Anti-inflammatory flavonoids from the rhizomes of Helminthostachys zeylanica

The traditional utilization, biological activity and chemical composition of edible fern species

ETHNOPHARMACOLOGICAL RELEVANCE

Ferns form an important part of the human diet. Young fern fiddleheads are mostly consumed as vegetables, while the rhizomes are often extracted for starch. These edible ferns are also often employed in traditional medicine, where all parts of the plant are used, mostly to prepare extracts. These extracts are applied either externally as lotions and baths or internally as potions, decoctions and teas. Ailments traditionally treated with ferns include coughs, colds, fevers, pain, burns and wounds, asthma, rheumatism, diarrhoea, or skin diseases (eczema, rashes, itching, leprosy).

AIM OF THE REVIEW

This review aims to compile the worldwide knowledge on the traditional medicinal uses of edible fern species correlating to reported biological activities and isolated bioactive compounds.

MATERIALS AND METHODS

The articles and books published on edible fern species were searched through the online databases Web of Science, Pubmed and Google Scholar, with critical evaluation of the hits. The time period up to the end of 2022 was included.

RESULTS

First, the edible fern species were identified based on the literature data. A total of 90 fern species were identified that are eaten around the world and are also used in traditional medicine. Ailments treated are often associated with inflammation or bacterial infection. However, only the most common and well-known fern species, were investigated for their biological activity. The most studied species are Blechnum orientale L., Cibotium barometz (L.) J. Sm., Diplazium esculentum (Retz.) Sw., Marsilea minuta L., Osmunda japonica Thunb., Polypodium vulgare L., and Stenochlaena palustris (Burm.) Bedd. Most of the fern extracts have been studied for their antioxidant, anti-inflammatory and antimicrobial activities. Not surprisingly, antioxidant capacity has been the most studied, with results reported for 28 edible fern species. Ferns have been found to be very rich sources of flavonoids, polyphenols, polyunsaturated fatty acids, carotenoids, terpenoids and steroids and most of these compounds are remarkable free radical scavengers responsible for the outstanding antioxidant capacity of fern extracts. As far as clinical trials are concerned, extracts from only three edible fern species have been evaluated.

CONCLUSIONS

The extracts of edible fern species exert antioxidant anti-inflammatory and related biological activities, which is consistent with their traditional medicinal use in the treatment of wounds, burns, colds, coughs, skin diseases and intestinal diseases. However, studies to prove pharmacological activities are scarce, and require chemical-biological standardization. Furthermore, correct botanical classification needs to be included in publications to simplify data acquisition. Finally, more in-depth phytochemical studies, allowing the linking of traditional use to pharmacological relevance are needed to be done in a standardized way.

Discovery of anti-inflammatory natural flavonoids: Diverse scaffolds and promising leads for drug discovery

Natural products have been utilized for medicinal purposes for millennia, endowing them with a rich source of chemical scaffolds and pharmacological leads for drug discovery. Among the vast array of natural products, flavonoids represent a prominent class, renowned for their diverse biological activities and promising therapeutic advantages. Notably, their anti-inflammatory properties have positioned them as promising lead compounds for developing novel drugs combating various inflammatory diseases. This review presents a comprehensive overview of flavonoids, highlighting their manifold anti-inflammatory activities and elucidating the underlying pathways in mediating inflammation. Furthermore, this review encompasses systematical classification of flavonoids, related anti-inflammatory targets, involved in vitro and in vivo test models, and detailed statistical analysis. We hope this review will provide researchers engaged in active natural products and anti-inflammatory drug discovery with practical information and potential leads.

Ugonin L inhibits osteoclast formation and promotes osteoclast apoptosis by inhibiting the MAPK and NF-κB pathways

Bone loss is a major issue for patients with osteoporosis, arthritis, periodontitis, and bone metastasis; however, anti-resorption drugs used to treat bone loss have been linked to a variety of adverse effects. Helminthostachys zeylanica (L.) Hook, belonging to the family Ophioglossaceae, is commonly used in traditional Chinese medicine to treat inflammation and liver problems. In the current study, ugonin L extracted from H. zeylanica was shown to reduce the receptor activator of nuclear factor kappa beta ligand (RANKL)-induced osteoclastogenesis in RAW264.7 cells in a concentration-dependent manner. Ugonin L treatment also inhibited the mRNA expression of osteoclast markers. Ugonin L was also shown to promote cell apoptosis in mature osteoclasts and suppress RANKL-induced ERK, p38, JNK, and NF-κB activation. Taken together, ugonin L appears to be a promising candidate for the development of novel anti-resorption therapies.

The Metabolite Content of the Post-Culture Medium of the Tree Fern Cyathea delgadii Sternb. Cell Suspension Cultured in the Presence of 2,4-D and BAP

The aim of this study was to demonstrate the metabolic profile of post-culture medium as an expression of cell suspension metabolic activity of the tree fern Cyathea delgadii Sternb. The molecular profile of the tree fern’s cell culture has been never described, according to our knowledge. The cell suspension was established using ½ MS medium supplemented with various concentrations of 2,4-D and BAP. The optimal concentrations were 2.0 mg·L−1 and 0.2 mg·L−1, respectively. The cell suspension initially showed an organized system of cell division and later unorganized cell proliferation. LC-MS and GC-MS were used to identify the chemical composition of the post-culture medium. The LC-MS analysis results suggested that the color of liquid medium could be due to the presence of flavonoid derivatives, as this group of compounds was represented by eight compounds. After GC-MS analysis based on retention indexes and thanks to mass spectra comparison, 130 natural products were recognized, belonging to various classes of primary and secondary metabolites.

