Flavonoid glycosides from the stem bark of Margaritaria discoidea demonstrate antibacterial and free radical scavenging activities

The flavonoid hydroxygenkwanin reduces inflammation and neointimal formation

BACKGROUND AND OBJECTIVES

Abnormal vascular smooth muscle cell (VSMC) proliferation and migration play crucial roles in neointimal hyperplasia and restenosis progression in response to stimulation with various inflammatory cytokines, such as platelet-derived growth factor-BB (PDGF-BB) and tumour necrosis factor-α (TNF-α). Hydroxygenkwanin (HGK) exerts remarkable anti-inflammatory, antitumour, antiproliferative and antimigratory effects. The aim of the study was to elucidate the therapeutic effect and regulatory mechanism of HGK on neointimal hyperplasia.

METHODS

Western blot analysis, cell cycle analysis, and MTT, BrdU incorporation, wound healing and adhesion assays were performed in vitro to determine the therapeutic effects of HGK in PDGF-BB- or TNF-α-treated VSMCs. Docking analysis and cellular thermal shift assay were also performed to elucidate the mechanism underlying the regulatory effect of HGK. Histological and immunohistochemical staining of denuded femoral arteries was conducted to elucidate the therapeutic effect of HGK in vivo.

RESULTS AND CONCLUSIONS

HGK inhibited the abnormal proliferation, migration, and inflammation of PDGF-BB- or TNF-α-treated VSMCs through regulation of the PDK1/AKT/mTOR pathway. In addition, HGK promoted circulating endothelial progenitor cell (EPC) chemotaxis. In an in vivo assay, HGK dramatically enhanced re-endothelization and reduced neointimal hyperplasia after femoral artery denudation with a guide wire in mice. These results suggest that HGK can serve as a therapeutic target drug or a functional food supplement for the treatment of restenosis.

Margaritaria nobilis L.f. (Phyllanthaceae) Ethanolic Extract: Low Acute Oral Toxicity and Antinociceptive Activity

Margaritaria nobilis L.f. (Phyllanthaceae), a native Brazilian tree occurring mainly in the Amazon, is used in folk medicine for the treatment of abscesses (bark) and cancer-like symptoms (leaves). The present study evaluates the safety of its acute oral administration and its effects on nociception and plasma leakage. The chemical constitution of the leaf's ethanolic extract is determined by ultra-performance liquid chromatography-high-resolution mass spectrometry (LC-MS. Its acute oral toxicity is evaluated in female rats at a dose of 2000 mg/kg, evaluating the occurrence of deaths and Hippocratic, behavioral, hematological, biochemical, and histopathological changes, as well as food and water consumption and weight gain. Antinociceptive activity is evaluated in male mice with acetic-acid-induced peritonitis (APT) and formalin (FT) tests. An open field (OF) test is performed to verify possible interferences in the animals' consciousness or locomotion. LC-MS analysis shows the presence of 44 compounds classified as phenolic acid derivatives, flavonoids and O-glycosylated derivatives, and hydrolyzable tannins. No deaths or significant behavioral, histological, or biochemical changes are observed in the toxicity assessment. In nociception tests, M. nobilis extract significantly reduces abdominal contortions in APT, demonstrating selectivity for inflammatory components (FT second phase), not interfering in neuropathic components (FT first phase) or consciousness and locomotion levels in OF. Additionally, M. nobilis extract inhibits plasma acetic-acid-induced leakage. These data demonstrate the low toxicity of M. nobilis ethanolic extract, as well as its effectiveness in modulating inflammatory nociception and plasma leakage, possibly related to the flavonoids and tannins present in its composition.

