Surface plasmon resonance biosensor for the detection of ochratoxin A in cereals and beverages.

Ochratoxins are a group of mycotoxins produced as secondary metabolites by fungi which contaminate a large variety of food and feed commodities. Due to their teratogenic and carcinogenic properties, ochratoxins present a serious hazard to human and animal health. There is an increasing need to establish a simple sensitive method to detect these toxins. Here we report a rapid and highly sensitive surface plasmon resonance (SPR) assay of ochratoxin A (OTA) using Au nanoparticles for signal enhancement on a mixed self-assembled monolayer (mSAM) surface. A competitive immunoassay format was used for the development of the OTA immunoassay, which is based on the immobilization of target OTA through its ovalbumin (OVA) conjugate with a polyethylene glycol (PEG) linker. The new OTA conjugate (OTA-PEG-OVA) showed remarkably enhanced performance characteristics compared with those based on the immobilization of a commercial bovine serum albumin BSA-OTA conjugate without a PEG linker. Although OTA concentrations as low as 1.5 ng mL(-1) could be directly detected on this surface, the limit of detection (LOD) can be dramatically improved to 0.042 ng mL(-1) for OTA by applying large gold nanoparticles (40 nm) for signal enhancement. Various chemical conditions to minimize the influence of the food matrix on assay performance were also investigated. Grain samples were simply extracted with 50% methanol and liquid samples treated with poly(vinylpyrrolidone) (PVP) (3 or 5%), without any sample clean-up or pre-concentration step prior to analysis. The LODs for OTA in oats and corn were 0.3 and 0.5 ng g(-1), respectively, while in wine and other beverages, LODs ranged from 0.058 to 0.4 ng mL(-1). No cross-reactivity was observed with three other common mycotoxins. In addition, the mSAM/OTA-PEG-OVA surface exhibited high stability with over 600 binding/regeneration cycles. This approach with simple sample preparation provides a powerful tool for the rapid and sensitive quantitative determination of OTA in food matrices.

Chemical composition and in vitro anti-inflammatory activity of apple phenolic extracts and of their sub-fractions.

Apple extract powders from three different manufacturers were investigated for their anti-inflammatory activity, their total phenolic content, and their chemical composition. The samples represented two production batches for two products and a single batch of a third. The samples showed similar, but clearly different, anti-inflammatory activities, and had substantially different total phenolic contents, and different chemical compositions. Differences in chemical composition for batches of the same product were significant, although not as great as differences between products. The samples were fractionated into chemical classes. The most active fractions were those that contained epicatechin, catechin with phloridzin and quercetin glycosides, or those that contained procyanidin polymers. It was not possible to link activity to the presence of individual components or combinations of these. If fruit extracts are to be reliably linked to validated health benefits, then the source materials, the extraction processes, and the final composition of such products need to be more clearly defined than at present.

Antifungal saponins from Paris polyphylla Smith.

Three steroidal saponins, including one new and two known compounds, were isolated from the rhizomes of Paris polyphylla Smith. One- and two-dimensional NMR, LC-MS, and interpretation of hydrolytic cleavage experiments led to the identification of the structure of the new saponin as ( 25R)-spirost-5-ene-3 beta,17 alpha-diol (pennogenin) 3- O-{ O- alpha- L-rhamnopyranosyl-(1-->2)- O-[ O- beta-xylopyranosyl-(1-->5)- alpha- L-arabinofuranosyl-(1-->4)]- beta- D-glucopyranoside}. The isolated saponins were evaluated for their antifungal activity against Cladosporium cladosporioides and Candida species and showed comparable activity to chemicals used in some commercial products.

A silychristin isomer and variation of flavonolignan levels in milk thistle (Silybum marianum) fruits.

A new natural product has been isolated from silymarin, the hepatoprotective extract of milk thistle (Silybum marianum) fruits. This was shown by NMR spectroscopy to be silychristin B (8), a diastereoisomer of the known silychristin (7). Levels of these and the other flavonolignans varied markedly in fruits of different S. marianum samples.

Fusarium graminearum, F. cortaderiae and F. pseudograminearum in New Zealand: molecular phylogenetic analysis, mycotoxin chemotypes and co-existence of species.

Fusarium graminearum and F. pseudograminearum are important plant pathogens in New Zealand and around the world. Headblight and crown rot diseases of cereals caused by these species are responsible for large economic losses due to reduction in seed quality and contamination of grain with tricothecene mycotoxins. In the current study we have used two different molecular phylogenetic approaches, AFLPs and gene genealogies, to gain insight into the evolutionary relationships between F. graminearum, and F. pseudograminearum in New Zealand. The worldwide genetic diversity of F. graminearum clade is represented by at least eight biogeographically distinct species (previously designated as lineages of F. graminearum). Our analysis demonstrated that this clade is represented by F. graminearum (= F. graminearum Lineage 7) and F. cortaderiae (= F. graminearum Lineage 8) in New Zealand. Through our analysis we also confirm the presence of F. pseudograminearum in New Zealand as a first record for this organism. Information on species is necessary for preventing the inadvertent intercontinental introduction of genetically unique foreign pathogens associated with world trade. The ability to place species information into a worldwide context enabled postulation that the New Zealand representatives of F. graminearum clade originated from at least two regions, and probably on at least two hosts. Correlation of species descriptions with biogeographical and host information revealed evidence for co-localisation of F. graminearum clade species with potential for genetic outcrossing in the field. Mycotoxin analysis showed F. graminearum (= lineage 7) isolates produce either nivalenol (NIV) or deoxnivalenol (DON). In contrast, F. cortaderiae isolates produced only NIV. These findings support earlier observations that mycotoxin production in the F. graminearum clade is not species specific, but suggest maintenance of chemotype diversity through speciation may have been restricted to a subset of species.

Pteroside A2--a new illudane-type sesquiterpene glucoside from pteridium caudatum L. Maxon, and the spectrometric characterization of caudatodienone.

Fractionation of an extract of Pteridium caudatum L. Maxon. (syn P. aquilinum L. Kuhn var. caudatum) which had earlier yielded the illudane-type sesquiterpene glucosides, ptaquiloside (1a), isoptaquiloside (1b), and caudatoside (1c) afforded a mixture containing 1a and two minor components. Preparative HPLC afforded ptaquiloside Z (1d) and a new pteroside glucoside (pteroside A2) (3e), which was identified using a combination of mass spectral and one- and two-dimensional NMR analyses. The (1)H and (13)C NMR and mass spectrometric characterization of caudatodienone (2b), an unstable dienone derived from the degradation of caudatoside (1c) in pyridine solution, and the GC-MS characterization of some pterosin-type degradation products produced by reacting this solution with cosolvents is also reported.