Anticlastogenic effects of galangin against mitomycin C-induced micronuclei in reticulocytes of mice

Galangin, a natural flavonoid reduces mitochondrial oxidative damage in streptozotocin-induced diabetic rats

Objective: We designed this study to observe the effect of galangin on damaged mitochondria in the liver of diabetic rats.

Methods: Male albino Wistar rats were made diabetic by injecting streptozotocin (STZ) intraperitoneally (40 mg kg⁻¹ body weight (BW)). Galangin (8 mg kg⁻¹ BW) or glibenclamide (600 µg kg⁻¹ BW) was given orally daily once for 45 days to both healthy and diabetic rats.

Results: Diabetic rats showed significant (P < 0.05) increase in liver mitochondrial oxidant [Thiobarbituric acid reactive substance (TBARS)] level and a significant decrease in enzymatic [superoxide dismutase (SOD), glutathione peroxidase (GPx)] and non-enzymatic (reduced glutathione (GSH)) antioxidant levels when compared with healthy rats. The mitochondrial enzymes isocitrate dehydrogenase (ICDH), alpha-ketoglutarate dehydrogenase (α-KGDH), succinate dehydrogenase (SDH) and malate dehydrogenase (MDH) and mitochondrial respiratory chain enzymes NADH-dehydrogenase and Cytochrome c-oxidase were decreased significantly (P < 0.05) in diabetic rats when compared with healthy rats. A natural flavonoid galangin administered to hyperglycemia-induced rats resulted in the following findings as compared to hyperglycemia-induced control rats: the oxidant levels decreased significantly (P < 0.05); the enzymatic and non-enzymatic antioxidant levels increased significantly (P < 0.05) and the function of mitochondrial enzymes and the mitochondrial respiratory chain enzymes increased significantly (P < 0.05).

Conclusion: From the results, we conclude that galangin could maintain liver mitochondrial function in diabetic rats.

Anticlastogenic effect of Eryngium foetidum L. assessed by erythrocyte micronucleus assay

The aim of this study was to investigate the anticlastogenicity as well as the clastogenicity of Eryngium foetidum leaf (EF) using the in vivo mouse peripheral blood erythrocyte micronucleus assay. Eighty ICR male mice were fed AIN-76 diet supplemented with ground freeze-dried EF at 0.0%, 0.8%, 1.6% and 3.2% for 2 weeks prior to the administration of both direct-acting, mitomycin C (MMC), and indirect-acting, 7, 12-dimethylbenz(a) anthracene (DMBA) clastogens. Peripheral blood samples were collected from mice just before administration of clastogen and at 24 and 48 h thereafter for MMC. Blood samples were collected at the same times and after 72 h for DMBA. Then, reticulocytes in blood samples were counted using fluorescent microscopy. The results indicated that EF had no clastogenic effect in mice. All doses of diets supplemented with EF decreased the number of micronucleated peripheral reticulocytes in all the MMC-treated groups in a dose dependent manner, but significant reduction was found only at 1.6% and 3.2% EF in the DMBA-treated groups. It can be concluded that EF has no clastogenicity, but possesses anticlastogenic potential against both direct- and indirect-acting types of clastogen in mice.

Investigation of antigenotoxic potential of Syzygium cumini extract (SCE) on cyclophosphamide-induced genotoxicity and oxidative stress in mice

The present study investigated the protective effects of Syzygium cumini extract (SCE; 100 and 200 mg/kg) against genotoxicity and oxidative stress (OS) induced by cyclophosphamide (CP) in mice. Animals were received 14 days pretreatment (oral) of SCE, followed by induction of genotoxicity by CP (40 mg/kg), 24 hours before sacrifice. Mice bone marrow chromosomal aberration assay, micronucleus assay, and sperm abnormality assay were employed for the study. Activities of hepatic antioxidant enzymes were also investigated. Phytochemical investigation was done to determine total phenolic and flavonoid content in SCE. Results showed that CP produced a significant increase in average percentage of aberrant metaphases and chromosomal aberrations (CAs) excluding gap, and micronuclei (MN) formation in polychromatic erythrocytes produced cytotoxicity in mouse bone marrow cells and induced abnormal sperms in a male germ line. CP also markedly inhibited the activities of superoxide dismutase (SOD), catalase (CAT), and reduced glutahione (GSH) and increased malondialdehyde (MDA) content. Pretreatments with SCE significantly inhibited the frequencies of aberrant metaphases, CAs, MN formation, and cytotoxicity in mouse bone marrow cells induced by CP. SCE also produced a significant reduction of abnormal sperm and antagonized the reduction of CP-induced SOD, CAT, and GSH activities and inhibited increased MDA content in the liver. Total phenolic content present in SCE was 24.68%, whereas total flavonoids were calculated as 3.80%. SCE has a protective effect against genotoxicity and OS induced by CP.

