Hongxiang Lou

Oridonin Confers Protection against Arsenic-Induced Toxicity through Activation of the Nrf2-Mediated Defensive Response

Background Groundwater contaminated with arsenic imposes a big challenge to human health worldwide. Using natural compounds to subvert the detrimental effects of arsenic represents an attractive strategy. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) is a critical regulator of the cellular antioxidant response and xenobiotic metabolism. Recently, activation of the Nrf2 signaling pathway has been reported to confer protection against arsenic-induced toxicity in a cell culture model. Objectives The goal of the present work was to identify a potent Nrf2 activator from plants as a chemopreventive compound and to demonstrate the efficacy of the compound in battling arsenic-induced toxicity. Results Oridonin activated the Nrf2 signaling pathway at a low subtoxic dose and was able to stabilize Nrf2 by blocking Nrf2 ubiquitination and degradation, leading to accumulation of the Nrf2 protein and activation of the Nrf2-dependent cytoprotective response. Pretreatment of UROtsa cells with 1.4 μM oridonin significantly enhanced the cellular redox capacity, reduced formation of reactive oxygen species (ROS), and improved cell survival after arsenic challenge. Conclusions We identified oridonin as representing a novel class of Nrf2 activators and illustrated the mechanism by which the Nrf2 pathway is activated. Furthermore, we demonstrated the feasibility of using natural compounds targeting Nrf2 as a therapeutic approach to protect humans from various environmental insults that may occur daily.

Naringenin-7-O-glucoside protects against doxorubicin-induced toxicity in H9c2 cardiomyocytes by induction of endogenous antioxidant enzymes.

Doxorubicin, a widely used chemotherapeutic agent, can give rise to severe cardiotoxicity that limits its clinical use by generation of reactive oxygen species (ROS) and apoptosis. Protection or alleviation of doxorubicin cardiotoxicity can be achieved by administration of natural phenolic compounds via activating endogenous defense systems and antiapoptosis. Naringenin-7-O-glucoside (NARG), isolated from Dracocephalum rupestre Hance, has been demonstrated to protect against cardiomyocyte apoptosis. In the present study, we investigated the effects of NARG on endogenous antioxidant enzymes against doxorubicin toxicity and the potential role of extracellular signal-regulated kinase (ERK) in regulation of NARG-induced Nrf2-dependent gene expression in H9c2 cardiomyocytes. The mRNA expression of glutamate-cysteine ligase modifier subunit (GCLM) and glutamate-cysteine ligase catalytic subunit (GCLC) was upregulated by NARG as detected by RT-PCR. NARG (10, 20, and 40microM) pretreatment increased NAD (P) H: quinone oxidoreductase (NQO1), ERK, and Nrf2 protein levels in cardiomyocytes as detected by Western blotting. These results suggest that NARG could prevent cardiomyocytes from doxorubicin-induced toxicity by induction of endogenous antioxidant enzymes via phosphorylation of ERK1/2 and nuclear translocation of Nrf2.

Catechin and proanthocyanidin B4 from grape seeds prevent doxorubicin-induced toxicity in cardiomyocytes.

The clinical use of doxorubicin, a highly active anticancer drug, is limited by its severe cardiotoxic side effects. Grape seed extract has been reported to exert protective effects on doxorubicin-induced cardiotoxicity. The cardiovascular protective effects of grape seed extract are believed to be ascribed to its antioxidative properties. A series of studies have has demonstrated that polyphenols are instrumental for the antioxidative properties of grape seed extract. This study was designed to investigate whether two major polyphenols isolated from grape seed extract, catechin and proanthocyanidin B4 (Pc B(4)), had protective effects against doxorubicin-induced toxicity in cardiomyocytes and their underlying mechanisms. The results showed that grape seed polyphenols catechin and Pc B(4) pretreatment would protect cardiomyocytes against doxorubicin-induced toxicity by decreasing reactive oxygen species generation as well as the number of apoptotic cells, preventing DNA fragmentation, regulating the expression levels of the pro-apoptotic protein Bax-alpha and the anti-apoptotic protein Bcl-2, and inhibiting apoptotic signaling pathways.

