Induction of quinone reductase as a primary screen for natural product anticarcinogens

The recent advances of glucosinolates and their metabolites: Metabolism, physiological functions and potential application strategies

Glucosinolates and their metabolites from Brassicaceae plants have received widespread attention due to their anti-inflammatory effects. Glucosinolates occurs an "enterohepatic circulation" in the body, and the glucosinolates metabolism mainly happens in the intestine. Glucosinolates can be converted into isothiocyanates by intestinal bacteria, which are active substances with remarkable anti-inflammatory, anti-cancer, anti-obesity and neuroprotective properties. This biotransformation can greatly improve the bioactivities of glucosinolates. However, multiple factors in the environment can affect the biotransformation to isothiocyanates, including acidic pH, ferrous ions and thiocyanate-forming protein. The derivatives of glucosinolates under those conditions are usually nitriles and thiocyanates, which may impair the potential health benefits. In addition, isothiocyanates are extremely unstable because of an active sulfhydryl group, which limits their applications. This review mainly summarizes the classification, synthesis, absorption, metabolism, physiological functions and potential application strategies of glucosinolates and their metabolites.

Microwave Assisted Green Synthesis of Benzimidazole Derivatives and Evaluation of Their Anticonvulsant Activity

Background:

Benzimidazole is the fused heterocyclic aromatic compound. It is an essential pharmacophore and privileged structure for the development of new drug molecules. These are bioactive molecules present in various anthelmintic drugs such as albendazole, mebendazole, parbendazole, triclabendazole etc.

Methods:

Benzimidazole derivatives are synthesized by reaction between orthophenylene diamine and anthranillic acid followed by acetylation in the presence of acetic anhydride. Finally, the acetylated products undergo Claisen-Schimdt condensation with various substituted benzaldehydes to produce corresponding benzimidazole derivatives or chalcones. Both conventional and microwave irradiation technology are followed to get the titled compounds. The titled compounds are screened for their anticonvulsant and neurotoxicity activity.

Results:

By the help of microwave synthesis, the yield of product was increased in less reaction time. So, it follows Green chemistry approach by making above reactions eco-friendly. Some of the compounds exhibited significant anticonvulsant activity as compared to standard drug.

Conclusion:

In the present investigation, we have synthesized novel benzimdazole derivatives with chalone moiety to improve the biological activity. The compounds were obtained under microwave reaction with high yield in a short reaction time.

Soy-derived phytoalexins: mechanism of in vivo biological effectiveness in spite of their low bioavailability

The well-demonstrated bioefficacy of phytochemicals in spite of their paradoxically low bioavailability has long puzzled scientists. Glyceollins, a family of soy-derived phytoalexins, have been reported to exert a variety of biological effects in vitro and in vivo systems in spite of poor systemic bioavailability after oral administration, suggesting that secondary messengers generated in gastrointestinal tract would transfer signals to target organs and tissues to manifest any effect. This review focuses on the potential mechanisms of how the poorly bioavailable glyceollins could still exert in vivo biological effects.

Activity-guided isolation of phase II enzyme inducers from buckwheat flour methanolic extracts

BACKGROUND

Buckwheat is an important alternative crop and a raw material for functional food formulation. Phase II detoxification proteins/enzymes provide cytoprotective roles against oxidative stress and inflammation originating from various stressors. We aimed to identify and characterize potential phase II enzyme inducers from methanolic extracts of buckwheat flour, using an activity-guided fractionation based on the induction of quinone reductase (QR) (EC 1.6.5.2) in Hepa 1c1c7 cells.

RESULTS

We isolated the QR inducers N-trans-feruloyltyramine (I), syringic acid (II), quercetin (III) and myricetin (IV). The relative QR-inducing ability, as well as the concentration required to double QR specific activity (CD values, in parentheses), decreased in the order: quercetin (3.0 µmol L^-1 ) > N-trans-feruloyltyramine (24 µmol L^-1 ) > myricetin (58 µmol L^-1 ) > syringic acid (5.4 mmol L^-1 ). Quercetin and N-trans-feruloyltyramine exhibited the greatest extent of QR induction of an approximately four-fold maximum induction and these compounds also exhibited the greatest values for the ratio of IC₅₀ (i.e. level to reduce viability by 50%): CD values of 11 and > 8.3, respectively, among the four QR inducers isolated. Isobologram analyses for binary combinations of compounds I-IV revealed primarily antagonistic interactions for QR induction.

CONCLUSION

These findings add to our understanding of the nutraceutical potential of buckwheat as a chemoprophylactic dietary component. © 2018 Society of Chemical Industry.

Carbazole-, Aspidofractinine-, and Aspidocarpamine-Type Alkaloids from Pleiocarpa pycnantha

Three new alkaloids, janetinine (1a), pleiokomenine A (2), and huncaniterine B (3a), and 13 known compounds, pleiomutinine (3b), huncaniterine A (3c), 1-carbomethoxy-β-carboline (4), evoxanthine (5), deformyltalbotine acid lactone (6), pleiocarpamine (7), N⁴-methyl-10-hydroxygeissoschizol (8), spegatrine (9), neosarpagine (10), aspidofractinine (11), N¹-methylkopsinin (12), pleiocarpine (13), and N¹-methylkopsinin- N⁴-oxide (14), were isolated from the stem bark of Pleiocarpa pycnantha. Janetinine (1a) is a carbazole alkaloid; in pleiokomenine A (2), two aspidofractinine-type alkaloids are bridged by a methylene unit in an unprecedented way, and huncaniterine B (3a) is a pleiocarpamine-aspidofractinine-type dimer. The structures and relative configurations of these compounds were elucidated on the basis of NMR and MS analyses. Their absolute configurations were defined by means of experimental and calculated ECD data, and additionally, the structures of 5 and 13 were determined by single crystal X-ray diffraction. Compounds 1a, 2, 3b, 4, 6, 9, and 12 displayed cancer chemopreventive properties through either quinone reductase induction ( CD = 30.7, 30.2, 29.9, 43.5, and 36.7 μM for 1a, 4, 6, 9, and 12, respectively) and/or NF-κB inhibition with IC₅₀ values of 13.1, 8.4, 9.4, and 8.8 μM for 2, 3b, 6, and 12, respectively.

