Sanda Vladimir-Knežević

Antioxidant activities and polyphenolic contents of three selected Micromeria species from Croatia.

Antioxidant activities of three selected Micromeria species growing in Croatia (M. croatica, M. juliana and M. thymifolia) were evaluated using five different antioxidant assays, in comparison with plant polyphenolic constituents and reference antioxidants. All studied ethanolic extracts exhibited considerable activity to scavenge DPPH and hydroxyl free radicals, reducing power, iron chelating ability and total antioxidant capacity in the order: M. croatica > M. juliana > M. thymifolia. Total polyphenol (9.69–13.66%), phenolic acid (5.26–6.84%), flavonoid (0.01–0.09%) and tannin (3.07–6.48%) contents in dried plant samples were determined spectrophotometrically. A strong positive correlation between antioxidant activities and contents of phenolic acids and tannins was found, indicating their responsibility for effectiveness of tested plants. Our findings established Micromeria species as a rich source of antioxidant polyphenols, especially the endemic M. croatica.

Differential hepatoprotective mechanisms of rutin and quercetin in CCl 4 -intoxicated BALB/cN mice

Aim:To investigate the mechanisms underlying the protective effects of quercetin-rutinoside (rutin) and its aglycone quercetin against CCl4-induced liver damage in mice.Methods:BALB/cN mice were intraperitoneally administered rutin (10, 50, and 150 mg/kg) or quercetin (50 mg/kg) once daily for 5 consecutive days, followed by the intraperitoneal injection of CCl4 in olive oil (2 mL/kg, 10% v/v). The animals were sacrificed 24 h later. Blood was collected for measuring the activities of ALT and AST, and the liver was excised for assessing Cu/Zn superoxide dismutase (SOD) activity, GSH and protein concentrations and also for immunoblotting. Portions of the livers were used for histology and immunohistochemistry.Results:Pretreatment with rutin and, to a lesser extent, with quercetin significantly reduced the activity of plasma transaminases and improved the histological signs of acute liver damage in CCl4-intoxicated mice. Quercetin prevented the decrease in Cu/Zn SOD activity in CCl4-intoxicated mice more potently than rutin. However, it was less effective in the suppression of nitrotyrosine formation. Quercetin and, to a lesser extent, rutin attenuated the inflammation in the liver by down-regulating the CCl4-induced activation of nuclear factor-kappa B (NF-κB), tumor necrosis factor-α (TNF-α) and cyclooxygenase (COX-2). The expression of inducible nitric oxide synthase (iNOS) was more potently suppressed by rutin than by quercetin. Treatment with both flavonoids significantly increased NF-E2-related factor 2 (Nrf2) and heme oxygenase (HO-1) expression in injured livers, although quercetin was less effective than rutin at an equivalent dose. Quercetin more potently suppressed the expression of transforming growth factor-β1 (TGF-β1) than rutin.Conclusion:Rutin exerts stronger protection against nitrosative stress and hepatocellular damage but has weaker antioxidant and anti-inflammatory activities and antifibrotic potential than quercetin, which may be attributed to the presence of a rutinoside moiety in position 3 of the C ring.

Acetylcholinesterase Inhibitory, Antioxidant and Phytochemical Properties of Selected Medicinal Plants of the Lamiaceae Family

The present study aimed to evaluate acetylcholinesterase (AChE) inhibitory and antioxidant activities of Lamiaceae medicinal plants growing wild in Croatia. Using Ellman’s colorimetric assay all tested ethanolic extracts and their hydroxycinnamic acid constituents demonstrated in vitro AChE inhibitory properties in a dose dependent manner. The extracts of Mentha x piperita, M. longifolia, Salvia officinalis, Satureja montana, Teucrium arduini, T. chamaedrys, T. montanum, T. polium and Thymus vulgaris at 1 mg/mL showed strong inhibitory activity against AChE. The antioxidant potential of the investigated Lamiaceae species was assessed by DPPH• scavenging activity and total antioxidant capacity assays, in comparison with hydroxycinnamic acids and trolox. The extracts differed greatly in their total hydroxycinnamic derivatives content, determined spectrophotometrically. Rosmarinic acid was found to be the predominant constituent in most of the investigated medicinal plants (by RP-HPLC) and had a substantial influence on their AChE inhibitory and antioxidant properties, with the exception of Teucrium species. These findings indicate that Lamiaceae species are a rich source of various natural AChE inhibitors and antioxidants that could be useful in the prevention and treatment of Alzheimer’s and other related diseases.

