Evelin Tiralongo

Sialic acid-specific lectins: occurrence, specificity and function

Abstract.Sialic acids consist of a family of acidic ninecarbon sugars that are typically located at the terminal positions of a variety of glycoconjugates. Naturally occurring sialic acids show an immense diversity of structure, and this reflects their involvement in a variety of biologically important processes. One such process involves the direct participation of sialic acids in recognition events through specific interactions with lectins, a family of proteins that recognise and bind sugars. This review will present a detailed overview of our current knowledge regarding the occurrence, specificity and function of sialic acid-specific lectins, particularly those that occur in viruses, bacteria and non-vertebrate eukaryotes.

Cytotoxic Effects of Bangladeshi Medicinal Plant Extracts

To investigate the cytotoxic effect of some Bangladeshi medicinal plant extracts, 16 Bangladeshi medicinal plants were successively extracted with n-hexane, dichloromethane, methanol and water. The methanolic and aqueous extracts were screened for cytotoxic activity against healthy mouse fibroblasts (NIH3T3) and three human cancer-cell lines (gastric: AGS; colon: HT-29; and breast: MDA-MB-435S) using the MTT assay. Two methanolic extracts (Hygrophila auriculata and Hibiscus tiliaceous) and one aqueous extract (Limnophila indica) showed no toxicity against healthy mouse fibroblasts, but selective cytotoxicity against breast cancer cells (IC50 1.1–1.6 mg mL−1). Seven methanolic extracts from L. indica, Clerodendron inerme, Cynometra ramiflora, Xylocarpus moluccensis, Argemone mexicana, Ammannia baccifera and Acrostichum aureum and four aqueous extracts from Hygrophila auriculata, Bruguiera gymnorrhiza, X. moluccensis and Aegiceras corniculatum showed low toxicity (IC50 > 2.5 mg mL−1) against mouse fibroblasts but selective cytotoxicity (IC50 0.2–2.3 mg mL−1) against different cancer cell lines. The methanolic extract of Blumea lacera showed the highest cytotoxicity (IC50 0.01–0.08 mg mL−1) against all tested cell lines among all extracts tested in this study. For some of the plants their traditional use as anticancer treatments correlates with the cytotoxic results, whereas for others so far unknown cytotoxic activities were identified.

Investigations into the antibacterial activities of phytotherapeutics against Helicobacter pylori and Campylobacter jejuni.

The prevalence of gastric diseases is increasing with H. pylori, the causative agent of acute and chronic gastritis, being a major predisposing factor for peptic ulcer disease and gastric carcinoma. C. jejuni is the most common cause of enteric infections, particularly among children, resulting in severe diarrhoea. Increasing drug resistance of these bacteria against standard antibiotics, and the more widespread use of herbal medicines, favours investigations into additional anti‐Helicobacter and anti‐Campylobacter effects of phytotherapeutics that are already used for their beneficial effects on bowel and digestive functions.

Two Trans-sialidase Forms with Different Sialic Acid Transfer and Sialidase Activities from Trypanosoma congolense

Trypanosomes express an enzyme called trans-sialidase (TS), which enables the parasites to transfer sialic acids from the environment onto trypanosomal surface molecules. Here we describe the purification and characterization of two TS forms from the African trypanosome Trypanosoma congolense. The purification of the two TS forms using a combination of anion exchange chromatography, isoelectric focusing, gel filtration, and subsequently, antibody affinity chromatography resulted, in both cases, in the isolation of a 90-kDa monomer on SDS-PAGE, which was identified as trans-sialidase using micro-sequencing. Monoclonal antibody 7/23, which bound and partially inhibited TS activity, was found in both cases to bind to a 90-kDa protein. Both TS forms possessed sialidase and transfer activity, but markedly differed in their activity ratios. The TS form with a high transfer-to-sialidase activity ratio, referred to as TS-form 1, possessed a pI of pH 4–5 and a molecular mass of 350–600 kDa. In contrast, the form with a low transfer-to-sialidase activity ratio, referred to as TS-form 2, exhibited a pI of pH 5–6.5 and a molecular mass of 130–180 kDa. Both TS forms were not significantly inhibited by known sialidase inhibitors and revealed no significant differences in donor and acceptor substrate specificities; however, TS-form 1 utilized various acceptor substrates with a higher catalytic efficiency. Interestingly, glutamic acid-alanine-rich protein, the surface glycoprotein, was co-purified with TS-form 1 suggesting an association between both proteins.

