Superoxide anion scavenging effect of coumarins

Pharmacological Activities of Plant-Derived Fraxin with Molecular Mechanisms: A Comprehensive Review

Fruits and vegetables serve not only as sources of nutrition but also as medicinal agents for the treatment of diverse diseases and maladies. These dietary components are significant resources of phytochemicals that demonstrate therapeutic properties against many illnesses. Fraxin is a naturally occurring coumarin glycoside mainly present in various species of Fraxinus genera, having a multitude of therapeutic uses against various diseases and disorders. This study focuses to investigate the pharmacological activities, botanical sources, and biopharmaceutical profile of the phytochemical fraxin based on different preclinical and non-clinical studies to show the scientific evidence and to evaluate the underlying molecular mechanisms of the therapeutic effects against various ailments. For this, data was searched and collected (as of February 15, 2024) in a variety of credible electronic databases, including PubMed/Medline, Scopus, Springer Link, ScienceDirect, Wiley Online, Web of Science, and Google Scholar. The findings demonstrated favorable outcomes in relation to a range of diseases or medical conditions, including inflammation, neurodegenerative disorders such as cerebral ischemia-reperfusion (I/R) and depression, viral infection, as well as diabetic nephropathy. The phytochemical also showed protective effects such as osteoprotective, renoprotective, pulmoprotective, hepatoprotective, and gastroprotective effects due to its antioxidant capacity. Fraxin has a great capability to diminish oxidative stress-related damage in different organs by stimulating the antioxidant enzymes, downregulating nuclear factor kappa B and NLRP3, and triggering the Nrf2/ARE signaling pathways. Fraxin exhibited poor oral bioavailability because of reduced absorption and a wide distribution into tissues of different organs. However, extensive research is required to decipher the biopharmaceutical profiles, and clinical studies are necessary to establish the efficacy of the natural compound as a reliable therapeutic agent.

Liver protective effect of chloroform extract of Bauhinia purpurea leaves is attributed partly to its antioxidant action and the presence of flavonoids

CONTEXT

Bauhinia purpurea L. (Fabaceae) is used in the Ayurvedic system to treat various oxidative-related ailments (e.g., wounds, ulcers etc.). Therefore, it is believed that the plant also has the potential to alleviate oxidative-related liver damage.

OBJECTIVE

This study elucidates the hepatoprotective activity of chloroform extract of B. purpurea leaves (CEBP) in paracetamol (PCM)-induced liver injury (PILI) rats.

MATERIALS AND METHODS

Male Sprague-Dawley rats (n = 6) were pre-treated once daily (p.o.) with CEBP (50-500 mg/kg) for seven consecutive days before being administered (p.o.) a hepatotoxic agent, 3 g/kg PCM. Liver enzyme levels were determined from the collected blood, while the collected liver was used to determine the activity of endogenous antioxidant enzymes and for histopathological examination. CEBP was also subjected to radical scavenging assays and phytochemical analysis.

RESULTS

CEBP significantly (p < 0.05) reversed the toxic effect of PCM by increasing the serum levels of AST and ALT, and the activity of endogenous catalase (CAT) and superoxide dismutase (SOD) while reducing the liver weight/body weight (LW/BW) ratio. Other than low TPC value and radical scavenging activity, CEBP had a high antioxidant capacity when evaluated using the oxygen radical absorbance capacity (ORAC) assay. UHPLC-ESI-MS analysis of CEBP showed the presence of flavonoids.

DISCUSSION AND CONCLUSIONS

CEBP exerts its hepatoprotective activity through a non-free radical scavenging pathway that involves activation of the endogenous enzymatic antioxidant defense system. Further study is needed to identify the responsible bioactive compounds before the plant can be developed as a future alternative hepatoprotective medicament for clinical use.

Proposed mechanisms of action of herbal drugs and their biologically active constituents in the treatment of coughs: an overview

Various medicinal plants find their use in cough treatment, based on traditions and long-term experience. Pharmacological principles of their action, however, are much less known. Herbal drugs usually contain a mixture of potentially active compounds, which can manifest diverse effects. Expectorant or antitussive effects, which can be accompanied by others, such as anti-inflammatory or antibacterial, are probably the most important in the treatment of coughs. The aim of this review is to summarize the current state of knowledge of the effects of medicinal plants or their constituents on cough, based on reliable pharmacological studies. First, a comprehensive description of each effect is provided in order to explain the possible mechanism of action in detail. Next, the results related to individual plants and substances are summarized and critically discussed based on pharmacological in vivo and in vitro investigation.

Effect of Esculetin on Tert-Butyl Hydroperoxide-Induced Oxidative Injury in Retinal Pigment Epithelial Cells In Vitro

Esculetin is a coumarin-derived compound with antioxidant and anti-inflammatory properties. The current study aims to evaluate the therapeutic implications of esculetin on retinal dysfunction and uncover the underlying mechanisms. Tert-butyl hydroperoxide (t-BHP) at a concentration of 300 μM was used to induce oxidative stress in human retinal pigment epithelial cell line (ARPE-19) cells. Esculetin at concentrations below 250 μM did not cause cytotoxicity to ARPE-19 cells. Cell viability analysis confirmed that t-BHP induced oxidative injury of ARPE-19 cells. However, ARPE-19 cells were protected from t-BHP-induced oxidative injury by esculetin in a concentration-dependent manner. As a result of the TUNEL assay to confirm apoptosis, esculetin treatment reduced the number of TUNEL-positive cells. Esculetin down-regulated the expression levels of Bax, Caspase-3, and PARP and up-regulated the expression level of Bcl2. Collectively, this study demonstrates that esculetin exerts potent antioxidant properties in ARPE-19 cells, inhibiting t-BHP-induced apoptosis under the regulation of apoptotic factors.

