A prolyl endopeptidase-inhibiting antioxidant from Phyllanthus ussurensis

Interactions of Polyphenolic Gallotannins with Amyloidogenic Polypeptides Associated with Alzheimer's Disease: From Molecular Insights to Physiological Significance

Polyphenols are natural compounds abundantly found in plants. They are known for their numerous benefits to human health, including antioxidant properties and anti-inflammatory activities. Interestingly, many studies have revealed that polyphenols can also modulate the formation of amyloid fibrils associated with disease states and can prevent the formation of cytotoxic oligomer species. In this review, we underline the numerous effects of four hydrolysable gallotannins (HGTs) with high conformational flexibility, low toxicity, and multi-targeticity, e.g., tannic acid, pentagalloyl glucose, corilagin, and 1,3,6-tri-O-galloyl-β-D-glucose, on the aggregation of amyloidogenic proteins associated with the Alzheimer's Disease (AD). These HGTs have demonstrated interesting abilities to reduce, at different levels, the formation of amyloid fibrils involved in AD, including those assembled from the amyloid β-peptide, the tubulin-associated unit, and the islet amyloid polypeptide. HGTs were also shown to disassemble pre-formed fibrils and to diminish cognitive decline in mice. Finally, this manuscript highlights the importance of further investigating these naturally occurring HGTs as promising scaffolds to design molecules that can interfere with the formation of proteotoxic oligomers and aggregates associated with AD pathogenesis.

Epilobiumpyrricholophum Extract Suppresses Porcine Pancreatic Elastase and Cigarette Smoke Extract-Induced Inflammatory response in a Chronic Obstructive Pulmonary Disease Model

Chronic airway exposure to harmful substances, such as deleterious gases, cigarette smoke (CS), and particulate matter, triggers chronic obstructive pulmonary disease (COPD), characterized by impaired lung function and unbridled immune responses. Emerging epigenomic and genomic evidence suggests that excessive recruitment of alveolar macrophages and neutrophils contributes to COPD pathogenesis by producing various inflammatory mediators, such as reactive oxygen species (ROS), neutrophil elastase, interleukin (IL) 6, and IL8. Recent studies showed that Epilobium species attenuated ROS, myeloperoxidase, and inflammatory cytokine production in murine and human innate immune cells. Although the Epilobium genus exerts anti-inflammatory, antioxidant, and antimicrobial effects, the question of whether the Epilobium species regulate lung inflammation and innate immune response in COPD has not been investigated. In this study, Epilobium pyrricholophum extract (EPE) suppressed inflammatory cell recruitment and clinical symptoms in porcine pancreatic elastase and CS extract-induced COPD mice. In addition, EPE attenuated inflammatory gene expression by suppressing MAPKs and NFκB activity. Furthermore, UPLC-Q-TOF MS analyses revealed the anti-inflammatory effects of the identified phytochemical constituents of EPE. Collectively, our studies revealed that EPE represses the innate immune response and inflammatory gene expression in COPD pathogenesis in mice. These findings provide insights into new therapeutic approaches for treating COPD.

Polyphenol-Peptide Interactions in Mitigation of Alzheimer's Disease: Role of Biosurface-Induced Aggregation

Alzheimer's disease (AD) is the most common age-related neurodegenerative disorder, responsible for nearly two-thirds of all dementia cases. In this review, we report the potential AD treatment strategies focusing on natural polyphenol molecules (green chemistry) and more specifically on the inhibition of polyphenol-induced amyloid aggregation/disaggregation pathways: in bulk and on biosurfaces. We discuss how these pathways can potentially alter the structure at the early stages of AD, hence delaying the aggregation of amyloid-β (Aβ) and tau. We also discuss multidisciplinary approaches, combining experimental and modelling methods, that can better characterize the biochemical and biophysical interactions between proteins and phenolic ligands. In addition to the surface-induced aggregation, which can occur on surfaces where protein can interact with other proteins and polyphenols, we suggest a new concept referred as "confinement stability". Here, on the contrary, the adsorption of Aβ and tau on biosurfaces other than Aβ- and tau-fibrils, e.g., red blood cells, can lead to confinement stability that minimizes the aggregation of Aβ and tau. Overall, these mechanisms may participate directly or indirectly in mitigating neurodegenerative diseases, by preventing protein self-association, slowing down the aggregation processes, and delaying the progression of AD.

