New Flavonol Glucuronides from the Flower Buds of Syzygium aromaticum (Clove)

Anti-inflammatory naphthoquinone-monoterpene adducts and neolignans from Eugenia caryophyllata

A phytochemical investigation on the buds of edible medicinal plant, Eugenia carvophyllata, led to the discovery of seven new compounds, caryophones A-G (1-7), along with two biogenetically-related known ones, 2-methoxy-7-methyl-1,4-naphthalenedione (8) and eugenol (9). Compounds 1-3 represent the first examples of C-5-C-1' connected naphthoquinone-monoterpene adducts with a new carbon skeleton. Compounds 4-7 are a class of novel neolignans with unusual linkage patterns, in which the C-9 position of one phenylpropene unit coupled with the aromatic core of another phenylpropene unit. The chemical structures of the new compounds were determined based on extensive spectroscopic analysis, X-ray diffraction crystallography, and quantum-chemical calculation. Among the isolates, compounds (-)-2, 3, 6, and 9 showed significant in vitro inhibitory activities against respiratory syncytial virus (RSV)-induced nitric oxide (NO) production in RAW264.7 cells.

Natural-derived acetophenones: chemistry and pharmacological activities

Acetophenones are naturally occurring phenolic compounds which have found in over 24 plant families and also fungi strains. They are exist in both free or glycosides form in nature. The biological activities of these compounds have been assayed and reported including cytotoxicity, antimicrobial, antimalarial, antioxidant and antityrosinase activities. Herein, we review the chemistry and biological activity of natural acetophenone derivatives that have been isolated and identified until January 2024. Taken together, it was reported 252 acetophenone derivatives in which the genera Melicope (69) and Acronychia (44) were the principal species as producers of acetophenones.

Holistic quality evaluation of Callicarpae Formosanae Folium by multi-chromatography-based qualitative and quantitative analysis of polysaccharides and small molecules

Callicarpae Formosanae Folium (CFF), derived from the leaves of Callicarpa formosana Rolfe, is a common Chinese medicinal herb used for the treatment of hematemesis. Phytochemical studies found that phenylpropanoids, flavonoids, terpenoids and polysaccharides were the main ingredients of CFF. However, there is limited scientific information concerning holistic quality method and quality consistency evaluation of CFF. In this study, a strategy integrating HPGPC-ELSD, HPLC-PDA, UV-VIS and UPLC-QTOF-MS/MS was firstly developed to simultaneously qualify and quantify polysaccharides, as well as representative small molecules in CFF. HPGPC-ELSD was applied to characterize the molecular weight distribution of polysaccharides, HPLC-PDA was developed to qualitatively and quantitatively determine monosaccharides. UV-VIS was used to determine the total polysaccharides content, and UPLC-QTOF-MS/MS was established to characterize the small molecules. The quality consistency of commercial CFF (CM-CFF) was also evaluated. It was shown that the relative molecular weights, the compositional monosaccharides and small molecules composition in CM-CFF and self-collected CFF (SC-CFF) samples were similar. A total of 32 small molecules including 6 phenylpropanoids, 7 flavonoids and 19 terpenoids were characterized in CFF. However, the variation was observed in the content of polysaccharides, luteolin, ursolic acid, as well as total contents of terponoids in CM-CFF samples, which implied that the holistic quality of CM-CFF was inconsistent. The results suggested that the proposed evaluation strategy could be applied as a potential approach for the quality control of CFF. And the quality of CM-CFF should be improved by Good Agriculture Practice (GAP) base and standard processing method.