Myricitrin exhibits antioxidant, anti-inflammatory and antifibrotic activity in carbon tetrachloride-intoxicated mice

Myricetin-3-O-α-rhamnoside (myricitrin) is a naturally occurring phenolic compound which possesses antioxidant and anti-inflammatory activity. The aim of this study was to determine the hepatoprotective effects of myricitrin. Myricitrin at doses of 10, 30 and 100 mg/kg and silymarin at dose of 100mg/kg were administered to BALB/cN mice by oral gavage, once daily for two consecutive days following carbon tetrachloride (CCl4)-intoxication. Myricitrin significantly ameliorated CCl4-induced increase in serum aspartate transaminase (AST) and alanine transaminase (ALT) levels and histopathological changes in the liver. Hepatic oxidative stress was reduced by myricitrin, as evidenced by the decrease in lipid peroxidation, with concomitant increase in glutathione (GSH) level and cytochrome P450 2E1 (CYP2E1) expression. In addition, cyclooxygenase-2 (COX-2) and tumor necrosis factor-alpha (TNF-α) overexpression in the liver was reduced, suggesting the suppression of inflammation. The expression of transforming growth factor-beta1 (TGF-β1) and alpha-smooth muscle actin (α-SMA) was markedly ameliorated, indicating the inhibition of profibrotic response. Myricitrin also improved the regeneration of hepatic tissue after CCl4-intoxication, as evidenced by increased proliferating cell nuclear antigen (PCNA) expression. The results of the current study suggest that myricitrin exhibits a significant hepatoprotective activity. Myricitrin provided better hepatoprotection when compared to silymarin, which is consistent with its higher in vitro antioxidant potential.

Evaluation of Antioxidant Potential of Lavandula x intermedia Emeric ex Loisel. 'Budrovka': A Comparative Study with L. angustifolia Mill.

A Croatian indigenous cultivar of lavandin, Lavandula x intermedia ‘Budrovka’ (Lamiaceae) was studied for the phenolic acids, flavonoids, anthocyanins, procyanidins and total tannins, as well as total polyphenols content, in the flower, inflorescence stalk and leaf ethanolic extracts. Antioxidant potentials on these plant part extracts were assessed by the DPPH free radical scavenging activity, iron chelating activity, reducing power, lipid peroxidation inhibition properties and total antioxidant capacity assays. All results were compared with those of Lavandula angustifolia, the only member of the Lavandula genus officially used in modern phytotherapy. Based on the results of our parallel study, we may suggest that Lavandula x intermedia ‘Budrovka’ is as potent an antioxidant as Lavandula angustifolia and the antioxidant activity of the Lavandula extracts is mainly due to the presence of rosmarinic acid. A good correlation was found between the polyphenol contents and antioxidant activities of the extracts.

Flavonoid aglycones can compete with Ochratoxin A for human serum albumin: A new possible mode of action

The mycotoxin Ochratoxin A (OTA) appears worldwide in cereals, plant products, different foods and drinks. Ochratoxin A binds to plasma albumin with a very high affinity. However, it is well known that natural flavonoids can also bind to human serum albumin (HSA) at the same binding site as OTA does (site I, subdomain IIA). A few experimental literature data suggest that reducing the bound fraction of OTA speeds up its elimination rate with a potential decrease in its toxicity. In our experimental model competitive binding properties of flavonoid aglycones were examined with a fluorescence polarization based approach. Our data show that some of the flavonoids are able to remove the toxin from HSA. We conclude that among the 13 studied flavonoid aglycones galangin and quercetin were the most effective competitors for OTA.

Fluorescence spectroscopic investigation of competitive interactions between ochratoxin A and 13 drug molecules for binding to human serum albumin

Ochratoxin A (OTA) is a highly toxic mycotoxin found worldwide in cereals, foods, animal feeds and different drinks. Based on previous studies, OTA is one of the major causes of the chronic tubulointerstitial nephropathy known as Balkan endemic nephropathy (BEN) and exerts several other adverse effects shown by cell and/or animal models. It is a well-known fact that OTA binds to various albumins with very high affinity. Recently, a few studies suggested that reducing the bound fraction of OTA might reduce its toxicity. Hypothetically, certain drugs can be effective competitors displacing OTA from its albumin complex. Therefore, we examined 13 different drug molecules to determine their competing abilities to displace OTA from human serum albumin (HSA). Competitors and ineffective chemicals were identified with a steady-state fluorescence polarization-based method. After characterization the competitive abilities of individual drugs, drug pairs were formed and their displacing activity were tested in OTA-HSA system. Indometacin, phenylbutazone, warfarin and furosemide showed the highest competing capacity but ibuprofen, glipizide and simvastatin represented detectable interaction too. Investigations of drug pairs raised the possibility of the presence of diverse binding sites of competing drugs. Apart from the chemical information obtained in our model, this explorative research might initiate future designs for epidemiologic studies to gain further in vivo evidence of long-term (potentially protective) effects of competing drugs administered to human patients.