Bioactive Compounds, Antioxidant, Anti-Inflammatory, Anti-Cancer, and Toxicity Assessment of Tribulus terrestris-In Vitro and In Vivo Studies

Tribulus terrestris L. belongs to the family Zygophyllaceae and integral part of various ancient medicinal systems including Chinese, Indian, and European to combat various health ailments. The aim of the present study was to assess the phytochemical constituents, in vitro antioxidant activity using DPPH, FRAP, and H2O2 assays, in vitro anticancer activity using MTT assay, and in vitro and in vivo anti-inflammatory properties of T. terrestris. The acute and sub-acute toxicity of extracts exhibiting most biological potential was examined using murine models. Liquid-liquid partitioning followed by RP-HPLC sub-fraction of crude extract was performed. After that, ESI-MS/MS analysis was done for the timid identification of bioactive metabolites responsible for bioactivities of sub-fractions and HPLC analysis to quantify the compounds using external standards. Among all extracts, T. terrestris methanol extract was noted to hold maximum phenolic (341.3 mg GAE/g) and flavonoid (209 mg QE/g) contents, antioxidant activity in DPPH (IC50 71.4 µg/mL), FRAP (35.3 mmol/g), and H2O2 (65.3% inhibition) assays, anti-inflammatory activities in vitro at 400 µg/mL (heat-induced hemolysis, % inhibition 68.5; egg albumin denaturation, % inhibition 75.6%; serum albumin denaturation, % inhibition 80.2), and in vivo at 200 mg/kg (carrageenan-induced paw edema, % inhibition 69.3%; formaldehyde-induced paw edema, % inhibition 71.3%) and anticancer activity against breast cancer cell (MCF-7) proliferation (IC50 74.1 µg/mL). Acute and sub-acute toxicity studies recorded with no change in body weight, behavior, hematological, serum, and histopathological parameters in treated rats with T. terrestris methanol extracts when compared to control group. Fraction B obtained through liquid-liquid partitioning resulted in more bioactive potential as compared to the parent methanol extract. RP-HPLC analysis of fraction B resulted with four sub-fractions (TBTMF1-TBTMF4), wherein TBTMF3 delineated notable bioactive capabilities as compared to other fractions and parent methanol extract. ESI-MS/MS analysis of TBTMF3 resulted with tentative identification of myricetin, rutin, liquitrigenin, physcion, and protodioscin. It can be stated that T. terrestris is a potential bearing herb and findings of current study further verify the claims made in ancient medicinal systems. However, after investigation of each identified compound, it must be considered for drug discovery.

Inhibition of Bacterial Neuraminidase and Biofilm Formation by Ugonins Isolated From Helminthostachys Zeylanica (L.) Hook

Bacterial neuraminidase (BNA) plays a pivotal role in the pathogenesis of several microbial diseases including biofilm formation. The aim of this study is to reveal the neuraminidase inhibitory potential of metabolites from Helminthostachys zeylanica (L.) Hook. which have diverse biological activities including PTP1B and α-glucosidase. The six ugonins (1–6) from the target plant showed significant neuraminidase inhibition. The inhibitory potencies were observed at a nanomolar level of 35–50 nM, which means they are 100 times more active than their corresponding mother compounds (eriodyctiol and luteolin). A detailed kinetic study revealed that all ugonins were reversible noncompetitive inhibitors. An in-depth investigation of the most potent compound 1 showed its time-dependent inhibition with the isomerization model having k₅ = 0.0103 min⁻¹, k₆ = 0.0486 min⁻¹, and K_i^app = 0.062 μM. The binding affinities (K_sv) were agreed closely with our prediction based on the inhibitory potencies. Particularly, ugonin J (1) blocked the biofilm formation of E. coli dose-dependently up to 150 µM without the inhibition of bacteria. The major compounds (1–6) in the extract were characterized by UPLC-ESI-Q-TOF/MS.

Flavonoids as inhibitors of human neutrophil elastase

Elastase is a proteolytic enzyme belonging to the family of hydrolases produced by human neutrophils, monocytes, macrophages, and endothelial cells. Human neutrophil elastase is known to play multiple roles in the human body, but an increase in its activity may cause a variety of diseases. Elastase inhibitors may prevent the development of psoriasis, chronic kidney disease, respiratory disorders (including COVID-19), immune disorders, and even cancers. Among polyphenolic compounds, some flavonoids and their derivatives, which are mostly found in herbal plants, have been revealed to influence elastase release and its action on human cells. This review focuses on elastase inhibitors that have been discovered from natural sources and are biochemically characterised as flavonoids. The inhibitory activity on elastase is a characteristic of flavonoid aglycones and their glycoside and methylated, acetylated and hydroxylated derivatives. The presented analysis of structure-activity relationship (SAR) enables the determination of the chemical groups responsible for evoking an inhibitory effect on elastase. Further study especially of the in vivo efficacy and safety of the described natural compounds is of interest in order to gain better understanding of their health-promoting potential.