Esculetin has therapeutic potential via the proapoptotic signaling pathway in A253 human submandibular salivary gland tumor cells

Esculetin is a natural lactone that is commonly derived from coumarins. According to previous experiments using human cancer cells, esculetin has potent antitumor activity; it also inhibits proliferation and induces the apoptosis of cancer cells. In the present study, the anti-proliferative effect of esculetin on the submandibular salivary gland tumor cell line, A253, was evaluated via in vitro and in vivo analyses. Furthermore, the anti-cancer effects of esculetin in A253 cells and a xenograft model of salivary gland tumors were determined using 3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium bromide and TUNEL assay, apoptosis protein array, quantitative polymerase chain reaction and western blot analysis. Esculetin (50-150 µM) was demonstrated to have an anti-proliferative effect in the A253 cell line in vitro; this observed effect was dependent on the dose and duration of treatment. Esculetin also increased the levels of Bax, cleaved caspase-3, cleaved-9 and cleaved poly (ADP-ribose) polymerase apoptosis-related proteins, and decreased the expression levels of the Bcl-2 anti-apoptotic protein. With respect to apoptosis regulation, esculetin significantly decreased the proliferation of tumor cells in a xenograft model (100 mg/kg/day) for 18 days. Overall, esculetin could be a potential oral anticancer drug against salivary gland cancer.

Selective recognition of aluminum ions using an esculetin@Q[8] host–guest supramolecular fluorescent probe

Esculetin (ESC) and non-toxic Q[8] form a supramolecular compound combination, which can effectively monitor Al3+ in the water environment.

Development of Amphiphilic Coumarin Derivatives as Membrane-Active Antimicrobial Agents with Potent In Vivo Efficacy against Gram-Positive Pathogenic Bacteria

Increases in drug-resistant pathogens are becoming a serious detriment to human health. To combat pathogen infections, a new series of amphiphilic coumarin derivatives were designed and synthesized as antimicrobial agents with membrane-targeting action. We herein report a lead compound, 25, that displayed potent antibacterial activity against Gram-positive bacteria, including MRSA. Compound 25 exhibited weak hemolytic activity and low toxicity to mammalian cells and can kill Gram-positive bacteria quickly (within 0.5 h) by directly disrupting the bacterial cell membranes. Additionally, compound 25 demonstrated excellent efficacy in a murine corneal infection caused by Staphylococcus aureus. These results suggest that 25 has great potential to be a potent antimicrobial agent for treating drug-resistant Gram-positive bacterial infections.

Inhibitory Effects of the Natural Product Esculetin on Phytophthora capsici and Its Possible Mechanism

Esculetin is an important plant-derived natural product that has multiple bioactivities and applications. Phytophthora capsici is a notorious plant pathogen capable of infecting a broad range of hosts. In this study, we evaluated the antifungal activity of esculetin against P. capsici. The baseline sensitivity of P. capsici to esculetin was established using 108 isolates collected from various geographical regions in the Jiangsu and Shandong Provinces of China. The median effective concentration (EC₅₀) values for esculetin ranged from 2.08 to 16.46 μg/ml (mean, 6.87 ± 2.70 μg/ml) and were normally distributed. Furthermore, both zoospore production and germination were strongly inhibited by esculetin. Importantly, esculetin exhibited protective as well as curative activities against P. capsici on tomato and was capable of restricting the early infection of P. capsici on Nicotiana benthamiana. We found that the esculetin treatment led to cell membrane damage of P. capsici, as revealed by morphological observations and measurements of relative conductivity and malondialdehyde (MDA). Finally, our results also suggested that esculetin may adversely affect P. capsici by inhibiting its DNA and protein synthesis. These findings will contribute to the broader evaluation of the use of esculetin to control diseases caused by P. capsici and toward a better understanding of its mode of action as a potential fungicide.

Polyphenolics and triterpenes presence in chloroform extract of Dicranopteris linearis leaves attenuated paracetamol-induced liver intoxication in rat

Introduction

Water-soluble, but not lipid-soluble, extract of Dicranopteris linearis leaves has been proven to possess hepatoprotective activity. The present study aimed to validate the hepatoprotective and antioxidant activities, and phytoconstituents of lipid-soluble (chloroform) extract of D. linearis leaves.

Methods

The extract of D. linearis leaves (CEDL; 50, 250 and 500 mg/kg) was orally administered to rats for 7 consecutive days followed by the oral administration of 3 g/kg PCM to induce liver injury. Blood was collected for liver function analysis while the liver was obtained for histopathological examination and endogenous antioxidant activity determination. The extract was also subjected to antioxidant evaluation and phytochemicals determination via phytochemical screening, HPLC and UPLC-HRMS analyses.

Results

CEDL exerted significant (p < 0.05) hepatoprotective activity at 250 and 500 mg/kg and significantly (p < 0.05) reversed the PCM-induced decrease in rat’s liver endogenous antioxidant (catalase and superoxide dismutase) level. CEDL possessed a high antioxidant capacity when measured using the ORAC assay, but a low total phenolic content value and radical scavenging activity as confirmed via several radical scavenging assays, which might be attributed particularly to the presence of triterpenes. Phytochemicals screening demonstrated the presence of triterpenes and flavonoids, while UPLC-HRMS analysis showed the presence of polyphenols belonging to the hydroxybenzoic acids, hydroxycinammates and flavonoid groups.

Discussion and conclusion

Lipid-soluble bioactive compounds of CEDL demonstrated hepatoprotective effect against PCM intoxication partly via the modulation of the endogenous antioxidant defense system, and exerted high antioxidant capacity. Further investigation is warranted to identify the potential hepatoprotective leads from CEDL for future drug development.

