Nektarios Aligiannis

Ursolic Acid Triggers Apoptosis and Bcl-2 Downregulation in MCF-7 Breast Cancer Cells

In this report we determine the ability of ursolic acid (UA) to induce apoptosis and to modulate glucocorticoid receptor (GR) and Activator Protein-1 (AP-1) in MCF-7 cells. The UA-induced apoptosis (53 μM), the PARP cleavage, and the decrease in Bcl-2 protein (53 μM) support the notion that UA induces apoptosis through the intrinsic mitochondrial pathway. UA binds GR (relative binding affinity: 2.57) and translocates GR into nucleus, suggesting its potential as a GR modulator. UA had no effect on GRE- or TRE-driven gene expression. In summary, UA is a GR modulator and may be considered as a potential anticancer agent in breast cancer.

Samioside, a new phenylethanoid glycoside with free-radical scavenging and antimicrobial activities from Phlomis samia.

A new phenylethanoid glycoside, samioside, was isolated from the aerial parts of Phlomis samia and identified as 1-O-3,4-(dihydroxyphenyl)ethyl beta-D-apiofuranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->3)-4-O-caffeoyl-beta-D-glucopyranoside (1). In addition, one known phenylethanoid glycoside and three known flavonoids were identified as acteoside (2), apigenin, chrysoeriol, and ermanin, respectively. The structure of 1 was elucidated on the basis of its spectroscopic data. Samioside (1) demonstrated scavenging properties toward the DPPH radical and antimicrobial activity against Gram-positive and -negative bacteria.

DNA protecting and genotoxic effects of olive oil related components in cells exposed to hydrogen peroxide

In search for compounds, able to protect nuclear DNA in cells exposed to oxidative stress, extracts from olive leaves, olive fruits, olive oil and olive mill waste water were tested by using the “single cell gel electrophoresis” methodology (comet assay). Jurkat cells in culture were exposed to continuously generated hydrogen peroxide (11.8±1.5 μM per min) by direct addition into the growth medium of the appropriate amount of the enzyme “glucose oxidase” in the presence or absence of the tested total extracts. The protective effects of the tested extracts or isolated compounds were evaluated from their ability to decrease hydrogen peroxide-induced formation of single strand breaks in the nuclear DNA, while the toxic effects were estimated from the increase of DNA damage when the extracts or isolated compounds were incubated directly with the cells. Significant protection was observed in extracts from olive oil and olive mill waste water. However, above a concentration of 100 μg/ml olive oil extracts exerted DNA damaging effects by themselves in the absence of any H2O2. Extracts from olive leaves and olive fruits although protective, were also able to induce DNA damage by themselves. Main compounds isolated from the above described total extracts, like oleuropein glucoside, tyrosol, hydroxytyrosol and caffeic acid, were tested in the same experimental system and found to exert cytotoxic (oleuropein glucoside), no effect (tyrosol) or protective effects (hydroxytyrosol and caffeic acid). In conclusion, cytoprotective as well as cytotoxic compounds with potential pharmaceutical properties were detected in extracts from olive oil related sources by using the comet assay methodology.

Correlation of total polyphenolic content with antioxidant and antibacterial activity of 24 extracts from Greek domestic Lamiaceae species.

Lamiaceae family species are considered important because of their use in folk medicine, culinary and flavouring throughout the world. Their interesting bioactivities are attributed mainly to essential oils, polyphenols and terpenes. However, there are only few studies about polyphenolic extracts from Lamiaceae plants. Thus, 24 polyphenolic extracts from three Lamiaceae genera, Salvia, Mentha and Sideritis, collected in Greece were examined for antioxidant and antibacterial activity in correlation with their polyphenolic content. The results showed that the tested polyphenolic extracts had strong free radical scavenging activity against DPPH· and ABTS(+) radicals and protected from hydroxyl and peroxyl radical-induced DNA damage. Moreover, five extracts inhibited Staphylococcus aureus growth. Furthermore, the results showed that the total polyphenolic content is not correlated with the above activities, although this relation was different within each plant genus. This is the first study regarding the antioxidant and antibacterial activity of Salvia pomifera ssp. calycina, S. pomifera ssp. pomifera, Mentha microphylla and Sideritis raeseri ssp. attica species, and one of the few concerning protection from DNA damage and antibacterial activity of polyphenolic extracts from the rest of the tested species.