Salkini M, Soliman GA, Alharthy KM, Hamad A, Abdel-Kader MS. Anti-ulcerative colitis effect of Calligonum comosum L'Hér. using rat model: Chemical, pharmacological and histopathological evidences

Calligonum comosum is a perennial shrub growing and widely used in traditional medicinal system in Saudi Arabia. The total phenolic content and in vitro antioxidant activity were compared between the water extract (WE) and methanol extract (ME). The protective potential against acetic acid (AA) induced ulcerative colitis (UC) was also evaluated in rats. The obtained results showed that the total phenolic content of the WE and ME were 8.378 ± 0.738 and 33.819 ± 0.488 µg/mL. The antioxidant properties of the two extracts were directly influenced by their total phenolic contents. The ME with higher phenolic contents and stronger antioxidant power was more effective than the WE in protection against AA-induced colitis. Phytochemical study of the ME led to the identification of three flavonoid derivatives: (-)-epi-catechin, quercetin-3-O-α-l-arabinofuranoside (Avicularin) and quercetin-3-O-β-d-glucuronide-6″-methyl ester by various spectroscopic methods. (-)-Epi-catechin was the major component while the other two compounds were obtained in minute quantities. The anti-ulcerative colitis effect of the ME can be explained by the presence of the antioxidant flavonoids since AA-induced colitis featured by imbalance between oxidant and antioxidant substances. Further support of such explanation was provided by HPLC quantification of (-)-epi-catechin in the ME and WE. The percentage in ME was higher than the WE but the difference was higher in term of Total Phenolic Content (TPC). These results support the traditional use of C. comosum as anti-ulcerative colitis.

Screening of Monoamine Oxidase B Inhibitors from Fragaria nubicola by Ligand Fishing and Their Neuroprotective Effects

Fragaria nubicola, known as Tibetan strawberry, is an edible plant possessing various health-promoting effects. However, its functional compositions were rarely studied. In this work, monoamine oxidase B (MAO-B) inhibitors in this plant were rapidly screened using the enzyme-functionalized magnetic nanoparticles coupled with UPLC-QTOF-MS. Two inhibitors, quercetin-3-O-β-d-glucuronide-6″-methyl ester (1) and kaempferol-3-O-β-d-glucuronide-6″-methyl ester (2), were identified from this plant with the IC₅₀ values of 19.44 ± 1.17 and 22.63 ± 1.78 μM, respectively. Enzyme kinetic analysis and molecular docking were carried out to investigate the mechanism of inhibition. Contents of both compounds as well as those of total phenolics and flavonoids were quantified to be 24.76 ± 1.26, 35.59 ± 1.17, 837.67 ± 10.62, and 593.46 ± 10.37 μg/g, respectively. In addition, both compounds exhibited significant neuroprotective effects on 6-hydroxydopamine-induced PC12 cells. This is the first report on the neuroprotective components of F. nubicola, suggesting its potential for developing neuroprotective functional food.

Chemical Compositions of Clove (Syzygium aromaticum (L.) Merr. & L.) Extracts and Their Potentials in Suppressing SARS-CoV-2 Spike Protein-ACE2 Binding, Inhibiting ACE2, and Scavenging Free Radicals

COVID-19 is initiated by binding the SARS-CoV-2 spike protein to angiotensin-converting enzyme 2 (ACE2) on host cells. Food factors capable of suppressing the binding between the SARS-CoV-2 spike protein and ACE2 or reducing the ACE2 availability through ACE2 inhibitions may potentially reduce the risk of SARS-CoV-2 infection and COVID-19. In this study, the chemical compositions of clove water and ethanol extracts were investigated, along with their potentials in suppressing SARS-CoV-2 spike protein-ACE2 binding, reducing ACE2 availability, and scavenging free radicals. Thirty-four compounds were tentatively identified in the clove water and ethanol extracts, with six reported in clove for the first time. Clove water and ethanol extracts dose-dependently suppressed SARS-CoV-2 spike protein binding to ACE2 and inhibited ACE2 activity. The water extract had stronger inhibitory effects than the ethanol extract on a dry weight basis. The clove water extract also had more potent free radical scavenging activities against DPPH^• and ABTS^•+ (536.9 and 3525.06 μmol TE/g, respectively) than the ethanol extract (58.44 and 2298.01 μmol TE/g, respectively). In contrast, the ethanol extract had greater total phenolic content (TPC) and relative HO^• scavenging capacity (HOSC) values (180.03 mg GAE/g and 2181.08 μmol TE/g, respectively) than the water extract (120.12 mg GAE/g and 1483.02 μmol TE/g, respectively). The present study demonstrated the potential of clove in reducing the risk of SARS-CoV-2 infection and COVID-19 development.