Why traditional herbal medicine promotes wound healing: Research from immune response, wound microbiome to controlled delivery

Impaired wound healing in chronic wounds has been a significant challenge for clinicians and researchers for decades. Traditional herbal medicine (THM) has a long history of promoting wound healing, making them culturally accepted and trusted by a great number of people in the world. However, for a long time, the understanding of herbal medicine has been limited and incomplete, particularly in the allopathic medicine-dominated research system. The therapeutic effects of individual components isolated from THM are found less pronounced compared to synthetic chemical medicine, and the clinical efficacy is always inferior to herbs. In the present article, we review and discuss underlying mechanisms of the skin microbiome involved in the wound healing process; THM in regulating immune responses and commensal microbiome. We additionally propose few pioneer ideas and studies in the development of therapeutic strategies for controlled delivery of herbal medicine. This review aims to promote wound care with a focus on wound microbiome, immune response, and topical drug delivery systems. Finally, future development trends, challenges, and research directions are discussed.

Drug discovery research in Ghana, challenges, current efforts, and the way forward

We have a long-term vision to develop drug discovery research capacity within Ghana, to tackle unmet medical needs in Ghana and the wider West African region. However, there are several issues and challenges that need to be overcome to enable this vision, including training, human resource, equipment, infrastructure, procurement, and logistics. We discuss these challenges from the context of Ghana in this review. An important development is the universities and research centres within Ghana working together to address some of these challenges. Therefore, while there is a long way to go to fully accomplish our vision, there are encouraging signs.

The effect of flavonols in Anacardium occidentale L. leaf extracts on skin pathogenic microorganisms

Cashew (Anacardium occidentale L.) leaf is traditionally used to treat skin infections. Although many flavonols have been identified from its leaf extract, their inhibitory effects on skin pathogens are not yet determined. The aims of this study were to determine the antimicrobial (against skin pathogenic microbes) and antioxidant activities of four flavonol glycosides from the crude extract and three flavonol aglycones from the hydrolyzed extract. The hydrolyzed extract was found to show higher activities than the crude extract. Myricetin showed the highest activity against all the tested bacteria and yeast with the lowest Minimum Inhibition Concentration (MIC) of 7.81 μg/mL on Corynebacterium minutissimum ATCC23348. Myricetin also exhibited good primary antioxidant activities with the effective concentration with 50% of activity (EC₅₀) values ranged between 2.23 μg/mL and 6.40 μg/mL. The highest secondary antioxidant activity was indicated by myricetin-3-O-rhamnoside. Thus, myricetin can be considered as a bioactive compound of the hydrolyzed extract.

Margaritaria nobilis L.F. (Phyllanthaceae): Ethnopharmacology and Application of Computational Tools in the Annotation of Bioactive Molecules

Margaritaria nobilis is a shrubby species widely distributed in Brazil from the Amazon to the Atlantic Rainforest. Its bark and fruit are used in the Peruvian Amazon for disinfecting abscesses and as a tonic in pregnancy, respectively, and its leaves are used to treat cancer symptoms. From analyses via UHPLC-MS/MS, we sought to determine the chemical profile of the ethanolic extract of M. nobilis leaves by means of putative analyses supported by computational tools and spectral libraries. Thus, it was possible to annotate 44 compounds, of which 12 are phenolic acid derivatives, 16 are O-glycosylated flavonoids and 16 hydrolysable tannins. Among the flavonoids, although they are known, except for kaempferol, which has already been isolated from this species, the other flavonoids (10, 14, 15, 21, 24–26, 28–30, 33–35, 40 and 41) are being reported for the first time in the genus. Among the hydrolysable tannins, six ellagitannins present the HHDP group (6, 19, 22, 31, 38 and 43), one presents the DHHDP group (5), and four contain oxidatively modified congeners (12, 20, 37 and 39). Through the annotation of these compounds, we hope to contribute to the improved chemosystematics knowledge of the genus. Furthermore, supported by a metric review of the literature, we observed that many of the compounds reported here are congeners of authentically bioactive compounds. Thus, we believe that this work may help in understanding future pharmacological activities.

