Ji Yeon Seo

Dehydroglyasperin C isolated from licorice caused Nrf2-mediated induction of detoxifying enzymes.

Our preliminary experiment demonstrated that a n-hexane/EtOH (9:1, volume) extract of Glycyrrhiza uralensis (licorice) caused a significant induction of NAD(P)H:oxidoquinone reductase (NQO1), one of the well-known phase 2 detoxifying enzymes. We isolated dehydroglyasperin C (DGC) as a potent phase 2 enzyme inducer from licorice. DGC induced NQO1 both in wild-type murine hepatoma Hepa1c1c7 and ARNT-lacking BPRc1 cells, indicating that the compound is a monofunctional inducer. The compound induced not only NQO1 but also some other phase 2 detoxifying/antioxidant enzymes, such as glutathione S-transferase, gamma-glutamylcysteine synthase, glutathione reductase, and heme oxygenase 1. Similar to most monofunctional inducers, DGC caused the accumulation of Nrf2 in the nucleus in dose- and time-dependent manners and thereby activated expression of phase 2 detoxifying enzymes. It also resulted in a dose-dependent increase in the luciferase activity in the reporter assay, in which HepG2-C8 cells transfected with antioxidant response element (ARE)-luciferase construct were used, suggesting that the induction of phase 2 detoxifying and antioxidant enzymes could be achieved through the interaction of Nrf2 with the ARE sequence in the promoter region of their genes.

Isoalantolactone from Inula helenium caused Nrf2-mediated induction of detoxifying enzymes.

Our previous study demonstrated that methanolic extract of Inula helenium (Elecampane) has the potential to induce detoxifying enzymes such as NAD(P)H:(quinone acceptor) oxidoreductase 1 (EC 1.6.99.2) (NQO1, QR) activity and glutathione S-transferase (GST) and found isoalantolactone and alantolactone as the active components. In this study we investigated the detoxifying enzyme-inducing potential of isoalantolactone, which is present in I. helenium and has a structure similar to that of alantolactone. The compound induced QR in a dose-dependent manner in both Hepa1c1c7 cells and its mutant BPRc1 cells lacking the arylhydrocarbon receptor translocator. Like with most phase 2 enzyme inducers, other phase 2 detoxifying enzymes, including GST, glutathione reductase, gamma-glutamylcysteine synthetase, and heme oxygenase-1, were also induced by isoalantolactone in a dose-dependent manner in the cultured cells. Furthermore, isoalantolactone caused a proportionate increase in luciferase activity depending upon concentration and exposure time in the reporter assay in which HepG2-C8 cells, transfectants carrying antioxidant response element-luciferase gene, were used. The nuclear translocation of nuclear factor-E2-related factor 2 (Nrf2) was stimulated by the compound and attenuated by phosphatidylinositol 3-kinase inhibitors such as LY294002 and wortmannin. In conclusion, isoalantolactone is a candidate for chemoprevention and acts as potent phase 2 enzyme inducer by stimulating the accumulation of Nrf2 in the nucleus.

Nrf2-mediated induction of detoxifying enzymes by alantolactone present in Inula helenium

Our previous study showed that a methanol extract of Inula helenium had the potential to induce detoxifying enzymes such as quinone reductase (QR) and glutathione S‐transferase (GST) activity. In this study the methanol extract was further fractionated using silica gel chromatography and vacuum liquid chromatography, to yield pure compounds alantolactone and isoalantolactone as QR inducers. Alantolactone caused a dose‐dependent induction of antioxidant enzymes including QR, GST, γ‐glutamylcysteine synthase, glutathione reductase, and heme oxygenase 1 in hepa1c1c7 mouse hepatoma cells. The compound increased the luciferase activity of HepG2‐C8 cells, transfectants carrying antioxidant response element (ARE)‐luciferase gene, in a dose‐dependent manner, suggesting ARE‐mediated transcriptional activation of antioxidant enzymes. Alantolactone also stimulated the nuclear accumulation of Nrf2 that was inhibited by phosphatidylinositol 3‐kinase (PI3K) inhibitors. In conclusion, alantolactone appears to induce detoxifying enzymes via activation of PI3K and JNK signaling pathways, leading to translocation of Nrf2, and subsequent interaction between Nrf2 and ARE in the encoding genes. Copyright