Chemical profile of pineapple cv. Vitória in different maturation stages using electrospray ionization mass spectrometry

BACKGROUND

Pineapple is the fruit of Ananas comosus var. comosus plant, being cultivated in tropical areas and has high energy content and nutritional value. Herein, 30 samples of pineapple cv. Vitória were analyzed as a function of the maturation stage (0-5) and their physico-chemical parameters monitored. In addition, negative-ion mode electrospray ionization mass spectrometry [ESI(-)FT-ICR MS] was used to identify and semi-quantify primary and secondary metabolites present in the crude and phenolic extracts of pineapple, respectively.

RESULTS

Physico-chemical tests show an increase in the total soluble solids (TSS) values and in the TSS/total titratable acidity ratio as a function of the maturity stage, where a maximum value was observed in stage 3 (¾ of the fruit is yellow, which corresponds to the color of the fruit peel). ESI(-)FT-ICR MS analysis for crude extracts showed the presence mainly of sugars as primary metabolites present in deprotonated molecule form ([M - H]^- and [2 M - H]^- ions) whereas, for phenolic fractions, 11 compounds were detected, being the most abundant in the third stage of maturation. This behavior was confirmed by quantitative analysis of total polyphenols.

CONCLUSION

ESI-FT-ICR MS was efficient in identifying primary (carbohydrates and organic acids) and secondary metabolites (13 phenolic compounds) presents in the crude and phenolic extract of the samples, respectively. © 2017 Society of Chemical Industry.

Indoline alkaloids from Tabernaemontana contorta with cancer chemopreventive activity

Two bisindoline alkaloids, contortarine A, 16-epi-pleiomutinine and a reaction product of pleiomutinine, namely N⁴-chloromethyl-pleiomutinine, were isolated from the roots of Tabernaemontana contorta Stapf. together with five known compounds: pleiomutinine, 1-carbomethoxy-β-carboline, strictosidine lactam, pleiocarpamine, and pleiocarpine. The structures and relative configuration of these alkaloids were determined by extensive 1D and 2D NMR, and MS measurements. The absolute configuration of these compounds was determined by comparison of experimental and calculated ECD spectra. Among the isolated compounds, contortarine A, 1-carbomethoxy-β-carboline and strictosidine lactam presented cancer chemopreventive properties through either quinone reductase (QR) induction with C_D values of 16.0 ± 2.5, 30.2 ± 6.1 and 23.1 ± 4.6 μM, respectively, while pleiomutinine and 16-epi-pleiomutinine displayed the inhibition of TNF-α induced NF-κB activity with IC₅₀ at 11.7 ± 2.6 and 3.4 ± 1.1 μM, respectively.

Chemopreventive glucosinolate accumulation in various broccoli and collard tissues: Microfluidic-based targeted transcriptomics for by-product valorization

Floret, leaf, and root tissues were harvested from broccoli and collard cultivars and extracted to determine their glucosinolate and hydrolysis product profiles using high performance liquid chromatography and gas chromotography. Quinone reductase inducing bioactivity, an estimate of anti-cancer chemopreventive potential, of the extracts was measured using a hepa1c1c7 murine cell line. Extracts from root tissues were significantly different from other tissues and contained high levels of gluconasturtiin and glucoerucin. Targeted gene expression analysis on glucosinolate biosynthesis revealed that broccoli root tissue has elevated gene expression of AOP2 and low expression of FMOGS-OX homologs, essentially the opposite of what was observed in broccoli florets, which accumulated high levels of glucoraphanin. Broccoli floret tissue has significantly higher nitrile formation (%) and epithionitrile specifier protein gene expression than other tissues. This study provides basic information of the glucosinolate metabolome and transcriptome for various tissues of Brassica oleracea that maybe utilized as potential byproducts for the nutraceutical market.

Cancer chemopreventive activity of compounds isolated from Waltheria indica

ETHNOPHARMACOLOGICAL RELEVANCE

Waltheria indica L. is traditionally used in several countries against inflammatory related diseases and cancer, mainly as a decoction of the aerial parts.

AIM OF THE STUDY

The transcription factor NF-κB is known to induce tumor promotion and progression and is considered a major player in inflammation-driven cancers. Therefore, inhibitors of this pathway possess cancer chemopreventive and chemotherapeutic activities. This study aimed first to confirm the use of Waltheria indica as a traditional anti-inflammatory remedy by assessing the NF-κB inhibitory activity and then to identify the major bioactive compounds. The isolated compounds were also tested for their QR inducing property, a complementary strategy in cancer chemoprevention able to target tumor initiation. Finally, the relevance of in vitro results was examined by investigating the occurrence of the active compounds in traditional preparations.

MATERIALS AND METHODS

Compounds were isolated from the dichloromethane extract of the aerial parts using flash chromatography and semi-preparative HPLC. NF-κB inhibitory activity of pure compounds from Waltheria indica was assessed using a luciferase reporter assay in HEK293 cells. Their QR inducing activity was also assessed in Hepa1c1c7 cells.

RESULTS

Twenty-nine compounds, of which 5 are new, were obtained from the dichloromethane extract and tested for their cancer chemoprevention activity. Eleven compounds inhibited NF-κB and/or induced QR in the low to mid µM range. Chrysosplenol E (20) was active in both tests. Two of the most potent NF-κB inhibitors, waltherione A (4) and waltherione C (5), as well as 20 were found in the traditional decoction, in which 4 and 5 were major compounds.

CONCLUSION

The presence of potent NF-κB inhibitors and QR inducing compounds in the decoction of the aerial parts of Waltheria indica supports its traditional use in inflammatory-related diseases and cancer chemoprevention.