Exploiting DNA Ligase III addiction of multiple myeloma by flavonoid Rhamnetin

Background

DNA ligases are crucial for DNA repair and cell replication since they catalyze the final steps in which DNA breaks are joined. DNA Ligase III (LIG3) exerts a pivotal role in Alternative-Non-Homologous End Joining Repair (Alt-NHEJ), an error-prone DNA repair pathway often up-regulated in genomically unstable cancer, such as Multiple Myeloma (MM). Based on the three-dimensional (3D) LIG3 structure, we performed a computational screening to identify LIG3-targeting natural compounds as potential candidates to counteract Alt-NHEJ activity in MM.

Methods

Virtual screening was conducted by interrogating the Phenol Explorer database. Validation of binding to LIG3 recombinant protein was performed by Saturation Transfer Difference (STD)—nuclear magnetic resonance (NMR) experiments. Cell viability was analyzed by Cell Titer-Glo assay; apoptosis was evaluated by flow cytometric analysis following Annexin V-7AAD staining. Alt-NHEJ repair modulation was evaluated using plasmid re-joining assay and Cytoscan HD. DNA Damage Response protein levels were analyzed by Western blot of whole and fractionated protein extracts and immunofluorescence analysis. The mitochondrial DNA (mtDNA) copy number was determined by qPCR. In vivo activity was evaluated in NOD-SCID mice subcutaneously engrafted with MM cells.

Results

Here, we provide evidence that a natural flavonoid Rhamnetin (RHM), selected by a computational approach, counteracts LIG3 activity and killed Alt-NHEJ-dependent MM cells. Indeed, Nuclear Magnetic Resonance (NMR) showed binding of RHM to LIG3 protein and functional experiments revealed that RHM interferes with LIG3-driven nuclear and mitochondrial DNA repair, leading to significant anti-MM activity in vitro and in vivo.

Conclusion

Taken together, our findings provide proof of concept that RHM targets LIG3 addiction in MM and may represent therefore a novel promising anti-tumor natural agent to be investigated in an early clinical setting.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03705-z.

Recent advances in nutritional composition, phytochemistry, bioactive, and potential applications of Syzygium aromaticum L. (Myrtaceae)

Syzygium aromaticum is an aromatic plant native to Indonesia, and introduced to tropical regions worldwide. As an ingredient in perfumes, lotions, and food preservation, it is widely used in the food and cosmetic industries. Also, it is used to treat toothache, ulcers, type 2 diabetes, etc. A variety of nutrients such as amino acids, proteins, fatty acids, and vitamins are found in S. aromaticum. In addition to eugenol, isoeugenol, eugenol acetate, β-caryophyllene and α-humulene are the main chemical constituents. The chemical constituents of S. aromaticum exhibit a wide range of bioactivities, such as antioxidant, antitumor, hypoglycemic, immunomodulatory, analgesic, neuroprotective, anti-obesity, antiulcer, etc. This review aims to comprehend the information on its taxonomy and botany, nutritional composition, chemical composition, bioactivities and their mechanisms, toxicity, and potential applications. This review will be a comprehensive scientific resource for those interested in pursuing further research to explore its value in food.

Biological Importance and Therapeutic Benefit of Rhamnocitrin: A Review of Pharmacology and Analytical Aspects

BACKGROUND

Humans have a long history of the uses of plant based products, including extracts and pure phytoconstituents for the treatment of human diseases in the different system of medicine. In the developing countries, phytoproducts play an important role in the healthcare systems due to their medicinal importance and pharmacological activities. Flavonoids class phytochemicals are beneficial for human beings because of their free radical scavenging properties and trace metals chelating potential. Flavonoids have inhibitory potential for the growth of bacteria and virus mainly through enzyme inhibition functions and viral translation. Rhamnocitrin is also called 7- methyl-kaempferol is important flavonoids, which has been isolated from different medicinal plants and has pharmacological activities in the medicine.