Chemical analysis of Greek pollen - Antioxidant, antimicrobial and proteasome activation properties

BackgroundPollen is a bee-product known for its medical properties from ancient times. In our days is increasingly used as health food supplement and especially as a tonic primarily with appeal to the elderly to ameliorate the effects of ageing. In order to evaluate the chemical composition and the biological activity of Greek pollen which has never been studied before, one sample with identified botanical origin from sixteen different common plant taxa of Greece has been evaluated.ResultsThree different extracts of the studied sample of Greek pollen, have been tested, in whether could induce proteasome activities in human fibroblasts. The water extract was found to induce a highly proteasome activity, showing interesting antioxidant properties. Due to this activity the aqueous extract was further subjected to chemical analysis and seven flavonoids have been isolated and identified by modern spectral means. From the methanolic extract, sugars, lipid acids, phenolic acids and their esters have been also identified, which mainly participate to the biosynthetic pathway of pollen phenolics. The total phenolics were estimated with the Folin-Ciocalteau reagent and the total antioxidant activity was determined by the DPPH method while the extracts and the isolated compounds were also tested for their antimicrobial activity by the dilution technique.ConclusionsThe Greek pollen is rich in flavonoids and phenolic acids which indicate the observed free radical scavenging activity, the effects of pollen on human fibroblasts and the interesting antimicrobial profile.

Methanolic Extract of Verbascum macrurum as a Source of Natural Preservatives against Oxidative Rancidity

The antioxidant properties of various fractions of a methanolic extract obtained from the aerial parts of Verbascum macrurum have been determined by monitoring their capacity to scavenge the stable free-radical DPPH. They were also evaluated as natural preservatives against oxidative rancidity using the accelerated Rancimat method. Their activities expressed as protection factor (PF(r)) indicated that the fractions rich with phenylpropanoid glycosides were more potent compared to alpha-tocopherol and of the same magnitude as BHT, which were used as reference standards. Ten natural compounds were identified as components of this methanolic extract and were isolated by medium-pressure liquid chromatography (MPLC). Assessment of their antioxidant activities established that acteoside, a polyhydroxylated phenylpropanoid glycoside derivative, is the most potent free radical scavenger and showed the highest protection factor (PF(r)) against sunflower-oil-induced oxidative rancidity. Its activity is comparable to the synthetic antioxidant BHT and clearly superior to natural alpha-tocopherol. This compound therefore represents a very interesting candidate for use in food preservation as natural protecting agent against oxidative rancidity.

Acteoside and martynoside exhibit estrogenic/antiestrogenic properties.

Acteoside and martynoside are plant phenylpropanoid glycosides exhibiting anticancer, cytotoxic and antimetastatic activities. We investigated their potential to activate estrogen receptor isoforms ERalpha and ERbeta in HeLa cells transfected with an estrogen response element (ERE)-driven luciferase (Luc) reporter gene and an ERalpha or ERbeta expression vector. Their estrogenic/antiestrogenic effects were also assessed in breast cancer cells (MCF7), endometrial cancer cells (Ishikawa) and osteoblasts (KS483), by measuring IGFBP3 levels, cell viability and number of mineralized nodules, respectively, seeking for a natural selective estrogen receptor modulator (SERM). Acteoside and martynoside antagonized both ERalpha and ERbeta (p<0.001), whereas they reversed the effect of E(2) mainly via ERalpha (p<0.001). Martynoside was a potent antiestrogen in MCF-7 cells, increasing, like ICI182780, IGFBP3 levels via the ER-pathway. In osteoblasts, martynoside induced nodule mineralization, which was abolished by ICI182780, implicating an ER-mediated mechanism. Furthermore, its antiproliferative effect on endometrial cells suggests that martynoside may be an important natural SERM. Acteoside was an antiestrogen in breast cancer cells and osteoblasts, without any effect on endometrial cells. Our study suggests that the nature is rich in selective ERalpha and ERbeta ligands, the discovery of which may lead to the development of novel neutraceutical agents.

