Hypolipidaemic effects of naringenin, rutin, nicotinic acid and their associations

Multi-Therapeutic Potential of Naringenin (4',5,7-Trihydroxyflavonone): Experimental Evidence and Mechanisms

Extensive research has been carried out during the last few decades, providing a detailed account of thousands of discovered phytochemicals and their biological activities that have the potential to be exploited for a wide variety of medicinal purposes. These phytochemicals, which are pharmacologically important for clinical use, primarily consist of polyphenols, followed by terpenoids and alkaloids. There are numerous published reports indicating the primary role of phytochemicals proven to possess therapeutic potential against several diseases. However, not all phytochemicals possess significant medicinal properties, and only some of them exhibit viable biological effects. Naringenin, a flavanone found in citrus fruits, is known to improve immunity, repair DNA damage, and scavenge free radicals. Despite the very low bioavailability of naringenin, it is known to exhibit various promising biological properties of medicinal importance, including anti-inflammatory and antioxidant activities. This review focuses on the various aspects related to naringenin, particularly its physicochemical, pharmacokinetic, and pharmacodynamic properties. Furthermore, various pharmacological activities of naringenin, such as anticancer, antidiabetic, hepatoprotective, neuroprotective, cardioprotective, nephroprotective, and gastroprotective effects, have been discussed along with their mechanisms of action.

Naringenin prevents doxorubicin-induced toxicity in kidney tissues by regulating the oxidative and inflammatory insult in Wistar rats

This study is undertaken to investigate the effects of naringenin on doxorubicin- (Dox) induced nephrotoxicity in Wistar rats. Dox 10 mg/kg body weight was administered intraperitoneally once and naringenin 50 and 100 mg/kg body weight was administered orally daily for 21 d. Dox-induced oxidative stress lead to steep elevation in blood urea nitrogen (BUN), creatinine, lactate dehydrogenase (LDH), and kidney injury molecule-1 (KIM-1), compared to control, treatment with naringenin preserved kidney functions. With Dox treatment significant decrease in antioxidant enzymes with increase in malondialdehyde (MDA) compared to control was observed. Naringenin treatment reversed these values compared to Dox in kidney tissue. Dox treatment showed increased tissue nitric oxide levels naringenin treatment decreased nitric oxide (NO) in kidney tissue. Furthermore, Dox-induced inflammatory burst as indicated by up-regulation of nuclear factor-κB (NF-κB), tumour necrosis factor-α (TNF-α) tissue levels and prostaglandin-E2 (PGE-2). All such events were normalised back to normal by naringenin treatment.

A spectrophotometric method for high-throughput screening of α-l-rhamnosidase activity on rutin coupled with a β-d-glucosidase assay

α-l-Rhamnosidase may biotransform rutin into isoquercetin with better bioavailability and bioactivity. To date, the high-throughput screening for the activity of α-l-rhamnosidases on rutin could not be achieved. Herein, based on the spectral differences between rutin and its aglycone quercetin in alkaline pH 10.0, we have developed a novel and simple spectrophotometric method for high-throughput screening of α-l-rhamnosidase activity on rutin by combining with a highly active β-d-glucosidase. Quercetin showed the maximum absorbance at 320 nm in alkaline pH 10.0, and could be considered as the characteristic peak of quercetin because rutin had low absorption at 320 nm. Meanwhile, rutin exhibited the maximum absorption at 400 nm and quercetin showed low absorption at 400 nm in pH 10.0. With this novel spectrophotometric method, the relative abilities of nine different α-l-rhamnosidases on rutin had been evaluated by monitoring the absorption values of the reaction mixture in alkaline pH 10.0 at 320 nm and 400 nm, and the trend in the activity on rutin was consistent with that obtained by HPLC. Moreover, the library from site-directed saturation mutagenesis at the residue Val338 in the α-l-rhamnosidase BtRha78A from Bacteroides thetaiotaomicron was constructed for high-throughput screening by this novel spectrophotometric method, and the mutant V338S with improved activity on rutin was obtained. The conversion rate of the mutant V338S on rutin increased by 21.7% and 16.8% than wild type when using whole cells and purified enzymes, respectively. Our findings demonstrated that this novel spectrophotometric method coupled with the β-d-glucosidase assay might be applied for high-throughput screening of different α-l-rhamnosidases and a great number of mutants from semi-rational design and directed evolution for α-l-rhamnosidase.

Naringenin (4,5,7-trihydroxyflavanone) suppresses the development of precancerous lesions via controlling hyperproliferation and inflammation in the colon of Wistar rats

Colon cancer is a world-wide health problem and one of the most dangerous type of cancer, affecting both men and women. Naringenin (4, 5, 7-trihydroxyflavanone) is one of the major flavone glycoside present in citrus fruits. Naringenin has long been used in Chinese's traditional medicine because of its exceptional pharmacological properties and non-toxic nature. In the present study, we investigated the chemopreventive potential of Naringenin against 1,2-dimethyhydrazine (DMH)-induced precancerous lesions, that is, aberrant crypt foci (ACF) and mucin depleted foci (MDF), and its role in regulating the oxidative stress, inflammation and hyperproliferation, in the colon of Wistar rats. Animals were divided into five groups. In groups 3-5, Naringenin was administered at the dose of 50 mg/kg b. wt. orally while in groups 2-4, DMH was administered subcutaneously in the groin at the dose of 20 mg/kg b. wt. once a week for first 5 weeks and animals were euthanized after 10 weeks. Administration of Naringenin ameliorated the development of DMH-induced lipid peroxidation, ROS formation, precancerous lesions (ACF and MDF) and it also reduced the infiltration of mast cells, suppressed the immunostaining of NF-κB-p65, COX-2, i-NOS PCNA and Ki 67 Naringenin treatment significantly attenuated the level of TNF-α and it also prevented the depletion of the mucous layer. Our findings suggest that Naringenin has strong chemopreventive potential against DMH-induced colon carcinogenesis but further studies are warranted to elucidate the precise mechanism of action of Naringenin.

Naringenin Decreases α-Synuclein Expression and Neuroinflammation in MPTP-Induced Parkinson's Disease Model in Mice

The present study was designed to ascertain the role of naringenin (NGN), a citrus fruit flavanone, against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced α-synuclein (SYN) pathology and neuroinflammation in a mouse model. NGN was administered to C57BL/6J mice once a day for 5 consecutive days prior to the MPTP intoxication. On day 5, 40-50 min after the NGN or vehicle administration, MPTP was injected in two divided doses (2× 40 mg/kg, i.p. at 16 h apart). The animals were observed for motor functions 48 h after the first MPTP injection. The animals were then euthanized, the brains collected to analyze SYN pathology, cytokines, and oxidative stress levels in the substantia nigra region. The NGN significantly downregulated SYN and upregulated dopamine transporter (DAT) and tyrosine hydroxylase (TH) protein expressions. It also downregulated tumor necrosis factor-α (TNFα) and interleukin 1β (IL1β) mRNA expressions and improved superoxide dismutase levels. It also reduced glutathione levels when compared to vehicle-treated PD animals. The upregulation of TH corroborates to an increase in dopamine, DOPAC, and homovanillic acid turnover and motor functions with NGN treatment. To summarize, NGN, a dietary flavone, has the potential to counteract MPTP-induced dopaminergic degeneration by regulating SYN pathology, neuroinflammation, and oxidative stress. This warrants the investigation of NGN's potential effects in a genetic model of PD.

