Waxy Maize Starch Nanocrystals as Filler in Natural Rubber

Starch nanocrystals obtained from acid hydrolysis of waxy maize starch granules consist in crystalline nanoplatelets about 6–8 nm thick with a length of 20–40 nm and a width of 15–30 nm. New nanocomposite materials, i.e. natural rubber (NR) filled with waxy maize starch nanocrystals were processed by casting. Dynamic mechanical analysis has shown that starch nanocrystals were a good reinforcing agent for NR at temperatures higher than the glass transition temperature of NR. Tensile tests have shown that until a weight fraction of 20 wt%, this new filler presented the advantage to reinforce natural rubber without decreasing significantly the strain at break of the material. These properties may be due to both the morphological nature of starch nanocrystals, and the formation of a percolating starch nanocrystals network within the NR matrix, resulting from hydrogen bonding forces between starch aggregates.     

Comparison of Different Extraction Solvents for Characterization of Antioxidant Potential and Polyphenolic Composition in Boletus edulis and Cantharellus cibarius Mushrooms from Romania

Edible mushrooms are well-known for their nutritional benefits and low energy density. In addition, mushroom extracts contain various bioactive compounds that account for their antioxidant activity; the applied extraction conditions influence the extraction efficiency of such compounds. Therefore, this study investigates the effects of four extractants on the content of polyphenols and antioxidant properties of Boletus edulis and Cantharellus cibarius mushrooms, aiming to optimize the extraction process. Powders of B. edulis and C. cibarius mushrooms were subjected to extraction with acidic water (10% CH₃COOH), ethanol/water/acetic acid (15:76.5:8.5, v/v/v), hexane, and diethyl ether to measure their total phenolic content (TPC), total flavonoid content (TFC), and Trolox equivalent antioxidant capacity (TEAC). Furthermore, the level of individual polyphenolic compounds in these extracts was quantified using an HPLC-DAD-ESI-MS method. Results showed that the type of solvent significantly influenced the TPC and TEAC of mushroom powder but insignificantly influenced the TFC. A very strong positive correlation was found between TPC and TEAC, but no correlation was found between TFC and TEAC or TPC and TFC. Acidic water extracted the highest amount of polyphenolic compounds from these mushroom powders. Therefore, the aqueous extract showed the highest TPC and strongest antioxidant activity. Thus, acidic water is recommended for polyphenol analysis in B. edulis and C. cibarius mushrooms.     

Intermolecular Hydrogen Bonding between Water and Pyrazine

Completely planar is the hydrogen-bonded complex of pyrazine and water (see sketch), which was obtained by supersonic expansion and investigated by rotational spectroscopy. The water molecule lies in the plane of the aromatic ring, and the lone pair of electrons on the nitrogen atom functions as the acceptor in the N⋅⋅⋅H–O hydrogen bond, not—as in the corresponding benzene complex—the π electrons.     

Pro-Apoptotic and Pro-Autophagic Properties of Cardenolides from Aerial Parts of Pergularia tomentosa

Pergularia tomentosa L., a milkweed tropical plant belonging to the family Asclepiadaceae, is a rich source of unusual cardiac glycosides, characterised by transfused A/B rings and a sugar moiety linked by a double link, generating a dioxanoid structure. In the present report, five cardenolides isolated from the aerial parts of the plant (calactin, calotropin, 12β-hydroxycalactin, 12β,6′-dihydroxycalotropin, and 16α-hydroxycalotropin) were investigated for their biological effects on a human hepatocarcinoma cell line. Cell viability was monitored by an MTT assay. The occurrence of apoptosis was evaluated by detecting caspase-3 activation and chromatin fragmentation. The ability of these compounds to induce autophagy was analysed by monitoring two markers of the autophagic process, LC3 and p62. Our results indicated that all cardenolides had cytotoxic effects, with IC₅₀ ranging from 0.127 to 6.285 μM. All compounds were able to induce apoptosis and autophagy, calactin being the most active one. Some of them also caused a reduction in cell migration and a partial block of the cell cycle into the S-phase. The present study suggests that selected cardenolides from aerial parts of P. tomentosa, particularly calactin, possess potentially desirable properties for further investigation as anticancer agents.     

A High Throughput Screening HPLC-FLD Method for Paralytic Shellfish Toxins (PSTs) Enabling Effective Official Control

Paralytic Shellfish Toxins (PSTs) are marine biotoxins, primarily produced by dinoflagellates of the genera Gymnodinium spp., Alexandrium spp. They can accumulate in shellfish and, through the food chain, be assimilated by humans, giving rise to Paralytic Shellfish Poisoning. The maximum permitted level for PSTs in bivalves is 800 μg STX·2HCl eqv/kg (Reg. EC N° 853/2004). Until recently, the reference analytical method was the Mouse Bioassay, but Reg. EU N° 1709/2021 entered into force on 13 October 2021 and identified in the Standard EN14526:2017 or in any other internationally recognized validated method not entailing the use of live animals as official methods. Then the official control laboratories had urgently to fulfill the new requests, face out the Mouse Bioassay and implement instrumental analytical methods. The “EURLMB SOP for the analysis of PSTs by pre-column HPLC-FLD according to OMA AOAC 2005.06” also introduced a simplified semiquantitative approach to discriminate samples above and below the regulatory limit. The aim of the present paper is to present a new presence/absence test with a cut-off at 600 μg STX·2HCl eqv/kg enabling the fast discrimination of samples with very low PSTs levels from those to be submitted to the full quantitative confirmatory EN14526:2017 method. The method was implemented, avoiding the use of a large number of certified reference standards and long quantification procedures, resulting in an efficient, economical screening instrument available for official control laboratories. The protocol was fully validated, obtaining good performances in terms of repeatability (<11%) and recovery (53–106%) and accredited according to ISO/IEC 17025. The method was applied to mollusks collected from March 2021 to February 2022 along the Marche region in the frame of marine toxins official control.     

Construction of molecularly imprinted nanoparticles by employing ultrasound waves for selective determination of doxepin from human plasma samples: Modeling and optimization

In this work, molecularly imprinted nanoparticles (MINPs) were applied as selective adsorbent for ultrasound‐assisted micro‐solid‐phase extraction (UAMSPE) of doxepin (DP) from human plasma samples, which was then cleaned up, pre‐concentrated and subjected to HPLC. The MINPs were synthesized based on a non‐covalent approach by precipitation polymerization utilizing methacrylic acid and styrene as functional monomers, DP as template, ethylene glycol dimethacrylate as cross‐linker and 2,2‐azobisisobutyronitrile (AIBN) as initiator. The obtained MINPs were characterized by Fourier transform‐infrared and field emission scanning electron microscopy. Factors influencing the efficiency of UAMSPE such as sonication time, volume of eluent solvent and amount of sorbent were investigated using a central composite design and the optimal points were identified as 4 min of sonication time, 380 μL of eluent solvent and 30 mg of sorbent. Under optimized conditions, the proposed method has linear responses in the range of 0.2–2000 ng mL^–1, with a satisfactory limit of detection of 0.04 ng mL^–1 and limit of quantification of 0.11 ng mL^–1.