Corilagin in Cancer: A Critical Evaluation of Anticancer Activities and Molecular Mechanisms

Corilagin (β-1-O-galloyl-3,6-(R)-hexahydroxydiphenoyl-d-glucose), an ellagitannin, is one of the major bioactive compounds present in various plants. Ellagitannins belong to the hydrolyzable tannins, a group of polyphenols. Corilagin shows broad-spectrum biological, and therapeutic activities, such as antioxidant, anti-inflammatory, hepatoprotective, and antitumor actions. Natural compounds possessing antitumor activities have attracted significant attention for treatment of cancer. Corilagin has shown inhibitory activity against the growth of numerous cancer cells by prompting cell cycle arrest at the G2/M phase and augmented apoptosis. Corilagin-induced apoptosis and autophagic cell death depends on production of intracellular reactive oxygen species in breast cancer cell line. It blocks the activation of both the canonical Smad and non-canonical extracellular-signal-regulated kinase/Akt (protein kinase B) pathways. The potential apoptotic action of corilagin is mediated by altered expression of procaspase-3, procaspase-8, procaspase-9, poly (ADP ribose) polymerase, and Bcl-2 Bax. In nude mice, corilagin suppressed cholangiocarcinoma growth and downregulated the expression of Notch1 and mammalian target of rapamycin. The aim of this review is to summarize the anticancer efficacy of corilagin with an emphasis on the molecular mechanisms involving various signaling pathways in tumor cells.

Mitigating Alzheimer’s Disease with Natural Polyphenols: A Review

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According to Alzheimer’s Disease International (ADI), nearly 50 million people worldwide were living with dementia in 2017, and this number is expected to triple by 2050. Despite years of research in this field, the root cause and mechanisms responsible for Alzheimer’s disease (AD) have not been fully elucidated yet. Moreover, promising preclinical results have repeatedly failed to translate into patient treatments. Until now, none of the molecules targeting AD has successfully passed the Phase III trial. Although natural molecules have been extensively studied, they normally require high concentrations to be effective; alternately, they are too large to cross the blood-brain barrier (BBB).

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In this review, we report AD treatment strategies, with a virtually exclusive focus on green chemistry (natural phenolic molecules). These include therapeutic strategies for decreasing amyloid-β (Aβ) production, preventing and/or altering Aβ aggregation, and reducing oligomers cytotoxicity such as curcumin, (-)-epigallocatechin-3-gallate (EGCG), morin, resveratrol, tannic acid, and other natural green molecules. We also examine whether consideration should be given to potential candidates used outside of medicine and nutrition, through a discussion of two intermediate-sized green molecules, with very similar molecular structures and key properties, which exhibit potential in mitigating Alzheimer’s disease.

Evaluation of prolyl oligopeptidase and acetylcholinesterase inhibition by Phyllanthus tenellus Roxb. from Brazil

Phyllanthus tenellus Roxb. (Phyllanthaceae) is a plant used in Brazilian folk medicine for the treatment of intestinal infections and diabetes. Despite its use in traditional medicine, it was reported that P. tenellus extract may cause several effects in the central nervous system (CNS) of animals, such as agitation and signs of depression. The aim of this study was to determine the main constituents of P. tenellus methanol extract and to investigate whether the extract is able to inhibit the enzymes prolyl oligopeptidase (POP), acetylcholinesterase (AChE) and dipeptidyl peptidase-IV (DPP-IV). Corilagin (1) was isolated as the main constituent of the P. tenellus extract, along with rutin (2) and vitexin-2″-O-rhamnoside (3). The extract presented the ability to inhibit mainly POP. Dichloromethane and ethyl acetate fractions showed the highest inhibitory potency against POP (IC₅₀ values of 1.7 ± 0.4 and 11.7 ± 2 µg/mL, respectively). All fractions were inactive against AChE. Corilagin displayed selective POP inhibition in a dose-dependent manner, with IC₅₀= 19.7 ± 2.6 µg/mL. Corilagin exhibited moderate capacity to pass through the phospholipid membrane by passive diffusion, presenting effective permeability (Pe) of 1.26 × 10^-7 cm/s.

Corilagin, a promising medicinal herbal agent

Corilagin, a gallotannin, is one of the major active components of many ethnopharmacological plants. It was isolated from Caesalpinia coriaria (Jacq.) Willd. (dividivi) by Schmidt in 1951 for the first time. In the past few decades, corilagin was reported to exhibit anti-tumor, anti-inflammatory and hepatoprotective activities, etc. However, little attention was paid to its pharmacological properties due to the complicated and inefficient extract method. In recent years, with the development of extraction technology corilagin was much easier to obtain than before. Thus, people return to pay attention to its anti-tumor, hepatoprotective, and anti-inflammatory activities, particularly as an anti-tumor agent candidate. Our research team had focused on the distribution, preparation and anti-tumor activity of corilagin since 2005. We found corilagin showed good anti-tumor activity on hepatocellular carcinoma and ovarian cancer. What's more, corilagin showed a low level of toxicity toward normal cells and tissues. Due to the extensive attention that corilagin has received, we present a systematic review of the pharmacological effects of corilagin. In this review, we summarized all the pharmacological effects of corilagin with a focus on the molecular mechanism of anti-tumor activity and show you how corilagin affected the signaling pathways of tumor cells as well as its physicochemical properties, distribution and preparation methods.