Evaluation of the possible protective role of naringenin on gentamicin-induced ototoxicity: A preliminary study

OBJECTIVES

The purpose of this study is to evaluate the possible protective role of naringenin in gentamicin-induced ototoxicity through an audiological, biochemical and histopathological evaluation.

METHODS

This study was conducted on 32 adult male rats that were randomized into 4 groups(control, gentamicin, naringenin + gentamicin, and naringenin). Naringenin was given to the rats via oral gavage in a dose of 50 mg/kg/day during the 14 day study period. Gentamicin was given by the intraperitoneal route in a dose of 120 mg/kg/day. Audiological assessment was performed by the distortion product otoacoustic emission (DPOAE) and auditory brainstem response (ABR) measurements, applied to all rats at the beginning of the study, and also on day 14. Biochemical parameters were calculated on day 14 to evaluate the oxidative and antioxidative status. Their cochleae were removed and examined histopathologically, also on day 14. The cochlea of animals were evaluated with the terminal deoxynucleotidyl transferase-mediated dUTPbiotin nick end labeling (TUNEL) method for apoptosis.

RESULTS

On days 14, DPOAE values and ABR thresholds were preserved in group 3(naringenin + gentamicin) when compared with group 2(gentamicin)(p < 0.008). The total oxidant status values and oxidative stress index values were significantly higher in group 2(gentamicin) than in other groups (p < 0.008). The total antioxidant status value was significantly higher in group 3(naringenin + gentamicin) and group 4(naringenin) than in group 2(gentamicin)(p < 0.008). The number of TUNEL positive cells in both the organ of Corti and the stria vascularis were found to be statistically lower in group 3(naringenin + gentamicin) than in group 2(gentamicin)(p < 0.05).

CONCLUSION

Our study has demonstrated that the ototoxic effect generated by gentamicin could be ameliorated with the concurrent use of naringenin.

Effect of Naringenin (A naturally occurring flavanone) Against Pilocarpine-induced Status Epilepticus and Oxidative Stress in Mice

BACKGROUND

Epilepsy is a disorder of the central nervous system characterized by recurrent seizures. It is a very common disease in which approximately 30% of patients do not respond favourably to treatment with anticonvulsants. Oxidative stress is associated with neuronal damage arising from epileptic seizures. The present study investigated the effects of naringenin in pilocarpine-induced epilepsy in mice. Naringenin, one of the most frequently occurring flavanone in citrus fruits, was evaluated for its shielding effect against the pilocarpine induced behavioural, oxidative and histopathological alterations in rodent model of epilepsy.

METHODOLOGY

Epilepsy was induced by giving pilocarpine (300mg/kg) and sodium valproate (300mg/kg) was given as standard anti-epileptic drug Pilocarpine was administered (300 mg /kg body weight) intraperitoneally to the mice on 15th day while naringenin was administered orally (20 and 40 mg/kg body weight) for 15 days prior to administration of pilocarpine.

RESULTS

The intraperitoneal administration of pilocarpine enhanced lipid peroxidation, caused reduction in antioxidant enzymes, viz., catalase, superoxide dismutase and glutathione reductase. Treatment of mice orally with naringenin (20 mg/kg body weight and 40 mg/kg body weight) resulted in a significant decrease in lipid peroxidation. There was significant recovery of glutathione content and all the antioxidant enzymes studied. Also in case of behavioural parameters studied, naringenin showed decrease in seizure severity. All these changes were supported by histological observations, which revealed excellent improvement in neuronal damage.

CONCLUSION

The higher dose of naringenin was more potent in our study and was comparable to the standard drug (sodium valproate) in effectiveness.

SUMMARY

Naringenin ameliorated the development of ROS formation in hippocamus.Naringenin helped in recovery of antioxidant enzymes.Naringenin decreased seizure severity.Naringenin treatment reduced lipid peroxidation. Abbreviations used: 6-OHDA: 6-hydroxydopamine, AED: Anti epileptic drugs, AIDS: Acquired immune deficiency syndrome, ANOVA: Analysis of variance, ATP: Adenosine triphosphate, CA: Cornu ammonis, CAT: Catalase, DG: Dentate gyrus, EDTA: Ethylenediamine tetra acetic acid, GR: Glutathione reductase, GSH: Glutathione reduced, HCl: Hydrochloric acid, IL-1β: Interleukin 1 beta, LPO: Lipid peroxidation, MDA: Malondialdehyde, NADPH: Nicotinamide adenine dinucleotide phosphate, PMS: post mitochondrial supernatant, SE: Status epilepticus, SEM: Standard error of the mean, SOD Superoxide dismutase, TBA: Thiobarbituric acid, TBARS: Thiobarbituric acid reactive substance, TLE: Temporal lobe epilepsy, TNF-α: Tumor necrosis factor alpha.

Effect of Naringenin (A naturally occurring flavanone) Against Pilocarpine-induced Status Epilepticus and Oxidative Stress in Mice

Background:

Epilepsy is a disorder of the central nervous system characterized by recurrent seizures. It is a very common disease in which approximately 30% of patients do not respond favourably to treatment with anticonvulsants. Oxidative stress is associated with neuronal damage arising from epileptic seizures. The present study investigated the effects of naringenin in pilocarpine-induced epilepsy in mice. Naringenin, one of the most frequently occurring flavanone in citrus fruits, was evaluated for its shielding effect against the pilocarpine induced behavioural, oxidative and histopathological alterations in rodent model of epilepsy.

Methodology:

Epilepsy was induced by giving pilocarpine (300mg/kg) and sodium valproate (300mg/kg) was given as standard anti-epileptic drug Pilocarpine was administered (300 mg /kg body weight) intraperitoneally to the mice on 15th day while naringenin was administered orally (20 and 40 mg/kg body weight) for 15 days prior to administration of pilocarpine.

Results:

The intraperitoneal administration of pilocarpine enhanced lipid peroxidation, caused reduction in antioxidant enzymes, viz., catalase, superoxide dismutase and glutathione reductase. Treatment of mice orally with naringenin (20 mg/kg body weight and 40 mg/kg body weight) resulted in a significant decrease in lipid peroxidation. There was significant recovery of glutathione content and all the antioxidant enzymes studied. Also in case of behavioural parameters studied, naringenin showed decrease in seizure severity. All these changes were supported by histological observations, which revealed excellent improvement in neuronal damage.

Conclusion:

The higher dose of naringenin was more potent in our study and was comparable to the standard drug (sodium valproate) in effectiveness.

SUMMARY

Naringenin ameliorated the development of ROS formation in hippocamus.

Naringenin helped in recovery of antioxidant enzymes.

Naringenin decreased seizure severity.

Naringenin treatment reduced lipid peroxidation.