Eriodictyol-7-O-glucoside, a novel Nrf2 activator, confers protection against cisplatin-induced toxicity

Eriodictyol-7-O-glucoside, a flavonoid isolated from Dracocephalum rupestre, is among the most potent free radical scavenger. In the present study, we identified eriodictyol-7-O-glucoside as a novel nuclear factor E2-related factor 2 (Nrf2) activator using a high-throughput cellular screening method. This compound activated Nrf2 signaling pathway and was able to stabilize Nrf2 by delaying Nrf2 degradation, resulting in accumulation of Nrf2 protein and activation of the Nrf2-dependent protective response. Recent studies have suggested that activation of Nrf2 pathway would confer protection against cisplatin-induced toxicity. The protective role of eriodictyol-7-O-glucoside in cisplatin-induced toxicity was investigated in a human renal mesangial cell line, HRMC. Cotreatment of HRMC cells with eriodictyol-7-O-glucoside significantly improved cell survival under cisplatin exposure. These findings demonstrated the feasibility of using natural compounds targeting Nrf2 as a therapeutic approach to subvert the side effects of cisplatin in normal cells.

Allelochemicals of the invasive neophyte Polygonum cuspidatum Sieb. & Zucc. (Polygonaceae)

Polygonum cuspidatum Sieb. and Zucc., a traditional Chinese medicine is now a wide-spread invasive neophyte in Europe and America. The novel weapon hypothesis states that some invasive weed species owe part of their success as invaders to allelopathy mediated by some allelochemicals. Previous HPLC/UV/ESI-MS analysis showed that the constituents of the roots of P. cuspidatum from China were obviously different from the species collected in Switzerland (present as an invasive neophyte) with respect to piceatannol glucoside, resveratroloside and some proanthocyanidin. This work isolated these special constituents from the invasive plant and studied their allelopathy effect, as well as the related structures by the seedling and growing model of Lepidium sativum (garden cress, Brassicaceae). The results revealed that stilbenes as piceatannol glucoside, resveratroloside and proanthocyanidins as catechin, epicatechin from this plant were comparatively stronger allelochemicals than the reported allelochemical (−)-catechin, which may partly explain the invasive behavior of this plant in Europe.

Chemical constituents of Asplenium ruta-muraria L.

A phytochemical study of Asplenium ruta-muraria L. (Aspleniaceae) led to the isolation of a new caffeic acid glycoside, 2-O-caffeoyl-β-D-fructofuranosyl-(2 → 1)-α-D-glucopyranoside and an (α, β)-isomeric pair of 2E-caffeoyl-D-glucopyranoside, together with kaempferol-3-O-β-D-[6-E-caffeoyl-β-D-glucopyranosyl-(1 → 2)glucopyranoside]-7-O-β-D-glucopyranoside, 1-O-caffeoyl glycoside, sucrose, diploptene and β-sitosterol. Their structures were established by means of MS and capillary NMR techniques. Additionally, aromatase inhibitory activity of the extracts and phenolic compounds was evaluated.

Synthesis of monoterpene alkaloid derivatives from the iridoid glucoside geniposide.

Nine novel monoterpene alkaloid derivatives (3(a)–(c), 4(a)–(c), 5(a)–(c)) were prepared as a reaction of genipin 2 with L-amino acid methyl hydrochlorides utilized the reaction of reductive amination. Genipin was obtained by β-glucosidase, catalyzed hydrolysis of the iridoid glucoside geniposide 1. The chemical structures were confirmed by 1D-, 2D-NMR and MS.

Polyphenolic compounds from Malus hupehensis and their free radical scavenging effects

Abstract One new 4-chromanone glycoside, 5-O-β-d-glucopyranoside-4-chromanone (1), together with 21 known polyphenols, was isolated from the leaves of Malus hupehensis. Their structures were elucidated on the basis of extensive spectroscopic methods including NMR (1D and 2D), mass (ESIMS and HRESIMS), IR, and by comparison with the data reported in the literature. Some of the isolated compounds were screened for antioxidant activity. Compounds 18 and 14 exhibited significant antioxidant activities with SC50 values 2.73 and 2.91 μg/mL, respectively, while 17, 19, 11, 7, 20, 22, 12 and 13 exhibited moderate activities with SC50 values ranging from 5.24–11.86 μg/mL. The HPLC fingerprint profiles of the leaves and fruits extracts were also analysed, which showed that the constituents were almost the same in both the extracts except for the content of phlorizin which was present in higher amount in the leaves.