The neuroprotective effect of maltol against oxidative stress on rat retinal neuronal cells

Maltol inhibits oxygen glucose deprivation‑induced chromatinolysis in SH‑SY5Y cells by maintaining pyruvate level

Maltol, a chemical isolated from ginseng root, has shown treatment effects on several pathological processes including osteoarthritis, diabetic peripheral neuropathy and liver fibrosis. Nevertheless, its effect on ischemia‑induced neuron death remains elusive. In the present study, the treatment effect of maltol on ischemia‑induced neuron damage was investigated by using oxygen and glucose deprivation (OGD) model in SH‑SY5Y cells. In vitro studies revealed that maltol protected SH‑SY5Y cells against OGD‑induced chromatinolysis by inhibiting two reactive oxygen species (ROS)‑regulated pathways. One was DNA double‑strand breaks and the other was nuclear translocation of apoptosis inducing factor. Mechanistically, maltol not only inhibited OGD‑induced depletion of glutathione and cysteine by maintaining cystine/glutamate antiporter (xCT) level, but also abrogated OGD‑induced catalase downregulation. Meanwhile, maltol also alleviated OGD‑induced inactivation of mTOR by attenuating OGD‑induced depletion of adenosine triphosphate and pyruvate and downregulation of pyruvate kinase M2, indicating that maltol inhibited the glycolysis dysfunction caused by OGD. Considering that activated mammalian target of the rapamycin (mTOR) could lead to enhanced xCT expression and decreased catalase degradation by autophagy, these findings indicated that maltol attenuated OGD‑induced ROS via inhibition of mTOR inactivation by maintaining pyruvate level. Taken together, it was demonstrated that maltol prevented OGD‑induced chromatinolysis in SH‑SY5Y cells via inhibiting pyruvate depletion.

Physicochemical Characteristics of Bambara Groundnut Speciality Malts and Extract

Speciality malts and their extracts have physicochemical characteristics such as colour, flavour, and aroma sorted for in food production. Speciality malts used in food production are mostly produced from cereal grains. Hence, this study aimed to produce speciality malts from Bambara groundnut (BGN) seeds and analyse their physicochemical characteristics and metabolites. The base, toasted, caramel, and roasted malt were produced by drying at different temperatures and times. Syrups were produced isothermally from the speciality malts. The speciality malts and syrups were assessed for colour, pH, protein, α and β-amylases, total polyphenols, antioxidants, and metabolite profiling. The BGN speciality malts were assayed for fatty acid methyl esters (FAME), hydrocarbons, sugar alcohols, sugars, acids, amino acids, and volatile components using capillary gas chromatography-mass spectrometry (GC-MS) and gas chromatography with flame ionisation detection (GC-FID). The colours of the speciality malts and syrups were significantly (p = 0.000) different. The protein content of the BGN speciality malts was significantly different (p = 0.000), while the protein content of the syrups was not significantly different. The amylase activities of the BGN speciality malt decreased with the change in kilning temperatures and time. The α- and β-amylase activities for the specialty malts were 1.01, 0.21, 0.29, 0.15 CU/g and 0.11, 0.10, 0.10, 0.06 BU/g. The total polyphenols and antioxidant activities differed for all BGN speciality malts. There were twenty-nine volatiles detected in the BGN speciality malts. Fifteen amino acids consisted of seven essential amino acids, and eight non-essential amino acids were detected in the speciality malts. Fatty acid methyl esters (FAME) identified were palmitoleic, oleic, linolelaidic, linoleic, and arachidic acid. The sugars, organic acids, and sugar alcohols consisted of lactic acid, fructose, sucrose, and myo-inositol. The BGN speciality malts exhibited good physicochemical characteristics and metabolites that can make them useful as household and industrial ingredients for food production, which could be beneficial to consumers.

Antioxidant activity and α-glucosidase inhibitability of Distichochlamys citrea M.F. Newman rhizome fractionated extracts: in vitro and in silico screenings

Distichochlamys citrea M.F. Newman (commonly known as “Black Ginger”) is an endemic plant to Vietnam and has been extensively exploited by folk medication for treatments of infection-related diseases and diabetes. In this work, its rhizomes were subjected to fractionated extraction, phytochemical examination, evaluation of antioxidant effect by DDPH free radical neutralization, and inhibitory activity toward α-glucosidase. The compositional components were subjected to in silico screening, including density functional theory calculation, molecular docking simulation, physicochemical analysis, and pharmacokinetic regression. In the trials, EtOAc fraction is found as the bioactive part of most effectiveness, regarding both antioxidant effect (IC₅₀ = 90.27 µg mL⁻¹) and α-glucosidase inhibitory activity (IC₅₀ = 115.75 μg mL⁻¹). Chemical determination reveals there are 13 components of its composition. DFT-based calculations find no abnormal constraints in their structures. Docking-based simulation provides order of inhibitory effectiveness: 3-P53341 > 12-P53341 > 7-P53341 > 4-P53341 > 11-P53341 > 10-P53341. QSARIS-based investigations implicate their biocompatibility. ADMET-based regressions indicate that all candidates are generally safe for medicinal applications. The findings would contribute to the basis for further studies on the chemical compositions of Distichochlamys citrea and their biological activities.