METHODS

Present paper describes the biological potential and health beneficial aspects of rhamnocitrin in the medicine through the data analysis of published papers in the recent years in the field of medicine and modern medical sciences. Scientific data on rhamnocitrin have been collected from electronic databases such as PubMed, Google Scholar, Google, Scopus and Science Direct in the present investigation and analyzed to know the biological importance and pharmacological activities of rhamnocitrin. Pharmacological scientific data of rhamnocitrin have been collected and analyzed in the present work with their analytical aspects.

RESULTS

Literature data analysis of different scientific work on rhamnocitrin revealed the biological importance of rhamnocitrin in medicine. Rhamnocitrin is known to be a promising phytoconstituents found to be present in medicinal plants with a wide range of biological activities. Rhamnocitrin was found to have pharmacological activities, including anti-atherogenic, anti-oxidant, anti-cancer, anti-bacterial, anti-inflammatory, enzymatic and neuroprotective potential. Further biological effect of rhamnocitrin on adipocyte differentiation has been also studied in the present work. Analytical data on rhamnocitrin signified the application of different analytical techniques for the separation, isolation and identification of rhamnocitrin in medicine.

CONCLUSION

Literature data analysis of different scientific research works revealed the biological importance and therapeutic benefit of rhamnocitrin in medicine.

Luteolin Promotes Apoptosis of Endometriotic Cells and Inhibits the Alternative Activation of Endometriosis-Associated Macrophages

Luteolin, a flavonoid present in several fruits, vegetables, nuts, and herbs reportedly exhibits anti-cancer and anti-inflammatory properties. However, the effect of luteolin on endometriosis, a painful condition characterized by the ectopic growth of endometrial tissue and pelvic inflammation, remains elusive. Herein, we observed that luteolin inhibited cell growth and induced apoptosis of 12Z human endometriotic cells by activating caspase-3, -8, and -9. Additionally, luteolin significantly inhibited the expression of key chemokines, C-C motif chemokine ligand 2 (CCL2) and CCL5, required for monocyte/macrophage influx at endometriotic sites. In macrophages stimulated by endometriotic cells, luteolin treatment suppressed the intracellular expression of M2 markers and endometriosis-promoting factors. Collectively, our data suggest that luteolin exerts anti-endometriotic effects by stimulating endometriotic cell apoptosis and hindering the alternative activation of macrophages.

Chemical Fingerprinting, Isolation and Characterization of Polyphenol Compounds from Heliotropium taltalense (Phil.) I.M. Johnst and Its Endothelium-Dependent Vascular Relaxation Effect in Rat Aorta

Heliotropium taltalense is an endemic species of the northern coast of Chile and is used as folk medicine. The polyphenolic composition of the methanolic and aqueous extract of the endemic Chilean species was investigated using Ultrahigh-Performance Liquid Chromatography, Heated Electrospray Ionization and Mass Spectrometry (UHPLC-Orbitrap-HESI-MS). Fifty-three compounds were detected, mainly derivatives of benzoic acid, flavonoids, and some phenolic acids. Furthermore, five major compounds were isolated by column chromatography from the extract, including four flavonoids and one geranyl benzoic acid derivative, which showed vascular relaxation and were in part responsible for the activity of the extracts. Since aqueous extract of H. taltalense (83% ± 9%, 100 μg/mL) produced vascular relaxation through an endothelium-dependent mechanism in rat aorta, and the compounds rhamnocitrin (89% ± 7%; 10⁻⁴ M) and sakuranetin (80% ± 6%; 10⁻⁴ M) also caused vascular relaxation similar to the extracts of H. taltalense, these pure compounds are, to some extent, responsible for the vascular relaxation.

Chemical Diversity and Biological Activity of African Propolis

Natural remedies have for centuries played a significant role in traditional medicine and continue to be a unique reservoir of new chemical entities in drug discovery and development research. Propolis is a natural substance, collected by bees mainly from plant resins, which has a long history of use as a folk remedy to treat a variety of ailments. The highly variable phytochemical composition of propolis is attributed to differences in plant diversity within the geographic regions from which it is collected. Despite the fact that the last five decades has seen significant advancements in the understanding of the chemistry and biological activity of propolis, a search of the literature has revealed that studies on African propolis to date are rather limited. The aim of this contribution is to report on the current body of knowledge of African propolis, with a particular emphasis on its chemistry and biological activity. As Africa is a continent with a rich flora and a vast diversity of ecosystems, there is a wide range of propolis phytochemicals that may be exploited in the development of new drug scaffolds.

