Didem Şöhretoğlu

Evaluation of antioxidative, protective effect against H2O2 induced cytotoxicity, and cytotoxic activities of three different Quercus species.

Quercus species are used as antidiarrheic, for the treatment of hemorrhoid, oral and anal mucosa inflammation. These tree species have been of interest to researchers because of their usage in folk medicine, consumption as food, beverage and especially usage of oak woods for construction in wine barrels. The DPPH, SO and NO radical scavenging activities, protective effect against H2O2 induced cytotoxicity as well as their cytotoxic activity against Hep-2 human larynx epidermoid carcinoma cell line of the MeOH and water extracts of the barks of Quercus cerris var. cerris, Quercusmacranthera subsp. syspirensis and Quercus aucheri were investigated for the first time. Total phenolic content of the extracts was also evaluated by Folin-Ciocalteu method. Results demonstrated that the extracts showed strong radical scavenging activity comparable to those of standard compounds. Extracts also showed good protective effect against H2O2 induced cytotoxicity on human erythrocytes comparing to ascorbic acid. On the other hand, while each extract showed dose dependent cytotoxic activity, MeOH extract of Q.macranthera subsp. syspirensis showed the strongest cytotoxicity against the tested cell line. Taken together, the results showed that Quercus species may be a promising alternative to synthetic substances as natural compound with high antioxidant and antiproliferative activities.

Isolation of an oleanane-type saponin active from Bellis perennis through antitumor bioassay-guided procedures

Abstract Context: Bellis perennis L. (Asteraceae) (common daisy) is a herbaceous perennial plant known as a traditional wound herb; it has been used for the treatment of bruises, broken bones, and wounds. Bellis perennis has also been used in the treatment of headache, common cold, stomachache, eye diseases, eczema, skin boils, gastritis, diarrhea, bleeding, rheumatism, inflammation, and infections of the upper respiratory tract in traditional medicine. Objective: Antitumor activities of different fractions of B. perennis flowers at different concentrations were evaluated and through bioassay-guided fractionation and isolation procedures a saponin derivative (1) was isolated from the active fraction obtained from the n-butanol extract of flowers of the title plant by column chromatography. Materials and methods: Antitumor activities of different fractions of B. perennis flowers at different concentrations were evaluated using Potato Disc Tumor Induction Bioassay. Structure elucidation of 1 was accomplished by spectroscopic methods [1D- and 2D-NMR, and LC-ESI(APCI)-TOF-MS(MSn)]. Results: The present study showed the antitumor activity of fractions obtained from B. perennis flowers for the first time. The most active fraction showed 99% tumor inhibition at 3000 mg/L. An oleanane-type saponin was isolated through bioassay-guided studies. Discussion and conclusion: Through antitumoral bioassay-guided fractionation and isolation procedures, 1 was isolated from the active fraction of B. perennis. The detailed NMR data of compound 1 is given for the first time.

α-Glucosidase inhibitory effect of Potentilla astracanica and some isoflavones: Inhibition kinetics and mechanistic insights through in vitro and in silico studies

α-Glucosidase enzyme inhibitors are clinically used for the treatment of Type 2 diabetes mellitus. We tested α-glucosidase inhibitory effects of Potentilla astracanica Jacq. extracts (1, 2), two compounds isolated from these extracts, prunetin 5-O-β-glucopyranoside (3) and genistein 5-O-β-glucopyranoside (4), and their aglycon forms (5 and 6). All the tested materials possessed remarkable α-glucosidase inhibitor activity compared to the positive control, acarbose. Genistein (6) showed the highest activity with an IC50 value of 1.47 (±0.11) μg/ml. An enzyme kinetics analysis revealed that 3 and 6 were uncompetitive, 5 was noncompetitive, and 4 was competitive inhibitors. Using molecular modeling techniques we tried to provide insight into molecular mechanisms of their activity and how allosteric binding of 6 affected binding interactions between the agonist (maltose) and the enzyme.