Galangin induces B16F10 melanoma cell apoptosis via mitochondrial pathway and sustained activation of p38 MAPK

Galangin, an active flavonoid present at high concentration in Alpinia officinarum Hance and propolis, shows cytotoxicity towards several cancer cell lines, including melanoma. However, the specific cellular targets of galangin-induced cytotoxicity in melanoma are still unknown. Here, we investigated the effects of galangin in B16F10 melanoma cells and explored the possible molecular mechanisms. Galangin significantly decreased cell viability of B16F10 cells, and also induced cell apoptosis shown by Hoechst 33342 staining and Annexin V-PI double staining flow cytometric assay. Furthermore, upon galangin treatment, disruption of mitochondrial membrane potential was observed by JC-1 staining. Western blotting analysis indicated that galangin activated apoptosis signaling cascades by cleavage of procaspase-9, procaspase-3 and PARP in B16F10 cells. Moreover, galangin significantly induced activation of phosphor-p38 MAPK in a time and dose dependent manner. SB203580, an inhibitor of p38, partially attenuated galangin-induced apoptosis in B16F10 cells. Taken together, this work suggests that galangin has the potential to be a promising agent for melanoma treatment and may be further evaluated as a chemotherapeutic agent.

Bioactivity guided isolation of anticancer constituents from leaves of Alnus sieboldiana (Betulaceae)

The leaves of the Japanese Alnus sieboldiana have been extracted with n-hexane and then with methanol. A bioactivity-guided approach based on MTT assay for growth inhibition and quantitative real-time PCR for TNF-α inhibitory activity was taken to identify the active compounds in EtOAc soluble fraction of the methanol extract. From this active fraction, seven compounds have been isolated and four compounds (pinosylvin, galangin, quercetin and methyl gallate) have been examined for their dose-response effect on the viability of A549 cells and on TNF-α inhibitory activity. Based on MTT assay, all of the four examined compounds inhibit growth of human lung cancer cells. Among four tested compounds only galangin (3,5,7-trihydroxyflavone) significantly inhibited TNF-α gene expression in A549 cells (IC₅₀ = 94 μM). Taken together, this finding suggests that galangin may be useful in cancer prevention.

Inhibitory effect of the plant flavonoid galangin on rat vas deferens in vitro

Flavonoids are phenolic compounds that are widely distributed in higher plants and therefore are ingested by humans and animals with their regular foods, but also have various pharmacological properties. In the present study we have investigated the effect of galangin, a member of the flavonol class, on the contractile response elicited by electrical field stimulation (EFS) in the rat isolated vas deferens. Galangin (10(-8)-3 x 10(-4) M) produced a concentration- dependent inhibition of the EFS-evoked contractile response, with only a minimal inhibitory effect on phenylephrine-induced contractions. The inhibitory effect of galangin was unaffected by atropine (10(-6) M) plus hexamethonium (10(-4) M), a combination of the NK(1) receptor antagonist SR 140333 (10(-7) M), the NK(2) receptor antagonist SR 48968 (10(-6) M) and the NK(3) receptor antagonist SR 142801 (10(-7) M), L-NAME (3 x 10(-4) M), naloxone (10(-6) M) or yohimbine (10(-7) M). However, the vanilloid receptor antagonist capsazepine (10(-5) M) significantly reduced the inhibitory effect of galangin. It is concluded that the galangin inhibits excitatory transmission of the rat vas deferens with a mechanism involving, at least in part, vanilloid receptors.

Effect of the flavonoid galangin on urinary bladder rat contractility in-vitro

Galangin is a flavanol with several biological activities. We have evaluated the effect of galangin on the contractile response elicited by electrical field stimulation (EFS) in the rat isolated urinary bladder. Galangin (10(-8)-10(-4) M) produced a concentration-dependent inhibition of the EFS contractile response without modifying the contractions produced by exogenous acetylcholine (10(-6) M). Blockade of adrenergic and cholinergic nerves with a combination of atropine (10(-6) M), phentolamine (10(-6) M) and propranolol (10(-6) M) or blockade of tachykinin NK1 and NK2 receptors with SR140333 (10(-7) M) and SR48968 (10(-6) M) did not modify the inhibitory effect of galangin. However, verapamil (10(-7) M) significantly reduced the inhibitory effect of galangin. It is concluded that the galangin inhibits EFS-induced contractions of the rat urinary bladder by acting on L-type calcium channels on presynaptic nerves.