Anticancer Effects of Helminthostachys zeylanica Ethyl acetate Extracts on Human Gastric Cancer Cells through Downregulation of the TNF-α-activated COX-2-cPLA2-PGE2 Pathway

Background: Gastric cancer (GC) is the second most prevalent cancer worldwide and the eighth most common cause of tumor-related death in Taiwan. Helminthostachys zeylanica, a flavonoid compound, has anti-inflammatory, immunomodulatory, and anticancer effects. We examined whether an extract of H. zeylanica (E1 and E2) has potential as a treatment for GC. Methods: We investigated the effects (pro-apoptosis, pro-autophagy, and antiproliferation ability) of H. zeylanica-E2 on cell viability in healthy gastric epithelial (GES-1) and GC cells (AGS and BGC823). H. zeylanica-E2 was toxic to GC cells but had little or no toxicity to normal cells. Results: In this study, H. zeylanica-E2 induced apoptosis through caspase 3/7, Bcl-2, Bax, cyclooxygenase-2 (COX-2), and cleaved poly (ADP-ribose) polymerase pathways in GC cells. In addition, it increased autophagy by stimulating autophagy-related protein (ATG)5, ATG7, LC3-I/LC3-II, and inhibiting COX-2 activity in GC cells. We also found that H. zeylanica-E2 exhibited antiproliferation ability through cell cycle arrest in G0/G1 and G2/M and suppressed the migration of GC cells. The anticancer effects of H. zeylanica-E2 in GC cells might be mediated partly through inhibition of tumor necrosis factor-α (TNF-α)-activated proinflammatory cytosolic phospholipase A2 (cPLA2)-COX-2-prostaglandin E₂ (PGE₂) pathway. Conclusions: Our results suggest that H. zeylanica-E2 has potential as a novel adjunctive agent for the treatment of GC.

Ugonin J Acts as a SARS-CoV-2 3C-like Protease Inhibitor and Exhibits Anti-inflammatory Properties

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection causes severe “flu-like” symptoms that can progress to acute respiratory distress syndrome (ARDS), pneumonia, renal failure, and death. From the therapeutic perspective, 3-chymotrypsin-like protein (3CLpro) is a plausible target for direct-acting antiviral agents because of its indispensable role in viral replication. The flavonoid ugonin J (UJ) has been reported to have antioxidative and anti-inflammatory activities. However, the potential of UJ as an antiviral agent remains unexplored. In this study, we investigated the therapeutic activity of UJ against SARS-CoV-2 infection. Importantly, UJ has a distinct inhibitory activity against SARS-CoV-2 3CLpro, compared to luteolin, kaempferol, and isokaempferide. Specifically, UJ blocks the active site of SARS-CoV-2 3CLpro by forming hydrogen bonding and van der Waals interactions with H163, M165 and E166, G143 and C145, Q189, and P168 in subsites S1, S1′, S2, and S4, respectively. In addition, UJ forms strong, stable interactions with core pharmacophore anchors of SARS-CoV-2 3CLpro in a computational model. UJ shows consistent anti-inflammatory activity in inflamed human alveolar basal epithelial A549 cells. Furthermore, UJ has a 50% cytotoxic concentration (CC₅₀) and a 50% effective concentration (EC₅₀₎ values of about 783 and 2.38 µM, respectively, with a selectivity index (SI) value of 329, in SARS-CoV-2-infected Vero E6 cells. Taken together, UJ is a direct-acting antiviral that obstructs the activity of a fundamental protease of SARS-CoV-2, offering the therapeutic potential for SARS-CoV-2 infection.

Effectiveness of cyclohexyl functionality in ugonins from Helminthostachys zeylanica to PTP1B and α-glucosidase inhibitions

Ugonins are unique flavonoids with cyclohexyl motif from Helminthostachys zeylanica. Ugonins (1-6) from the target plant displayed significant inhibitions against both PTP1B (IC₅₀s = 0.6-7.3 μM) and α-glucosidase (IC₅₀s = 3.9-32.9 μM), which are crucial enzymes associated with diabetes. A cyclohexyl motif was proved to be the key functionality for PTP1B and α-glucosidase. For example, 1 was 26-fold effective to PTP1B and 15-fold to α-glucosidase than its mother compound, luteolin. This tendency was well elucidated with distinctive differences of binding affinities (K_SV) between ugonins and mother compounds to PTP1B enzyme. Inhibitory mechanisms to PTP1B and α-glucosidase were fully characterized to be competitive, non-competitive and mixed type I according to the position of cyclohexyl functionality. In particular, the ugonin J (1) has a cyclohexyl on the B ring was estimated as a reversible, competitive and a slow binding inhibitor with parameters: K_i^app = 0.1234 μM, k₃ = 0.5713 μM^-1 min^-1, and k₄ = 0.0705 min^-1. In-depth molecular docking experiments disclosed the specific binding sites and residues of competitive inhibitor (1) and non-competitive inhibitor (4) to PTP1B enzymes. As well, all six ugonins (1-6) also inhibited α-glucosidase effectively, in which cyclohexyl motif was also the key functionality of inhibitions.