Abbreviations used: 6-OHDA: 6-hydroxydopamine, AED: Anti epileptic drugs, AIDS: Acquired immune deficiency syndrome, ANOVA: Analysis of variance, ATP: Adenosine triphosphate, CA: Cornu ammonis, CAT: Catalase, DG: Dentate gyrus, EDTA: Ethylenediamine tetra acetic acid, GR: Glutathione reductase, GSH: Glutathione reduced, HCl: Hydrochloric acid, IL-1β: Interleukin 1 beta, LPO: Lipid peroxidation, MDA: Malondialdehyde, NADPH: Nicotinamide adenine dinucleotide phosphate, PMS: post mitochondrial supernatant, SE: Status epilepticus, SEM: Standard error of the mean, SOD Superoxide dismutase, TBA: Thiobarbituric acid, TBARS: Thiobarbituric acid reactive substance, TLE: Temporal lobe epilepsy, TNF-α: Tumor necrosis factor alpha

Rutin attenuates isoflurane-induced neuroapoptosis via modulating JNK and p38 MAPK pathways in the hippocampi of neonatal rats

An increasing number of infants and children undergo surgery and are exposed to anesthesia as a part of medical care each year. Isoflurane is a commonly used anesthetic in the pediatric population. However, previous studies have reported widespread isoflurane-induced neuroapoptosis and cognitive impairments in neonatal animal models, raising concerns over the administration of isoflurane in the pediatric population. The current study investigated the effects of rutin, a flavonoid, on isoflurane-induced neuroapoptosis in a neonatal rodent model. Groups of neonatal rat pups were administered rutin at doses of 10, 20 or 40 mg/kg body weight from postnatal day 1 (P1) to P15. On P7, pups were exposed to 0.75% isoflurane for 6 h. Rat pups in the control groups did not receive rutin, and did not receive anesthesia in one group. Neuroapoptosis following isoflurane exposure was determined by TUNEL assay. The expression levels of cleaved caspase-3, apoptotic pathway proteins [Bcl2-associated agonist of cell death (Bad), phospho-Bad, Bax, B-cell lymphoma 2 (Bcl-2) and Bcl-xL and mitogen-activated protein kinases (MAPK)] signalling pathway proteins [c-Jun N-terminal kinase (JNK), phospho-JNK, extracellular-signal-regulated kinase 1/2 (ERK1/2), phosphoERK1/2, p38, phospho-p38 and phospho-c-Jun], were determined by western blot analysis. The Morris water maze test was used to assess the learning and memory of pups on P30 and P31. The present study found that rutin at the tested doses of 10, 20 and 40 mg significantly reduced (P<0.05) the isoflurane-induced elevation in apoptotic cell count. The expression levels of caspase-3, Bad, Bax and MAPK proteins, which were increased following isoflurane treatment, were rescued by rutin treatment. Furthermore, rutin prevented the increase in Bcl-xL, Bcl-2 and phospho-Bad expression following isoflurane treatment, and enhanced the memory of the rats. Rutin provided neuroprotection against isoflurane-induced neuronal apoptosis and improved the learning and memory of rats by effectively regulating the expression levels of proteins in the MAPK pathway.

Physical properties and biological activities of hesperetin and naringenin in complex with methylated β-cyclodextrin

The aim of this work is to improve physical properties and biological activities of the two flavanones hesperetin and naringenin by complexation with β-cyclodextrin (β-CD) and its methylated derivatives (2,6-di-O-methyl-β-cyclodextrin, DM-β-CD and randomly methylated-β-CD, RAMEB). The free energies of inclusion complexes between hesperetin with cyclodextrins (β-CD and DM-β-CD) were theoretically investigated by molecular dynamics simulation. The free energy values obtained suggested a more stable inclusion complex with DM-β-CD. The vdW force is the main guest–host interaction when hesperetin binds with CDs. The phase solubility diagram showed the formation of a soluble complex of A_L type, with higher increase in solubility and stability when hesperetin and naringenin were complexed with RAMEB. Solid complexes were prepared by freeze-drying, and the data from differential scanning calorimetry (DSC) confirmed the formation of inclusion complexes. The data obtained by the dissolution method showed that complexation with RAMEB resulted in a better release of both flavanones to aqueous solution. The flavanones-β-CD/DM-β-CD complexes demonstrated a similar or a slight increase in anti-inflammatory activity and cytotoxicity towards three different cancer cell lines. The overall results suggested that solubilities and bioactivities of both flavanones were increased by complexation with methylated β-CDs.

Phytochemical analysis and modulation of antibiotic activity by Luehea paniculata Mart. & Zucc. (Malvaceae) in multiresistant clinical isolates of Candida spp

The high incidence of fungal infections has led to the continuous search for new drugs. Extracts of Luehea paniculata, a tree of multiple medicinal uses, were evaluated for anti-Candida activity, as well as its modulator potential of the Fluconazole antibiotic. Chemical prospecting of ethanol extracts of leaf and bark was carried out, the quantification of total phenols and flavonoids, characterized by the HPLC-DAD technique. The rosmarinic acid and the vitexin flavonoid were observed as major constituents in ELELP and ESWELP, respectively. Antioxidant activity was also evaluated by the method of scavenging the free radical DPPH, and quercetin was used as standard, obtaining IC₅₀ values: 0.341 (mg/mL) for ELELP and 0.235 (mg/mL) for ESWELP. The microdilution assay was performed for antifungal activity against strains of Candida albicans, C. krusei, and C. tropicalis and showed minimum inhibitory concentrations values ≥1024 μg/mL. In the modulator action of extracts on Fluconazole against multiresistant clinical isolates of Candida (subinhibitory concentration minimum of 128 μg/mL), a significant synergism was observed, indicating that the extracts potentiated the antifungal effect against C. tropicalis, where antioxidant flavonoids could be responsible. This is the first report about modifying activity of the antibiotic action of a species of the genus Luehea.

Antiartherosclerotic effects of plant flavonoids

Atherosclerosis is the process of hardening and narrowing the arteries. Atherosclerosis is generally associated with cardiovascular diseases such as strokes, heart attacks, and peripheral vascular diseases. Since the usage of the synthetic drug, statins, leads to various side effects, the plants flavonoids with antiartherosclerotic activity gained much attention and were proven to reduce the risk of atherosclerosis in vitro and in vivo based on different animal models. The flavonoids compounds also exhibit lipid lowering effects and anti-inflammatory and antiatherogenic properties. The future development of flavonoids-based drugs is believed to provide significant effects on atherosclerosis and its related diseases. This paper discusses the antiatherosclerotic effects of selected plant flavonoids such as quercetin, kaempferol, myricetin, rutin, naringenin, catechin, fisetin, and gossypetin.

Naringenin inhibits α-glucosidase activity: a promising strategy for the regulation of postprandial hyperglycemia in high fat diet fed streptozotocin induced diabetic rats

Obesity and the onset of diabetes are two closely linked medical complications prevalent globally. Postprandial hyperglycemia is one of the earliest abnormalities of glucose homeostasis associated with type 2 diabetes (T2D). Postprandial glucose levels can be regulated through α-glucosidase inhibition. The present study aims to demonstrate the potent inhibitory role of naringenin against α-glucosidase activity. The mode of inhibition of naringenin was examined by measuring enzyme activity in vitro with different concentrations of substrate using Lineweaver-Burk plot analysis. It shows competitive inhibition towards mammalian α-glucosidase thereby competing with α-limit dextrins and oligosaccharide residues for binding in the active site. Similar results have been obtained from the molecular docking analyses, where naringenin shows preferential binding for the active sites in each of the evaluated human intestinal α-glucosidase enzymes. Post-docking intramolecular hydrogen bonding analysis shows water molecule mediated hydrogen bonding for N-terminal maltase glucoamylase and N-terminal sucrase isomaltase. Naringenin's docked pose in the C-terminal maltase glucoamylase active site does not show any particular water mediated interaction similar to the co-crystallized acarbose. Further, our results suggest that naringenin (25 mg/kg) exerts significant inhibition of intestinal α-glucosidase activity in vivo thereby delaying the absorption of carbohydrates in T2D rats, thus resulting in significant lowering of postprandial blood glucose levels. Both in vitro and in vivo results were compared to the commercially available α-glucosidase inhibitor acarbose. Our findings clearly indicate that naringenin dampens postprandial glycemic response and offers a potential complementary approach in the management of T2D.