1, 2-trans-Stereoselective 7-O-Glycosylation of Flavonoids with Unprotected Pyranoses by Mitsunobu Reaction

The glycosylation of protecting-group-free pyranoses with flavonoids to generate flavonoid O-glycosides under Mitsunobu conditions was reported. The methodology allows to prepare a wide range of natural 7-flavonoid O -glycosides and their derivatives from commercially available chemicals in good to excellent yields with exclusive 1,2- trans -stereoselectivity regardless the anomeric configuration of employed pyranoses. The highly regioselective glycosylation was also achieved among different types of hydroxyl groups on the glycosyl acceptors.

Plant-Based Phytochemicals as Possible Alternative to Antibiotics in Combating Bacterial Drug Resistance

The unprecedented use of antibiotics that led to development of resistance affect human health worldwide. Prescription of antibiotics imprudently and irrationally in different diseases progressed with the acquisition and as such development of antibiotic resistant microbes that led to the resurgence of pathogenic strains harboring enhanced armors against existing therapeutics. Compromised the treatment regime of a broad range of antibiotics, rise in resistance has threatened human health and increased the treatment cost of diseases. Diverse on metabolic, genetic and physiological fronts, rapid progression of resistant microbes and the lack of a strategic management plan have led researchers to consider plant-derived substances (PDS) as alternative or in complementing antibiotics against the diseases. Considering the quantitative characteristics of plant constituents that attribute health beneficial effects, analytical procedures for their isolation, characterization and phytochemical testing for elucidating ethnopharmacological effects has being worked out for employment in the treatment of different diseases. With an immense potential to combat bacterial infections, PDSs such as polyphenols, alkaloids and tannins, present a great potential for use, either as antimicrobials or as antibiotic resistance modifiers. The present study focuses on the mechanisms by which PDSs help overcome the surge in resistance, approaches for screening different phytochemicals, methods employed in the identification of bioactive components and their testing and strategies that could be adopted for counteracting the lethal consequences of multidrug resistance.

Cytotoxicity of 91 Kenyan indigenous medicinal plants towards human CCRF-CEM leukemia cells

ETHNOPHARMACOLOGICAL RELEVANCE

Plants from Kenyan flora are traditionally used against many ailments, including cancer and related diseases. Cancer is characterized as a condition with complex signs and symptoms. Recently there are recommendations that ethnopharmacological usages such as immune and skin disorders, inflammatory, infectious, parasitic and viral diseases should be taken into account when selecting plants that treat cancer.

AIM

The present study was aimed at investigating the cytotoxicity of a plethora of 145 plant parts from 91 medicinal plants, most of which are used in the management of cancer and related diseases by different communities in Kenya, against CCRF-CEM leukemia cell line.

MATERIALS AND METHODS

Extracts from different plant parts (leaves, stems, stem bark, roots, root barks, aerial parts and whole herb) were obtained by cold percolation using different solvent systems, such as (1:1v/v) dichloromethane (CH2Cl2) and n-hexane (1), methanol (MeOH) and CH2Cl2 (2); neat MeOH (3), 5% H2O in MeOH (4) and with ethanol (EtOH, 5); their cytotoxicities were determined using the resazurin reduction assay against CCRF-CEM cells.

RESULTS

At a single concentration of 10μg/mL, 12 out of 145 extracts exhibited more than 50% cell inhibition. These include samples from the root bark of Erythrina sacleuxii (extracted with 50% n-hexane-CH2Cl2), the leaves of Albizia gummifera, and Strychnos usambarensis, the stem bark of Zanthoxylum gilletii, Bridelia micrantha, Croton sylvaticus, and Albizia schimperiana; the root bark of Erythrina burttii and E. sacleuxii (extracted with 50% CH2Cl2-MeOH), the stem bark of B. micrantha and Z. gilletii (extracted using 5% MeOH-H2O) and from the berries of Solanum aculeastrum (extracted with neat EtOH). The EtOH extract of the berries of S. aculeastrum and A. schimperiana stem bark extract displayed the highest cytotoxicity towards leukemia CCRF-CEM cells, with IC50 values of 1.36 and 2.97µg/mL, respectively. Other extracts having good activities included the extracts of the stem barks of Z. gilletii and B. micrantha and leaves of S. usambarensis with IC50 values of 9.04, 9.43 and 11.09µg/mL, respectively.

