New highly in vitro antioxidative 3,8″-linked Biflav(an)ones and Flavanone-C-glycosides from Garcinia buchananii stem bark

Chromones and biflavonoids from Garcinia pedunculata and Garcinia nujiangensis and their anti-inflammatory activity

Plants of the Garcinia genus were rich in structurally diverse and naturally bioactive components, while limited studies have been reported for Garcinia pedunculata Roxb. and G. nujiangensis C. Y. Wu & Y. H. Li. Four previously undescribed compounds including three chromones, garpedunchromones A-C (1-3), and one biflavonoid, nujiangbiflavone A (14), along with fifteen known analogs (4-13, 15-19) were isolated from G. pedunculata and G. nujiangensis. The structures of the isolated compounds were determined based on their HRESIMS data, extensive NMR spectroscopic analyses, and ECD calculations. The chromone derivatives were isolated from Garcinia for the first time. Compound 14 was a rare biflavonoid with C-3─C-6″ linkage. The biological evaluation of these isolates against NO production was conducted in the LPS-induced RAW 264.7 cells, resulting in the identification of a series of potent NO inhibitors, of which garpedunchromone B (2) was the most active with an IC50 value of 18.11 ± 0.96 μM. In the network pharmacology studies, the potential targets of compounds and inflammation were obtained from PharmMapper and GeneCards database. GO and KEGG enrichment analysis revealed that the overlapped targets were closely related to the major pathogenic processes linked to inflammation. Garpedunchromone B and proteins binding sites were being predicted.

Developments in the stereoselective synthesis of benzopyran, benzopyrone and flavonoid based natural product analogues using C-glycosides as an intrinsic chiral synthon

Stereoselective synthesis is essential for propelling mainstream academia toward a relentless pursuit of novel and cutting-edge strategies for constructing molecules with unparalleled precision. Naturally derived benzopyrans, benzopyrones, and flavonoids are an essentially prominent group of oxa-heterocycles, highly significant targets in medicinal chemistry owing to their extensive abundance in biologically active natural products and pharmaceuticals. The molecular complexity and stereoselectivity induced by heterocycles embedded with C-glycosides have attracted considerable interest and emerged as a fascinating area of research for synthetic organic chemists. This present article emphasizes the existing growths in the strategies involving the diastereoselective synthesis of C-glycosylated benzopyrans, benzopyrones, and flavonoids using naturally acquired glycones as chiral synthons.

A new gnidiflavanone-flavonol dimer and other constituents from Gnidia apiculata

A new 3,8''-flavanone-flavonol dimer gnidiflavanone-flavonol (1) and 10 known compounds (2-11), including four rare primula-type flavones 2-5, were isolated from the roots of Gnidia apiculata. Compounds 2-5 and 7 were reported for the first time from the plant family Thymelaeceae. Structures of the isolated compounds were established by spectroscopic data, including 1D and 2D NMR (COSY, HMBC, HSQC and ROESY) and mass spectrometry, as well as by the comparison with literature data. The crude roots extract and isolated compounds were evaluated for antimicrobial and antiplasmodial activities. Among isolated compounds, 6-hydroxyflavone (4) and 6-O-acetylflavone (4a) showed antiplasmodial activity against chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum.

Proceedings of Chemistry, Pharmacology, Pharmacokinetics and Synthesis of Biflavonoids

Biflavonoids, composed of two monoflavonoid residues, occur naturally in angiosperms, bryophytes, ferns, and gymnosperms. More than 592 biflavonoids have been structurally elucidated, and they can be classified into two groups of C-C and C-linear fragments-C, based on whether the linker between the two residues contains an atom. As the linker can be established on two arbitrary rings from different residues, the C-C type contains various subtypes, as does the C-linear fragment-C type. Biflavonoids have a wide range of pharmacological activities, including anti-inflammatory, antioxidant, antibacterial, antiviral, antidiabetic, antitumor, and cytotoxic properties, and they can be applied in Alzheimer's disease and Parkinson's disease. This review mainly summarizes the distribution and chemistry of biflavonoids; additionally, their bioactivities, pharmacokinetics, and synthesis are discussed.

Two new phenolic glucosides from marine-derived fungus Aspergillus sp

Two new phenolic glucosides, including a new O-glycoside (1) and a new C-glycoside (2), were isolated from a marine-derived fungus Aspergillus sp. The structures of new compounds were elucidated through interpretations of spectroscopic evidence and high-resolution electrospray ionization mass spectrometry. The hexose unit of 1 was identified as β-D-glucose by comparison with an authentic sample via HPLC after acid hydrolysis and derivatization. All compounds were evaluated for their ability to inhibit LPS-induced NO production in RAW264.7 macrophages, but none of them displayed significant activity.