Endogenous Antioxidant and LOX-Mediated Systems Contribute to the Hepatoprotective Activity of Aqueous Partition of Methanol Extract of Muntingia calabura L. Leaves against Paracetamol Intoxication

Methanol extract of Muntingia calabura L. (family Muntingiaceae) leaf has been reported to exert various pharmacological activities including hepatoprotection. The present study was carried out to identify the most effective hepatoprotective partition derived from the extract and to determine the mechanisms of action involved. The extract was partitioned using solvents with different polarity to yield petroleum ether (PEMC), ethyl acetate (EAMC), and aqueous (AQMC) extracts. Each extract, at 250 mg/kg, was subjected to the paracetamol (PCM)-induced hepatotoxic assay and several parameters such as liver weight, liver/body weight ratio, serum liver enzymes' level, and histopathological examinations were determined. Each partition was also tested for their antioxidant and anti-inflammatory potentials. The most effective extract (AQMC) was prepared in additional dose of 50 and 500 mg/kg, and then subjected to the same liver toxicity test in addition to the endogenous antioxidant enzymes assay. Moreover, AQMC was also subjected to the phytochemical screening and HPLC analysis. Overall, from the results obtained: AQMC exerted significant (p < 0.05): (i) antioxidant activity when assessed using the DPPH, SOD and ORAC assays with high TPC detected; (ii) anti-inflammatory activity via LOX, but not XO pathway; (iii) hepatoprotective activity indicated by its ability to reverse the effect of PCM on the liver weight and liver/body weight ratio, the level of serum liver enzymes (ALT, AST, and ALP), and activity of several endogenous antioxidant enzymes (SOD and CAT). Phytochemicals analyses demonstrated the presence of several flavonoid-based bioactive compounds such as gallic acid and quercetin, which were reported to possess hepatoprotective activity. In conclusion, AQMC exerts hepatoprotective activity against the PCM-induced toxicity possibly by having a remarkable antioxidant potential and ability to activate the endogenous antioxidant system possibly via the synergistic action of its phytoconstituents.

Fraxinus: A Plant with Versatile Pharmacological and Biological Activities

Fraxinus, a member of the Oleaceae family, commonly known as ash tree is found in northeast Asia, north America, east and western France, China, northern areas of Pakistan, India, and Afghanistan. Chemical constituents of Fraxinus plant include various secoiridoids, phenylethanoids, flavonoids, coumarins, and lignans; therefore, it is considered as a plant with versatile biological and pharmacological activities. Its tremendous range of pharmacotherapeutic properties has been well documented including anticancer, anti-inflammatory, antioxidant, antimicrobial, and neuroprotective. In addition, its bioactive phytochemicals and secondary metabolites can be effectively used in cosmetic industry and as a competent antiaging agent. Fraxinus presents pharmacological effectiveness by targeting the novel targets in several pathological conditions, which provide a spacious therapeutic time window. Our aim is to update the scientific research community with recent endeavors with specifically highlighting the mechanism of action in different diseases. This potentially efficacious pharmacological drug candidate should be used for new drug discovery in future. This review suggests that this plant has extremely important medicinal utilization but further supporting studies and scientific experimentations are mandatory to determine its specific intracellular targets and site of action to completely figure out its pharmacological applications.

Esculetin exerts antitumor effect on human gastric cancer cells through IGF-1/PI3K/Akt signaling pathway

In this study, we aimed to investigate the antitumor effect of esculetin, a coumarin derivative extracted from natural plants, on human gastric cancer cells, and to illustrate the potential mechanisms. The results showed that esculetin exhibited anti-proliferative effects against gastric cancer cells and induced their apoptosis in a dose dependent manner with lower toxicity against normal gastric epithelial cells. Mechanism study indicated that esculetin induced gastric cancer MGC-803 cells apoptosis by triggering the activation of mitochondrial apoptotic pathway through reducing the mitochondrial membrane potential (MMP), increasing Bax/Bcl-2 ratio, activating caspase-3 and caspase-9 activity, and increasing cytochrome c release from mitochondria. Further study showed that the pro-apoptotic effects of esculetin were associated with down-regulation of insulin-like growth factor-1/ phosphatidylinositide 3-kinase/protein kinase B (IGF-1/PI3K/Akt) signaling pathway. Activation of IGF-1/PI3K/Akt pathway by IGF-1 abrogated the pro-apoptotic effects of esculetin, while inhibition of IGF-1/PI3K/Akt pathway by triciribine or LY294002 enhanced the pro-apoptotic effects of esculetin. In addition, esculetin inhibited in vivo tumor growth with no obvious toxicity following subcutaneous inoculation of MGC-803 cells in nude mice, and inhibited activation of IGF-1/PI3K/Akt pathway in tumor tissue.

CONCLUSION

These results indicate that esculetin could inhibit cell proliferation and induce apoptosis of gastric cancer cells through IGF-1/PI3K/Akt mediated mitochondrial apoptosis pathway, and may be a novel effective chemotherapeutic agent against gastric cancer.

Esculetin induces apoptosis of SMMC-7721 cells through IGF-1/PI3K/Akt-mediated mitochondrial pathways

Esculetin (6,7-dihydroxycoumarin) is a coumarin derivative extracted from natural plants and has been reported to have anticancer activity. However, the mechanism by which esculetin prevents human hepatic cancer cell growth is still largely unknown. In this study, we investigated the effect of esculetin on human hepatocellular carcinoma (HCC) SMMC-7721 cells and explored the cell signal mechanism. Our data indicated that esculetin induced apoptosis in SMMC-7721 cells, which were supported by DAPI staining and Annexin V/PI staining. Meanwhile, esculetin increased the activities of caspase-3 and caspase-9, promoted bax expression, decreased bcl-2 expression, and triggered collapse of mitochondrial membrane potential, and increased cytochrome c release from mitochondria. In addition, the inactivation of IGF-1, PI3K, and Akt was observed after esculetin administration. Furthermore, pretreatment with IGF-1 before esculetin administration abrogated the pro-apoptotic effects of esculetin, while PI3K inhibitor increased the pro-apoptotic effects of esculetin. These results indicated that esculetin induced the apoptosis of SMMC-7721 cells through IGF-1/PI3K/Akt-regulated mitochondrial dysfunction.