Mushroom lectins: specificity, structure and bioactivity relevant to human disease.

Lectins are non-immunoglobulin proteins that bind diverse sugar structures with a high degree of selectivity. Lectins play crucial role in various biological processes such as cellular signaling, scavenging of glycoproteins from the circulatory system, cell–cell interactions in the immune system, differentiation and protein targeting to cellular compartments, as well as in host defence mechanisms, inflammation, and cancer. Among all the sources of lectins, plants have been most extensively studied. However, more recently fungal lectins have attracted considerable attention due to their antitumor, antiproliferative and immunomodulatory activities. Given that only 10% of mushroom species are known and have been taxonomically classified, mushrooms represent an enormous unexplored source of potentially useful and novel lectins. In this review we provide an up-to-date summary on the biochemical, molecular and structural properties of mushroom lectins, as well as their versatile applications specifically focusing on mushroom lectin bioactivity.

Antibacterial metabolites from Australian macrofungi from the genus Cortinarius

In this study, ethyl acetate and aqueous fractions from 117 collections of Australian macrofungi belonging to the mushroom genus Cortinarius were screened for antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa. Overall, the lipophilic fractions were more active than the aqueous fractions. The ethyl acetate fractions of most or all collections of 13 species, namely Cortinarius ardesiacus, C. archeri, C. austrosaginus, C. austrovenetus, C. austroviolaceus, C. coelopus, C. [Dermocybe canaria](2), C. clelandii, C. [D. kula], C. memoria-annae, C. persplendidus, C. sinapicolor, C. vinosipes and forty seven collections of un-described Cortinarius species exhibited IC(50) values of 0.09 mg/mL against S. aureus. In contrast, most or all collections of only four species, namely C. abnormis, C. austroalbidus, C. [D. kula], C. persplendidus, and eleven un-described Cortinarius collections exhibited similar effects against P. aeruginosa (IC(50) <or= 0.09 mg/mL). Anthraquinonoid pigments isolated from C. basirubescens together with emodin physcion and erythrogluacin were assessed for their antimicrobial activity. The fungal octaketides austrocortilutein, austrocortirubin, torosachrysone, physcion and emodin were found to strongly inhibit the growth of S. aureus (IC(50) 0.7-12 microg/mL) whereas only physcion and emodin exhibited potency against P. aeruginosa (IC(50) 1.5 and 2.0 microg/mL, respectively).

(2S,3S)-sulfated pterosin C, a cytotoxic sesquiterpene from the Bangladeshi mangrove fern Acrostichum aureum.

Two new sesquiterpenes, (2R,3S)-sulfated pterosin C (1) and (2S,3S)-sulfated pterosin C (2), along with two known derivatives, (2S,3S)-pterosin C and (2R)-pterosin P, were isolated from a methanolic extract of the aerial parts of Acrostichum aureum. The structures of 1 and 2 were determined by the interpretation of their spectroscopic data. The isolated pterosins were evaluated for their cytotoxic activity against the AGS, HT-29, MDA-MB-231, and MCF-7 human cancer cell lines and the NIH3T3 normal mouse fibroblast cell line, using the MTT assay. Compound 2 showed IC50 values in the range 23.9-68.8 μM. The lowest IC50 value (23.9 μM) was recorded against AGS gastric adenocarcinoma cells. Compound 2 was found to exert an apoptotic effect on AGS cells within 24 h of treatment, which increased with time and was greater than the positive control, cycloheximide. The cytotoxicity of 2 seems to be due in part to the sulfate group on C-14 and the configuration at C-2.

