The aza-Diels Alder reaction has become one of the most widely used synthetic tools for the preparation of N-containing 6-membered heterocycles. Numerous important developments have been reported to render this reaction catalytic and enantioselective. This tutorial review highlights strategies and recent advances to achieve high efficiency and selectivity through the use of organocatalysts and transition metal complexes, allowing also the extension of this transformation substrate scope.
Aspergillus flavus is a pathogenic fungus associated with food safety issues worldwide. This study investigated the antifungal activity of citrus peel extracts prepared using food-grade solvents (hot water or ethanol). Mandarin (Citrus reticulata) peel ethanol extracts inhibited the mycelial growth of A. flavus (39.60%) more effectively than those of orange (32.31%) and lemon (13.51%) after 7 days of incubation. The growth of A. flavus could be completely inhibited by mandarin extracts at 300-400 mg mL-1, depending on the extraction solvent. Solid-phase extraction (SPE) separated the polyphenol-rich fractions, which showed up to 40% higher antifungal activity than crude extracts. Twelve polyphenols (2 phenolic acids and 10 flavonoids) were identified by HPLC-DAD, narirutin and hesperidin were the most abundant. In conclusion, citrus peels are promising bioresources of antifungal agents with potential applications in food and other industries.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Aronia melanocarpa (Michx.) Elliott (black chokeberry) skin wastes from the production of Aronia fruit juice were extracted using a batch extraction method and a novel integrated extraction‐adsorption process. Optimum conditions for batch extraction were as follows: 60 °C, 3 h, acid (0.1% v/v hydrochloric acid), biomass‐to‐solvent ratio of 1:16, and biomass‐to‐solid phase extraction resin ratio of 1:1. The integrated extraction‐adsorption process gave improved anthocyanin yields of higher quality when the process was performed for 3 h without cooling of the circulating liquid, and with a flow rate of 1.3 ml s −1 . Overall, the new method showed better anthocyanin yield and purity compared with the batch method, increasing the extraction yield by ca . 20% (5.25→6.34 mg g −1 dry weight of pomace) and increasing anthocyanin content by ca . 40% (19.9%→28.4% w/w dry weight of extract). This method also simplified the process as three steps were eliminated saving time and energy. Furthermore, the integrated extraction‐adsorption method is industrially scalable to produce large quantities of anthocyanins. In the batch method, anthocyanins present in A. melanocarpa skins were identified as cyanidin‐3‐ O ‐galactoside (38.8%), cyanidin‐3‐ O ‐arabinoside (6.4%), cyanidin‐3‐ O ‐glucoside (3.6%), cyanidin‐3‐ O ‐xyloside (0.5%), and the cyanidin aglycon (50.7%); in the continuous method, anthocyanin content was cyanidin‐3‐ O ‐galactoside (45.7%), cyanidin‐3‐ O ‐arabinoside (16%), cyanidin‐3‐ O ‐glucoside (3.6%), cyanidin‐3‐ O ‐xyloside (2.7%), and the cyanidin aglycon (32%). The integrated extraction‐adsorption method was shown to be substantially less susceptible to acid‐catalysed anthocyanin decomposition processes. All anthocyanins were derived from only one anthocyanidin parent structure (cyanidin), and only monosaccharide glycosides were identified, which is unusual when compared with other berries that typically have more anthocyanidins and/or greater glycosylation diversity.
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