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Other Modes of Green Synthesis
Published in Piyal Mondal, Mihir Kumar Purkait, Green Synthesized Iron-based Nanomaterials, 2023
Piyal Mondal, Mihir Kumar Purkait
A plausible formation mechanism of porous iron oxide is schematically presented in Figure 6.2, assuming that epigallocatechin gallate (EGCG) or gallocatechin gallate (GCG) works as surfactant, which might be deprotonated at elevated temperature and pressure during the hydrothermal process. The initial octahedral aqua complex of iron (III), Fe(H2O)6, which is formed in water instantaneously decomposes into several soluble low molecular weight species (such as [Fe(OH2)(OH)]2+, [Fe(OH2)4(OH)2]+) via deprotonation of coordinated water molecule (Khaleel, 2004). The hydrolyzed iron species could form a complex with B and D ring of deprotonated EGCG (Figure 6.2) at halfway of the hydrothermal process (comparatively at low temperature and pressure) (Ryan and Hynes, 2007; El-Ayaan et al., 1998). As the other side of EGCG (A-ring side) is comparatively hydrophobic in nature, a tendency of aggregation might occur forming a structure shown in Figure 6.2. With the increase in the temperature a phase transformation of iron species [Fe(OH)2]+ might occur forming primary particles (Fe2O3) of several nanometer. These primary particles have high surface energy and aggregate quickly to minimize their surface energy (Wan et al., 2011). The EGCG or GCG molecules might be decomposed at high temperature and the decomposed products are dispersed into water leaving pore in the particles.
The Newer Chemistry of Condensed Tannins and Its Foams Application
Published in Tatjana Stevanovic, Chemistry of Lignocellulosics: Current Trends, 2018
However, different A- and B-ring couplings occurs in pine and other bark tannin species (Drovou et al., 2015, Pizzi 1983, Porter 1974, Navarrete et al. 2010, 2013, Ucar et al. 2013, Abdalla et al., 2014a,2014b, Saad et al. 2012, Vazquez et al. 2013). In this only two main patterns occur, predominantly phloroglucinol A-ring with catechol B-ring and two secondary patterns in much lower proportion of phloroglucinol A-ring with phenol B-ring (afzelechin) or of fisetinidin (resorcinol A-ring, catechol-B-ring) (Pizzi 1983, Porter 1974, Navarrete et al., 2010, 2013, Ucar et al., 2013, Abdalla et al., 2014a,2014b, Saad et al., 2012, Vazquez et al., 2013). In several procyanidin tannins such as some pine tannins and exotic African woods, catechin gallate or gallocatechin gallate does also occur as a constitutive unit of the tannin (Fig. 3).
Minireview: Recent advances in the determination of flavonoids by capillary electrophoresis
Published in Instrumentation Science & Technology, 2018
Tingni Wu, Changzhu Yu, Rong Li, Jun Li
A MEKC method was developed for determination of theanine, theobromine, theophylline, (−)-gallocatechin, caffeine, catechin, (−)-epigallocatechin, (−)-epicatechin gallate, (−)-gallocatechin gallate, vitamin C, (−)-epicatechin gallate, (−)-epicatechin, gallic acid, and theaflavin during tea fermentation. The electrophoretic conditions were 10 mM phosphate, 4 mM borate, 45 mM lauryl sodium sulfate, and 0.5% ethanol (pH 7.0), using dimensions of 25 µm × 47 cm × 38.5 cm.[43] Gott et al.[44] developed a chiral cyclodextrin-MEKC determination method for differentiation of more than twenty tea samples of different geographical origins (China, Japan, Ceylon). (−)-Epicatechin, (+)-catechin, (−)-catechin, (−)-epigallocatechin, (−)-epigallocatechin gallate, (−)-epicatechin gallate, (−)-gallocatechin gallate, (−)-gallocatechin, (+)-gallocatechin, caffeine, and theobromine were determined. Sun et al. determined catechin, naringenin, kaempferol, apigenin, myricetin, and quercetin in 10 wines using 40 mM borate, 40 mM lauryl sodium sulfate, 20% propan-1-ol (pH 9.0), with dimensions of 75 µm × 60 cm × 52 cm.[45] MEKC was a powerful tool for separating flavonoids. Additional applications of MEKC for the determination of flavonoids are listed in Table 2.