Phenolic C-Glycosides and Aglycones from Marine-Derived Aspergillus sp. and Their Anti-Inflammatory Activities

A chemical investigation of the secondary metabolites of a marine-derived Aspergillus sp. led to the isolation and characterization of 13 phenolic compounds, including 10 new compounds (1-10). Seven new compounds (1-7) are unusual phenolic C-glycosides, while the other new compounds (8-10) are structurally related aglycones. The chemical structures of these new compounds were elucidated by 1D and 2D NMR and HRESIMS spectroscopic analyses. The absolute configurations of these new C-glycosides were determined by comparison of experimental electronic circular dichroism spectra with those of calculated ones. In addition, the anti-inflammatory activities of these compounds were evaluated, and compound 9 significantly inhibited nitric oxide production with an IC₅₀ value of 6.0 ± 0.5 μM in lipopolysaccharide-induced RAW264.7 cells. Moreover, compound 9 also showed anti-inflammatory activity by inhibiting the NF-κB-activated pathway.

Construction and Application of a Database for a Five-Dimensional Identification of Natural Compounds in Garcinia Species by Means of UPLC-ESI-TWIMS-TOF-MS: Introducing Gas Phase Polyphenol Conformer Drift Time Distribution Intensity Ratios

Thirty-four reference compounds from G. buchananii were analyzed by means of UPLC-ESI-IMS-TOF-MS to build a database consisting of retention time, accurate m/ z of precursors and fragment ions, and rotationally averaged collision cross-sectional area (CCS). The CCS value of six selected compounds analyzed in bark extract in different concentrations and solvent systems showed excellent intra- and interday precision (RSD ≤ 0.9%). The established database was applied on different organs of G. buchananii as well as G. kola, G. mangostana, and G. cambogia enabling a fast and reliable identification of these natural bioactives. For several compounds, more than one drift time species could be highlighted, which we propose to be hydrogen bond stabilized rotational isomers transferred from solution to gas phase. We used all CCS values of one compound, and we propose to add also the intensity ratio of the conformers as a new and additional characteristic compound parameter in compound identification/screening/database applications to reduce dereplication and false positives and to strengthen the identification.

(2R,3S,2″R,3″R)-Manniflavanone Protects Proliferating Skeletal Muscle Cells against Oxidative Stress and Stimulates Myotube Formation

We investigated the antioxidative properties of (2R,3S,2″R,3″R)-manniflavanone (MF) using in vitro assays and examined its effects on myogenesis and lactate-induced oxidative stress in C2C12 cells. MF was purified from Garcinia buchananii stem bark. H₂O₂ and oxygen radical absorbance capacity assays demonstrated that MF is a powerful antioxidant. This finding was supported by diphenylpicrylhydrazine radical scavenging activity of MF. MF was less cytotoxic to C2C12 cells compared to ascorbic acid and myricetin. Moreover, MF accelerated myotube formation in the differentiated C2C12 cells by up-regulating myogenic proteins such as MyoG and myosin heavy chain. Furthermore, MF rescued late differentiation of myoblast suppressed by lactate treatment and up-regulated the expression levels of Nrf2 in lactate-induced oxidative stress, indicating that MF stimulates antioxidative activity inside C2C12 cells. Collectively, MF is a potent antioxidant with a higher safety profile than ascorbic acid and myricetin. It reduces oxidative stress-induced delaying of skeletal muscle differentiation by scavenging reactive oxygen species and regulating myogenic proteins factors.

Anvillea garcinii extract inhibits the oxidative burst of primary human neutrophils

BACKGROUND

Anvillea garcinii Coss. & Durieu (Anv) plant is used as a traditional North African medicine against several diseases associated with inflammation. At inflammatory sites, reactive oxygen species (ROS) produced in excess by activated phagocyte NADPH oxidase (NOX2) can accentuate inflammatory responses. Thus, we investigated if Anv-water soluble polysaccharides could modulate primary human neutrophil oxidative burst in vitro.

METHODS

Human neutrophils were isolated from fresh whole blood and O₂^.- generation was measured by cytochrome c reduction assays. Western blots were used to analyse the translocation of PKC, p47^phox (a key component of NOX2 activity) to neutrophil plasma membrane. Also, myeloperoxidase (MPO) release in the extracellular medium was studied by western blots. Flow cytometric analysis was used to detect CD11b membrane expression.

RESULTS

Water soluble polysaccharides from Anv dose-dependently inhibited N-formyl-methionyl-leucyl-phenylalanine (fMLF)- and phorbol myristate acetate (PMA)-induced O₂^.- generation by human neutrophils. Moreover, Anv-polysaccharides strongly inhibited PMA-induced PKCβ and p47^phox translocation to membranes and p47^phox phosphorylation on Ser328, a main PKC target. In contrast, polysaccharides extract from Zygophyllum gaetulum plant, which is also used as a traditional North African medicine against inflammatory diseases, was ineffective on this PKCβ-p47phox pathway. Further, Anv inhibited important neutrophil degranulation markers corresponding to myeloperoxidase (MPO) release and CD11b membrane expression.