Exogenous Methyl Jasmonate and Salicylic Acid Induce Subspecies-Specific Patterns of Glucosinolate Accumulation and Gene Expression in Brassica oleracea L

Glucosinolates have anti-carcinogenic properties. In the recent decades, the genetics of glucosinolate biosynthesis has been widely studied, however, the expression of specific genes involved in glucosinolate biosynthesis under exogenous phytohormone treatment has not been explored at the subspecies level in Brassica oleracea. Such data are vital for strategies aimed at selective exploitation of glucosinolate profiles. This study quantified the expression of 38 glucosinolate biosynthesis-related genes in three B. oleracea subspecies, namely cabbage, broccoli and kale, and catalogued associations between gene expression and increased contents of individual glucosinolates under methyl jasmonate (MeJA) and salicylic acid (SA) treatments. Glucosinolate accumulation and gene expression in response to phytohormone elicitation was subspecies specific. For instance, cabbage leaves showed enhanced accumulation of the aliphatic glucoiberin, progoitrin, sinigrin and indolic neoglucobrassicin under both MeJA and SA treatment. MeJA treatment induced strikingly higher accumulation of glucobrassicin (GBS) in cabbage and kale and of neoglucobrassicin (NGBS) in broccoli compared to controls. Notably higher expression of ST5a (Bol026200), CYP81F1 (Bol028913, Bol028914) and CYP81F4 genes was associated with significantly higher GBS accumulation under MeJA treatment compared to controls in all three subspecies. CYP81F4 genes, trans-activated by MYB34 genes, were expressed at remarkably high levels in all three subspecies under MeJA treatment, which also induced in higher indolic NGBS accumulation in all three subspecies. Remarkably higher expression of MYB28 (Bol036286), ST5b, ST5c, AOP2, FMOGS-OX5 (Bol031350) and GSL-OH (Bol033373) was associated with much higher contents of aliphatic glucosinolates in kale leaves compared to the other two subspecies. The genes expressed highly could be utilized in strategies to selectively increase glucosinolate compounds in B. oleracea subspecies. These results promote efforts to develop genotypes of B. oleracea and other species with enhanced levels of desired glucosinolates.

Statistical Correlations between HPLC Activity-Based Profiling Results and NMR/MS Microfraction Data to Deconvolute Bioactive Compounds in Mixtures

Recent approaches in natural product (NP) research are leading toward the discovery of bioactive chemical entities at the microgram level. In comparison to classical large scale bioassay-guided fractionation, the use of LC-MS metabolite profiling in combination with microfractionation for both bioactivity profiling and NMR analysis, allows the identification of bioactive compounds at a very early stage. In that context, this study aims to assess the potential of statistic correlation analysis to enable unambiguous identification of features related to bioactive compounds in mixtures, without the need for complete isolation. For that purpose, a mixture of NPs was microfractionated by rapid small-scale semi-preparative HPLC for proof-of-concept. UHPLC-ESI-TOFMS profiles, micro-flow CapNMR spectra and a cancer chemopreventive assay carried out on every microfraction were analysed by statistical correlations.

Induction of NAD(P)H:Quinone Oxidoreductase 1 (NQO1) by Glycyrrhiza Species Used for Women's Health: Differential Effects of the Michael Acceptors Isoliquiritigenin and Licochalcone A

For the alleviation of menopausal symptoms, women frequently turn to botanical dietary supplements, such as licorice and hops. In addition to estrogenic properties, these botanicals could also have chemopreventive effects. We have previously shown that hops and its Michael acceptor xanthohumol (XH) induced the chemoprevention enzyme,

NAD(P)H

quinone oxidoreductase 1 (NQO1), in vitro and in vivo. Licorice species could also induce NQO1, as they contain the Michael acceptors isoliquiritigenin (LigC) found in Glycyrrhiza glabra (GG), G. uralensis (GU), G. inflata (GI), and licochalcone A (LicA) which is only found in GI. These licorice species and hops induced NQO1 activity in murine hepatoma (Hepa1c1c7) cells; hops ≫ GI > GG ≅ GU. Similar to the known chemopreventive compounds curcumin (turmeric), sulforaphane (broccoli), and XH, LigC and LicA were active dose-dependently; sulforaphane ≫ XH > LigC > LicA ≅ curcumin ≫ liquiritigenin (LigF). Induction of the antioxidant response element luciferase in human hepatoma (HepG2-ARE-C8) cells suggested involvement of the Keap1-Nrf2 pathway. GG, GU, and LigC also induced NQO1 in nontumorigenic breast epithelial MCF-10A cells. In female Sprague-Dawley rats treated with GG and GU, LigC and LigF were detected in the liver and mammary gland. GG weakly enhanced NQO1 activity in the mammary tissue but not in the liver. Treatment with LigC alone did not induce NQO1 in vivo most likely due to its conversion to LigF, extensive metabolism, and its low bioavailability in vivo. These data show the chemopreventive potential of licorice species in vitro could be due to LigC and LicA and emphasize the importance of chemical and biological standardization of botanicals used as dietary supplements. Although the in vivo effects in the rat model after four-day treatment are minimal, it must be emphasized that menopausal women take these supplements for extended periods of time and long-term beneficial effects are quite possible.

Exogenous methyl jasmonate treatment increases glucosinolate biosynthesis and quinone reductase activity in kale leaf tissue

Methyl jasmonate (MeJA) spray treatments were applied to the kale varieties ‘Dwarf Blue Curled Vates’ and ‘Red Winter’ in replicated field plantings in 2010 and 2011 to investigate alteration of glucosinolate (GS) composition in harvested leaf tissue. Aqueous solutions of 250 µM MeJA were sprayed to saturation on aerial plant tissues four days prior to harvest at commercial maturity. The MeJA treatment significantly increased gluconasturtiin (56%), glucobrassicin (98%), and neoglucobrassicin (150%) concentrations in the apical leaf tissue of these genotypes over two seasons. Induction of quinone reductase (QR) activity, a biomarker for anti-carcinogenesis, was significantly increased by the extracts from the leaf tissue of these two cultivars. Extracts of apical leaf tissues had greater MeJA mediated increases in phenolics, glucosinolate concentrations, GS hydrolysis products, and QR activity than extracts from basal leaf tissue samples. The concentration of the hydrolysis product of glucoraphanin, sulforphane was significantly increased in apical leaf tissue of the cultivar ‘Red Winter’ in both 2010 and 2011. There was interaction between exogenous MeJA treatment and environmental conditions to induce endogenous JA. Correlation analysis revealed that indole-3-carbanol (I3C) generated from the hydrolysis of glucobrassicin significantly correlated with QR activity (r = 0.800, P<0.001). Concentrations required to double the specific QR activity (CD values) of I3C was calculated at 230 µM, which is considerably weaker at induction than other isothiocyanates like sulforphane. To confirm relationships between GS hydrolysis products and QR activity, a range of concentrations of MeJA sprays were applied to kale leaf tissues of both cultivars in 2011. Correlation analysis of these results indicated that sulforaphane, NI3C, neoascorbigen, I3C, and diindolylmethane were all significantly correlated with QR activity. Thus, increased QR activity may be due to combined increases in phenolics (quercetin and kaempferol) and GS hydrolysis product concentrations rather than by individual products alone.