Effects of flavonoids isolated from Scutellariae radix on cytochrome P-450 activities in human liver microsomes

A series of flavonoids isolated from Scutellariae radix were evaluated for their effects on cytochrome P-450 (CYP) activities in human liver microsomes. All flavonoids did not substantially inhibit pentoxyresorufin O-deethylation (CYP2B 1), mephenytoin 4-hydroxylation (CYP2C19), dextromethorphan O-demethylation (CYP2D6), and chlorzoxazone 6-hydroxylation (CYP2E1) activities (IC50: >50 microM). Baicalein and 2',5,6',7-tetrahydroxyflavone inhibited hepatic testosterone 6beta-hydroxylation (CYP3A4) activity with a IC50 of 17.4 and 7.8 microM, respectively. Oroxylin A inhibited diclofenac 4-hydroxylation (CYP2C9) activity with a IC50 of 6.7 microM. In contrast, all flavonoids tested inhibited hepatic caffeine N'-demethylation (CYP1A2) with IC50 values ranging from 0.7 to 51.3 microM. Kinetic analysis revealed that the mechanism of inhibition varied according to the flavonoids. These results suggest that flavonoids tested are inhibitors of hepatic CYP1A2 and that the extracts of Scutellariae radix, widely used as a hepatoprotective agent, may protect the liver through the prevention of CYPIA2-induced metabolic activation of protoxicants.

Anticlastogenic activity of cacao: inhibitory effect of cacao liquor polyphenols against mitomycin C-induced DNA damage

Oxidative DNA damage has been implicated as a factor playing a role in mutagenesis and carcinogenesis. We investigated the anticlastogenic activity of cacao: the inhibitory effect of cacao liquor polyphenols on DNA strand cleavage induced by mitomycin C (MMC) in vitro and the anticlastogenic effect of cacao liquor extract against formation of micronuclei induced by MMC in bone marrow cells and peripheral blood cells of mice. In the DNA strand cleavage test, cacao liquor polyphenols inhibited cleavage of RFI DNA. In the micronuclei test, the frequency of occurrence of micronucleated cells among bone marrow cells and peripheral blood cells were reduced significantly when cacao liquor extract was administered orally to mice 6 h before intraperitoneal injection of MMC. These findings suggest that cacao liquor polyphenols are effective in preventing DNA damage, and one of the mechanisms of action might involve scavenging of active oxygen radicals generated in reactions initiated by MMC.

Anti-genotoxicity of galangin as a cancer chemopreventive agent candidate

Flavonoids are polyphenolic compounds that are present in plants. They have been shown to possess a variety of biological activities at non-toxic concentrations in organisms. Galangin, a member of the flavonol class of flavonoid, is present in high concentrations in medicinal plants (e.g. Alpinia officinarum) and propolis, a natural beehive product. Results from in vitro and in vivo studies indicate that galangin with anti-oxidative and free radical scavenging activities is capable of modulating enzyme activities and suppressing the genotoxicity of chemicals. These activities will be discussed in this review. Based on our review, galangin may be a promising candidate for cancer chemoprevention.

Antigenotoxicity of galangin against N-methyl-N-nitrosourea

Using the Ames bacterial mutagenicity test and an in vivo micronucleus test, we investigated the antigenotoxic effect of galangin against the genotoxicity of N-methyl-N-nitrosourea (MNU). In the Ames assay, galangin showed an antimutagenic effect towards MNU-induced mutagenicity of Salmonella typhimurium TA 100. In mice, galangin showed an anticlastogenic effect against MNU-induced micronuclei in polychromatic erythrocytes in the MNPCE in mouse bone marrow cells. On the other hand, galangin is neither mutagenic nor clastogenic in both assays. Results from our in vitro and in vivo studies indicate that galangin is capable of suppressing the mutagenicity and clastogenicity of MNU. Therefore, galangin may be a useful chemopreventive agent against potential long-term health effects from genotoxic environmental agents.

Metabolism of galangin by rat cytochromes P450: relevance to the genotoxicity of galangin

The mutagenicity of flavonols seems to depend on the number and position of hydroxyl groups in the B ring. Galangin is a flavonol that does not have any hydroxyl group in the B ring and has been suggested to be a substrate of cytochromes P450 which, through the hydroxylation of the B ring, could metabolise it to more genotoxic products. The present study was undertaken to test this hypothesis. Using high performance liquid chromatography we show that glangin is sequentially transformed to kaempferol and then to quercetin by a mechanism dependent on cytochrome P450 reactions. The metabolites of galangin are responsible for its mutagenicity in Salmonella typhimurium reversion assay and for the induction of chromosomal aberrations in V79 cells.