CONCLUSION

The process of down-regulating NADPH oxidase by polysaccharides extracts from Anv provides new insights into the mechanism of Anv's anti-inflammatory actions.

Polyprenylated Benzoylphloroglucinols with DNA Polymerase Inhibitory Activity from the Fruits of Garcinia schomburgkiana

Chemical investigation of the fruits of Garcinia schomburgkiana collected in Vietnam led to the isolation of eight new schomburgkianones, A-H (1-8), four known (9-12) polyprenylated benzoylphloroglucinols, and four known biflavonoids. The structures of these compounds were elucidated by spectroscopic and chemical means. The absolute configuration at C-40 of 1 and 2 was determined by (1)H NMR analyses of their MPA esters. The configuration of the bicyclo[3.3.1]nonane core of the polyprenylated benzoylphloroglucinols was assigned by comparison of their experimental ECD spectra with those of related compounds. The polyprenylated benzoylphloroglucinols exhibited inhibitory activities against mammalian DNA polymerases α and λ, with IC50 values ranging from 5.0 to 8.8 μM. Compounds 1, 2, 4, 5, and 9-11 showed cytotoxic effects against HeLa human cervical cancer cells with median lethal dose values lower than 10 μM.

(2R,3S,2'' R,3''R)-manniflavanone, a new gastrointestinal smooth muscle L-type calcium channel inhibitor, which underlies the spasmolytic properties of Garcinia buchananii stem bark extract

Garcinia buchananii Baker stem bark extract (GBB) is a traditional medication of diarrhea and dysentery in sub-Saharan Africa. It is believed that GBB causes gastrointestinal smooth muscle relaxation. The aim of this study was to determine whether GBB has spasmolytic actions and identify compounds underlying these actions. Calcium (Ca²⁺) imaging was used to analyze the effect of GBB on Ca²⁺ flashes and Ca²⁺ waves in guinea pig gallbladder and distal colon smooth muscle. Intracellular microelectrode recording was used to determine the effect of GBB, six fractions of GBB, M1–5 and M7, and (2R,3S,2”R,3”R)-manniflavanone, a compound isolated from M3 on action potentials in gallbladder smooth muscle. The technique was also used to analyze the effect of GBB, M3, and (2R,3S,2”R,3”R)-manniflavanone on action potentials in the circular muscle of mouse and guinea pig distal colons, and the effect of GBB and (2R,3S,2”R,3”R)-manniflavanone on slow waves in porcine ileum. GBB inhibited Ca²⁺ flashes and Ca²⁺ waves. GBB, M3 and (2R,3S,2”R,3”R)-manniflavanone inhibited action potentials. L-type Ca²⁺ channel activator Bay K 8644 increased the discharge of action potentials in mouse colon but did not trigger or increase action potentials in the presence of GBB and (2R,3S,2”R,3”R)-manniflavanone. GBB and (2R,3S,2”R,3”R)-manniflavanone inhibited action potentials in the presence of Bay K 8644. GBB and (2R,3S,2”R,3”R)-manniflavanone reduced the amplitude but did not alter the frequency of slow waves in the porcine ileum. In conclusion, GBB and (2R,3S,2”R,3”R)-manniflavanone relax smooth muscle by inhibiting L-type Ca²⁺ channels, thus have potential for use as therapies of gastrointestinal smooth muscle spasms, and arrhythmias.

Antioxidative compounds from Garcinia buchananii stem bark

An aqueous ethanolic extract of the stem bark of Garcinia buchananii showed strong antioxidative activity using H2O2 scavenging, oxygen radical absorbance capacity (ORAC), and Trolox equivalent antioxidant capacity (TEAC) assays. Activity-guided fractionation afforded three new compounds, isomanniflavanone (1), an ent-eriodictyol-(3α→6)-dihydroquercetin-linked biflavanone, 1,5-dimethoxyajacareubin (2), and the depsidone garcinisidone-G (3), and six known compounds, (2″R,3″R)-preussianon, euxanthone, 2-isoprenyl-1,3,5,6-tetrahydroxyxanthone, jacareubin, isogarcinol, and garcinol. All compounds were described for the first time in Garcinia buchananii. The absolute configurations were determined by a combination of NMR, ECD spectroscopy, and polarimetry. These natural products showed high in vitro antioxidative power, especially isomanniflavanone, with an EC50 value of 8.5 μM (H2O2 scavenging), 3.50/4.95 mmol TE/mmol (H/L-TEAC), and 7.54/14.56 mmol TE/mmol (H/L-ORAC).