Inhibitory effect of esculetin on free-fatty-acid-induced lipid accumulation in human HepG2 cells through activation of AMP-activated protein kinase

This study aimed to determine the lipid-lowering effect of esculetin (6,7-dihydroxycoumarin), a coumarin derivative, using a cell model of steatosis induced by a mixture of free fatty acids (FFAs). Esculetin dose-dependently inhibited intracellular lipid accumulation by down-regulating the protein expression of lipogenic genes such as sterol regulatory element-binding protein-1c (SREBP1c) and fatty acid synthase (FAS) in FFAs-induced HepG2 cells. Moreover, esculetin significantly elevated the activation of the adenosine monophosphate-activated protein kinase (AMPK) signaling pathways in HepG2 hepatocytes. The anti-lipogenic effects of esculetin mediated by AMPK activation were abolished when FFAs-induced HepG2 cells were treated with a specific inhibitor of AMPK, i.e., compound C. These results suggest that esculetin attenuates hepatic lipid accumulation by inhibiting lipogenesis through the modulation of AMPK signaling pathway on FFAs-induced steatosis in HepG2 cells and may be used for the prevention of nonalcoholic fatty liver disease (NAFLD).

Esculetin induces antiproliferative and apoptotic response in pancreatic cancer cells by directly binding to KEAP1

BACKGROUND

A handful of studies have exploited antitumor potential of esculetin, a dihydroxy coumarine derivative; the targets to which it binds and the possible downstream mechanism for its cytotoxicity in cancer cells remain to be elucidated. Using pancreatic cancer cell lines as a model system, herein the study was initiated to check the efficacy of esculetin in inhibiting growth of these cancer cells, to decipher mechanism of its action and to predict its direct binding target protein.

METHODS

The cytotoxicity of esculetin was determined in PANC-1, MIA PaCa-2 and AsPC-1 cell lines; followed by an inspection of intracellular levels of ROS and its associated transcription factor, p65-NF-κB. The interaction between transcription factor, Nrf2 and its regulator KEAP1 was studied in the presence and absence of esculetin. The effect of Nrf2 on gene expression of antioxidant response element pathway was monitored by real time PCR. Thereafter, potential binding target of esculetin was predicted through molecular docking and then confirmed in vitro.

RESULTS

Esculetin treatment in all three pancreatic cancer cell lines resulted in significant growth inhibition with G1-phase cell cycle arrest and induction of mitochondrial dependent apoptosis through activation of caspases 3, 8 and 9. A notable decrease was observed in intracellular ROS and protein levels of p65-NF-κB in PANC-1 cells on esculetin treatment. Antioxidant response regulator Nrf2 has been reportedly involved in crosstalk with NF-κB. Interaction between Nrf2 and KEAP1 was found to be lost upon esculetin treatment in PANC-1 and MIA Paca-2 cells. Nuclear accumulation of Nrf2 and an upregulation of expression of Nrf2 regulated gene NQO1, observed on esculetin treatment in PANC-1 further supported the activation of Nrf2. To account for the loss of Nrf2-KEAP1 interaction on esculetin treatment, direct binding potential between esculetin and KEAP1 was depicted in silico using molecular docking studies. Pull down assay using esculetin conjugated sepharose beads confirmed the binding between esculetin and KEAP1.

CONCLUSIONS

We propose that esculetin binds to KEAP1 and inhibits its interaction with Nrf2 in pancreatic cancer cells. This thereby promotes nuclear accumulation of Nrf2 in PANC-1 cells that induces antiproliferative and apoptotic response possibly by attenuating NF-κB.

Esculetin prevents non-alcoholic fatty liver in diabetic mice fed high-fat diet

This study investigated the effects and mechanism of esculetin (6,7-dihydroxycoumarin) on non-alcoholic fatty liver in diabetic mice fed high-fat diet (HFD). The diabetic mice model was induced by injection of streptozotocin, after which they were fed HFD diet with or without esculetin for 11 weeks. Non-diabetic mice were provided a normal diet. Diabetes induced hepatic hypertrophy, lipid accumulation and droplets; however, esculetin reversed these changes. Esculetin treatment in diabetic mice fed HFD significantly down-regulated expression of lipid synthesis genes (Fasn, Dgat2 and Plpp2) and inflammation genes (Tlr4, Myd88, Nfkb, Tnfα and Il6). Moreover, the activities of hepatic lipid synthesis enzymes (fatty acid synthase and phosphatidate phosphohydrolase) and gluconeogenesis enzyme (glucose-6-phosphatase) in the esculetin group were decreased compared with the diabetic group. In addition, esculetin significantly reduced blood HbA_1c, serum cytokines (TNF-α and IL-6) and chemokine (MCP-1) levels compared with the diabetic group without changing the insulin content in serum and the pancreas. Hepatic SOD activity was lower and lipid peroxidation level was higher in the diabetic group than in the normal group; however, esculetin attenuates these differences. Overall, these results demonstrated that esculetin supplementation could protect against development of non-alcoholic fatty liver in diabetes via regulation of lipids, glucose and inflammation.