Therapeutic Potential of Polyphenols from Epilobium Angustifolium (Fireweed)

Epilobium angustifolium is a medicinal plant used around the world in traditional medicine for the treatment of many disorders and ailments. Experimental studies have demonstrated that Epilobium extracts possess a broad range of pharmacological and therapeutic effects, including antioxidant, anti-proliferative, anti-inflammatory, antibacterial, and anti-aging properties. Flavonoids and ellagitannins, such as oenothein B, are among the compounds considered to be the primary biologically active components in Epilobium extracts. In this review, we focus on the biological properties and the potential clinical usefulness of oenothein B, flavonoids, and other polyphenols derived from E. angustifolium. Understanding the biochemical properties and therapeutic effects of polyphenols present in E. angustifolium extracts will benefit further development of therapeutic treatments from this plant. Copyright © 2016 John Wiley & Sons, Ltd.

The Genus Phyllanthus: An Ethnopharmacological, Phytochemical, and Pharmacological Review

The plants of the genus Phyllanthus (Euphorbiaceae) have been used as traditional medicinal materials for a long time in China, India, Brazil, and the Southeast Asian countries. They can be used for the treatment of digestive disease, jaundice, and renal calculus. This review discusses the ethnopharmacological, phytochemical, and pharmacological studies of Phyllanthus over the past few decades. More than 510 compounds have been isolated, the majority of which are lignins, triterpenoids, flavonoids, and tannins. The researches of their remarkable antiviral, antioxidant, antidiabetic, and anticancer activities have become hot topics. More pharmacological screenings and phytochemical investigations are required to support the traditional uses and develop leading compounds.

α-Amylase inhibitors from an Indonesian medicinal herb, Phyllanthus urinaria

BACKGROUND

Diabetes mellitus and associated diseases are an increasing problem around the world. One of the hyperglycemic remedies is glucose absorption reduction by suppressing carbohydrate digestion due to utilization of α-amylase inhibitors.

RESULTS

Prospective herbs were analyzed by in vitro enzyme assay to evaluate their inhibitory activity against porcine pancreatic amylase (PPA), and it was found that Phyllanthus urinaria and three other herbs to showed a potent inhibitory activity. A 50% aqueous methanol-soluble extract of the leaves of P. urinaria was chromatographed using a silica gel column. The active fractions were further purified by preparative high-performance liquid chromatography to isolate active principles against PPA. Structural determination revealed that these isolated compounds were gallic acid, corilagin, and macatannin B, and showed mild activity against PPA (activity in 1 mmol L⁻¹ concentration: 23%, 21%, 33%, respectively).

CONCLUSION

P. urinaria extracts show inhibitory activity against PPA. This activity, together with the information on isolated compounds, may benefit further exploration of P. urinaria utilization in the management of borderline diabetes patients.

DPPH Radical Scavenging and Xanthine Oxidase Inhibitory Activity of Terminalia macroptera Leaves

From a methanol extract of the leaves of the Malian medicinal tree Terminalia macroptera, cis-polyisoprene (1), chebulic acid trimethyl ester (2), methyl gallate (3), shikimic acid (4), corilagin (5), rutin (6), narcissin (7), chebulagic acid (8) and chebulinic acid (9), were isolated. Cis-polyisoprene (1) was the major non-polar constituent. The novel compound 2 showed high radical scavenging activity (IC50 4.7 μg/mL), but was inactive as xanthine oxidase inhibitor. The major substituent of the crude extract, substance 5, showed a high radical scavenger effect (IC50 2.7 μg/mL) and weak xanthine oxidase inhibition (IC50 ca 105 μg/mL). The antioxidant and radical scavenging effects of some of the substances identified in this study may to some extent explain the medical use of this tree in West Africa.

Corilagin prevents tert-butyl hydroperoxide-induced oxidative stress injury in cultured N9 murine microglia cells

Oxidative stress plays an important role in neurodegenerative diseases. Reactive oxygen species (ROS)-mediated stress in microglia in vivo could result in cellular injuries and preferentially induces neuronal injury. Corilagin, a novel member of the phenolic tannin family, has been shown to possess antioxidant properties. In this study, we investigated the effects of corilagin on tert-butyl hydroperoxide (TBHP)-induced injury in cultured N9 murine microglial cells and the underlying mechanisms by a methyltetrazolium assay and oxidative damage assay. We found that exposure of N9 cells to TBHP induced cytotoxicity as demonstrated by cell shrinkage, loss of cell viability, increased lactate dehydrogenase (LDH) leakage, and increased intracellular levels of ROS. By contrast, TBHP reduced both superoxide dismutase activity and total cell anti-oxidation capacity, but glutathione was not reduced. Moreover, TBHP treatment was associated with the loss of mitochondrial membrane potential, and it induced cell apoptosis through the mitochondrial-mediated pathway involving the down-regulation of Bcl-2 expression and up-regulation of the Bax/Bcl-2 ratio. Interestingly, pre-treatment with corilagin reversed these reactions. These data collectively indicated that corilagin could attenuate TBHP-induced oxidative stress injury in microglial cells, and its protective effects may be ascribed to its antioxidant and antiapoptotic properties. Our findings suggest that corilagin should be a potential candidate for the treatment of oxidative stress-induced neurodegenerative diseases.