CONCLUSIONS

The results of this study provided information related to the possible use of some Kenyam medicinal plants, and mostly S. aculeastrum, A. schimperiana, C. sylvaticus, Z. gilletii, B. micrantha and S. usambarensis in the treatment of leukemia. The reported data helped to authenticate the claimed traditional use of these plants. However, most plants are used in combination as traditional herbal concoctions. Hence, the cytotoxicity of corresponding plant combinations should be tested in vitro to authenticate the traditional medical practitioners actual practices.

Discovery and resupply of pharmacologically active plant-derived natural products: A review

Medicinal plants have historically proven their value as a source of molecules with therapeutic potential, and nowadays still represent an important pool for the identification of novel drug leads. In the past decades, pharmaceutical industry focused mainly on libraries of synthetic compounds as drug discovery source. They are comparably easy to produce and resupply, and demonstrate good compatibility with established high throughput screening (HTS) platforms. However, at the same time there has been a declining trend in the number of new drugs reaching the market, raising renewed scientific interest in drug discovery from natural sources, despite of its known challenges. In this survey, a brief outline of historical development is provided together with a comprehensive overview of used approaches and recent developments relevant to plant-derived natural product drug discovery. Associated challenges and major strengths of natural product-based drug discovery are critically discussed. A snapshot of the advanced plant-derived natural products that are currently in actively recruiting clinical trials is also presented. Importantly, the transition of a natural compound from a "screening hit" through a "drug lead" to a "marketed drug" is associated with increasingly challenging demands for compound amount, which often cannot be met by re-isolation from the respective plant sources. In this regard, existing alternatives for resupply are also discussed, including different biotechnology approaches and total organic synthesis. While the intrinsic complexity of natural product-based drug discovery necessitates highly integrated interdisciplinary approaches, the reviewed scientific developments, recent technological advances, and research trends clearly indicate that natural products will be among the most important sources of new drugs also in the future.

Gastroprotective and antioxidant potentials of ethanolic stem bark extract of Margaritaria discoidea (Euphorbiaceae) in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Decoctions prepared from the bark of Margaritaria discoidea (Baill.) G. L. Webster (Euphorbiaceae) are used in Nigeria and other parts of West Africa in the treatment of wounds and ulcers. The study was conducted to investigate the gastric ulcer protective effect of ethanolic stem bark extract of M. discoidea in rats.

MATERIALS AND METHODS

Antiulcer assays were performed using ethanol, indomethacin and pylorus ligation-induced ulcer models at the dose of 50, 100 and 150 mg/kg, p.o. The antioxidant effect of the extract was evaluated in vitro and by studying its effect on antioxidant enzymes (superoxide dismutase, catalase, and reduced glutathione) and lipid peroxidation in the stomach tissue of rats in ethanol-induced model. Solvent fractions (hexane, dichloromethane, ethyl acetate, butanol and aqueous) from the crude extract were investigated for antiulcerogenic effects in ethanol-induced ulcer model at the dose of 150 mg/kg. GC-MS analysis of the active hexane fraction was also carried out.

RESULTS

The extract significantly (P<0.05) reduced gastric lesion in ethanol and indomethacin-induced ulcer models. The extract had significant influence on in vivo antioxidant status in ethanol-induced model. In pylorus ligation-induced model, only the dose of 150 mg/kg showed significant reduction (88.89%, P<0.05) of ulcer lesions. There was no significant reduction in the gastric juice volume and total acidity. The solvent fractions showed ulcer inhibition in varying degrees but significance (P<0.01) was only observed in the hexane fraction. Ethyl esters of palmitic and linoleic acids were found as the major compounds in the GC-MS analysis of the hexane fraction.