Helminthostachys zeylanica alleviates hepatic steatosis and insulin resistance in diet-induced obese mice

Background

Obesity and its associated health conditions, type 2 diabetes mellitus (T2DM) and nonalcoholic fatty liver disease (NAFLD), are worldwide health problems. It has been shown that insulin resistance is associated with increased hepatic lipid and causes hepatic steatosis through a myriad of mechanisms, including inflammatory signaling.

Methods

Helminthostachys zeylanica (HZ) is used widely as a common herbal medicine to relieve fever symptoms and inflammatory diseases in Asia. In the present study, we evaluated whether HZ has therapeutic effects on obesity, NAFLD and insulin resistance. The protective effects of HZ extract were examined using free fatty acid-induced steatosis in human HuS-E/2 cells and a high-fat diet-induced NAFLD in mice.

Results

The major components of the HZ extract are ugonins J and K, confirmed by HPLC. Incubation of human hepatocytes, HuS-E/2 cells, with palmitate markedly increased lipid accumulation and treatment with the HZ extract significantly decreased lipid deposition and facilitated AMPK and ACC activation. After 12 weeks of a high-fat diet with HZ extract treatment, the HFD mice were protected from hyperlipidemia and hyperglycemia. HZ extract prevented body weight gain, adipose tissue expansion and adipocyte hypertrophy in the HFD mice. In addition, fat accumulation was reduced in mice livers. Moreover, the insulin sensitivity-associated index, which evaluates insulin function, was also significantly restored.

Conclusions

These results suggest that HZ has a promising pharmacological effect on high-fat diet-induced obesity, hepatic steatosis and insulin resistance, which may have the potential for clinical application.

Hepatoprotective Effect of Ugonin M, A Helminthostachyszeylanica Constituent, on Acetaminophen-Induced Acute Liver Injury in Mice

The present study aimed to discover the possible effectiveness of Ugonin M, a unique flavonoid isolated from Helminthostachys zeylanica-a traditional Chinese medicine used as anti-inflammatory medicine-and to elucidate the potential mechanisms of Ugonin M in the acute liver injury induced by acetaminophen (APAP). In this study, Ugonin M significantly ameliorated APAP-induced histopathological changes and the typical liver function biomarkers (i.e., alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total bilirubin (T-Bil)). It also affected APAP-induced abnormal lipid metabolism including total cholesterol (TC) and triglyceride (TG) in the serum. In inflammatory pharmacological action, Ugonin M suppressed the pro-inflammatory mediators such as nitric oxide (NO) and the lipid peroxidation indicator malondialdehyde (MDA). In addition, Ugonin M reinforced hemeoxygenase-1 (HO-1) protein expression and the production of antioxidant enzymes viz superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT). Furthermore, inflammation-associated cytokines including tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and IL-1β as well as proteins such as inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) were decreased by the pretreatment of Ugonin M. Moreover, this study found that pretreatment of Ugonin M apparently decreased nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinases (MAPKs) activation via inhibition of the degradation of NF-κB, inhibitory κB-α (IκB-α), extracellular regulated kinase (ERK), c-Jun-N-terminal (JNK), and p38 active phosphorylation. In conclusion, Ugonin M significantly showed a protective effect against APAP-induced liver injury by reducing oxidative stress and inflammation. Thus, Ugonin M could be one of the effective components of H. zeylanica that plays a major role in the treatment of inflammatory disorders.

Antibacterial Prenylated Isoflavonoids from the Stems of Millettia extensa

The first phytochemical investigation of the stem extract of Millettia extensa resulted in the isolation and identification of six new isoflavones, millexatins A-F (1-6), together with 16 known compounds. The structures of these new compounds were determined on the basis of their spectroscopic data. Millexatin A (1) is a rare isoflavone containing three isoprenyl units on a modified A ring. Compounds 1, 6, 10, 11, and 14 displayed promising antibacterial activity with MIC values of 2-8 μg/mL.

Suppressive activities and mechanisms of ugonin J on vascular smooth muscle cells and balloon angioplasty-induced neointimal hyperplasia

Neointimal hyperplasia (or restenosis) is primarily attributed to excessive proliferation and migration of vascular smooth muscle cells (VSMCs). In this study, we investigated the inhibitory effects and mechanisms of ugonin J on VSMC proliferation and migration as well as neointimal formation. Cell viability and the cell-cycle distribution were, respectively, analyzed using an MTT assay and flow cytometry. Cell migration was examined using a wound-healing analysis and a transwell assay. Protein expressions and gelatinase activities were, respectively, measured using Western blot and gelatin zymography. Balloon angioplasty-induced neointimal formation was induced in a rat carotid artery model and then examined using immunohistochemical staining. Ugonin J induced cell-cycle arrest at the G₀ /G₁ phase and apoptosis to inhibit VSMC growth. Ugonin J also exhibited marked suppressive activity on VSMC migration. Ugonin J significantly reduced activations of focal adhesion kinase, phosphoinositide 3-kinase, v-akt murine thymoma viral oncogene homolog 1, and extracellular signal-regulated kinase 1/2 proteins. Moreover, ugonin J obviously reduced expressions and activity levels of matrix metalloproteinase-2 and matrix metalloproteinase-9. In vivo data indicated that ugonin J prevented balloon angioplasty-induced neointimal hyperplasia. Our study suggested that ugonin J has the potential for application in the prevention of balloon injury-induced neointimal formation.

