Xincun Zhang,Fan Yue,Hui Li,Yan Huang,Yi Zhang,Hongmei Wen,Jide Wang
We systematically investigated the reversibility, time lapse, and oxygenation-deoxygenation properties of 15 natural α -amino acid–Co(II) complexes through UV-vis spectrophotometer, polarographic oxygen electrode, and DFT calculations, respectively, to explore the relationship between the coordinating structure and reversible oxygenation of α -amino acid–Co(II) complexes. Results revealed that the α -amino acid structure plays a key role in the reversible oxygenation properties of these complexes. The specific configuration of the α -amino acid group affects the electron of Co(II) transfer to the π ⁎ orbit of O 2 ; this phenomenon also favors the reversible formation and dissociation of Co–O 2 bond when O 2 coordinates with Co(II) complexes. Therefore, the co-coordination of amino and carboxyl groups is a determinant of Co complexes to absorb O 2 reversibly. The group adjacent to the α -amino acid unit evidently influences the dioxygen affinity and antioxidation ability of the complexes. The presence of amino (or imino) and hydroxy groups adjacent to the α -amino acid group increases the oxygenation-deoxygenation rate and the number of reversible cycles. Our findings demonstrate a new mechanism to develop reversible oxygenation complexes and to reveal the oxygenation of oxygen carriers.
Meng Shi,Dan-Yang Ying,Mya Myintzu Hlaing,Jian-Hui Ye,Luz Sanguansri,Mary Ann Augustin
Novel delivery systems for epigallocatechin gallate (EGCG) were developed using broccoli by-products and their fractions as carriers. Puree and pomace from broccoli by-products had higher adsorption capacities for EGCG than juice at 25 °C (43.20 mg g −1 , 39.47 mg g −1 and 25.22 mg g −1 dry weight for pomace, puree and juice respectively). Chemical sorption is the rate-controlling step for EGCG-broccoli interactions. Langmuir and Freundlich models well described the adsorption of EGCG onto puree and pomace. FTIR results indicated that EGCG-puree had stronger interaction than EGCG-pomace. When the same level of EGCG (∼26 mg) was added to different matrices, more EGCG (∼20%) was recovered from the in vitro digestion system of EGCG-loaded puree than from the EGCG-loaded pomace (14%) and neat EGCG (9%). The antioxidant capacity of the whole digesta was positively correlated with the EGCG levels. Broccoli by-products are promising carriers for delivering and stabilizing EGCG through gastrointestinal digestion.
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