Trans-Sialidase-Like Sequences from Trypanosoma congolense Conserve Most of the Critical Active Site Residues Found in Other Trans-Sialidases

Abstract Trypanosoma congolense is the agent of Nagana, the trypanosomiasis in African ruminants. Trypanosomes express an enzyme called trans-sialidase, which is believed to play an important role in maintaining pathogenicity of the parasites. Thus far, only two complete trans-sialidase sequences have been characterised, one from the American trypanosome T. cruzi and one from the African trypanosome T. brucei brucei. Although the crystal structure of T. cruzi trans-sialidase has recently been published [Buschiazzo et al., Mol. Cell 10 (2002), pp. 757 768], a number of questions concerning the exact transfer mechanism remain unanswered. The availability of further trans-sialidase sequences will ensure a better understanding of how transfer activity can be achieved and will provide the opportunity to develop highly specific, structure-based trans-sialidase inhibitors. Utilising a PCR-based approach two different trans-sialidase gene copies from T. congolense were identified, which share only 50% identity with each other, but show significant similarity with known viral, bacterial and trypanosomal sialidases and trans-sialidases. In both partial sequences most of the critical active site residues common to other trypanosomal sialidases and trans-sialidases are conserved. This is further illustrated by modelling the active site of the longer of the two partial gene sequences.

Predictors of complementary and alternative medicine use by people with type 2 diabetes

AIMS   This paper is a report of a study into factors predicting complementary and alternative medicine use in people with type 2 diabetes. BACKGROUND   The growing incidence of type 2 diabetes is emerging as a major health issue throughout the world. While the rate of complementary and alternative medicine use in this population is high, it is not clear what predicts its use, in this population. METHODS   A cross-sectional survey, using a structured interview, was undertaken among people with type 2 diabetes attending diabetic clinics in three census regions in Taiwan, between July 2006 and February 2007. The survey instrument, derived from a review of Taiwanese and international literature, was developed using the Health Belief Model. RESULTS   A total of 326 participants with type 2 diabetes were interviewed (87·4% response rate). In people with type 2 diabetes, complementary and alternative medicine use was associated with a history of its use, a positive attitude towards it, stronger health beliefs about diabetes and the efficacy of complementary and alternative medicine in treating diabetes, a higher degree of self-care activities by the individual and a longer duration of diabetes. CONCLUSIONS   The results of this study indicate that complementary and alternative medicine use in people with type 2 diabetes is influenced by peoples experience, beliefs, attitudes towards complementary and alternative medicine, and their behaviour towards disease management rather than their demographic characteristics. Nurses and healthcare professionals should consider the patients background, health history, health beliefs and cultural background when planning specific strategies designed to modify lifestyle.

Evaluation of cytotoxic activity of patriscabratine, tetracosane and various flavonoids isolated from the Bangladeshi medicinal plant Acrostichum aureum.

Context: Acrostichum aureumL. (Pteridaceae), a mangrove fern, has been used as a Bangladeshi traditional medicine for a variety of diseases including peptic ulcer. Objective: Isolation and structural elucidation of cytotoxic secondary metabolites from the methanol extract of the aerial parts of A. aureum. Materials and methods: Compounds were isolated using HPLC. The compound structures were elucidated by 1D and 2D NMR, MS and other spectroscopic methods using published data. The compounds were tested for their cytotoxic activity against healthy and cancer cells using the MTT assay. Active compounds were further evaluated for apoptosis–and necrosis-inducing potential against gastric cancer cells (AGS) using the FITC Annexin V apoptosis assay. Results and discussion:Seven known compounds, patriscabratine, tetracosane and 5 flavonoids (quercetin-3-O-β-d-glucoside, quercetin-3-O-β-d-glucosyl-(6→1)-α-l-rhamnoside, quercetin-3-O-α-l-rhamnoside, quercetin-3-O-α-l-rhamnosyl-7-O-β-d-glucoside and kaempferol) were isolated. Patriscabratine was found moderately cytotoxic against AGS, MDA-MB-231 and MCF-7 cells with IC50 values ranging from 69.8 to 197.3 μM. Tetracosane showed some cytotoxic activity against AGS, MDA-MB-231, HT-29 and NIH 3T3 cells with IC50 values ranging from 128.7 to >250 μM. Patriscabratine and tetracosane displayed an apoptotic effect (10%) on AGS cells within 24 h which was increased (20%) after 48 h, and was comparable to, if not greater, than the positive control, cycloheximide. Conclusion:Except for quercetin-3-O-β-d-glucoside and kaempferol; compounds were isolated for the first time from this plant and evaluated for their cytotoxic activity. The results highlight the potential of this plant as a source of bioactive compounds and provide a rationale for its traditional use in peptic ulcer treatment.