Potential of Potentilla inclinata and its polyphenolic compounds in α-glucosidase inhibition: Kinetics and interaction mechanism merged with docking simulations

In the present study we aimed to identify the α-glucosidase enzyme inhibitory potential of Potentilla inclinata Vill. MeOH and n-BuOH extracts which possessed remarkable α-glucosidase enzyme inhibitory effects with IC50 values of 1.06±0.02 and 0.93±0.01μg/ml respectively, compared to that of acarbose (IC50 31.92±0.17). Thus, BuOH extract was chosen for further phytochemical investigations. A phenolic acid, six flavonol glycosides, and two hydrolysable tannins were isolated from the most active n-BuOH extract of the title plant. Structures of the isolated compounds were elucidated by 1D- and 2D-NMR experiments. All the compounds exhibited remarkable α-glucosidase inhibitory activity compared to the positive control, acarbose. Rutin (2) showed the highest activity with an IC50 value of 26.31±0.02μg/ml. An enzyme kinetics analysis revealed that compounds 5 and 7 were competitive, 4 and 6 noncompetitive, and 3 was uncompetitive inhibitors of α-glucosidase enzyme. Molecular docking studies were performed to get insights into inhibition mechanisms of the isolates considering their inhibition type using various binding sites of the enzyme model we previously reported.

Evaluation of antihemolytic and antioxidant activities of Geranium tuberosum subsp. tuberosum with in vitro models

Context: There are 33 Geranium species growing in Turkey characterized by the presence of polyphenolic compounds. Some Geranium (Geraniaceae) species are used as antidiabetics, hemostatics, antihemorrhoidals, antidiarrheics and for the treatment of pain, fevers, and gastrointestinal ailments, or are consumed as food. Objective: The in vitro antioxidant activity and antihemolytic effect of ethyl acetate (EtOAc), n-butanol (BuOH), methanol (MeOH) and water extracts of Geranium tuberosum L. subsp. tuberosum (Geraniaceae), a medicinal food plant, have been evaluated. Materials and methods: The two antioxidant enzyme activities of human erythrocyte, namely superoxide dismutase (SOD) and catalase (CAT), after in vitro incubation with the extracts, were examined in order to see whether the observed effects are related to altered enzymatic efficiency. Reduced glutathione (GSH) levels were also measured as oxidative stress marker. Antihemolytic activity of extracts was shown by hemolysis assay in erythrocytes. Furthermore, total phenolic content of extracts was measured by Folin–Ciocalteu method. Results: All extracts enhanced GSH levels, and the activity of SOD and CAT. The EtOAc extracts seems to be the most potent antioxidant at 100 µg/mL (SOD activity 173.736 ± 8.33, CAT activity 133.218 ± 3.31, GSH level 2.264 ± 2.21). However, apart from the MeOH extracts at 100 µg/mL (68.699 ± 3.93), they didn’t increase the resistance of erythrocytes to H2O2 induced cytotoxicity. Therefore, while a significant antioxidant effect was observed in these samples, antihemolytic effect was not determined. Discussion and conclusion: The title plant has shown high antioxidant activity without cytotoxicity up to 100 µg/mL, thus could be a potent source as natural antioxidant.

Recent advances in chemistry, therapeutic properties and sources of polydatin

Abstract Polydatin (PLD), the 3-O-β-glucopyranoside of the well-known stilbenoid compound resveratrol, is a major compound of Fallopia japonica (Houtt.) R. Decr. (Japanese knotweed), which is widely used in traditional Chinese medicine to treat infection, inflammatory diseases and circulatory problems. It has shown a wide range of biological activities including anti-inflammatory, anti-oxidant, anti-cancer, neuroprotective, hepatoprotective, nephroprotective and immunostimulatory effects. Although resveratrol has similar beneficial effects, its low bioavailability has remained a problem. Glycosylation increases solubility of resveratrol in an aqueous environment, thus improving its bioavailability. This has led to a growing interest in PLD. Promising results obtained from bioactivity studies have boosted an intense research on this compound. The aim of this review is to give a comprehensive overview of the botanical sources, pharmacology, biosynthesis, biotechnological production, and bioactivities of PLD, and to discuss clinical studies on this compound.