Esculetin induces apoptosis in human gastric cancer cells through a cyclophilin D-mediated mitochondrial permeability transition pore associated with ROS

Esculetin is a coumarin derivative from natural plants that has been commonly used as a folk medicine and has been reported to have beneficial pharmacological and biochemical activities; however, the mechanism by which esculetin prevents human gastric cancer cell growth is still largely unknown. In this study, we investigated the effect of esculetin on human gastric cancer cells and explored the cell death mechanism. Our data indicated that esculetin inhibited the growth of human gastric cancer cells in a dose- and time-dependent manner and apoptosis was the main cause of decreased cell viability in esculetin-treated cells. Additionally, esculetin treatment increased the activity of caspase-9 and caspase-3, and resulted in the appearance of the PARP cleavage product; and esculetin-induced cell death and apoptosis was decreased by pretreatment with CsA and NAC, but not BA; these results demonstrate that esculetin induced apoptosis via the caspase-dependent mitochondrial pathway in human gastric cancer cells in which cyclophilin D mediated the cytotoxic action by triggering the opening of the mitochondrial permeability transition pore; and the generation of ROS not only was a consequence of mitochondrial dysfunction, but also triggered esculetin-induced apoptosis. These results reveal a novel mechanism of esculetin on gastric cancer cells and suggest that esculetin could be a novel agent in the treatment of gastric cancer.

Gastroprotective activity of chloroform extract of Muntingia calabura and Melastoma malabathricum leaves

CONTEXT

Muntingia calabura L. (family Muntingiaceae) and Melastoma malabathricum L. (family Melastomaceae) are traditionally used to treat gastric ulcer.

OBJECTIVE

The present study determines the mechanisms of gastroprotective activity of the chloroform extract of leaves obtained from both the plants using several in vitro and in vivo assays.

MATERIALS AND METHODS

Phytochemical screening, HPLC analysis, and antioxidant activity of the respective extract were carried out. Gastroprotective activity was determined using ethanol-induced gastric ulcer assay while the mechanisms of gastroprotection were determined using the pyloric ligation assay. The test solutions [8% Tween-80 (vehicle), 20 mg/kg omeprazole, and different doses of extracts (50, 250, or 500 mg/kg] were administered orally once daily for 7 consecutive days before the animals were subjected to ethanol induced gastric ulcers.

RESULTS

The chloroform-extracted M. calabura (CEMC) contains tannins, polyphenolics, triterpenes, and steroids while the chloroform-extracted M. malabathricum (CEMM) contains only triterpenes and steroids. CEMC, but not CEMM, exerted remarkably strong antioxidant activity in the 2,2-diphenyl-1-picrylhydrazyl (DPPH)- (86% versus 16%) and superoxide- (73% versus 36%) radical scavenging assays. Both extracts demonstrated significant (p < 0.05) gastroprotection with the EC50 value recorded at 192.3 or 297.7 mg/kg, respectively. In the pylorus ligation assay, CEMC and CEMM significantly (p < 0.05) reduced the total and free acidity and volume; while increased the pH of gastric juice as well as the gastric wall mucus content in comparison with the vehicle-treated group.

DISCUSSION AND CONCLUSION

CEMC and CEMM exert gastroprotective effects in animals with ethanol-induced gastric ulcers via antioxidant and anti-secretory effects.

Esculetin, a Coumarin Derivative, Exhibits Anti-proliferative and Pro-apoptotic Activity in G361 Human Malignant Melanoma

BACKGROUND

Although esculetin, a coumarin compound, is known to induce apoptosis in human cancer cells, the effects and molecular mechanisms on the apoptosis in human malignant melanoma (HMM) cells are not well understood yet. In this study, we investigated the anti-proliferative effects of esculetin on the G361 HMM cells.

METHODS

We analyzed the anti-proliferative effects and molecular mechanisms of esculetin on G361 cells by a 3-(4,5-dimethylthiazol- 2-yl)-5-(3-carboxymethoxy phenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay, 4',6-diamidino-2-phenylindole staining and Western blotting.

RESULTS

Esculetin exhibited significant anti-proliferative effects on the HMM cells in a dose-dependent manner. Interestingly, we found that esculetin induced nuclear shrinkage and fragmentation, typical apoptosis markers, by suppression of Sp1 transcription factor (Sp1). Notably, esculetin modulated Sp1 downstream target genes including p27, p21 and cyclin D1, resulted in activation of apoptosis signaling molecules such as caspase-3 and PARP in G361 HMM cells.

CONCLUSIONS

Our results clearly demonstrated that esculetin induced apoptosis in the HMM cells by downregulating Sp1 protein levels. Thus, we suggest that esculetin may be a potential anti-proliferative agent that induces apoptotic cell death in G361 HMM cells.

Antioxidant and anti-inflammatory activities contribute to the prophylactic effect of semi-purified fractions obtained from the crude methanol extract of Muntingia calabura leaves against gastric ulceration in rats

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional medicine, the leaves, flowers, barks and roots of Muntingia calabura L. (Muntingiaceae) have been employed as a treatment for various ailments including dyspepsia and to relieve pain caused by gastritis and peptic ulcer disease. The methanolic extract of Muntingia calabura leaves (MEMC) has been proven in the previous study to possess significant antiulcer activity. In this study, we attempted to determine the prophylactic effect of the fractions obtained from MEMC against ethanol-induced gastric lesion in rats and the involvement of antioxidants and anti-inflammatory mediators.

MATERIALS AND METHODS

The MEMC was fractionated with petroleum ether (PEF), ethyl acetate (EAF) and distilled water (AQF). These fractions were investigated for possible antiulcer property using ethanol-induced gastric ulcer rat model. The rats were administered orally once daily with 8% Tween 80 (control), 100mg/kg ranitidine, or the fractions, in the doses of 100, 250, and 500 mg/kg, for 7 days, followed by ulcer induction using absolute ethanol. The rats were euthanized; macroscopic and histological observations of the stomach were done. The ulcer area (UA) was determined and the percentage protection afforded by the fractions was calculated. The fractions were subjected to antioxidant studies including the superoxide and 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, oxygen radical absorbance capacity (ORAC) and total phenolic content (TPC) assay. Involvement of nitric oxide (NO) and inflammatory mediators such as lipoxygenase (LOX) and xanthine oxidase (XO) were evaluated. Phytochemical screening and HPLC analysis of the fractions were also conducted.