Quality Control of the Root and Rhizome of Helminthostachys zeylanica (Daodi-Ugon) by HPLC Using Quercetin and Ugonins as Markers

Daodi-Ugon is the dried root and rhizome of Helminthostachys zeylanica (L.) Hook. and has been used for centuries in the treatment of inflammation, fever, pneumonia, burns, and various disorders. However, the chromatographic methods to determine the phytochemical composition of H. zeylanica have never been reported. This study not only aims to develop a valid high-performance liquid chromatography (HPLC) method and to establish a chromatographic fingerprint for the quality control of H. zeylanica, it also establish the proposed content limits of Quercetin, Ugonin J, and Ugonin M. An HPLC method with a RP₁₈ column (250 × 4.6 mm, 5 μm) was developed for the quantitative analysis of Quercetin, Ugonin J, and Ugonin M in H. zeylanica. A simple gradient of (A) methanol/(B) phosphoric acid in water (5–45 min, 70–80% A; 50–55 min, 80–70% A) was used and 360 nm was selected as the detection wavelength. The average contents and proposed content limits for H. zeylanica were calculated with a t-test and a measurement uncertainty test based on 20 batches of authentic H. zeylanica samples. Limits of detection (LOD), quantification (LOQ), linearity, precision, repeatability, stability, and recovery of the developed method were validated. All of the validation results of quantitative determination and fingerprinting methods were satisfactory. The developed method was then applied to assay the contents of Quercetin, Ugonin J, and Ugonin M and to acquire the fingerprints of all of the collected H. zeylanica samples. At the 99% confidence level, the calculated content limits were 56.45, 112.15, and 277.98 mg/kg for Quercetin, Ugonin J, and Ugonin M, respectively. Those validated HPLC quantitative method, fingerprinting profile, and the proposed content limits of three chemical markers that could be used in the quality control of H. zeylanica in the market.

Ugonin M, a Helminthostachys zeylanica Constituent, Prevents LPS-Induced Acute Lung Injury through TLR4-Mediated MAPK and NF-κB Signaling Pathways

Helminthostachys zeylanica (L.) Hook. is plant that has been used in traditional Chinese medicine for centuries for the treatment of inflammation, fever, pneumonia, and various disorders. The aims of the present study are to figure out the possible effectiveness of the component Ugonin M, a unique flavonoid isolated from H. zeylanica, and to elucidate the mechanism(s) by which it works in the LPS-induced ALI model. In this study, Ugonin M not only inhibited the production of pro-inflammatory mediators such as NO, TNF-α, IL-1β, and IL-6, as well as infiltrated cellular counts and protein content in the bronchoalveolar lavage fluid (BALF) of lipopolysaccharides (LPS)-induced acute lung injury (ALI) mice, but also ameliorated the severity of pulmonary edemas through the score of a histological examination and the ratio of wet to dry weight of lung. Moreover, Ugonin M was observed to significantly suppress LPS-stimulated protein levels of iNOS and COX-2. In addition, we found that Ugonin M not only obviously suppressed NF-κB and MAPK activation via the degradation of NF-κB and IκB-α as well as ERK and p38MAPK active phosphorylation but also inhibited the protein expression level of TLR4. Further, Ugonin M treatment also suppressed the protein levels of MPO and enhanced the protein expressions of HO-1 and antioxidant enzymes (SOD, GPx, and CAT) in lung tissue of LPS-induced ALI mice. It is anticipated that through our findings, there is strong evidence that Ugonin M may exert a potential effect against LPS-induced ALI mice. Hence, Ugonin M could be one of the major effective components of H. zeylanica in the treatment of inflammatory disorders.

Anti-inflammatory and Antiosteoporosis Flavonoids from the Rhizomes of Helminthostachys zeylanica

Chemical investigation of the rhizomes of Helminthostachys zeylanica led to the isolation of eight new flavonoids including six cyclized geranylflavonoids, ugonins V-X (1-3), (10R,11S)-ugonin N (4), (10R,11S)-ugonin S (5), and ugonin Y (6), as well as two quercetin glucosides, quercetin-4'-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside (7) and quercetin-3-O-β-d-glucopyranosyl-4'-O-β-d-glucopyranosyl-(1→2)-β-d-glucopyranoside (8). The structures of these compounds were established by spectroscopic analyses and acid hydrolysis of the sugar moiety. Among the isolated compounds, 1, 2, 5, 6, ugonins J-S (9-13), ugonstilbene A (14), and ugonin L (23) were evaluated for their anti-inflammatory activity on lipopolysaccharide-induced nitric oxide (NO) production in microglial cells. Except for 1, 5, and 13, all other compounds inhibited NO production with IC₅₀ values of 6.2-10.1 μM and were more potent than the positive control, pyrrolidine dithiocarbamate. Compounds 1, 2, 5, 6, and 10-13 were tested for antiosteoporotic activities, and ugonin K (10) exhibited the highest inhibitory activity against RANKL-induced osteoclast differentiation in RAW264.7 cells with an IC₅₀ value of 1.8 ± 0.2 μM.