Effect of simvastatin and naringenin coadministration on rat liver DNA fragmentation and cytochrome P450 activity: an in vivo and in vitro study

This study was designed to assess the effect of naringenin (NRG) on simvastatin (SV)-induced hepatic damage in rat and to investigate the effects of these drugs on cytochrome P450 (CYP) 2E1 and 3A1/2 isoforms in order to evaluate the possibility of their coadministration. Hepatic damage in rat was induced by SV (20 and 40 mg/kg/day, po for 30 days). The protective effect of NRG (50 mg/kg/day, po) was identified by estimating liver functions and oxidative stress markers such as lipid peroxidation, reduced glutathione, superoxide dismutase, glutathion s-transferase, and catalase as well as protein profile. DNA fragmentation and histopathological study were carried out to confirm the hepatic damage. An in vitro study was conducted to further evaluate the effect of SV and/or NRG administration on the activities of two microsomal CYP isoenzymes including CYP2E1 and CYP3A1/2. SV exerted an oxidative stress which may contribute to the hepatotoxicity. Administration of NRG in combination with SV significantly improved the liver functions, state of oxidative stress, protein profile, DNA fragmentation, and the histopathological changes. SV and/or NRG have a potential to inhibit CYP3A1/2 and CYP2E1. This study concluded that concurrent administration of NRG with SV provided a protection of liver tissue against the SV-induced hepatic damage. The inhibition of CYP2E1 and CYP3A1/2 by the SV and NRG should be taken into account in order to adjust doses to avoid interaction between SV and NRG and adverse effects of SV.

Effect of simvastatin and naringenin coadministration on rat liver DNA fragmentation and cytochrome P450 activity: an in vivo and in vitro study

This study was designed to assess the effect of naringenin (NRG) on simvastatin (SV)-induced hepatic damage in rat and to investigate the effects of these drugs on cytochrome P450 (CYP) 2E1 and 3A1/2 isoforms in order to evaluate the possibility of their coadministration. Hepatic damage in rat was induced by SV (20 and 40 mg/kg/day, po for 30 days). The protective effect of NRG (50 mg/kg/day, po) was identified by estimating liver functions and oxidative stress markers such as lipid peroxidation, reduced glutathione, superoxide dismutase, glutathion s-transferase, and catalase as well as protein profile. DNA fragmentation and histopathological study were carried out to confirm the hepatic damage. An in vitro study was conducted to further evaluate the effect of SV and/or NRG administration on the activities of two microsomal CYP isoenzymes including CYP2E1 and CYP3A1/2. SV exerted an oxidative stress which may contribute to the hepatotoxicity. Administration of NRG in combination with SV significantly improved the liver functions, state of oxidative stress, protein profile, DNA fragmentation, and the histopathological changes. SV and/or NRG have a potential to inhibit CYP3A1/2 and CYP2E1. This study concluded that concurrent administration of NRG with SV provided a protection of liver tissue against the SV-induced hepatic damage. The inhibition of CYP2E1 and CYP3A1/2 by the SV and NRG should be taken into account in order to adjust doses to avoid interaction between SV and NRG and adverse effects of SV.

Transgenic rice seed synthesizing diverse flavonoids at high levels: a new platform for flavonoid production with associated health benefits

Flavonoids possess diverse health-promoting benefits but are nearly absent from rice, because most of the genes encoding enzymes for flavonoid biosynthesis are not expressed in rice seeds. In the present study, a transgenic rice plant producing several classes of flavonoids in seeds was developed by introducing multiple genes encoding enzymes involved in flavonoid synthesis, from phenylalanine to the target flavonoids, into rice. Rice accumulating naringenin was developed by introducing phenylalanine ammonia lyase (PAL) and chalcone synthase (CHS) genes. Rice producing other classes of flavonoids, kaempferol, genistein, and apigenin, was developed by introducing, together with PAL and CHS, genes encoding flavonol synthase/flavanone-3-hydroxylase, isoflavone synthase, and flavone synthases, respectively. The endosperm-specific GluB-1 promoter or embryo- and aleurone-specific 18-kDa oleosin promoters were used to express these biosynthetic genes in seed. The target flavonoids of naringenin, kaempferol, genistein, and apigenin were highly accumulated in each transgenic rice, respectively. Furthermore, tricin was accumulated by introducing hydroxylase and methyltransferase, demonstrating that modification to flavonoid backbones can be also well manipulated in rice seeds. The flavonoids accumulated as both aglycones and several types of glycosides, and flavonoids in the endosperm were deposited into PB-II-type protein bodies. Therefore, these rice seeds provide an ideal platform for the production of particular flavonoids due to efficient glycosylation, the presence of appropriate organelles for flavonoid accumulation, and the small effect of endogenous enzymes on the production of flavonoids by exogenous enzymes.

Molecular spectroscopic on interaction between Methyl hesperidin and Buman serum albumin

The interaction of Methyl hesperidin (MH) with Buman serum albumin was studied by spectroscopic methods including Fluorescence quenching technology, UV absorbance spectra and Fourier transform infrared (FT-IR) spectroscopy under simulative physiological conditions. The result of fluorescence titration revealed that Methyl hesperidin could quench the intrinsic fluorescence of BSA and the quenching mechanism should be a combined quenching process. The binding constants at three temperatures (296, 303, and 310 K) were 1.82, 2.69, and 3.4 × 10(4)L mol(-1), respectively. The distance between donor (BSA) and acceptor (MH) was 5.54 nm according to the Förster theory of non-radiation energy transfer. In addition, FT-IR spectroscopy showed that the binding of MH to BSA changed the secondary structure of protein.

Biosynthesis, natural sources, dietary intake, pharmacokinetic properties, and biological activities of hydroxycinnamic acids

Hydroxycinnamic acids are the most widely distributed phenolic acids in plants. Broadly speaking, they can be defined as compounds derived from cinnamic acid. They are present at high concentrations in many food products, including fruits, vegetables, tea, cocoa, and wine. A diet rich in hydroxycinnamic acids is thought to be associated with beneficial health effects such as a reduced risk of cardiovascular disease. The impact of hydroxycinnamic acids on health depends on their intake and pharmacokinetic properties. This review discusses their chemistry, biosynthesis, natural sources, dietary intake, and pharmacokinetic properties.

Naringenin ameliorates Alzheimer's disease (AD)-type neurodegeneration with cognitive impairment (AD-TNDCI) caused by the intracerebroventricular-streptozotocin in rat model

Oxidative stress is involved in Alzheimer's disease (AD)-type neurodegeneration with cognitive impairment (AD-TNDCI) as well as age related cognitive deficit. The present study was designed to investigate the pre-treatment effects of naringenin (NAR), a polyphenolic compound on cognitive dysfunction, oxidative stress in the hippocampus, and hippocampal neuron injury in a rat model of AD-TNDCI. The rats were pre-treated with NAR at a selective dose (50mg/kg, orally) for 2 weeks followed by intracerebroventricular-streptozotocin (ICV-STZ) (3mg/kg; 5μl per site) injection bilaterally. Behavioral alterations were monitored after 2 weeks from the lesion using passive avoidance test and Morris water maze paradigm. Three weeks after the lesion, the rats were sacrificed for measuring non-enzymatic [4-hydroxynonenal (4-HNE), malonaldehyde (MDA), thiobarbituric reactive substances (TBARS), hydrogen peroxide (H(2)O(2)), protein carbonyl (PC), reduced glutathione (GSH)] content and enzymatic [glutathione peroxidase (GPx), glutathione reductase (GR), glutathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT) and Na(+)/K(+)-ATPase] activity in the hippocampus, and expression of choline acetyltransferase (ChAT) positive neuron, and histopathology of hippocampal neurons. The non-enzymatic level and enzymatic activity was significantly increased and decreased, respectively, with striking impairments in spatial learning and memory, loss of ChAT positive neuron and severe damage to hippocampal neurons in the rat induced by ICV-STZ. These abnormalities were significantly improved by NAR pre-treatment. The study suggests that NAR can protect against cognitive deficits, neuronal injury and oxidative stress induced by ICV-STZ, and may be used as a potential agent in treatment of neurodegenerative diseases such as AD-TNDCI.