Neuroprotective Effects of Fingolimod in a Cellular Model of Optic Neuritis

Visual dysfunction resulting from optic neuritis (ON) is one of the most common clinical manifestations of multiple sclerosis (MS), characterized by loss of retinal ganglion cells, thinning of the nerve fiber layer, and inflammation to the optic nerve. Current treatments available for ON or MS are only partially effective, specifically target the inflammatory phase, and have limited effects on long-term disability. Fingolimod (FTY) is an FDA-approved immunomodulatory agent for MS therapy. The objective of the current study was to evaluate the neuroprotective properties of FTY in the cellular model of ON-associated neuronal damage. R28 retinal neuronal cell damage was induced through treatment with tumor necrosis factor-α (TNFα). In our cell viability analysis, FTY treatment showed significantly reduced TNFα-induced neuronal death. Treatment with FTY attenuated the TNFα-induced changes in cell survival and cell stress signaling molecules. Furthermore, immunofluorescence studies performed using various markers indicated that FTY treatment protects the R28 cells against the TNFα-induced neurodegenerative changes by suppressing reactive oxygen species generation and promoting the expression of neuronal markers. In conclusion, our study suggests neuroprotective effects of FTY in an in vitro model of optic neuritis.

Maltol inhibits the progression of osteoarthritis via the nuclear factor-erythroid 2-related factor-2/heme oxygenase-1 signal pathway in vitro and in vivo

Osteoarthritis (OA) is a common degenerative joint disease characterized by articular cartilage degeneration and inflammation. Currently, there is hardly any effective treatment for OA due to its complicated pathology and the severe side effects of the treatment drugs used. It has been reported that maltol, a Maillard reaction product derived from ginseng, inhibits inflammation and oxidative stress in several animal models. However, the potential anti-inflammatory effects of maltol in OA treatment are unknown. This study aimed to evaluate the anti-inflammatory effects of maltol on interleukin (IL)-1β-induced mouse chondrocytes and protective effects of maltol on these chondrocytes in medial meniscus destabilization (DMM) OA mouse models. Mice, randomly divided into maltol (n = 15), vehicle (n = 15) and control (n = 15) groups were treated with the same dose of maltol or saline, respectively. The cartilage tissues were extracted for histological analysis 8 weeks postoperative. For the in vitro studies, chondrocytes were treated with 10 ng mL-1 IL-1β combined with maltol at different concentrations. In vitro assays showed that the maltol pre-treatment significantly inhibited the expressions of multiple inflammatory factors induced by IL-1β, such as inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2), nitric oxide (NO), interleukin-6 (IL-6) and tumor necrosis factor (TNF-α). In addition, maltol alleviated the degradation of the extracellular matrix (ECM) by inhibiting the expressions of matrix metalloproteinase-13 (MMP13) and thrombospondin motif 5 (ADAMTS5), as well as reversing the degradation of aggrecan and collagen II. Moreover, maltol suppressed nuclear factor kappa B (NF-κB) signaling by activating the nuclear factor-erythroid 2-related factor-2 (Nrf2) in in vitro and in vivo studies. These findings indicate that maltol reduces the inflammation induced by IL-1β in chondrocytes. Therefore, the results of this study indicated that maltol may be a potential drug for the effective treatment of OA.

Physiological and pharmacological features of the non-saponin components in Korean Red Ginseng

Panax ginseng, a medicinal plant, has been used as a blood-nourishing tonic for thousands of years in Asia, including Korea and China. P. ginseng exhibits adaptogen activity that maintains homeostasis by restoring general biological functions and non-specifically enhancing the body's resistance to external stress. Several P. ginseng effects have been reported. Korean Red Ginseng, in particular, has been reported in both basic and clinical studies to possess diverse effects such as enhanced immunity, fatigue relief, memory, blood circulation, and anti-oxidation. Moreover, it also protects against menopausal symptoms, cancer, cardiac diseases, and neurological disorders. The active components found in most Korean Red Ginseng varieties are known to include ginsenosides, polysaccharides, peptides, alkaloids, polyacetylene, and phenolic compounds. In this review, the identity and bioactivity of the non-saponin components of Korean Red Ginseng discovered to date are evaluated and the components are classified into polysaccharide and nitrogen compounds (protein, peptide, amino acid, nucleic acid, and alkaloid), as well as fat-soluble components such as polyacetylene, phenols, essential oils, and phytosterols. The distinct bioactivity of Korean Red Ginseng was found to originate from both saponin and non-saponin components rather than from only one or two specific components. Therefore, it is important to consider saponin and non-saponin elements together.