RESULTS

Pre-treatment of PEF and EAF significantly (p<0.001) attenuated the gastric lesions as compared to the control group in a dose-dependent manner. On the other hand, 100 and 250 mg/kg of AQF significantly (p<0.001) prevented the ulcer formation but at the highest dose (500 mg/kg), AQF failed to significantly reduce the ulcer formation, showing a dose-independent antiulcerative effect of AQF. The histological evaluation supported the observed gastroprotective activity of PEF, EAF and AQF. All the fractions showed high superoxide and DPPH scavenging activity, meanwhile the EAF showed highest TPC followed by PEF and AQF. These fractions also significantly (p<0.05) inhibited the NO while maintaining the viability of the cells. EAF exhibited high inhibition towards both the LOX and XO enzymes, meanwhile PEF and AQF exerted high LOX inhibition but low XO inhibition. Phytochemical screening and HPLC profiling suggested the presence of flavonoid- and tannin based compounds in PEF and EAF.

CONCLUSION

It can be concluded that the prophylactic effect of the fractions on gastric ulceration in rats is associated with its high antioxidant activity and its ability to effectively inhibit the inflammation mediators. Presence of several flavonoids and gallic acid explains the effectiveness of the fractions in affording protection against gastric damages.

Esculetin Downregulates the Expression of AML1-ETO and C-Kit in Kasumi-1 Cell Line by Decreasing Half-Life of mRNA

One of the most frequent genetic aberrations in acute myeloid leukemia (AML) is chromosomal translocation between AML1/RUNX1 on chromosome 21 and ETO gene on chromosome 8 resulting in the expression of chimeric oncogene AML1-ETO. Although patients with t(8;21) translocation have good prognosis, 5-year survival is observed only in 50% of the cases. AML1-ETO translocation is usually accompanied by overexpression of mutant C-Kit, a tyrosine kinase, which contributes to uncontrolled proliferation of premature blood cells leading to relapse and poor prognosis. We illustrate the potential use of esculetin on leukemic cell line, Kasumi-1, bearing t(8;21) translocation and mutated C-Kit gene. Esculetin decreases the expression of AML1-ETO at both protein and transcript level within 24 hours of treatment. Half-life of AML1-ETO mRNA was reduced from 7 hours to 1.5 hours. Similarly half-life of C-Kit mRNA was reduced to 2 hours from 5 hours in esculetin treated cells. Esculetin also perturbed the expression of ectopically expressed AML1-ETO in U937 cells. The decreased expression of AML1-ETO chimeric gene was associated with increased expression of LAT1 and RUNX3 genes, targets of AML1. We envisage that discovery of a drug candidate which could target both these mutated genes would be a considerable breakthrough for future application.

Mechanism(s) of action involved in the gastroprotective activity of Muntingia calabura

ETHNOPHARMACOLOGICAL RELEVANCE

Muntingia calabura L. (Muntingiaceae) is locally known as kerukup siam. Its leaves, flowers, barks and roots have been used traditionally in East Asia and South America to treat various diseases including ulcer-related diseases. The present study aimed to investigate the mechanism(s) of gastroprotective effect of methanol extract of Muntingia calabura leaves (MEMC) using the pylorus ligation induced gastric ulceration in rats.

MATERIALS AND METHODS

Five groups of rats (n=6) were administered orally once daily for 7 days with 8% Tween 80 (negative control), 100 mg/kg ranitidine (positive control), or MEMC (100, 250 or 500 mg/kg), followed by the ulcer induction via ligation of the pyloric part of the rat's stomach. This was followed by the macroscopic analysis of the stomach, evaluation of gastric content parameters, and quantification of mucus content. The antioxidant (measured using the superoxide anion and 2,2-diphenyl-1-picrylhydrazyl (DPPH)-radical scavenging, oxygen radical absorbance capacity (ORAC) and total phenolic content (TPC) assays), anti-inflammatory (evaluated using the in vitro lipoxygenase and xanthine oxidase assays), phytoconstituents and HPLC analysis of MEMC were also carried out.

RESULTS

The MEMC significantly (p<0.05) reduced gastric lesion in this model. Furthermore, the extract also significantly (p<0.01) reduced the volume of gastric content whereas the total acidity was significantly (p<0.05) reduced in the doses of 100 and 500 mg/kg MEMC. Moreover, the mucus content increased significantly (p<0.01) in MEMC-treated rats. The extract also showed high antioxidant and anti-inflammatory activities in all assays tested, and demonstrated the presence of high tannins and saponins followed by flavonoids.

CONCLUSION

The MEMC exerted gastroprotective effect via several mechanisms including the anti-secretory, antioxidant and anti-inflammatory activities. These activities could be attributed to the presence of tannins, saponins and flavonoids (e.g. rutin, quercitrin, fisetin and dihydroquercetin).