Optimisation of infrared-assisted extraction of rutin from crude Flos Sophorae Immaturus using response surface methodology and HPLC analysis

INTRODUCTION

Rutin, one of main constituents in Flos Sophorae Immaturus, has been proven to possess several pharmacological properties such as anti-oxidant, anti-platelet, anti-inflammatory effects and so on. However, optimisation of the extraction of rutin from Flos Sophorae Immaturus has rarely been reported. Thus, it is important to develop an effective method to obtain maximum yields of rutin from Flos Sophorae Immaturus.

OBJECTIVE

To develop an infrared-assisted extraction method for maximum rutin yield from crude Flos Sophorae Immaturus using response surface methodology and HPLC analysis.

METHODOLOGY

Through single factor experiments, ranges of the main variables (including methanol concentration, liquid:solid ratio, extraction time and infrared power) affecting the extraction yield of rutin were confirmed. A Box-Behnken design consisting of 24 experimental runs and five replicates at zero point was then applied and a regression model was obtained to predict the optimal extraction yield.

RESULTS

The ANOVA analysis indicated that the regression equation fits very well with the actual situation. The optimal conditions were as follows: infrared power 204.90 W, liquid:solid ratio 30.00 mL/g, methanol concentration 70.00% and extraction time 4.80 min. Under optimal conditions the predicted maximum yield (125.70 mg rutin/0.5 g raw material) was consistent with the experimental value (126.32 ± 0.67 mg rutin/0.5 g raw material) (n = 3).

CONCLUSION

The application of response surface methodology was reliable and feasible in the optimisation of infrared-assisted extraction of rutin from crude Flos Sophorae Immaturus.

(2S)-naringenin from Typha angustata inhibits vascular smooth muscle cell proliferation via a G0/G1 arrest

ETHNOPHARMACOLOGICAL RELEVANCE

Typha angustata is used in traditional Chinese medicine for a variety of clinical disorders. Its pharmacological actions include beneficial effects on hyperlipidemia and myocardial infarction, as well as labor-inducing and antibacterial effects.

AIM OF THE STUDY

We investigated the mechanism underlying the ability of (2S)-naringenin, an active compound from Typha angustata, to inhibit the proliferation of vascular smooth muscle cells (VSMCs).

MATERIALS AND METHODS

After measuring the antiproliferative effect of (2S)-naringenin on VSMC proliferation using cell proliferation and viability assays, the possible involvement of a signaling pathway associated with platelet-derived growth factor receptor β (PDGF-Rβ), extracellular signal regulated kinase 1/2 (ERK1/2), phosphatidylinositol 3-kinase (PI3K)-linked protein kinase B (Akt/PKB), or phospholipase C-γ1 (PLCγ1) was investigated by immunoblotting. Moreover, the effect of (2S)-naringenin on DNA synthesis and the cell cycle was examined using a [(3)H]-thymidine incorporation assay and flow cytometry.

RESULTS

(2S)-Naringenin significantly inhibited PDGF-BB-induced VSMC proliferation in a concentration-dependent manner, but did not affect signaling pathways associated with PDGF-Rβ, Akt/PKB, ERK1/2, or PLCγ1. However, (2S)-naringenin suppressed DNA synthesis via a G(0)/G(1) cell cycle arrest. Accordingly, the expression of cyclins D1 and E and cyclin-dependent kinases 2 and 4 was inhibited in a concentration-dependent manner; moreover, the phosphorylation of retinoblastoma protein was suppressed.

CONCLUSIONS

Our results show that (2S)-naringenin inhibited the PDGF-BB-induced proliferation of VSMCs via a G(0)/G(1) arrest; thus, (2S)-naringenin may be valuable as a therapeutic agent for managing atherosclerosis and/or vascular restenosis.

Naringenin in combination with vitamins C and E potentially protects oxidative stress-mediated hepatic injury in cadmium-intoxicated rats

Cadmium (Cd)-induced oxidative stress and hepatic injury is one of the major outcomes of chronic Cd toxicity, which can be ameliorated by numerous antioxidants. The present study was undertaken to find the therapeutic efficacy of naringenin (NGN) plus vitamins C and E on Cd-induced oxidative hepatotoxicity in Wistar rats. It has been noticed that Cd intoxication significantly elevates the levels of serum hepatic marker enzymes such as alanine amino transferase, aspartate amino transferase, alkaline phosphatase, lactate dehydrogenase, γ glutamyl transferase, total bilirubin, and hepatic thiobarbituric acid reactive substances, lipid hydroperoxides, conjugated dienes and protein carbonyls. In addition, Cd also decreases the activities of hepatic enzymatic antioxidants superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase, glutathione reductase and glucose-6-phosphate dehydrogenase and the levels of non-enzymatic antioxidants total sulphydryl groups, reduced glutathione, vitamins C and E and histopathological changes in liver. Treatment with NGN and vitamins C and E in combination more significantly improved the altered biochemical and histopathological changes in the liver of Cd-intoxicated rats than the NGN or vitamins C and E treatment alone.

CONCLUSION

The present data suggest that combined administration of NGN with vitamins C and E proved to be more beneficial in the treatment of Cd-hepatotoxicity than NGN treatment alone.

Dietary naringenin increases hepatic peroxisome proliferators-activated receptor α protein expression and decreases plasma triglyceride and adiposity in rats

BACKGROUND

Naringenin, a flavonoid present in grapefruit, has recently been shown to exert hypolipidemic and hypocholesterolemic effects, which has a particular importance for protecting against chronic diseases. However, the lipid-lowering potential of naringenin at the concentrations in the dietary range and its underlying mechanisms have yet to be fully elucidated.

AIM

The aim of the present study was (1) to investigate the effects of dietary naringenin on plasma and hepatic triglyceride and cholesterol levels and on adipose deposition in rat and (2) to determine the contribution of hepatic peroxisome proliferators-activated receptor α (PPARα) expression to fatty acid oxidation.

METHODS

Male Long-Evans hooded rats were fed a diet supplemented with naringenin (0.003, 0.006, and 0.012%) for 6 weeks. We analyzed plasma and hepatic lipid contents and determined the protein expression of PPARα, carnitine-palmitoyl transferase 1L (CPT-1), and uncoupling protein 2 (UCP2), all of which are critical genes for fatty acid oxidation.

RESULTS

Naringenin supplementation caused a significant reduction in the amount of total triglyceride and cholesterol in plasma and liver. In addition, naringenin supplementation lowered adiposity and triglyceride contents in parametrial adipose tissue. Naringenin-fed animals showed a significant increase in PPARα protein expression in the liver. Furthermore, expression of CPT-1 and UCP2, both of which are known to be regulated by PPARα, was markedly enhanced by naringenin treatment.

CONCLUSIONS

Our results indicate that the activation of PPARα transcription factor and upregulation of its fatty acid oxidation target genes by dietary naringenin may contribute to the hypolipidemic and anti-adiposity effects in vivo.