Rhamnazin attenuates inflammation and inhibits alkali burn-induced corneal neovascularization in rats

The purpose of our study was to determine whether rhamnazin inhibits corneal neovascularization in the rat alkali burn model, and alleviates the inflammatory response of the cornea. Rhamnazin inhibited the proliferation of HUVEC cells in a dose-dependent manner, and it also inhibited the migration and luminal formation of HUVEC cells. 20 μM rhamnazin eye drops were applied to an animal model of corneal alkali burn neovascularization 4 times a day for 14 days. The corneal neovascularization in the rhamnazin group was obviously less than that in the PBS control group. In the rhamnazin group, the inflammatory index of the cornea decreased gradually over time, whereas the inflammatory index of the PBS group decreased only slightly with time. The corneal CNV area in the PBS group was significantly larger than that in the rhamnazin group. The expression level of VEGF protein of the rhamnazin group was lower than that in the PBS group, and the expression level of PEDF was significantly higher than that of the PBS group. Rhamnazin downregulated the expression of VEGFR2 protein and decreased the expression levels of p-STAT3, p-MAPK and p-Akt proteins. This study provides a new idea for the study of the molecular mechanism of corneal neovascularization.

The purpose of our study was to determine whether rhamnazin inhibits corneal neovascularization in the rat alkali burn model, and alleviates the inflammatory response of the cornea.

Effect of Kumatakenin Isolated From Cloves on the Apoptosis of Cancer Cells and the Alternative Activation of Tumor-Associated Macrophages

The flower bud of Syzygium aromaticum (clove) has been used for centuries as a spice and herbal medicine. The biological activities of kumatakenin, a flavonoid that has recently been isolated from cloves, are poorly characterized. In the present study, the anticancer effects of kumatakenin in human ovarian cancer cells and tumor-associated macrophages (TAMs) were investigated. We found that kumatakenin exhibited significant cytotoxic activity in human ovarian cancer cells, SKOV3 and A2780. A propidium iodide and Annexin V-FITC staining assay showed that kumatakenin induces apoptosis in ovarian cancer cells. Kumatakenin treatment increased the activity of caspase-3, -8, and -9, and caspase inhibitors attenuated kumatakenin-induced SKOV3 cell death. In addition, kumatakenin was found to reduce the expressions of MCP-1 and RANTES, which are major determinants of macrophage recruitment at tumor sites in ovarian cancer cells. Moreover, kumatakenin inhibited the expression of M2 markers and cancer-promoting factors, including IL-10, MMP-2/-9, and VEGF, in macrophages stimulated by the ovarian cancer cells. In conclusion, these results suggest that kumatakenin shows anticancer activities by inducing apoptosis of ovarian cancer cells and inhibiting the alternative activation of TAM.

Glucuronidated Flavonoids in Neurological Protection: Structural Analysis and Approaches for Chemical and Biological Synthesis

Both plant and mammalian cells express glucuronosyltransferases that catalyze glucuronidation of polyphenols such as flavonoids and other small molecules. Oral administration of select polyphenolic compounds leads to the accumulation of the corresponding glucuronidated metabolites at μM and sub-μM concentrations in the brain, associated with amelioration of a range of neurological symptoms. Determining the mechanisms whereby botanical extracts impact cognitive wellbeing and psychological resiliency will require investigation of the modes of action of the brain-targeted metabolites. Unfortunately, many of these compounds are not commercially available. This article describes the latest approaches for the analysis and synthesis of glucuronidated flavonoids. Synthetic schemes include both standard organic synthesis, semisynthesis, enzymatic synthesis and use of synthetic biology utilizing heterologous enzymes in microbial platform organisms.