Anti-inflammatory Prenylated Flavonoids from Helminthostachys zeylanica

Two new [neougonins A (1) and B (2)] and nine known prenylated flavonoids were isolated from the whole plants of Helminthostachys zeylanica. The structures of the new isolates were elucidated by extensive NMR techniques, including one and two dimensional (1D)- and (2D)-NMR experiments, as well as comparison with spectroscopic data of known analogous compounds. Moreover, compound 1 inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW264.7 cells with an IC50 value of 3.32 µM.

Ugonin U stimulates NLRP3 inflammasome activation and enhances inflammasome-mediated pathogen clearance

The NOD-like receptor pyrin domain 3 (NLRP3) inflammasome contains Nod-like receptors, a subclass of pattern recognition receptors, suggesting that this complex has a prominent role in host defenses. Various structurally diverse stimulators activate the NLRP3 inflammasome through different signaling pathways. We previously reported that ugonin U (UgU), a natural flavonoid isolated from Helminthostachys zeylanica (L) Hook, directly stimulates phospholipase C (PLC) and triggers superoxide release in human neutrophils. In the present study, we showed that UgU induced NLRP3 inflammasome assembly and subsequent caspase-1 and interleukin (IL)-1β processing in lipopolysaccharide-primed human monocytes. Moreover, UgU elicited mitochondrial superoxide generation in a dose-dependent manner, and a specific scavenger of mitochondrial reactive oxygen species (ROS) diminished UgU-induced IL-1β and caspase-1 activation. UgU induced Ca²⁺ mobilization, which was inhibited by treatment with inhibitors of PLC or inositol triphosphate receptor (IP₃R). Blocking Ca²⁺ mobilization, PLC, or IP₃R diminished UgU-induced IL-1β release, caspase-1 activation, and mitochondrial ROS generation. These data demonstrated that UgU activated the NLPR3 inflammasome activation through Ca²⁺ mobilization and the production of mitochondrial ROS. We also demonstrated that UgU-dependent NLRP3 inflammasome activation enhanced the bactericidal function of human monocytes. The ability of UgU to stimulate human neutrophils and monocytes, both of which are professional phagocytes, and its capacity to activate the NLRP3 inflammasome, which is a promising molecular target for developing anti-infective medicine, indicate that UgU treatment should be considered as a possible novel therapy for treating infectious diseases.

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The immuno-stimulatory effects UgU in human monocytes were evaluated.

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UgU induces Ca²⁺ mobilization and eventually activates the NLRP3 inflammasome.

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UgU facilitates the bactericidal function of human monocytes.

Evaluation of Anti-Inflammatory Effects of Helminthostachys zeylanica Extracts via Inhibiting Bradykinin-Induced MMP-9 Expression in Brain Astrocytes

Phytochemicals present in vegetables, fruits, and herbs are believed to reduce the risk of several major diseases including cardiovascular or neurodegenerative disorders. The roots of the fern Helminthostachys zeylanica (L.) Hook. (Ophioglossaceae) have been used for centuries in the treatment of inflammation and as a folk medicine in several countries. The plant has been shown to possess an array of medicinal properties, including antioxidants and anti-inflammatory activities. Moreover, a rising level of matrix metalloproteinase-9 (MMP-9) has been found in blood fluid of these patients suffering from brain inflammatory diseases, which may be considered an inflammatory biomarker in several inflammatory diseases including the central nervous system (CNS) inflammation. Previously, we have demonstrated the signaling mechanisms of bradykinin (BK)-induced MMP-9 expression in brain astrocytes. Herein, we evaluate the effects of H. zeylanica extracts on BK-induced MMP-9 expression in brain astrocytes and its influencing mechanism. The results showed that H. zeylanica extracts, including E0, E1, and E2 significantly reduce MMP-9 induced by BK in brain astrocytes (RBA-1 cells). These H. zeylanica extracts can inhibit BK-stimulated phosphorylation of c-Src, Pyk2, and PKC(α/δ). Moreover, BK-stimulated NADPH oxidase (Nox)-derived reactive oxygen species (ROS) generation has also been attenuated by pretreatment with these extracts, suggesting that the H. zeylanica extracts have an antioxidative activity. We further demonstrated that the H. zeylanica extracts blocked activation of MAPKs (e.g., ERK1/2 and p38 MAPK) by BK. These data indicated that the H. zeylanica extracts may be has anti-inflammatory activity by reducing BK-induced ROS-dependent MMP-9 expression via these related pathways in brain astrocytes.

Antagonism of human formyl peptide receptor 1 with natural compounds and their synthetic derivatives

Formyl peptide receptor 1 (FPR1) regulates a wide variety of neutrophil functional responses and plays an important role in inflammation and the pathogenesis of various diseases. To date, a variety of natural and synthetic molecules have been identified as FPR1 ligands. Here, we review current knowledge on natural products and natural product-inspired small molecules reported to antagonize and/or inhibit the FPR1-mediated responses. Based on this literature, additional screening of selected commercially available natural compounds for their ability to inhibit fMLF-induced Ca(2+) mobilization in human neutrophils and FPR1 transfected HL-60 cells, and pharmacophore modeling, natural products with potential as FPR1 antagonists are considered and discussed in this review. The identification and characterization of natural products that antagonize FPR1 activity may have potential for the development of novel therapeutics to limit or alter the outcome of inflammatory processes.