Disposition of naringenin via glucuronidation pathway is affected by compensating efflux transporters of hydrophilic glucuronides

The purposes of this study were to investigate how efflux transporters and UDP-glucuronosyltransferases (UGT) affect the disposition of naringenin. A rat intestinal perfusion model with bile duct cannulation was used along with rat intestinal and liver microsomes. In the intestinal perfusion model, both absorption and subsequent excretion of naringenin metabolites were rapid and site-dependent (p < 0.05). Naringenin was absorbed the most in colon, and its glucuronides were excreted the most in duodenum. In metabolism studies, the intrinsic clearance value of naringenin glucuronidation was the highest in jejunum microsomes, followed by liver, ileal and colonic microsomes. The rapid metabolism in microsomes did not always translate into more efficient excretion in the rat perfusion model, however, because of presence of rate-limiting efflux transporters. When used separately, MK-571 (an inhibitor of multidrug resistance-related protein 2 or Mrp2) or dipyridamole (an inhibitor of breast cancer resistance protein or Bcrp1) did not affect excretion of naringenin glucuronides, but when used together, they significantly (p < 0.05) decreased intestinal and biliary excretion of naringenin glucuronides. In conclusion, efflux transporters Mrp2 and Bcrp1 are shown to compensate for each other and enable the intestinal excretion of flavonoid (i.e., naringenin) glucuronides.

Impact of Naringenin on Oxytetracycline-Mediated Oxidative Damage in Kidney of Rats

The aim of this study was to investigate the effect of naringenin on oxytetracycline-induced nephrotoxicity in rats. Oxytetracycline (200 mg/kg body weight, ip) was administered in 0.5 ml of sterile physiological saline for 15 days, resulting in a significant increase in serum urea and creatinine and reduction in creatinine clearance. A significant increase in lipid peroxidation markers (TBARS and lipid hydroperoxide) and decrease in antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) and low molecular weight antioxidants (vitamin C, vitamin E, and reduced glutathione) levels were also observed in oxytetracycline-treated rats. The oral administration of naringenin (50 mg/kg body weight) attenuated the oxytetracycline-induced nephrotoxicity by significantly decreased levels of serum urea and creatinine with the significant normalization of creatinine clearance. Upon the administration of naringenin, the depleted renal antioxidant defense system (enzymatic and non-enzymatic antioxidants) was significantly increased in rats treated with oxytetracycline. These biochemical observations were supplemented by histopathological examination of kidney section. The present results suggest that the supplementation of naringenin might be helpful to alleviate the oxytetracycline-induced oxidative injury in kidney.

Simultaneous determination of the flavonoid aglycones diosmetin and hesperetin in human plasma and urine by a validated GC/MS method: in vivo metabolic reduction of diosmetin to hesperetin

Diosmetin and hesperetin are the aglycones of the flavonoid glycosides diosmin and hesperidin which occur naturally in citrus fruit. A GC/MS method for the simultaneous determination of diosmetin and hesperetin in human plasma and urine has been developed and validated. The method was linear in the 2-300 ng/mL concentration range for both diosmetin and hesperetin in plasma and urine (r > 0.999). The precision of the method was better than 6.01 and 7.16% for diosmetin and hesperetin, respectively, and the accuracy was 96.76-100.40% and 95.00-105.50% for diosmetin and hesperetin, respectively. The lower limit of quantitation was found to be 2 ng/mL for both analytes in plasma and urine. Recovery of diosmetin, hesperetin and internal standard naringenin was greater than 82.5%. The method has been applied for the determination of diosmetin and hesperetin in plasma and urine samples obtained from a healthy male subject following a single oral 1000 mg dose of the flavonoid glycoside diosmin. The presence of hesperetin in plasma and urine samples indicates the metabolic reduction of diosmetin to its flavanone analogue hesperetin through reduction of the 2,3 double bond of the C-ring by the enzymes of bacteria of the intestinal microflora.

Absorption, metabolism and excretion of flavanones from single portions of orange fruit and juice and effects of anthropometric variables and contraceptive pill use on flavanone excretion

Oranges are rich sources of flavonoids that are bioactive and may protect against age-related diseases. The absorption of orange flavanones may be affected by factors such as processing and subject anthropometric variables, and the bioactivity of the absorbed phytochemicals depends on how they are metabolised during absorption. In a randomised cross-over study, twenty subjects consumed a single portion of orange fruit (150 g) or juice (300 g) that contained the flavanones narirutin and hesperidin, and an additional 109 subjects across a broad age range (18-80 years) consumed the juice. Flavanone metabolites were measured in regularly collected samples of plasma and urine. After consumption of fruit or juice, flavanone conjugates, but not the aglycones, were detected in plasma and urine. The flavanone conjugates were shown to include the 7- and 4'-O-monoglucuronides of naringenin, the 7- and 3'-O-monoglucuronides of hesperetin, two hesperetin diglucuronides and a hesperetin sulfo-glucuronide, but no aglycones or rutinosides. Analysis of the plasma pharmacokinetic and urinary excretion data on a dose-adjusted basis indicated no difference in absorption or excretion of either flavanone between the fruit and juice matrices. In the extended urinary excretion dataset the individual variation was very large (range 0-59 % urinary yield). There was a small but significant (P < 0.05) decrease in the excretion of hesperetin (but not naringenin) with increasing age (P < 0.05), but the effects of sex, BMI and contraceptive pill use were shown not to be associated with the variation in flavanone excretion.

Modulatory effects of rutin on biochemical and hematological parameters in hypercholesterolemic Golden Syrian hamsters

Flavonoids have been reported to exhibit several pharmacological properties, mainly in cardiovascular and inflammatory diseases. In the present study, we observed that rutin, a known glycosylated flavonoid isolated from Dimorphandra mollis, had a lowering effect on plasma triglyceride levels of diet-induced hypercholesterolemic Golden Syrian hamsters, but did not change total cholesterol and high-density lipoprotein cholesterol levels. Moreover, high-fat or rutin supplemented diets showed no immunotoxic effects, since no significant changes were observed on total white blood cells, granulocytes and mononuclear cells, as well as on the neutrophil apoptosis degree, when compared to untreated animals. Therefore, rutin seems to be a selective and non-toxic modulator of hypercholesterolemia, which can be promising for the development of new drugs.

Naringenin protects against cadmium-induced oxidative renal dysfunction in rats

Cadmium (Cd) is an environmental and industrial pollutant that affects various organs in human and experimental animals. Naringenin is a naturally occurring plant bioflavonoid found in citrus fruits, which has been reported to have a wide range of pharmacological properties. A body of evidence has accumulated implicating the free radical generation with subsequent oxidative stress in the biochemical and molecular mechanisms of cadmium toxicity. Since kidney is the critical target organ of chronic Cd toxicity, we carried out this study to investigate the effects of naringenin on Cd-induced toxicity in the kidney of rats. In experimental rats, oral administration of cadmium chloride (5mg/(kgday)) for 4 weeks significantly induced the renal damage which was evident from the increased levels of serum urea, uric acid, creatinine with a significant (p<0.05) decrease in creatinine clearance. Cadmium also significantly decreased the levels of urea, uric acid and creatinine in urine. A markedly increased levels of lipid peroxidation markers (thiobarbituric acid reactive substances and lipid hydroperoxides) and protein carbonyl contents with significant (p<0.05) decrease in non-enzymatic antioxidants (total sulfhydryl groups, reduced glutathione, vitamin C and vitamin E) and enzymatic antioxidants (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione S-transferase (GST)) as well as glutathione metabolizing enzymes (glutathione reductase (GR) and glutathione-6-phosphate dehydrogenase (G6PD)) were also observed in cadmium-treated rats. Co-administration of naringenin (25 and 50mg/(kgday)) along with Cd resulted in a reversal of Cd-induced biochemical changes in kidney accompanied by a significant decrease in lipid peroxidation and an increase in the level of renal antioxidant defense system. The histopathological studies in the kidney of rats also showed that naringenin (50mg/(kgday)) markedly reduced the toxicity of Cd and preserved the normal histological architecture of the renal tissue. The present study suggest that the nephroprotective potential of naringenin in Cd toxicity might be due to its antioxidant and metal chelating properties, which could be useful for achieving optimum effects in Cd-induced renal damage.