Optimization of methyl jasmonate application to broccoli florets to enhance health-promoting phytochemical content

BACKGROUND

Spray treatment of methyl jasmonate (MeJA) has been shown to increase glucosinolate (GS) concentrations and health-promoting activity in Brassica vegetables. Since there is no reported standardized protocol, several MeJA treatment studies have been conducted to maximize human health bioactivity using the F1 broccoli cultivar 'Green Magic'.

RESULTS

Foliar MeJA application 4 days prior to harvest of broccoli at commercial maturity resulted in enhanced total GS concentrations. Although a single application of 250 µmol L(-1) MeJA maximized GS concentrations in broccoli florets, two days of consecutive treatments (4 and 3 days prior to harvest) of 250 µmol L(-1) MeJA further enhanced neoglucobrassicin concentrations and floret extract quinone reductase (QR)-inducing activity. With increasing concentrations of MeJA in spray applications to broccoli florets, concentrations of the glucosinolates glucoraphanin, gluconasturtiin and neoglucobrassicin and the isothiocyanate sulforaphane as well as anticancer and anti-inflammatory bioactivities as measured by QR induction and inhibition of nitric oxide (NO) production respectively were significantly increased. Concentrations of these phytochemicals showed strong positive correlations with QR-inducing and NO-inhibitory activities.

CONCLUSION

These application protocols were found to maximize GS and GS hydrolysis product concentrations and putatively enhance the health-promoting properties of broccoli heads for consumers.

Cancer chemopreventive diterpenes from Salvia corrugata

NMR and NP-HPLC-UV profiling of the exudate of Salvia corrugata revealed that its secondary metabolite composition was largely dominated by α-hydroxy-β-isopropyl-benzoquinone diterpenoids. Among them, four diterpenes not described previously were isolated and identified as fruticulin C (3), 7α-methoxy-19-acetoxy-royleanone (4), 7α,19-diacetoxy-royleanone (5), and 7-dehydroxy-conacytone (7). In addition, the known diterpenes fruticulin A (1), demethyl-fruticulin A (2) and 7α-O-methyl-conacytone (6) were also obtained. The isolated compounds were evaluated for their cancer chemopreventive activity by measuring quinone reductase induction activity and histone deacetylase inhibition. Three compounds (1, 2 and 5) showed promising activity.

Synergistic activation of the Nrf2-signaling pathway by glyceollins under oxidative stress induced by glutathione depletion

Oxidative stress state such as depletion of the intracellular glutathione (GSH) is associated with the development of cancer. Some dietary phytochemicals have been shown to possess a cancer preventive effect, although the understanding of the involved mechanisms is still limited. Recent study has shown that glyceollins, phytoalexins derived from soybean by biotic elicitor, might have a cancer preventive effect through induction of detoxifying/antioxidant enzymes. The objective of this study was to investigate the effects of glyceollins on the Nrf2 signaling pathway under excessive oxidative stress induced by GSH depletion. In mouse hepatoma cells (Hepa1c1c7) subjected to the buthionine sulfoximine (BSO), an inhibitor of γ-glutamylcysteine synthetase (γGCS), the intracellular GSH content was significantly lowered. On the other hand, incubation with glyceollins in the presence of BSO increased the level of GSH, expression of γGCS, and nuclear translocation of NF-E2-related factor-2 (Nrf2), compared to the cells treated with BSO only. Nrf2-antioxidant responsive element (ARE)-reporter activity assay in HepG2-C8 showed that BSO increased the ARE-reporter activity in a dose-dependent manner, compared to vehicle-treated cells, whereas cotreatment with glyceollins caused further increase in reporter luciferase activity relative to BSO alone. Taken together, glyceollins synergistically activated the Nrf2 signaling pathway and subsequently the expression of phase 2/antioxidant enzymes in the presence of BSO, suggesting that BSO-induced oxidative stress and that glyceollins regulate the expression of phase 2/antioxidant enzymes through different mechanisms from each other.

Antioxidant and quinone reductase-inducing constituents of black chokeberry (Aronia melanocarpa) fruits

Using in vitro hydroxyl radical-scavenging and quinone reductase-inducing assays, bioactivity-guided fractionation of an ethyl acetate-soluble extract of the fruits of the botanical dietary supplement, black chokeberry (Aronia melanocarpa), led to the isolation of 27 compounds, including a new depside, ethyl 2-[(3,4-dihydroxybenzoyloxy)-4,6-dihydroxyphenyl] acetate (1), along with 26 known compounds (2-27). The structures of the isolated compounds were identified by analysis of their physical and spectroscopic data ([α](D), NMR, IR, UV, and MS). Altogether, 17 compounds (1-4, 9, 15-17, and 19-27) showed significant antioxidant activity in the hydroxyl radical-scavenging assay, with hyperin (24, ED(50) = 0.17 μM) being the most potent. The new compound (1, ED(50) = 0.44 μM) also exhibited potent antioxidant activity in this assay. Three constituents of black chokeberry fruits doubled quinone reductase activity at concentrations <20 μM, namely, protocatechuic acid [9, concentration required to double quinone reductase activity (CD) = 4.3 μM], neochlorogenic acid methyl ester (22, CD = 6.7 μM), and quercetin (23, CD = 3.1 μM).