Influence of extraction procedures on phenolic content and antioxidant activity of Cretan barberry herb

The main goal of present study was the development, optimization and application of different extraction protocols, especially those employing green technologies, in order to obtain from Berberis cretica extracts with high antioxidant capacity. For this purpose, the applied methods: maceration, ASE and SFE coupled with ASE were incorporated. The antioxidant assessment was carried out using DPPH and total phenolic content (Folin-Ciocalteu) assays. Major constituents were elucidated using HPLC-DAD and UHPLC-HRMS/MS (hybrid IT-Orbital trap spectrometer) equipped with an ESI probe. The chromatographic and spectral data revealed the presence of several simple phenolic acids, derivatives of both caffeic and benzoic acids, and flavonoids in the produced extracts. It was clearly evidenced that the extraction method and solvents used affected both the activity and the chemical content of the results, significantly. The most beneficial conditions were calculated for methanol and water:ethanol (50:50) extracts derived from the combination of SFE and ASE methodologies. Obtained results classify Cretan barberry as a strong antioxidant agent.

Flavonoid glycosides isolated from unique legume plant extracts as novel inhibitors of xanthine oxidase.

Legumes and the polyphenolic compounds present in them have gained a lot of interest due to their beneficial health implications. Dietary polyphenolic compounds, especially flavonoids, exert antioxidant properties and are potent inhibitors of xanthine oxidase (XO) activity. XO is the main contributor of free radicals during exercise but it is also involved in pathogenesis of several diseases such as vascular disorders, cancer and gout. In order to discover new natural, dietary XO inhibitors, some polyphenolic fractions and pure compounds isolated from two legume plant extracts were tested for their effects on XO activity. The fractions isolated from both Vicia faba and Lotus edulis plant extracts were potent inhibitors of XO with IC50 values range from 40–135 µg/mL and 55–260 µg/mL, respectively. All the pure polyphenolic compounds inhibited XO and their Ki values ranged from 13–767 µM. Ten of the compounds followed the non competitive inhibitory model whereas one of them was a competitive inhibitor. These findings indicate that flavonoid isolates from legume plant extracts are novel, natural XO inhibitors. Their mode of action is under investigation in order to examine their potential in drug design for diseases related to overwhelming XO action.

Leishmanicidal activity assessment of olive tree extracts.

Leishmaniasis, a protozoan parasitic disease that remains a major worldwide health problem with high endemicity in developing countries, is prevalent around the Mediterranean basin. High cost, systemic toxicity, and diminished efficacy due to development of parasite resistance are the serious drawbacks of current treatment options. Thus, identifying new, effective, and safer anti-leishmanial drug(s) is of paramount importance. Here we tested the anti-promastigote and anti-amastigote activity of five natural products, including oleuropein and hydroxytyrosol, present in olive tree leaves and olive mill wastewater. These products are recognized as low-cost starting materials rich in bioactive compounds, particularly biophenols. Oleuropein and hydroxytyrosol exhibited the best inhibitory effect among the natural products tested in both stationary and middle logarithmic phase promastigotes of L. infantum, L. donovani, and L. major. Similarly, oleuropein and hydroxytyrosol demonstrated the highest selectivity index ratio against L. donovani amastigotes that parasitize J774A.1 macrophages. Moreover, oleuropein was tested in vivo in an experimental visceral leishmaniasis model. L. donovani-infected BALB/c mice received intraperitoneal oleuropein a total of 14 times at intervals of every other day. Three days after treatment termination, the spleen parasitic burden was reduced >80%. Of interest, this effect of oleuropein persisted and was even enhanced 6 weeks after the termination of the treatment, as determined by parasite depletion of >95% in liver and spleen. These findings contribute to the potential development of natural products as effective drugs against parasites of the Leishmania genus, with low cost and diminished cytotoxicity.