, it is used during cemetery visits in some regions. Although it is a well-known plant in cosmetics, and there is a lot of studies about its different medical properties, anticancer studies performed using its different extracts or oils are not so much, but increasing. We collected these anticancer property-related studies in this review.