A Sensitive and Selective Method for Determination of Aesculin in Cortex Fraxini by Liquid Chromatography Quadrupole Time-of-Flight Tandem Mass Spectrometry and Application in Pharmacokinetic Study

A rapid and sensitive method for determining aesculin of Cortex fraxini in rat was developed using high-performance liquid chromatography (HPLC) quadrupole time-of-flight (QTOF) tandem mass (MS/MS). Rat plasma was pretreated by fourfold methanol to remove plasma proteins. Chromatographic separation was performed on a reverse phase column. A tandem mass spectrometric detection with an electrospray ionization (ESI) interface was achieved using collision-induced dissociation (CID) under positive ionization mode. The MS/MS patterns monitored were m/z 341.2716 → m/z 179.1043 for aesculin and m/z 248.3025 → m/z 120.9130 for tinidazole (internal standard). The linear range was calculated to be 10.0-1500.0 ng/mL with a detection limit of 2.0 ng/mL. The inter- and intraday accuracy and precision were within ±7.0%. Pharmacokinetic study showed that aesculin was confirmed to be a one-compartment open model. The method is believed to have good linear range, high sensitivity and recoveries, and superior analytical efficiency. It will probably be an alternative for pharmacokinetic study of aesculin.

4-methylcoumarin derivatives inhibit human neutrophil oxidative metabolism and elastase activity

Increased neutrophil activation significantly contributes to the tissue damage in inflammatory illnesses; this phenomenon has motivated the search for new compounds to modulate their effector functions. Coumarins are natural products that are widely consumed in the human diet. We have evaluated the antioxidant and immunomodulator potential of five 4-methylcoumarin derivatives. We found that the 4-methylcoumarin derivatives inhibited the generation of reactive oxygen species by human neutrophils triggered by serum-opsonized zymosan or phorbol-12-myristate-13-acetate; this inhibition occurred in a concentration-dependent manner, as revealed by lucigenin- and luminol-enhanced chemiluminescence assays. Cytotoxicity did not mediate this inhibitory effect. The 7,8-dihydroxy-4-methylcoumarin suppressed the neutrophil oxidative metabolism more effectively than the 6,7- and 5,7-dihydroxy-4-methylcoumarins, but the 5,7- and 7,8-diacetoxy-4-methylcoumarins were less effective than their hydroxylated counterparts. An analysis of the biochemical pathways suggested that the 6,7- and 7,8-dihydroxy-4-methylcoumarins inhibit the protein kinase C-mediated signaling pathway, but 5,7-dihydroxy-4-methylcoumarin, as well as 5,7- and 7,8-diacetoxy-4-methylcoumarins do not significantly interfere in this pathway of the activation of the human neutrophil oxidative metabolism. The 4-methylcoumarin derivatives bearing the catechol group suppressed the elastase and myeloperoxidase activity and reduced the 1,1-diphenyl-2-picrylhydrazyl free radical the most strongly. Interestingly, the 5,7-dihydroxy-4-methylcoumarin scavenged hypochlorous acid more effectively than the o-dihydroxy-substituted 4-methylcoumarin derivatives, and the diacetoxylated 4-methylcoumarin derivatives scavenged hypochlorous acid as effectively as the 7,8-dihydroxy-4-methylcoumarin. The significant influence of small structural modifications in the inhibitory potential of 4-methylcoumarin derivatives on the effector functions of neutrophil makes them interesting candidates to develop new drugs for the treatment of inflammatory diseases mediated by increased neutrophil activation.

Attenuation of potassium bromate-induced nephrotoxicity by coumarin (1,2-benzopyrone) in Wistar rats: chemoprevention against free radical-mediated renal oxidative stress and tumor promotion response

We report the modulatory effect of coumarin (1,2-benzopyrone) on potassium bromate (KBrO(3)) mediated nephrotoxicity in Wistar rats. KBrO(3) (125 mg/kg body weight, i.p.) enhances gamma-glutamyl transpeptidase, renal lipid peroxidation, xanthine oxidase and hydrogen peroxide (H(2)O(2)) generation with reduction in renal glutathione content and antioxidant enzymes. It also enhances blood urea nitrogen, serum creatinine, ornithine decarboxylase (ODC) activity and [(3)H]-thymidine incorporation into renal DNA. Treatment of rats orally with coumarin (10 mg/kg body weight and 20 mg/kg body weight) resulted in a significant decrease in gamma-glutamyl transpeptidase, lipid peroxidation, xanthine oxidase, H(2)O(2) generation, blood urea nitrogen, serum creatinine, renal ODC activity and DNA synthesis (P < 0.001). Renal glutathione content (P < 0.01) and antioxidant enzymes were also recovered to significant level (P < 0.001). These results show that coumarin may be used as an effective chemopreventive agent against KBrO(3)-mediated renal oxidative stress, toxicity and tumor promotion response in Wistar rats.

Extraction and quantitation of coumarin from cinnamon and its effect on enzymatic browning in fresh apple juice: a bioinformatics approach to illuminate its antibrowning activity

Enzymatic browning by polyphenoloxidase (PPO) affects food quality and taste in fruits and vegetables. Thus, the study was designed to reduce browning in apple juice by coumarin. The ethanolic extract of cinnamon was prepared and its coumarin content was quantitated by HPLC, using authentic coumarin (AC) as standard. The effect of cinnamon extract (CE) and AC on enzymatic browning, its time dependent effects, and the specific activity of PPO and peroxidase (POD) were studied in apple juice. The docking of coumarin with PPO and POD was also performed to elucidate its antibrowning mechanism. The CE (73%) and AC (82%) showed better reduction in browning, maintained its antibrowning effect at all time points, and significantly (p < 0.05) reduced the specific activity of PPO and POD when compared with controls. Coumarin showed strong interaction with binding pockets of PPO and POD, suggesting its potential use as inhibitor to enzyme mediated browning in apple juice.