Discovery of potent α-glucosidase inhibitor flavonols: Insights into mechanism of action through inhibition kinetics and docking simulations

Beside other pharmaceutical benefits, flavonoids are known for their potent α-glucosidase inhibition. In the present study, we investigated α-glucosidase inhibitory effects of structurally related 11 flavonols, among which quercetin-3-O-(3″-O-galloyl)-β-galactopyranoside (8) and quercetin 3-O-(6″-O-galloyl)-β-glucopyranoside (9) showed significant inhibition compared to the positive control, acarbose, with IC50 values of 0.97 ± 0.02 and 1.35 ± 0.06 µM, respectively. It was found that while sugar substitution to C3-OH of C ring reduced the α-glucosidase inhibitory effect, galloyl substitution to these sugar units increased it. An enzyme kinetics analysis revealed that 7 was competitive, whereas 1, 2, 8, and 9 were uncompetitive inhibitors. In the light of these findings, we performed molecular docking studies to predict their inhibition mechanisms at atomic level.

Plant-Derived Antiinflammatory Steroid Analogs for Neuroprotection: A Recent Update

Abstract Inflammation is an important part of the immune response and is a tightly regulated process. Glucocorticoids (GCs) are a key part of the feedback mechanism in the immune system and tune immune activity (inflammation) down. Failure of this feedback mechanism results in chronic inflammation, which is the basis of a variety of degenerative diseases. A wide range of natural products that have antiinflammatory properties seem to contribute to the prevention of neurodegenerative diseases through alleviation of chronic inflammation. This review will focus on natural products that may be considered analogs of the steroid hormones, normally regulating the immune response. The compounds under discussion cover triterpenes and phytosterols, and phytoestrogens (notably flavones and isoflavones), which are known to interact with sterol receptors in the human body and are likely to directly interfere with the cell signaling pathways that lie at the base of the inflammation process.

Mantarlardan Elde Edilen Alkaloitler

Mantarlar (makrofunguslar) besin kaynagi ve ilac olarak ozellikle Dogu Asya’da yuzyillardir diyetin bir parcasidir. Son zamanlarda uzerlerinde yapilan calismalarin sayisinin artmasi nedeniyle mantarlarin ve ekstrelerinin tibbi amacla kullanimi daha populer hale gelmistir. Mantarlar cogunlukla polisakkaritler, terpenler ve steroller tasimaktadir. Alkaloitler cok dusuk dozlarda bile biyoaktif etki gosterirler ve genellikle Angiospermlerde bulunurlar. Bu grup bilesiklerin makrofunguslarda bulunuslari oldukca sinirlidir ve haklarinda polisakkaritler ya da terpenler gibi diger bilesiklerin mantarlarda yayilislari kadar detayli bilgi yoktur. Bu derlemede, mantarlarda bulunan alkaloitlerin dagilimi ve biyoaktivitelerine odaklandik.

Tyrosinase inhibition by some flavonoids: Inhibitory activity, mechanism by in vitro and in silico studies

Flavonoids are main polyphenolic groups widely distributed to fruits, vegetables and beverages we consumed daily. They exhibit many biological effects. We tested tyrosinase inhibitor potential of structurally related (1-9) flavonoids and found that all the tested materials possessed tyrosinase inhibitory effect compared to the positive control, kojic acid. 2 exhibited the strongest tyrosinase inhibitory effect with an IC50 value of 40.94 ± 0.78 µM in a competitive manner. According to kinetic analysis 1, 4 and 7 were found to be competitive inhibitors, 3, 5, and 6 noncompetitive inhibitors of tyrosinase. According to the docking studies, A and C ring of the flavonoid structure, hydroxyl substituent at the 7th position, and hydroxyl substituents at para or para and meta position of ring B play key role for competitive inhibition of the enzyme.