Tartary buckwheat sprout powder lowers plasma cholesterol level in rats

We examined the effects of different types of buckwheat sprouts on the plasma cholesterol concentration, fecal steroid excretion and hepatic mRNA expression related to cholesterol metabolism in rats. Rats were fed a cholesterol-free diet with 5 g of Kitawasesoba common buckwheat sprout powder (KS)/100 g, 5 g of Hokkai T no. 8 tartary buckwheat sprout powder (HS-8)/100 g or 5 g of Hokkai T no. 9 tartary buckwheat sprout powder (HS-9)/100 g of diet for 4 wk. Control rats were fed a diet with alpha-cornstarch instead of sprout powder for 4 wk. There were no significant differences in food intake, body weight, liver weight or cecal contents among the groups. Plasma total cholesterol concentrations in the HS-8 and HS-9 groups were significantly lower than in the control group, whereas there was no significant difference between the KS and control groups. Fecal bile acid excretion and cecal short-chain fatty acid concentrations in the KS, HS-8 and HS-9 groups were significantly greater than in the control group. Furthermore, fecal matter excretion in the KS, HS-8 and HS-9 groups tended to be increased compared to the control group, with that in the HS-8 group being significantly higher than in the control group. Hepatic cholesterol 7alpha-hydroxylase mRNA expression in the KS, HS-8 and HS-9 groups and hepatic HMG-CoA reductase mRNA expression in the HS-9 group were significantly higher than in the control group. The results suggest that tartary buckwheat sprout powder has a serum cholesterol-lowering function by enhancing fecal bile acid excretion through increased fecal matter excretion or the upregulation of hepatic cholesterol 7alpha-hydroxylase mRNA expression in rats.

Pharmacokinetics of selected chiral flavonoids: hesperetin, naringenin and eriodictyol in rats and their content in fruit juices

The majority of pharmacokinetic studies of individual flavonoids or after ingestion of foodstuffs have overlooked the chirality of some of these xenobiotics. In order to characterize for the first time the stereoselective pharmacokinetics of three flavonoids, hesperetin, naringenin and eriodictyol were intravenously administered (20 mg/kg) to male Sprague-Dawley rats, and their stereospecific content was assessed in various fruit juices. Concentrations in serum, urine and fruit juices were characterized via HPLC and verified by LC/MS. Short half-lives (3-7 h) in serum were observed, while a better estimation of half-life (12-48 h) and the other pharmacokinetic parameters was observed using urinary data. The three flavonoids are predominantly excreted via non-renal routes (fe values of 3-7%), and undergo rapid and extensive phase II metabolism. The (2S)-epimers of the flavonoid glycosides and the S(-)-enantiomers of the aglycones were predominant and in some instances the organic fruit juices had higher concentrations than the conventional fruit juices. This study reports for the first time the stereospecific pharmacokinetics of three chiral flavonoids and their stereospecific content in fruit juices. It also reports for the first time the stereospecific pharmacokinetics of flavonoids employing urine as a more reliable biological matrix.

In vivo metabolic effects of naringenin in the ethanol consuming rat and the effect of naringenin on adipocytes in vitro

Naringenin is a bioactive flavanone involved in the inhibition of drug metabolism which exhibits antioxidant, anti-inflammatory and anticancerogenic properties and which recently appeared to be a factor mitigating the hyperlipidaemic effects in rats and rabbits. In the performed experiment, the effect of naringenin, administered intragastrically (50 mg/kg) for 2 weeks to normal and ethanol drinking rats, on insulin and leptin levels and on some metabolic parameters was investigated. Naringenin did not change the hormone levels in any group of rats. Blood glucose, triglyceride, total, esterified and free cholesterol and high-density lipoprotein-cholesterol concentrations were also unaffected by this compound. Only free fatty acids were elevated after the naringenin treatment in the water-drinking rats. In spite of unchanged glucose and insulin concentrations in blood, the tested flavanone reduced the glucose/insulin ratio in ethanol-receiving rats. Liver triglycerides, elevated due to ethanol ingestion, were partially normalized by naringenin. Other tested parameters like liver glycogen and cholesterol, muscle triglycerides and glycogen were not altered in any group of rats. The influence of naringenin (62.5, 125, 250 and 500 microM) on basal and insulin-stimulated glucose conversion to lipids (lipogenesis) as well as on basal and epinephrine-stimulated glycerol release (lipolysis) in the isolated rat adipocytes was also tested. The basal and the stimulated lipogenesis tended to be decreased in the presence of the flavanone (250 microM). This inhibitory effect intensified and was statistically significant at the highest concentration of naringenin. The tested compound did not evoke any effect on basal lipolysis while the epinephrine-stimulated process was limited at the highest concentration of the flavanone. Naringenin (62.5, 125, 250 and 500 microM) had no effect on leptin secretion from the isolated rat adipocytes. Results obtained in our studies demonstrate that naringenin exerts a very weak influence on carbohydrate and lipid metabolism of normal and ethanol-consuming rats and on metabolism of isolated rat adipocytes.

Influence of naringenin on oxytetracycline mediated oxidative damage in rat liver

Naringenin is a naturally occurring citrus flavanone, which has been reported to have a wide range of pharmacological properties. The present work was carried out to evaluate the effect of naringenin on antioxidant and lipid peroxidation status in liver of oxytetracycline-intoxicated rats. Intraperitonial administration of oxytetracycline 200 mg/kg for 15 days resulted a significant elevation in serum hepatospecific markers such as aspartate transaminase, alanine transaminase, alkaline phosphatase, lactate dehydrogenase, and bilirubin and the levels of lipid peroxidation markers (thiobarbituric acid reactive substances (TBARS) and lipid hydroperoxides) in liver. Oxytetracycline also caused a significant reduction in the activities of superoxide dismutase, catalase, glutathione peroxidase, reduced glutathione (GSH), vitamin C and vitamin E in liver. Oral administration of naringenin (50 mg/kg b.w.t.) with oxytetracycline significantly decreased the activities of serum aspartate transaminase, alanine transaminase, alkaline phosphatase, lactate dehydrogenase and the levels of bilirubin along with significant decrease in the levels of lipid peroxidation markers in the liver. In addition, naringenin significantly increased the activities of superoxide dismutase, catalase and GSH peroxidase as well as the level of GSH, vitamin C and vitamin E in liver of the oxytetracycline-treated rats. Our results demonstrate that naringenin exhibited antioxidant property and decrease the lipid peroxidation against oxytetracycline-induced oxidative stress in liver.

Methods of analysis and separation of chiral flavonoids

Although the analysis of the enantiomers and epimers of chiral flavanones has been carried out for over 20 years, there often remains a deficit within the pharmaceutical, agricultural, and medical sciences to address this issue. Hence, despite increased interest in the potential therapeutic uses, plant physiology roles, and health-benefits of chiral flavanones, the importance of stereoselectivity in agricultural, nutrition, pharmacokinetic, pharmacodynamic, pharmacological activity and disposition has often been ignored. This review presents both the general principles that allow separation of chiral flavanones, and discusses both the advantages and disadvantages of the available chromatographic assay methods and procedures used to separately quantify flavanone enantiomers and epimers in biological matrices.