Extracellular melanogenesis inhibitory activity and the structure-activity relationships of ugonins from Helminthostachys zeylanica roots

Ugonin J, K, and L, which are luteolin derivatives, were isolated from Helminthostachys zeylanica roots by a series of chromatographic separations of a 50% ethanol/water extract. They were identified using nuclear magnetic resonance (NMR), ultraviolet (UV) spectra, and ultra-performance liquid chromatography coupled to time-of-flight mass spectrometry (UPLC-TOF-MS). In this study, the intra and extracellular melanogenic activity of the ugonins were determined using B16 melanoma cells. The results showed that ugonin J at 12.5, 25, and 50μM reduced extracellular melanin contents to 75, 16, and 14%, respectively, compared to the control. This indicates that ugonin J showed a stronger activity than arbutin, used as the positive control. Moreover, ugonin K showed a more potent inhibition with 19, 8, and 9% extracellular melanin reduction at the same concentrations, than that shown by ugonin J. In contrast, ugonin L did not inhibit intra- or extracellular melanogenic activity. Furthermore, in order to investigate the structure-activity relationships of the ugonins, the intra- and extracellular melanogenic activity of luteolin, methylluteolin, quercetin, eriodictyol, apigenin, and chrysin were determined. Consequently, it was suggested that the catechol and flavone skeleton of ugonin K is essential for the extracellular melanogenic inhibitory activity, and the low polarity substituent groups on the A ring of ugonin K may increase the activity.

In vitro screening for anti-acetylcholiesterase, anti-oxidant, anti-glucosidase, anti-inflammatory and anti-bacterial effect of three traditional medicinal plants

In this study we investigated the phytoconstituents Calluna vulgaris, Ferula hermonis and Tribulus terrestris, and then assessed their possible biological activities by using standard methods. A preliminary phytochemical investigation of the three extracts revealed the presence of alkaloids, flavonoids, proteins, lipids, phenolic compounds, saponins, sterols and amino acids. Three extracts showed anti-oxidant effect as they inhibited the 1,1-diphenyl-2-picryl hydrazyl (DPPH) oxidation and production of thiobarbituric acid reactive substances (TBARS). Moreover, three extracts showed anti-acetylcholiesterase (AChE) and this effect was concentration dependent. C. vulgaris was the most potent inhibitor of AChE. Furthermore, the three plant extracts had an inhibitory effect toward α-glucosidase. The inhibitory effect was concentration dependent and the most potent inhibitor for α-glucosidase was the extract from T. terrestris. Calluna vulgaris showed anti-inflammatory effect at tested concentrations while the other two extracts exhibited this effect only at concentration of 25 μg/mL. Finally, C. vulgaris had a significant effect against pathogenic bacteria (Agrobacterium tumefaciens, Erwinia sp., Klebsiella pneumonia and Pseudomonas aeruginosa) in comparison to other extracts from Ferula sp., or Tribulus sp. In conclusion, all tested extracts could be promising sources for the treatment of diabetes, Alzheimer's disease, infectious diseases and oxidative stress related disorders because they are rich in phenols and flavonoids that give anti-oxidant molecules and produce an inhibitory effect against the tested enzymes.

A novel immunomodulatory effect of ugonin U in human neutrophils via stimulation of phospholipase C

Neutrophils have a crucial role in the immune system and are the first line of defense against pathogenic invaders. Neutrophil activation is required for their defensive function and can be induced by diverse stimuli, through either binding to cell surface receptors or direct intracellular target molecule stimulation. In this study, we found that 4″a,5″,6″,7″,8″,8″a-hexahydro-5,3',4'-trihydroxy-5″,5″,8″a-trimethyl-4H-chromeno [2″,3″:7,6]flavone (ugonin U), a flavonoid isolated from Helminthostachys zeylanica (L) Hook, significantly induced superoxide production and release in a time- and concentration-dependent manner. A series of experiments was performed to dissect the mechanism of ugonin U-induced respiratory burst in human neutrophils. Our results demonstrated that ugonin U induced a slow increase in intracellular Ca(2+), which was necessary for ugonin U-stimulated superoxide release. Use of a formyl peptide receptor (FPR) blocker, G protein inhibitor, and protein tyrosine kinase (PTK) inhibitor proved that FPR, G proteins, and PTKs were not associated with ugonin U-induced respiratory burst. Additionally, immunoblotting results revealed that ugonin U did not affect the phosphorylation of mitogen-activated protein kinases and protein tyrosine. Nevertheless, a phospholipase C (PLC) inhibitor and an inositol triphosphate (IP3) receptor antagonist considerably suppressed ugonin U-stimulated Ca(2+) mobilization and subsequent superoxide release. Ugonin U also induced an increase in intracellular IP3 formation, which could be blocked using a PLC inhibitor. In conclusion, our study reveals that ugonin U represents the first identified natural flavonoid compound to directly stimulate PLC. Moreover, ugonin U induces respiratory burst via the PLC/IP3/Ca(2+) pathway in human neutrophils.

A systematic review on biological activities of prenylated flavonoids

CONTEXT

Prenylated flavonoids are a unique class of naturally occurring flavonoids that exist especially for the plant's self-defensive strategy. This special class of flavonoids increases the bioactivities of their backbone flavonoids with non-prenylation; therefore, prenylated flavonoids have more potential to be developed and utilized.