Identification of major phenolic compounds from Nephelium lappaceum L. and their antioxidant activities

Nephelium lappaceum is a tropical fruit whose peel possesses antioxidant properties. Experiments on the isolation and identification of the active constituents were conducted, and on their antioxidant activity using a lipid peroxidation inhibition assay. The methanolic extract of N. lappaceum peels exhibited strong antioxidant properties. Sephadex LH-20 chromatography was utilized in the isolation of each constituent and the antioxidant properties of each was studied. The isolated compounds were identified as ellagic acid (EA) (1), corilagin (2) and geraniin (3). These compounds accounted for 69.3% of methanolic extract, with geraniin (56.8%) as the major component, and exhibited much greater antioxidant activities than BHT in both lipid peroxidation (77-186 fold) and DPPH* (42-87 fold) assays. The results suggest that the isolated ellagitannins, as the principal components of rambutan peels, could be further utilized as both a medicine and in the food industry.

A prolyl oligopeptidase inhibitor, Z-Pro-Prolinal, inhibits glyceraldehyde-3-phosphate dehydrogenase translocation and production of reactive oxygen species in CV1-P cells exposed to 6-hydroxydopamine

We studied the ability of prolyl oligopeptidase (POP) inhibitors, Z-Pro-Prolinal and JTP-4819, to prevent translocation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and formation of reactive oxygen species (ROS), in 6-hydroxydopamine (6-OHDA) and cytosine arabinoside (Ara-C) treated monkey fibroblast (CV1-P) and human neuroblastoma (SH-SY5Y) cells. The cells were pretreated with POP inhibitors (30 min) before addition of toxicants. GAPDH was analyzed by Western hybridization, ROS by fluorescent 2'7'-dichlorodihydro-fluorescein diacetate, and viability by the MTT method. Both toxicants induced GAPDH translocation to the particulate fraction (mitochondria and nuclei). Z-Pro-Prolinal was able to inhibit the translocation in 6-OHDA-exposed CV1-P cells. In SH-SY5Y cells and in JTP-4819 pretreated cells, no prevention of translocation was seen. However, the intensity of GAPDH in cytosolic fraction increased. Both inhibitors blocked 6-OHDA-induced ROS-production to the control level in CV1-P but, not in SH-SY5Y cells, without affecting their viability. In conclusion, POP inhibitors are able to prevent certain cell stress related factors such as ROS production or GAPDH translocation.

Antiatherogenic Effects of Phyllanthus Emblica Associated with Corilagin and its Analogue

Oxidized low-density lipoprotein (ox-LDL) is the main etiologic factor in atherogenesis, and antioxidants are accepted as effective treatment of atherosclerosis. The aim of this study was to clarify whether the mechanism of the antiatherogenic effects of the herb Phyllanthus Emblica, which is widely used to treat atherosclerosis-related diseases, is associated with ox-LDL via its compounds of soluble tannin, corilagin (beta-1-O-galloyl-3,6-(R)-hexahydroxydiphenoyl-d-glucose), and its analogue Dgg16 (1,6-di-O-galloyl-beta-d-glucose). Human umbilical vein endothelial cells, ECV-304, were incubated with ox-LDL (50 mg/l), treated with corilagin or Dgg16 at different doses (0.0001-0.1 mmol/l), and then incubated with monocytes. Malondialdehyde (MDA) in the culture media was determined and the number of monocytes adhering to ECV-304 cells was counted with cytometry. In another experiment, the rat vascular smooth muscular cells (VSMC) were incubated in media with or without ox-LDL (50 mg/l), and with corilagin or Dgg16 also at different doses (0.0001-0.1 mol/l), the proliferation of which was assayed with MTT. The results showed that both corilagin and Dgg16 were able to decrease MDA, prevented ECV-304 cells from being adhering to by monocytes, and inhibited VSMC proliferation activated by ox-LDL. The results suggest that the two compounds are effective in inhibiting the progress of atherosclerosis by alleviating oxidation injury or by inhibiting ox-LDL-induced VSMC proliferation, which may be promising mechanisms for treating atherosclerosis.