Acylated pregnane glycosides from Caralluma sinaica

Caralluma sinaica is sold on local markets of Saudi Arabia for various health benefits however no phytochemical study has specifically been performed on this species. NMR and UHPLC-ESI-TOF-MS profilings of the ethanolic extract of the whole plant reveal a very complex phytochemical composition dominated by pregnanes. Detailed information on its constituents was obtained after isolation. Six pregnane glycosides were obtained and characterized based on the extensive spectroscopic analysis (including IR, ¹H NMR, ¹³C NMR and MS data), in addition to ten known compounds (seven pregnanes and three flavonoids). The compounds were identified as 12β-O-benzoyl-20-O-acetyl boucerin-3-O-6-deoxy-3-O-methyl-β-D-glucopyranosyl-(1-->4)-β-D-cymaropyranosyl-(1-->4)-β-D-cymaropyranoside, 12β-O-tigloyl-20-O-acetyl boucerin-3-O-β-D-glucopyranosyl-(1-->4)-β-D-cymaropyranoside, 12β-O-benzoyl-20-O-acetyl boucerin-3-O-β-D-glucopyranosyl-(1-->4)-β-D-digitalopyranosyl-(1-->4)-β-D-cymaropyranosyl-(1-->4)-β-D-cymaropyranoside, 12β-O-benzoyl-20-O-acetyl boucerin-3-O-β-D-glucopyranosyl-(1-->4)-hevetopyranosyl-(1-->4)-β-D-cymaropyranosyl-(1-->4)-β-D-cymaropyranoside, 12β-O-benzoyl-20-O-tigloyl boucerin-3-O-β-D-glucopyranosyl-(1-->4)-β-D-cymaropyranoside, 12β-20-O-dibenzoyl boucerin-3-O-β-D-glucopyranosyl-(1-->4)-β-D-cymaropyranosyl-(1-->4)-β-D-cymaropyranoside. Finally, the isolated compounds were evaluated for their quinone reductase induction.

Discovery of Multi-Target Agents for Neurological Diseases via Ligand Design

The incidence of neurological disorders in the developed world is rising in concert with an increase in human life expectancy, due in large part to better nutrition and health care. Even as drug discovery efforts are refocused on these disorders, there has been a dearth in the introduction of new disease-modifying therapies to prevent or delay their onset, or reverse their progression. Mounting evidence points to complex and heterogeneous etiopathologies that underlie these diseases. Therefore, it is unlikely that disorders in this class will be mitigated by any single drug that acts exclusively on a single pathway or target. The rational design of novel drug entities with the ability to simultaneously address multiple drug targets of a complex pathophysiology has recently emerged as a new paradigm in drug discovery. Similarly to the concept of multi-target agents within the psychopharmacology field, ligand design has gained an increasing prominence within the medicinal chemistry community. In this chapter we discuss several examples of select chemical scaffolds (polyamines, alkylxanthines, and propargyl carbamates) wherein these concepts were applied to develop novel drug candidates for Alzheimer's disease and Parkinson's disease.

Resveratrol derivatives as promising chemopreventive agents with improved potency and selectivity

SCOPE

Despite scores of investigations, the actual impact of resveratrol (3,5,4'-trihydroxy-trans-stilbene) on human health, as a dietary component or supplement, remains moot. This is due to many factors, such as relatively low potency, pleiotropic mechanisms, and rapid metabolism. Nonetheless, as a promiscuous molecule that interacts with numerous targets, resveratrol can be viewed as a scaffold for designing structural relatives potentially capable of mediating more intense responses with greater mechanistic stringency.

METHODS AND RESULTS

We currently report the synthesis and biological evaluation of 92 stilbene analogs. The compounds were tested with in vitro assays for activation of quinone reductase 1, inhibition of quinone reductase 2, nitric oxide production, aromatase, NFκB, 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced ornithine decarboxylase, or cyclooxygenase-1 and -2, quenching of 2,2-diphenyl-1-picrylhydrazyl free radical, interaction with estrogen receptors, and as antiproliferative agents. Several compounds were found to mediate responses with much greater potency than resveratrol; some mediated pleiotropic responses, as is the case with the parent molecule, but others were highly specific or totally inactive. When administered to rats, higher serum concentrations and greater stability was demonstrated with prototype lead molecules.

CONCLUSION

Owing to structural simplicity, facile syntheses are available for large-scale production. These data support the promise of more advanced development of novel resveratrol derivatives as drug entities.

Recent advances in the multitarget-directed ligands approach for the treatment of Alzheimer's disease

With 27 million cases worldwide documented in 2006, Alzheimer's disease (AD) constitutes an overwhelming health, social, economic, and political problem to nations. Unless a new medicine capable to delay disease progression is found, the number of cases will reach 107 million in 2050. So far, the therapeutic paradigm one-compound-one-target has failed. This could be due to the multiple pathogenic mechanisms involved in AD including amyloid β (Aβ) aggregation to form plaques, τ hyperphosphorylation to disrupt microtubule to form neurofibrillary tangles, calcium imbalance, enhanced oxidative stress, impaired mitochondrial function, apoptotic neuronal death, and deterioration of synaptic transmission, particularly at cholinergic neurons. Approximately 100 compounds are presently been investigated directed to single targets, namely inhibitors of β and γ secretase, vaccines or antibodies that clear Aβ, metal chelators to inhibit Aβ aggregation, blockers of glycogen synthase kinase 3β, enhancers of mitochondrial function, antioxidants, modulators of calcium-permeable channels such as voltage-dependent calcium channels, N-methyl-D-aspartate receptors for glutamate, or enhancers of cholinergic neurotransmission such as inhibitors of acetylcholinesterase or butyrylcholinesterase. In view of this complex pathogenic mechanisms, and the successful treatment of chronic diseases such as HIV or cancer, with multiple drugs having complementary mechanisms of action, the concern is growing that AD could better be treated with a single compound targeting two or more of the pathogenic mechanisms leading to neuronal death. This review summarizes the current therapeutic strategies based on the paradigm one-compound-various targets to treat AD. A treatment that delays disease onset and/or progression by 5 years could halve the number of people requiring institutionalization and/or dying from AD. 