Antioxidant activities of licorice-derived prenylflavonoids

Glycyrrhiza uralensis (or licorice) is a widely used Oriental herbal medicine from which the phenylflavonoids dehydroglyasperin C (DGC), dehydroglyasperin D (DGD), and isoangustone A (IsoA) are derived. The purpose of the present study was to evaluate the antioxidant properties of DGC, DGD, and IsoA. The three compounds showed strong ferric reducing activities and effectively scavenged DPPH, ABTS+, and singlet oxygen radicals. Among the three compounds tested, DGC showed the highest free radical scavenging capacity in human hepatoma HepG2 cells as assessed by oxidant-sensitive fluorescent dyes dichlorofluorescein diacetate and dihydroethidium bromide. In addition, all three compounds effectively suppressed lipid peroxidation in rat tissues as well as H2O2-induced ROS production in hepatoma cells. This study demonstrates that among the three phenylflavonoids isolated from licorice, DGC possesses the most potent antioxidant activity, suggesting it has protective effects against chronic diseases caused by reactive oxygen species as well as potential as an antioxidant food additive.

Neuroprotective Effects of Dehydroglyasperin C through Activation of Heme Oxygenase-1 in Mouse Hippocampal Cells

Licorice, the root of the Glycyrrhiza species ( Glycyrrhiza uralensis Fisher), is known to have antioxidant, anti-inflammatory, antiviral, and antitumor properties. The objective of this study is to explore the neuroprotective effect of dehydroglyasperin C (DGC) against glutamate-induced oxidative stress in mouse hippocampal HT22 cells. DGC significantly reduced cytotoxicity and reactive oxygen species (ROS) generation induced by glutamate in HT22 cells, whereas DGC did not restore glutathione depletion caused by glutamate. In addition, it was further investigated whether DGC affected the expression of heme oxygenase (HO)-1, one of the major cellular antioxidant defense systems, and it was found that DGC dose-dependently increased HO-1 expression. DGC-mediated cytoprotection of HT22 neuronal cells from glutamate insult was abrogated by either HO-1 inhibitor (Tin protoporphyrin, SnPP) or AKT inhibitor (LY294002). In conclusion, the present results demonstrate for the first time that DGC protects neuronal cells against glutamate-induced oxidative injury through the induction of HO-1 expression, which is, in turn, activated maybe through Nrf2-Keap1 and PI3K/AKT signaling pathways.

Neuroprotective and Cognition-Enhancing Effects of Compound K Isolated from Red Ginseng

The present study was aimed at elucidating the effect of compound K derived from red ginseng on memory function in mouse model and glutamate-induced cytotoxicity in mouse hippocampal HT22 cells. Compound K induced antioxidant enzymes in nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-mediated manner, and effectively attenuated cytotoxicity and mitochondrial damage induced by glutamate in HT22 cells. However, the cytoprotective effect by compound K was abolished by heme oxygenase-1 inhibitor, tin protophorphyrin IX, suggesting that neuroprotective effect of compound K was caused by its Nrf2-mediated induction of antioxidant enzymes. Further, memory deficit induced by scopolamine was restored by compound K, which did not inhibit acetylcholine esterase, in C57BL/6 mice but not in Nrf2 knockout mice as assessed by passive avoidance test, Y-maze and water maze tests, suggesting that scopolamine-induced memory impairment was overcome by the induction of Nrf2-mediated antioxidant enzymes by the compound K. Overall, our data indicate that compound K could be useful in prevention and treatment of reactive oxygen species-induced neurological disorders such as Alzheimers disease.

Antiobesity Effect of Oil Extract of Ginseng

In a preliminary study we found that incubating raw ginseng in oil facilitated autolysis and extensive metabolism of ginseng, releasing flavor and lipophilic compounds into the oil so that it could be used as an ingredient for high value-added foods, while the residue could be utilized for making ginseng extract. Here, we report the effect of oil (grapeseed oil [GSO]) extract of ginseng (OEG) on body weight gain and lipid metabolism in a mouse model. OEG, but not GSO, inhibited porcine pancreatic lipase. Plasma triglyceride (TG) levels were lower in male ICR mice at 1, 2, 3, and 4 hours after oral administration of the lipid emulsion plus OEG (1 g/kg of body weight) than in the group administered only the lipid emulsion or lipid emulsion plus GSO. Next, male C57BL/6J mice were fed a standard diet, a high fat (HF) diet containing 30% lard, or diets including 30% OEG or GSO based on the standard diet for 14 weeks. Consumption of OEG-containing diet significantly lowered the body weight gain, feed efficiency, visceral fat accumulation, plasma TG, and hepatic and white epididymal adipocyte sizes, as well as expression of peroxisome proliferator-activated receptor γ (PPARγ) in liver and adipose tissue. In conclusion, dietary OEG improved obesity-related parameters in blood, liver, and adipose tissue in a mouse model and suppressed obesity induced by HF diet, possibly by regulating lipid metabolism by modulating PPARγ protein expression.

