Validation and uncertainty estimation of analytical method for quantification of phytochelatins in aquatic plants by UPLC-MS.

Phytochelatins (PCs) are peptides that play an important role in homeostasis and detoxification of heavy metal in plants. Furthermore, they have been proposed as earlier potential biomarkers of aquatic pollution by heavy metals. Nowadays, several researchers have reported on current methods for quantification of glutathione (GSH) and the PCs (phytochelatin 2, phytochelatin 3, phytochelatin 4) quantification in plants. However, no method has reported the uncertainty of the measurement, which helps to improve the accuracy and quality assurance in the PC quantification. In this work, a new methodology using ultra-high-performance liquid chromatography coupled to mass spectrometry (UPLC-MS) to measure with high precision and accuracy the PCs in aquatic plants, was validated. Selectivity, linearity, limit of detection, limit of quantification, precision, trueness and uncertainty estimation were examined as parts of the method validation. The described method shows excellent linearity in different ranges for all analytes with coefficients of determination higher than 0.99. The relative standard deviation for intra-day precision was <3% and for inter-day <10%. All LOD and LOQ analytes ranged from 0.02 to 0.08 µg ml-1, and from 0.03 to 0.09 µg ml-1, respectively. The recoveries varied from 61% to 89%. In order to obtain an interval of results with the highest confidence levels, the uncertainty associated with the measurements was evaluated. The calibration curve (>50%) and recovery (19-44%) were the most important contributors to the total uncertainty. The proposed method was applied to quantify GSH and PCs in the aquatic plants Lemna gibba L., Myriophyllum heterophyllum Michx., Arenaria paludicola and Hydrocotyle ranunculoides L. fil., showing statistical differences in the mass fraction of the analytes.

Aqueous extract of Sedum oxypetalum induces mineralization and osteogenic differentiation by human Periodontal Ligament-Derived cells.

ETHNOPHARMACOLOGICAL RELEVANCE: The medicinal plant Sedum oxypetalum Kunth (Crassulaceae), locally known as Jiote or in general Siempreviva (always alive) has been traditionally used by people of the Mexican community of Tenango del Valle as a home remedy to treat periodontal diseases, inducing teeth strengthening. Consequently, the aim of this work was to investigate its capacity directed to mineralized tissues regeneration. MATERIALS AND METHODS: The aerial parts of the plant were processed and its aqueous extract (AE) was chemically characterized. The AE and its components sedoheptulose and syngenite were tested for either osteogenic differentiation or mineral-nucleation induction respectively. RESULTS: The AE and one of its components (sedoheptulose) were shown to promote the proliferation and/or osteogenic differentiation by Human Periodontal Ligament-Derived Cells (hPDLs), while inducing the mineralization process. The AE also promoted the nucleation of octacalcium phosphate and its component syngenite, the hydroxyapatite crystals formation in vitro. CONCLUSION: The findings reported herein support the traditional use of S. oxypetalum due to its potential capacity to promote the regeneration of mineralized tissues.

(S)-(+)-cis-4'-Benzyl-oxypraziquantel.

The asymmetric unit of the title compound, C26H30N2O3 {systematic name (S)-(+)-2-[cis-4-(benz-yloxy)cyclo-hexa-ne-carb-on-yl]-1,2,3,6,7,11b-hexa-hydro-4H-pyrazino-[2,1-a]isoquin-olin-4-one}, consists of two independent mol-ecules in which the O= Camide group is syn to the N-C(C=Olactam) moiety, making dihedral angles of 2.0 (8) and 3.7 (8)°. The conformation of the 1,4-disubstituted cyclo-hexane ring is cis in each independent mol-ecule, with the carbonyl group occupying an equatorial position and the benz-yloxy group an axial position. In one mol-ecule, two C and one O atom of the benz-yloxy group are disordered over two sets of sites, with a refined occupancy ratio of 0.772 (8):0.228 (8). In the crystal, mol-ecules are linked by C-H⋯O inter-actions, forming ribbons parallel to the b-axis direction.

Synthesis of Fischer type-carbene complexes containing a coordinated thioimidate structural motif.

This paper describes a tandem strategy to synthesize a series of new Fischer carbene complexes [(CO)(4)M=C[N-(CH(2))(4)-]CH=C(NRR')(SR'); M = Cr, W; R = Ar, R' = Me, -(CH(2))(2)-] with a thioimide or thiazoline fragment, in which the sulfur or nitrogen atom is coordinated to a metal center, depending on the nature of alkylating groups included as R'. We have trapped by protonation the proposed intermediate as the thioamide 12 [(CO)(5)W=[N-(CH(2))(4)-]CH(2)C(S)NHPh], which reveals the pathway of this reaction.