Neurotoxicity of e-cigarettes

It appears that electronic cigarettes (EC) are a less harmful alternative to conventional cigarette (CC) smoking, as they generate substantially lower levels of harmful carcinogens and other toxic compounds. Thus, switching from CC to EC may be beneficial for smokers. However, recent accounts of EC- or vaping-associated lung injury (EVALI) has raised concerns regarding their adverse health effects. Additionally, the increasing popularity of EC among vulnerable populations, such as adolescents and pregnant women, calls for further EC safety evaluation. In this state-of-the-art review, we provide an update on recent findings regarding the neurological effects induced by EC exposure. Moreover, we discuss possible neurotoxic effects of nicotine and numerous other chemicals which are inherent both to e-liquids and EC aerosols. We conclude that in recognizing pertinent issues associated with EC usage, both government and scientific researchers must address this public health issue with utmost urgency.

Playing with Structural Parameters: Synthesis and Characterization of Two New Maltol-Based Ligands with Binding and Antineoplastic Properties

Two maltol-based ligands, N,N′-bis((3-hydroxy-4-pyron-2-yl)methyl)-1,4-piperazine (L1) and N,N′,N′-tris((3-hydroxy-4-pyron-2-yl)methyl)-N-methylethylendiamine (L2), were synthesized and characterized. L1 and L2, containing, respectively, two and three maltol units spaced by a diamine fragment, were designed to evaluate how biological and binding features are affected by structural modifications of the parent compound malten. The acid-base behavior and the binding properties towards transition, alkaline-earth (AE) and rare-earth (RE) cations in aqueous solution, studied by potentiometric, UV-Vis and NMR analysis, are reported along with biological studies on DNA and leukemia cells. Both ligands form stable complexes with Cu(II), Zn(II) and Co(II) that were studied as metallo-receptors for AE and RE at neutral pH. L1 complexes are more affected than L2 ones by hard cations, the L1-Cu(II) system being deeply affected by RE. The structural modifications altered the mechanism of action: L1 partially maintains the ability to induce structural alterations of DNA, while L2 provokes single strand (nicks) and to a lesser extent double strand breaks of DNA.

Maltol Improves APAP-Induced Hepatotoxicity by Inhibiting Oxidative Stress and Inflammation Response via NF-κB and PI3K/Akt Signal Pathways

Maltol, a food-flavoring agent and Maillard reaction product formed during the processing of red ginseng (Panax ginseng, C.A. Meyer), has been confirmed to exert a hepatoprotective effect in alcohol-induced oxidative damage in mice. However, its beneficial effects on acetaminophen (APAP)-induced hepatotoxicity and the related molecular mechanisms remain unclear. The purpose of this article was to investigate the protective effect and elucidate the mechanisms of action of maltol on APAP-induced liver injury in vivo. Maltol was administered orally at 50 and 100 mg/kg daily for seven consecutive days, then a single intraperitoneal injection of APAP (250 mg/kg) was performed after the final maltol administration. Liver function, oxidative indices, inflammatory factors—including serum alanine and aspartate aminotransferases (ALT and AST), tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), liver glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA), cytochrome P450 E1 (CYP2E1) and 4-hydroxynonenal (4-HNE) were measured. Results demonstrated that maltol possessed a protective effect on APAP-induced liver injury. Liver histological changes and Hoechst 33258 staining also provided strong evidence for the protective effect of maltol. Furthermore, a maltol supplement mitigated APAP-induced inflammatory responses by increasing phosphorylated nuclear factor-kappa B (NF-κB), inhibitor kappa B kinase α/β (IKKα/β), and NF-kappa-B inhibitor alpha (IκBα) in NF-κB signal pathways. Immunoblotting results showed that maltol pretreatment downregulated the protein expression levels of the B-cell-lymphoma-2 (Bcl-2) family and caspase and altered the phosphorylation of phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) in a dose-dependent manner. In conclusion, our findings clearly demonstrate that maltol exerts a significant liver protection effect, which may partly be ascribed to its anti-inflammatory and anti-apoptotic action via regulation of the PI3K/Akt signaling pathway.

Maltol, a food flavor enhancer, attenuates diabetic peripheral neuropathy in streptozotocin-induced diabetic rats

SCOPE

Maltol (3-hydroxy-2-methy-4-pyrone), a potent antioxidative agent, typically is used to enhance flavor and preserve food. This study evaluated its effects on preventing diabetic peripheral neuropathy (DPN) in streptozotocin (STZ)-induced diabetic rats and explored its mechanisms.