CONCLUSION

Our results suggest that M. discoidea possesses gastroprotective activity possibly mediated through antioxidant mechanism. The data obtained in this study provide some support to the traditional use of M. discoidea in the treatment of gastric ulcer.

Chemical constituents and biological activities of Albizia myriophylla wood

CONTEXT

Albizia myriophylla Benth (Leguminosae) is a medicinal plant widely used in Thailand and other Asian countries as a folk medicine remedy for many ailments.

OBJECTIVE

The objective of this study is to investigate the chemical compositions, antibacterial activity, and cytotoxicity of A. myriophylla wood.

MATERIALS AND METHODS

The structure identification of the isolated compounds was established using spectroscopic methods. In vitro antibacterial activity against Streptococcus mutans, Staphylococcus aureus, and Bacillus cereus and the cytotoxicity against KB cells of extracts and compounds from A. myriophylla were performed using broth microdilution and resazurin microplate assays, respectively. The lupinifolin content in A. myriophylla extracts was quantified by high-performance liquid chromatography.

RESULTS

A rare flavan-3,4-diol (1) together with eight known compounds (2-9) were isolated from the wood of A. myriophylla. Compounds 4-9 exhibited anti-S. mutans activity, of which lupinifolin (5) was the most potent with an MIC value of 0.98 µg/mL, followed by its dihydroxy derivative 4 with an MIC value of 62.5 µg/mL. Compounds 4 and 5 also displayed marked antibacterial activity against B. cereus and S. aureus (MIC value 15.63-125 µg/mL) and showed strong cytotoxic activity against KB cells (IC50 value 4.95-12.55 µg/mL). The lupinifolin contents in ethanol extracts from two different collections of this plant originating from central and southern Thailand were 93.85 and 0.04 mg/g, respectively.

CONCLUSION

This is the first report of compounds 1-4 from A. myriophylla. Compounds 4 and 5 showed potent antibacterial and cytotoxic activities compared with other isolates. The anti-S. mutans activity of A. myriophylla extracts seems to be related to the lupinifolin content.

Cytotoxic effects of stem bark extracts and pure compounds from Margaritaria discoidea on human ovarian cancer cell lines

Margaritaria discoidea (Baill.) G. L. Webster (Euphorbiaceae) is a well-known medicinal plant in Africa used for the treatment of various diseases. So far, no cytotoxic effects of plant extracts on cancer cell lines have been reported.

AIM OF THE STUDY

To evaluate the cytotoxicity against human ovarian cancer cells of extracts of M. discoidea and characterize the major bioactive compounds.

METHODS

Both organic and aqueous extracts of this plant were obtained by maceration. The sulforhodamine B cell proliferation assay was used for evaluation of their cytotoxic activities and the potential bioactive compounds were characterized by gas chromatography-mass spectrometry.

RESULTS

The organic extract of M. discoidea showed stronger cytotoxicity than the aqueous extract with IC50 values of 14.4±3.0, 14.2±1.2 and 34.7±0.5µg/ml on OVCAR-8, A2780 and cisplatin-resistant A2780cis ovarian cancer cells, respectively. The organic extract was further subjected to bioassay-guided fractionation by partitioning with n-hexane, ethyl acetate, and n-butanol in water. The ethyl acetate fraction was the most potent on the three ovarian cancer cell lines. A GC-MS analysis of trimethylsilyl derivatives of this fraction indicated the presence of phenolic compounds such as gallic acid and the alkaloid securinine. The IC50 values of these two compounds were determined to be in the range of 3-16µM, which indicated that they could contribute to the cytotoxic activity of the extract of M. discoidea.

CONCLUSIONS

This study has evaluated the cytotoxicity of stem bark extracts of M. discoidea against ovarian cancer cells and provided a basis of further development of this plant for the treatment of ovarian cancer.