Pharmacokinetics of the citrus flavanone aglycones hesperetin and naringenin after single oral administration in human subjects

BACKGROUND AND OBJECTIVE

Hesperetin and naringenin, the aglycones of the flavanone glycosides hesperidin and naringin, occur naturally in citrus fruits. They exert interesting pharmacological properties such as antioxidant, anti-inflammatory, blood lipid and cholesterol lowering and are considered to contribute to health benefits in humans. However, no information is available on the pharmacokinetics of the citrus flavanones hesperetin and naringenin after their oral administration to humans as pure aglycones. Therefore, the objective of the present investigation was the evaluation of the pharmacokinetic parameters of hesperetin and naringenin in plasma and urine, after their single oral administration in humans in the form of solid dispersion capsules, and also to improve the absorption rate of flavanones by using aglycones rather than the naturally occurring glycosides.

DESIGN

Six healthy volunteers received orally 135 mg of each compound, hesperetin and naringenin, under fasting conditions. Blood samples were collected at 14 different time points over a 12 h period. Urine was collected over 24 h, in five sequential timed intervals. Plasma and urine hesperetin and naringenin concentrations, after enzymatic hydrolysis of their conjugated forms, were measured using validated high-pressure liquid chromatography methods. Pharmacokinetic parameters for hesperetin and naringenin, such as C(max), T(max), AUC(0-t), AUC(0-infinity), CL/F, V/F, t(1/2), MRT, A(e), A(e)((0-24)), and R(max) were calculated from their plasma or urine concentrations.

RESULTS

Pharmacokinetic analysis showed that both hesperetin and naringenin were rapidly absorbed and their concentrations in plasma observed 20 min after dosing and reached a peak in 4.0 and 3.5 h, respectively. The mean peak plasma concentration (C(max)) for hesperetin and naringenin were 825.78+/-410.63 ng/ml (2731.8+/-1358.4 nmol/l) and 2009.51+/-770.82 ng/ml (7386.6+/-2833.4 nmol/l), respectively and the mean AUC(0-infinity) values were 4846.20+/-1675.99 ng h/ml and 9424.52+/-2960.52 ng h/ml for hesperetin and naringenin, respectively. The elimination half-life for hesperetin was found to be 3.05+/-0.91 h and for naringenin 2.31+/-0.40 h, respectively. The mean values of the relative cumulative urinary excretion, as percentage of the administered dose, for hesperetin and naringenin, were found to be 3.26+/-0.44 and 5.81+/-0.81%, respectively.

CONCLUSIONS

Oral administration of the flavanone aglycones, hesperetin and naringenin, lead to their rapid absorption as their conjugated forms. The cumulative urinary recovery data indicated low bioavailability for both flavanone aglycones, owing to extensive first-pass metabolism partly by cleavage of the C-ring by the enzymes of intestinal bacteria leading to degradation products such as phenolic acids.

Comparative studies of some phenolic compounds (quercetin, rutin, and ferulic acid) affecting hepatic fatty acid synthesis in mice

The physiological activities of some phenolic compounds affecting hepatic fatty acid synthesis in mice were compared. Male ICR mice were fed an experimental diet containing 1% quercetin dihydrate, rutin, or ferulic acid or a control diet free of phenolic compounds for 15 days. Quercetin significantly lowered serum cholesterol and phospholipid levels in mice. Also, the serum triacylglycerol level was considerably lower in mice fed the quercetin-containing diet than in those fed a diet free of phenolic compounds, although the difference was not significant. Rutin and ferulic acid did not affect these parameters. Quercetin significantly reduced the activity and mRNA levels of various enzymes involved in hepatic fatty acid synthesis. Rutin reduced a few of the parameters for lipogenesis, but ferulic acid did not affect any of the parameters. It was suggested that a reduction in hepatic lipogenesis is the mechanism underlying the hypolipidemic effect of quercetin.

Inhibition of intestinal and renal Na+-glucose cotransporter by naringenin

Reduction in glucose uptake constitutes a possible means of controlling diabetic hyperglycemia. Using purified intestinal brush border membrane vesicles and everted intestinal sleeves, we have demonstrated that naringenin, a flavonoid present in citrus fruits and juices, significantly inhibited glucose uptake in the intestine. In addition, naringenin also elicited inhibitory actions towards glucose uptake in renal brush border membrane vesicles. Naringin, a glycoside of naringenin, was totally inactive in these aspects. Naringenin exhibited moderate inhibitory action on glucose uptake in rabbit intestinal brush border membrane vesicles, and showed strong inhibitory action in rat everted intestinal sleeves. The IC(50) values were 205.9 and 2.4 micromol/l, respectively. Lineweaver-Burk analysis demonstrated that naringenin inhibited glucose uptake in rat everted intestinal sleeves in a competitive manner with a K(i) value of 1.1 micromol/l. Glucose uptake activities in both the intestinal and renal brush border membrane vesicles of diabetic rats were significantly higher than in normal rats. Naringenin (500 microM) reduced glucose uptake by more than 60% in both the intestinal and renal brush border membrane vesicles of diabetic rats to a level similar to that of the normal rats. The IC(50) values of naringenin in the renal brush border membrane vesicles of normal and diabetic rats were 323.9 and 166.1 micromol/l, respectively. These results suggest that inhibition of intestinal glucose uptake and renal glucose reabsorption explains, in part at least, the in vivo antihyperglycemic action of naringenin and its derivatives. The possible application of these natural compounds in controlling hyperglycemia warrants further investigations.

Hepatolipidemic effects of naringenin in high cornstarch- versus high coconut oil-fed rats

The effects of naringenin (Nar) on hepatic neutral and polar lipids were examined in rats that were fed either a high (27.98%) cornstarch (CornS) or a high (19.05%) coconut oil (CocoO) diet, with or without supplementation with 0.60% NAR, for 40 days. Liver weights and total, neutral, and polar lipids were significantly increased following the feeding of CocoO (P <.01) when compared with the CornS-fed rats. Furthermore, significant elevations in liver weight and total neutral lipids were observed (P <.01) with the CornS-Nar compared with the CornS diet; cholesterol esters (CE), CE:cholesterol (CE:C) ratio, triglycerides (TG), and phosphatidylethanolamine (PE) were significantly increased (P <.01). When Nar was added to the CocoO diet, liver protein, total lipids, and total neutral and polar lipids were significantly decreased (P <.01). Of the neutral lipids, CE, CE:C ratio, TG, free fatty acids (FFA), mono- and diglycerides (P <.01), and C (P <.05) were significantly decreased. CE and TG were more significantly decreased than C, while FFA decreased most markedly (P <.01). Of the hepatic polar lipids, lysophosphatidylcholine, sphingomyelin, phosphatidylcholine, phosphatidylserine and -inositol, PE, and phosphatidic acid were significantly elevated (P <.001) following the feeding of the high CocoO diet compared with the high CornS diet. When Nar was added to the CornS diet, PE was significantly elevated (P <.01), and the outer membrane to inner membrane lipids ratio was significantly decreased (P <.01). When Nar was added to the CocoO diet, all of the polar lipids examined were significantly decreased when compared with the CocoO diet (P <.01). Dietary Nar supplementation significantly reduced both hepatic neutral and polar lipids in rats fed a high CocoO diet, but not in the CornS-fed rats.