METHODS AND RESULTS

We intraperitoneally injected Sprague-Dawley (SD) rats with STZ (65 mg kg-1, ip) and treated the rats with different doses of maltol after 4 weeks of injection. During treatment, we evaluated motor nerve conduction velocity (MNCV) and thermal and mechanical hyperalgesia and assayed the oxidative stress, Na+-K+-ATPase activity, and apoptosis. Repeated treatment with maltol for 12 weeks significantly improved thermal and mechanical hyperalgesia, increased the MNCV, elevated the Na+-K+-ATPase activity, and ameliorated oxidative stress and apoptosis in STZ-induced diabetic rats. We coincubated RSC96 cells, a Schwann cell line, with maltol and hydrogen peroxide (H2O2, 0.6 mM). Evidently, maltol increased cell viability and inhibited apoptosis after injury by H2O2.

CONCLUSIONS

Maltol was demonstrated to prevent DPN development and may provide a new alternative for the treatment of DPN.

The protective effects of maltol on cisplatin-induced nephrotoxicity through the AMPK-mediated PI3K/Akt and p53 signaling pathways

Cisplatin, a potent anticancer drug, is usually causing nephrotoxicity; limiting its therapeutic application and efficiency. Maltol may be used to prevent such toxic effect. The aim of this study was to investigate the underlying protective mechanisms of maltol on nephrotoxicity by cisplatin using a cisplatin-treated mouse model and a cellular toxicity model of HEK293 cells. The blood urea nitrogen (BUN), creatinine (CRE) and neutrophil gelatinase-associated lipocalin (NGAL) levels in mice were increased by cisplatin but decreased to normal ranges by maltol pretreatment (50 and 100 mg/kg) for ten days. Besides, maltol pretreatment decreased oxidative stress, lipid peroxidation and apoptosis in cisplatin-treated mice. The inhibitory action of maltol on inflammatory responses was achieved by reducing the expressions in NF-κB, IL-1β, iNOS, and TNF-α in the mice in vivo. Additionally, maltol restored the reduction of PI3K/Akt and mTOR levels by cisplatin through increasing AMPK expression in cisplatin-treated HEK293 cells. Maltol also suppressed the expression of Bax and caspase 3 by inhibiting the p53 activity in HEK293 cells. Overall, maltol may serve as a valuable potential drug to prevent cisplatin-induced nephrotoxicity, and the underlying molecular mechanisms of maltol action may involve intracellular AMPK/PI3K/Akt and p53 signaling pathways.

The Liver Protection Effects of Maltol, a Flavoring Agent, on Carbon Tetrachloride-Induced Acute Liver Injury in Mice via Inhibiting Apoptosis and Inflammatory Response

The purpose of this research was to evaluate whether maltol could protect from hepatic injury induced by carbon tetrachloride (CCl₄) in vivo by inhibition of apoptosis and inflammatory responses. In this work, maltol was administered at a level of 100 mg/kg for 15 days prior to exposure to a single injection of CCl₄ (0.25%, i.p.). The results clearly indicated that the intrapulmonary injection of CCl₄ resulted in a sharp increase in serum aspartate transaminase (AST) and alanine transaminase (ALT) activities, tumor necrosis factor-α (TNF-α), irreducible nitric oxide synthase (iNOS), nuclear factor-kappa B (NF-κB) and interleukin-1β (IL-1β) levels. Histopathological examination demonstrated severe hepatocyte necrosis and the destruction of architecture in liver lesions. Immunohistochemical staining and western blot analysis suggested an accumulation of iNOS, NF-κB, IL-1β and TNF-α expression. Maltol, when administered to mice for 15 days, can significantly improve these deleterious changes. In addition, TUNEL and Hoechst 33258 staining showed that a liver cell nucleus of a model group diffused uniform fluorescence following CCl₄ injection. Maltol pretreatment groups did not show significant cell nuclear condensation and fragmentation, indicating that maltol inhibited CCl₄-induced cell apoptosis. By evaluating the liver catalase (CAT), glutathione (GSH), superoxide dismutase (SOD) activity, and further using a single agent to evaluate the oxidative stress in CCl₄-induced hepatotoxicity by immunofluorescence staining, maltol dramatically attenuated the reduction levels of hepatic CAT, GSH and SOD, and the over-expression levels of CYP2E1 and HO-1. In the mouse model of CCl₄-induced liver injury, we have demonstrated that the inflammatory responses were inhibited, the serum levels of ALT and AST were reduced, cell apoptosis was suppressed, and liver injury caused by CCl₄ was alleviated by maltol, demonstrating that maltol may be an efficient hepatoprotective agent.