Protection by Chrysanthemum zawadskii extract from liver damage of mice caused by carbon tetrachloride is maybe mediated by modulation of QR activity

Our previous study demonstrated that methanolic extract of Chrysanthemum zawadskii Herbich var. latilobum Kitamura (Compositae) has the potential to induce detoxifying enzymes such as NAD(P)H:(quinone acceptor) oxidoreductase 1 (EC 1.6.99.2) (NQO1, QR) and glutathione S-transferase (GST). In this study we further fractionated methanolic extract of Chrysanthemum zawadskii and investigated the detoxifying enzyme-inducing potential of each fraction. The fraction (CZ-6) shown the highest QR-inducing activity was found to contain (+)-(3S,4S,5R,8S)-(E)-8-acetoxy-4-hydroxy-3-isovaleroyloxy-2-(hexa-2,4-diynyliden)-1,6-dioxaspiro [4,5] decane and increased QR enzyme activity in a dose-dependent manner. Furthermore, CZ-6 fraction caused a dose-dependent enhancement of luciferase activity in HepG2-C8 cells generated by stably transfecting antioxidant response element-luciferase gene construct, suggesting that it induces antioxidant/detoxifying enzymes through antioxidant response element (ARE)-mediated transcriptional activation of the relevant genes. Although CZ-6 fraction failed to induce hepatic QR in mice over the control, it restored QR activity suppressed by CCl4 treatment to the control level. Hepatic injury induced by CCl4 was also slightly protected by pretreatment with CZ-6. In conclusion, although CZ-6 fractionated from methanolic extract of Chrysanthemum zawadskii did not cause a significant QR induction in mice organs such as liver, kidney, and stomach, it showed protective effect from liver damage caused by CCl4.

Protective Effect of Artemisia annua L. Extract against Galactose-Induced Oxidative Stress in Mice

Artemisia annua L. (also called qinghao) has been well known as a source of antimalarial drug artemisinins. In addition, the herb was reported to have in vitro antioxidative activity. The present study investigated the protective effect of aqueous ethanol extract of Qinghao (AA extract) against D-galactose-induced oxidative stress in C57BL/6J mice. Feeding AA extract-containing diet lowered serum levels of malondialdehyde and 8-OH-dG that are biomarkers for lipid peroxidation and DNA damage, respectively. Furthermore, AA extract feeding enhanced the activity of NQO1, a typical antioxidant marker enzyme, in tissues such as kidney, stomach, small intestine, and large intestine. In conclusion, AA extract was found to have antioxidative activity in mouse model.

Protective effects of dehydroglyasperin c against carbon tetrachloride-induced liver damage in mice

Dehydroglyasperin C (DGC) isolated from licorice has been shown to exhibit antioxidant activity as well as induce phase 2 detoxifying enzymes in mouse hepatoma cells. This study investigated whether or not DGC exerts hepatoprotective effects through modulation of phase 1 and 2 detoxifying enzymes. ICR mice were divided into five groups with 10 mice per group: (1) negative control, (2) positive control injected with carbon tetrachloride (CCl4, 0.6 mL/kg BW) alone, (3) ICR mice injected with DGC (5 mg/kg BW) alone, (4) ICR mice injected with DGC followed by CCl4, and (5) ICR mice injected with DGC and CCl4 simultaneously. Mice were adapted for 1 week, followed by injection with DGC on day 7, CCl4 on day 8, and sacrifice on day 9 of the experiment. Treatment with DGC induced NQO1 activity in kidney only, but not in the other tissues of mice. Compared to mice injected with CCl4 alone, mice simultaneously injected with both DGC and CCl4 showed reduced lipid droplet formation in liver tissue, as assessed by histological examination. Further, DGC demonstrated a slight protective effect against centrilobular injury caused by CCl4 injection, perhaps through suppression of CYP2E1 expression. In conclusion, DGC possesses hepatoprotective effects against CCl4-induced injury.