OBJECTIVE

The number, position and type of the prenyl group on the flavonoids backbone structure may have close relationships with the bioactivities of flavonoids.

METHODS

PubMed and WEB OF KNOWLEDGE® were used to search articles published in English between 1 January 2002 and 31 December 2012, which discuss the structure-activity relationship between prenylated flavonoids and their bioactivities.

RESULTS

It is proposed that the prenyl-moiety makes the backbone compound more lipophilic, which leads to its high affinity with cell membranes. The prenylation brings the flavonoids with enhancement of antibacterial, anti-inflammatory, antioxidant, cytotoxicity, larvicidal as well as estrogenic activities. However, it is reported that the prenyl-moiety decreases the bioavailability and plasma absorption of prenylated flavonoids.

CONCLUSION

The prenyl group affects the bioactivities of flavonoids in certain ways, while the action mechanisms and the structure-activity relationship as well as more in vivo studies even clinical validation trials need to be further investigated.

Cyclohexylmethyl Flavonoids Suppress Propagation of Breast Cancer Stem Cells via Downregulation of NANOG

Breast cancer stem cells (CSCs) are highly tumorigenic and possess the capacity to self-renew. Recent studies indicated that pluripotent gene NANOG involves in regulating self-renewal of breast CSCs, and expression of NANOG is correlated with aggressiveness of poorly differentiated breast cancer. We initially confirmed that breast cancer MCF-7 cells expressed NANOG, and overexpression of NANOG enhanced the tumorigenicity of MCF-7 cells and promoted the self-renewal expansion of CD24^−/lowCD44⁺ CSC subpopulation. In contrast, knockdown of NANOG significantly affected the growth of breast CSCs. Utilizing flow cytometry, we identified five cyclohexylmethyl flavonoids that can inhibit propagation of NANOG-positive cells in both breast cancer MCF-7 and MDA-MB231 cells. Among these flavonoids, ugonins J and K were found to be able to induce apoptosis in non-CSC populations and to reduce self-renewal growth of CD24^−/lowCD44⁺ CSC population. Treatment with ugonin J significantly reduced the tumorigenicity of MCF-7 cells and efficiently suppressed formation of mammospheres. This suppression was possibly due to p53 activation and NANOG reduction as either addition of p53 inhibitor or overexpression of NANOG can counteract the suppressive effect of ugonin J. We therefore conclude that cyclohexylmethyl flavonoids can possibly be utilized to suppress the propagation of breast CSCs via reduction of NANOG.

Novel quercetin glucosides from Helminthostachys zeylanica root and acceleratory activity of melanin biosynthesis

Two novel quercetin glucosides, namely 4'-O-β-D-glucopyranosyl-quercetin-3-O-β-D-glucopyranosyl-(1→4)-β-D-glucopyranoside (compound 1) and 4'-O-β-D-glucopyranosyl-(1→2)-β-D-glucopyranosyl-quercetin-3-O-β-D-glucopyranosyl-(1→4)-β-D-glucopyranoside (compound 2), were isolated from Helminthostachys zeylanica root 50 % EtOH extract. Structural analysis of isolated compounds was achieved mainly by 600 MHz and 800 MHz NMR, UPLC-TOFMS and GC-MS. Of the two quercetin glucosides, compound 1 showed a high melanogenic acceleratory effect, 2.7 times higher than control, at 10 μM concentration in murine B16 melanoma cells, with no cytotoxic effect.

Ugonin K promotes osteoblastic differentiation and mineralization by activation of p38 MAPK- and ERK-mediated expression of Runx2 and osterix

Ugonin K is a flavonoid isolated from the roots of Helminthostachys zeylanica, a folk medicine used to strengthen bone mass and cure bone fracture. It is of interest to determine whether ugonin K has beneficial effect on osteoblast maturation. In this study, MC3T3-E1 osteoblasts were treated with ugonin K. Cell differentiation and mineralization were identified by alkaline phosphatase (ALP) activity and Alizarin red S staining, respectively. RT-PCR and Western blot were used to analyze osteoblast-associated gene expression and signaling pathways. Our results showed that ugonin K significantly induced the increase of ALP activity, expressions of bone sialoprotein (BSP) and osteocalcin (OCN), and mineralization. The mRNA expressions of the transcription factors Runx2 and osterix were also up-regulated by ugonin K. Ugonin K increased the phosphorylated level of p38 and ERK, respectively. In the presence of SB203580, ugonin K induced expressions of Runx2 and osterix, ALP activity, BSP level and bone nodule formation were all completely inhibited, but ugonin K induced OCN expression was not affected. On the other hand, ugonin K-induced ALP activity and mineralization were mildly attenuated by PD98059, but the over-expressed Runx2, osterix, BSP and OCN also were significantly repressed by PD98059. These suggested that both p38 and ERK participate in regulating ugonin K evoked osteogenesis but p38 seemed to play a more important role. Take together, the potential anabolic effect of ugonin K on bone might act through activations of p38- and ERK-mediated Runx2 and osterix expressions to induce the synthesis of osteoids and formation of bone nodule.

A two step synthesis of BzR/GABAergic active flavones via a Wacker-related oxidation

A general route for the synthesis of biologically important flavones is reported via a two step sequence employing a catalytic Wacker-Cook oxidation4b as the key step.