Nrf2-mediated induction of phase 2 detoxifying enzymes by glyceollins derived from soybean exposed to Aspergillus sojae

Numerous antioxidants have been reported to cause transcriptional activation of several antioxidant enzymes through binding antioxidant-response element on their promoter region. We, therefore, attempted to examine whether glyceollins, which share common structural features with many phase 2 enzyme inducers and antioxidant activity, could induce detoxifying/antioxidant enzymes. Glyceollins induced NAD(P)H:quinone oxidoreductase activity in a dose-dependent manner in both mouse hepatoma Hepa1c1c7 and its mutant BPRc1 cells. The compounds also increased the expression of some representative antioxidant enzymes, such as heme oxygenase 1,gamma-glutamylcysteine synthase, and glutathione reductase, by promoting nuclear translocation of the NF-E2-related factor-2 (Nrf2). Furthermore, phosphorylation of Akt and antioxidant response element-mediated reporter gene expression were enhanced by glyceollins but suppressed by LY294002, an inhibitor of phosphoinositide 3-kinases (PI3K). This suggests that glyceollins may cause Nrf2-mediated phase 2 enzyme induction through activation of the PI3K signaling pathway as well as interaction with Keap1. Our molecular docking simulations also suggest that the glyceollin isomers tightly bind into the binding pocket around Cys151, preventing Nrf2 from docking to Keap1. In conclusion, the current data suggest that glyceollins induced phase 2 detoxifying enzymes likely through promoting nuclear translocation of Nrf2, which is known to be regulated by phosphorylation of Nrf2 and/or disrupting Keap1-Nrf2 complex formation.

Cellular stress responses, the hormesis paradigm, and vitagenes: novel targets for therapeutic intervention in neurodegenerative disorders

Despite the capacity of chaperones and other homeostatic components to restore folding equilibrium, cells appear poorly adapted for chronic oxidative stress that increases in cancer and in metabolic and neurodegenerative diseases. Modulation of endogenous cellular defense mechanisms represents an innovative approach to therapeutic intervention in diseases causing chronic tissue damage, such as in neurodegeneration. This article introduces the concept of hormesis and its applications to the field of neuroprotection. It is argued that the hormetic dose response provides the central underpinning of neuroprotective responses, providing a framework for explaining the common quantitative features of their dose-response relationships, their mechanistic foundations, and their relationship to the concept of biological plasticity, as well as providing a key insight for improving the accuracy of the therapeutic dose of pharmaceutical agents within the highly heterogeneous human population. This article describes in mechanistic detail how hormetic dose responses are mediated for endogenous cellular defense pathways, including sirtuin and Nrf2 and related pathways that integrate adaptive stress responses in the prevention of neurodegenerative diseases. Particular attention is given to the emerging role of nitric oxide, carbon monoxide, and hydrogen sulfide gases in hormetic-based neuroprotection and their relationship to membrane radical dynamics and mitochondrial redox signaling.

Potency ranking of triterpenoids as inducers of a cytoprotective enzyme and as inhibitors of a cellular inflammatory response via their electron affinity and their electrophilicity index

Electron affinity (EA) and electrophilicity index (omega) of 16 synthetic triterpenoids (TP), previously identified as inducers of cytoprotective enzymes and as inhibitors of cellular inflammatory responses, have been calculated by the molecular orbital method. Linear correlations were obtained by plotting the values of EA, as well as those of omega versus (i) the potencies of induction of NAD(P)H quinone reductase (NQO1, EC 1.6.99.2), a cytoprotective enzyme, expressed via the concentration of TP required to double the specific activity of NQO1 (CD value) and (ii) the values of their anti-inflammatory activity expressed via the IC-50 of TP for suppression of upregulation of inducible nitric oxide synthase (iNOS, EC 1.14.13.39), both previously experimentally determined. The observed correlations demonstrate quantitatively for a series of triterpenoids that their electrophilicity is a major factor determining their potency as inducers of the cytoprotective phase 2 response and as inhibitors of inflammatory processes.

Cancer chemopreventive activity and metabolism of isoliquiritigenin, a compound found in licorice

Isoliquiritigenin (2',4',4-trihydroxychalcone; ILG), a chalcone found in licorice root and many other plants, has shown potential chemopreventive activity through induction of phase II enzymes such as quinone reductase-1 in murine hepatoma cells. In this study, the in vivo metabolism of ILG was investigated in rats. In addition, ILG glucuronides and ILG-glutathione adducts were observed in human hepatocytes and in livers from rats treated with ILG. ILG glucuronides were detected in both plasma and rat liver tissues. In addition, in a full-term cancer chemoprevention study conducted with 7,12-dimethylbenz(a)anthracene-treated female Sprague-Dawley rats, dietary administration of ILG slightly increased tumor latency but had a negative effect on the incidence of mammary tumors starting at approximately 65 days after 7,12-dimethylbenz(a)anthracene administration. Further, no significant induction of phase II enzymes was found in mammary glands, which is consistent with the low level of ILG observed in these tissues. However, ILG significantly induced quinone reductase-1 activity in the colon, and glutathione as well as glutathione S-transferase in the liver. Analysis of mRNA expression in tissues of rats treated with ILG supported these findings. These results suggest that ILG should be tested for chemopreventive efficacy in nonmammary models of cancer.