Flavonoid diosmetin increases ATP levels in kidney cells and relieves ATP depleting effect of ochratoxin A

Diosmetin (DIOS) is a flavone aglycone commonly occurring in citrus species and olive leaves, in addition it is one of the active ingredients of some medications. Based on both in vitro and in vivo studies several beneficial effects are attributed to DIOS but the biochemical background of its action seems to be complex and it has not been completely explored yet. Previous investigations suggest that most of the flavonoid aglycones have negative effect on ATP synthesis in a dose dependent manner. In our study 17 flavonoids were tested and interestingly DIOS caused a significant elevation of intracellular ATP levels after 6- and 12-h incubation in MDCK kidney cells. In order to understand the mechanism of action, intracellular ATP and protein levels, ATP/ADP ratio, cell viability and ROS levels were determined after DIOS treatment. In addition, impacts of different enzyme inhibitors and effect of DIOS on isolated rat liver mitochondria were also tested. Finally, the influence of DIOS on the ATP depleting effect of the mycotoxin, ochratoxin A was also investigated. Our major conclusions are the followings: DIOS increases intracellular ATP levels both in kidney and in liver cells. Inhibition of glycolysis or citric acid cycle does not decrease the observed effect. DIOS-induced elevation of ATP levels is completely abolished by the inhibition of ATP synthase. DIOS is able to completely reverse the ATP-depleting effect of the mycotoxin, ochratoxin A. Most probably the DIOS-induced impact on ATP system does not originate from the antioxidant property of DIOS. Based on our findings DIOS may be promising agent to positively influence ATP depletion caused by some metabolic poisons.

Antioxidant and Anticholinesterase Potential of Six Thymus Species

The present study aimed to evaluate antioxidant and acetylcholinesterase (AChE) inhibitory activities of the ethanolic extracts of six selected Thymus species growing in Croatia (T. longicaulis, T. praecox subsp. polytrichus, T. pulegioides, T. serpyllum subsp. serpyllum, T. striatus, and T. vulgaris). Antioxidant effectiveness was assessed using six different assays, in comparison with rosmarinic acid, luteolin, and reference antioxidants. All tested Thymus extracts possessed DPPH (IC50 = 3–6 μg/mL) and nitric oxide (IC50 = 70–177 μg/mL) free radical scavenging activities, strong reducing properties (IC50 = 11–15 μg/mL), ferrous ion chelating activity (IC50 = 126–389 μg/mL), ability to inhibit lipid peroxidation (IC50 = 34–80 μg/mL), and high total antioxidant capacities (238–294 mg AAE/g). AChE inhibitory activity was examined using Ellmans colorimetric method and all tested extracts showed anti-AChE activity in a dose dependent manner. The values of 10–28%, 23–39%, and 64–86% were obtained for tested concentrations of 0.25, 0.5, and 1 mg/mL, respectively. Additionally, the contents of total hydroxycinnamic derivatives, flavonoids, and tannins in dried plant samples were determined spectrophotometrically. Our results highlighted Thymus species as a rich source of natural antioxidants and AChE inhibitors that could be useful in preventing and treating Alzheimers disease and other neurodegenerative disorders.

Trichome micromorphology in Teucrium (Lamiaceae) species growing in Croatia

Micromorphological investigation of the types, dimensions and distribution of characteristic trichomes in leaves and stems in Teucrium L. species (T. arduini L., T. chamaedrys L., T. flavum L., T. montanum L., T. polium L., and T. scordium L. subsp. scordioides Schreb.) distributed in Croatia was carried out as part of the taxonomical study of the genus Teucrium. Secretory types of hairs, peltate and capitate hairs were observed on the epidermis of stems and leaves of all investigated species. Non-secretory, acicular hairs were almost completely lacking on stems of T. scordium subsp. scordioides. Flagelliform hairs were not found in T. flavum and T. polium. Cladose hairs were present only in T. polium. The largest micromorphological variability was established between wild and cultivated samples of T. arduini and T. scordium subsp. scordioides, while cultivated and wild specimens of T. polium were almost identical. Differences were primarily observed in trichome dimensions and much less in micromorphological features.