Syntheses and evaluation of the antioxidant activity of novel methoxypsoralen derivatives

A series of 5- and 8-methoxypsoralen (MOP) analogs, suitable for structure-antioxidative/anti-inflammatory activity relationship studies, were synthesized using as key-reactions the selective monobromination of MOPs with N-bromosaccharin and either a Heck reaction or a Suzuki coupling or a Suzuki coupling followed by a Wittig reaction to install side-chains of the acrylate- or benzoate- or cinnamate-type, respectively. The 8-MOP analogs 19 and 24, incorporating at position 5 of the psoralen nucleus a butyl acrylate or a tert-butyl cinnamate moiety, were the most powerful inhibitors of soybean LOX and inhibited effectively lipid peroxidation. Analog 19 was a more potent anti-inflammatory agent than the reference compound indomethacin and of comparable cytocompatibility to 8-MOP whereas analog 24 was a weaker inhibitor of inflammation than indomethacin and significantly more cytotoxic than 8-MOP. The results of the biological tests are discussed in terms of structural characteristics.

Antioxidant role of coumarin on streptozotocin-nicotinamide-induced type 2 diabetic rats

The purpose of this study was to investigate the antioxidant role of coumarin on streptozotocin-nicotinamide-induced Type 2 diabetic rats. In experimental rats, the levels of plasma glucose, insulin, and the levels of thiobarbituric acid reactive substances, lipid hydroperoxides, conjugated dienes, and the activities of superoxide dismutase, catalase, glutathione-S-transferase, and glutathione peroxidase were assayed in liver and kidney. Diabetic rats showed elevated levels of plasma glucose and lipid peroxidation markers and reduced plasma insulin and antioxidant enzymes. Oral administration of coumarin resulted in a significant reduction in the plasma glucose and lipid peroxides and a significant increase in the plasma insulin and antioxidant enzymes. Chronic treatment of coumarin remarkably restored the normal status of the histopathological changes observed in the selected tissues. It can be concluded that coumarin has antioxidant effect in Type 2 diabetic rats.

In vitro antioxidant activity of pet ether extract of black pepper

Objective:

To investigate the in vitro antioxidant activity of different fractions (R1, R2 and R3) obtained from pet ether extract of black pepper fruits (Piper nigrum Linn.)

Materials and Methods:

The fractions R1, R2 and R3 were eluted from pet ether and ethyl acetate in the ratio of 6:4, 5:5 and 4:6, respectively.

1,1-Diphenyl-2-picryl-hydrazyl (DPPH) radical, superoxide anion radical, nitric oxide radical, and hydroxyl radical scavenging assays were carried out to evaluate the antioxidant potential of the extract.

Results:

The free radical scavenging activity of the different fractions of pet ether extract of P. nigrum (PEPN) increased in a concentration dependent manner. The R3 and R2 fraction of PEPN in 500 µg/ml inhibited the peroxidation of a linoleic acid emulsion by 60.48±3.33% and 58.89±2.51%, respectively. In DPPH free radical scavenging assay, the activity of R3 and R2 were found to be almost similar. The R3 (100µg/ml) fraction of PEPN inhibited 55.68±4.48% nitric oxide radicals generated from sodium nitroprusside, whereas curcumin in the same concentration inhibited 84.27±4.12%. Moreover, PEPN scavenged the superoxide radical generated by the Xanthine/Xanthine oxidase system. The fraction R2 and R3 in the doses of 1000µg/ml inhibited 61.04±5.11% and 63.56±4.17%, respectively. The hydroxyl radical was generated by Fenton's reaction. The amounts of total phenolic compounds were determined and 56.98 µg pyrocatechol phenol equivalents were detected in one mg of R3.

Conclusions:

P. nigrum could be considered as a potential source of natural antioxidant.

Aesculetin-induced apoptosis through a ROS-mediated mitochondrial dysfunction pathway in human cervical cancer cells

Aesculetin (1) is an important coumarin found in various plant materials. It has been shown to have antiproliferative effects on several types of human cancer cells, but its effect on cervical cancer cells in vitro is unknown. In this study, we investigated that the cytotoxic effect of 1 on a non-cancer cell line (293) was smaller than on a tumor cell line (HeLa). This is the first report showing the possible mechanism of antiproliferative effect of 1 for the prevention of cervical cancer in cell culture models. It was found that 1 inhibited cell viability by inducing apoptosis, as evidenced by the formation of apoptotic bodies, generation of reactive oxygen species (ROS), and the accumulation of cells in the sub-G1 phase. Treatment with compound 1 decreased the cell growth in a dose-dependent manner with an IC(50) value of 37.8 microM. Aesculetin-induced apoptosis was correlated with mitochondrial dysfunction (DeltaPsi(m)), leading to the release of cytochrome c from the mitochondria to the cytosol, as well as the proteolytic activation of caspases in HeLa cells. These results indicate that 1 induces apoptosis in HeLa cells through a ROS-mediated mitochondrial dysfunction pathway.

An in vitro screening cascade to identify neuroprotective antioxidants in ALS

Amyotrophic lateral sclerosis (ALS) is an adult-onset neurodegenerative disease, characterized by progressive dysfunction and death of motor neurons. Although evidence for oxidative stress in ALS pathogenesis is well described, antioxidants have generally shown poor efficacy in animal models and human clinical trials. We have developed an in vitro screening cascade to identify antioxidant molecules capable of rescuing NSC34 motor neuron cells expressing an ALS-associated mutation of superoxide dismutase 1. We have tested known antioxidants and screened a library of 2000 small molecules. The library screen identified 164 antioxidant molecules, which were refined to the 9 most promising molecules in subsequent experiments. Analysis of the in silico properties of hit compounds and a review of published literature on their in vivo effectiveness have enabled us to systematically identify molecules with antioxidant activity combined with chemical properties necessary to penetrate the central nervous system. The top-performing molecules identified include caffeic acid phenethyl ester, esculetin, and resveratrol. These compounds were tested for their ability to rescue primary motor neuron cultures after trophic factor withdrawal, and the mechanisms of action of their antioxidant effects were investigated. Subsequent in vivo studies can be targeted using molecules with the greatest probability of success.