Cancer Chemopreventive and Anticancer Evaluation of Extracts and Fractions from Marine Macro- and Microorganisms Collected from Twilight Zone Waters around Guam[1]

The cancer chemopreventive and cytotoxic properties of 50 extracts derived from Twilight Zone (50–150 m) sponges, gorgonians and associated bacteria, together with 15 extracts from shallow water hard corals, as well as 16 fractions derived from the methanol solubles of the Twilight Zone sponge Suberea sp, were assessed in a series of bioassays. These assays included: Induction of quinone reductase (QR), inhibition of TNF-α activated nuclear factor kappa B (NFκB), inhibition of aromatase, interaction with retinoid X receptor (RXR), inhibition of nitric oxide (NO) synthase, inhibition 2,2-diphenyl-1-picrylhydrazyl radical scavenging (DPPH), and inhibition of HL-60 and MCF-7 cell proliferation. The results of these assays showed that at least 10 extracts and five fractions inhibited NFκB by greater than 60%, two extracts and two fractions inhibited DPPH by more than 50%, nine extracts and two fractions affected the survival of HL-60 cells, no extracts or fractions affected RXR, three extracts and six fractions affected quinone reductase (QR), three extracts and 12 fractions significantly inhibited aromatase, four extracts and five fractions inhibited nitric oxide synthase, and one extract and no fractions inhibited the growth of MCF-7 cells by more than 95%. These data revealed the tested samples to have many and varied activities, making them, as shown with the extract of the Suberea species, useful starting points for further fractionation and purification. Moreover, the large number of samples demonstrating activity in only one or sometimes two assays accentuates the potential of the Twilight Zone, as a largely unexplored habitat, for the discovery of selectively bioactive compounds. The overall high hit rate in many of the employed assays is considered to be a significant finding in terms of “normal” hit rates associated with similar samples from shallower depths.

Extraction methods determine the antioxidant capacity and induction of quinone reductase by soy products in vitro

Gastrointestinal (GI) mimic and organic solvent extracts of whole soybean powder (WSP), soy protein concentrate (SPC), and soy protein isolate (SPI) as well as soy isoflavone concentrate (SIC) were analyzed for total phenols; quinone reductase (QR) induction in hepa1c1c7 cells; antioxidant scavenging of DPPH, HOCl, ONOO(-), and O(2) (-.); and total antioxidant capacity via FRAP and ORAC assays. GI extracts of all the soy products had higher concentrations of total phenols than from acidified methanol (MeOH) but lower antioxidant potency. The MeOH extract of SPC was most potent in quenching HOCl and ONOO(-) and increasing FRAP and ORAC, but did not induce QR. Despite weak antioxidant activity, hexane (HX) extracts induced QR more than GI and MeOH extracts with WSP > SPC > SPI > IC. Soy extracts were ineffective scavengers of DPPH and O(2) (-.). Thus, extraction methods markedly affect the antioxidant profile and QR induction capacity of soy products.

Memoquin: a multi-target-directed ligand as an innovative therapeutic opportunity for Alzheimer's disease

Alzheimer's disease is currently thought to be a complex, multifactorial syndrome, unlikely to arise from a single causal factor; instead, a number of related biological alterations are thought to contribute to its pathogenesis. This may explain why the currently available drugs, developed according to the classic drug discovery paradigm of "one-molecule-one-target," have turned out to be palliative. In light of this, drug combinations that can act at different levels of the neurotoxic cascade offer new avenues toward curing Alzheimer's and other neurodegenerative diseases. In parallel, a new strategy is emerging-that of developing a single chemical entity able to modulate multiple targets simultaneously. This has led to a new paradigm in medicinal chemistry, the "multi-target-directed ligand" design strategy, which has already been successfully exploited at both academic and industrial levels. As a case study, we report here on memoquin, a new molecule developed following this strategy. The in vitro and in vivo biological profile of memoquin demonstrates the suitability of the new strategy for obtaining innovative drug candidates for the treatment of neurodegenerative diseases.

Phenolic derivatives from soy flour ethanol extract are potent in vitro quinone reductase (QR) inducing agents

The fractionation of soy flour directed by a cellular bioassay for induction of phase 2 detoxification enzymes was used to identify quinone reductase (QR) inducing agents. A phospholipid-depleted, 80% methanol-partitioned isolate from a crude ethanol extract of soy flour was resolved using normal phase medium-pressure liquid chromatography (MPLC). Early eluting fractions were found to be the most potent QR inducing agents among the separated fractions. Fraction 2 was the most potent, doubling QR at <2 mug/mL. Further fractionation of this isolate led to the identification of several constituents. Fatty acids and sn-1 and sn-2 monoacylglycerols were identified, but were not highly potent QR inducers. Benzofuran-3-carbaldehyde, 4-hydroxybenzaldeyde, 4-ethoxybenzoic acid, 4-ethoxycinnamic acid, benzofuran-2-carboxylic ethyl ester, and ferulic acid ethyl ester (FAEE) were also identified as QR inducing constituents of this fraction. FAEE was the most potent of the identified constituents, doubling QR specific activity at 3.2 muM in the cellular bioassay.

Coordinate regulation of enzyme markers for inflammation and for protection against oxidants and electrophiles

An elaborate network of highly inducible phase 2 proteins protects aerobic cells against the cumulative damaging effects of reactive oxygen intermediates and toxic electrophiles, which are the major causes of malignancy and chronic degenerative diseases. Many chemical and phytochemical agents, all of which react with thiol groups, induce the phase 2 response through their reactivity with critical cysteine thiols of Keap1. We recently found that the anti-inflammatory potencies (suppression of iNOS and COX-2 expression) of a series of triterpenoids with Michael reaction centers were closely correlated with the potencies of these agents to induce the phase 2 response. We now report that representatives of seven recognized chemical classes of inducers, including isothiocyanates, bisbenzylidenes, arsenicals, heavy metals, and vicinal dithiols, showed highly correlated inducer and anti-inflammatory potencies spanning more than six orders of magnitude of concentrations in established cells and in primary mouse peritoneal macrophages. Potency measurements were expressed as the D(m) values (median effect concentration) by use of the Median Effect Equation. Whereas the phase 2 induction required the functional integrity of both the repressor Keap1 and the transcription factor Nrf2, the effectiveness of inducers in blocking the up-regulation of iNOS by inflammatory cytokines was related to the nature of the cytokine and the inducer concentration. These studies identify suppression of inflammation as a consistent property of inducers of the phase 2 response and strongly suggest that this property is a central aspect of their chemoprotective actions.

Angelica sinensis and its alkylphthalides induce the detoxification enzyme NAD(P)H: quinone oxidoreductase 1 by alkylating Keap1

The roots of Angelica sinensis (Oliv.) Diels (Dang Gui; Apiaceae) have a long history in traditional Chinese medicine as a remedy for women's disorders and are often called "lady's ginseng". Currently, extracts of A. sinensis are commonly included in numerous dietary supplements used for women's health and as antiaging products. In the present study, we examined the potential chemopreventive activity of A. sinensis extracts by measuring the relative ability to induce the detoxification enzyme, NAD(P)H:quinone oxidoreductase 1 (NQO1). The lipophilic partitions showed strong NQO1 induction with concentrations to double the enzyme activity (CD) of 5.5 +/- 0.7 (petroleum ether) and 3.9 +/- 0.5 microg/mL (chloroform). Fractionation led to the isolation of phenolic esters and alkylphthalides, especially Z-ligustilide, the main lipophilic compound, which showed strong NQO1 inducing properties (CD = 6.9 +/- 1.9 microM). Transcription of many detoxifying enzymes is regulated through the antioxidant response element (ARE) and its transcription factor Nrf2, which is repressed under basal conditions by Keap1. However, exposure to electrophilic inducers that alkylate Keap1 results in higher concentrations of free Nrf2 and ARE activation. The ARE reporter activity was therefore analyzed in HepG2-ARE-C8 cells after incubation with lipophilic extracts of A. sinensis or ligustilide for 24 h. Under these conditions, both the extract and the ligustilide increased ARE-luciferase reporter activity in a dose-dependent manner. Incubation of ligustilide with GSH and subsequent LC-MS-MS analysis revealed that ligustilide as well as oxidized ligustilide species covalently modified GSH. In addition, using MALDI-TOF mass spectrometry and LC-MS-MS, it was demonstrated that the lipophilic extracts, ligustilide, and monooxygenated ligustilide alkylated important cysteine residues in human Keap1 protein, thus activating Nrf2 and transcription of ARE regulated genes. These observations suggest that A. sinensis dietary supplements standardized to ligustilide have potential as chemopreventive agents through induction of detoxification enzymes.

Anti-inflammatory, antiproliferative, and cytoprotective activity of NO chimera nitrates of use in cancer chemoprevention

Nonsteroidal anti-inflammatory drugs (NSAIDs) have shown promise in colorectal cancer (CRC), but they are compromised by gastrotoxicity. NO-NSAIDs are hybrid nitrates conjugated to an NSAID designed to exploit the gastroprotective properties of NO bioactivity. The NO chimera ethyl 2-((2,3-bis(nitrooxy)propyl)disulfanyl)benzoate (GT-094), a novel nitrate containing an NSAID and disulfide pharmacophores, is effective in vivo in rat models of CRC and is a lead compound for design of agents of use in CRC. Preferred chemopreventive agents possess 1) antiproliferative and 2) anti-inflammatory actions and 3) the ability to induce cytoprotective phase 2 enzymes. To determine the contribution of each pharmacophore to the biological activity of GT-094, these three biological activities were studied in vitro in compounds that deconstructed the structural elements of the lead GT-094. The anti-inflammatory and antiproliferative actions of GT-094 in vivo were recapitulated in vitro, and GT-094 was seen to induce phase 2 enzymes via the antioxidant responsive element. In the variety of colon, macrophage-like, and liver cell lines studied, the evidence from structure-activity relationships was that the disulfide structural element of GT-094 is the dominant contributor in vitro to the anti-inflammatory activity, antiproliferation, and enzyme induction. The results provide a direction for lead compound refinement. The evidence for a contribution from the NO mimetic activity of nitrates in vitro was equivocal, and combinations of nitrates with acetylsalicylic acid were inactive.

In vitro activity of almond skin polyphenols for scavenging free radicals and inducing quinone reductase

Observational studies and clinical trials suggest nut intake, including almonds, is associated with an enhancement in antioxidant defense and a reduction in the risk of cancer and cardiovascular disease. Almond skins are rich in polyphenols (ASP) that may contribute to these putative benefits. To assess their potential mechanisms of action, we tested the in vitro effect of ASP extracted with methanol (M) or a gastrointestinal juice mimic (GI) alone or in combination with vitamins C (VC) or E (VE) (1-10 micromol/L) on scavenging free radicals and inducing quinone reductase (QR). Flavonoid profiles from ASP-M and -GI extracts were different from one another. ASP-GI was more potent in scavenging HOCl and ONOO (-) radicals than ASP-M. In contrast, ASP-M increased and ASP-GI decreased QR activity in Hepa1c1c7 cells. Adding VC or VE to ASP produced a combination- and dose-dependent action on radical scavenging and QR induction. In comparison to their independent actions, ASP-M plus VC were less potent in scavenging DPPH, HOCl, ONOO (-), and O 2 (-) (*). However, the interaction between ASP-GI plus VC promoted their radical scavenging activity. Combining ASP-M plus VC resulted in a synergistic interaction, inducing QR activity, but ASP-GI plus VC had an antagonistic effect. On the basis of their total phenolic content, the measures of total antioxidant activity of ASP-M and -GI were comparable. Thus, in vitro, ASP act as antioxidants and induce QR activity, but these actions are dependent upon their dose, method of extraction, and interaction with antioxidant vitamins.

Quinone reductase 2 is a catechol quinone reductase

The functions of quinone reductase 2 have eluded researchers for decades even though a genetic polymorphism is associated with various neurological disorders. Employing enzymatic studies using adrenochrome as a substrate, we show that quinone reductase 2 is specific for the reduction of adrenochrome, whereas quinone reductase 1 shows no activity. We also solved the crystal structure of quinone reductase 2 in complexes with dopamine and adrenochrome, two compounds that are structurally related to catecholamine quinones. Detailed structural analyses delineate the mechanism of quinone reductase 2 specificity toward catechol quinones in comparison with quinone reductase 1; a side-chain rotational difference between quinone reductase 1 and quinone reductase 2 of a single residue, phenylalanine 106, determines the specificity of enzymatic activities. These results infer functional differences between two homologous enzymes and indicate that quinone reductase 2 could play important roles in the regulation of catecholamine oxidation processes that may be involved in the etiology of Parkinson disease.