| 1. |
- Gulshan Kazi, Zubaida, et al.
(författare)
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Glycoside hydrolases for extraction and modification of polyphenolic antioxidants
- 2013
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Ingår i: Advances in enzyme biotechnology. - New Delhi : Springer India. - 9788132210931 - 9788132210948 ; , s. 9-21
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Bokkapitel (refereegranskat)abstract
- Antioxidants are important molecules that are widely used by humans, both as dietary supplements and as additives to different types of products. In this chapter, we review how flavonoids, a class of polyphenolic antioxidants that are often found in glycosylated forms in many natural resources, can be extracted and modified using glycoside hydrolases (GHs). Glycosylation is a fundamental enzymatic process in nature, affecting function of many types of molecules (glycans, proteins, lipids as well as other organic molecules such as the flavonoids). Possibilities to control glycosylation thus mean possibilities to control or modify the function of the molecule. For the flavonoids, glycosylation affect both the antioxidative power and solubility. In this chapter we overview results on in vitro deglycosylation and glycosylation of flavonoids by selected GHs. For optimal enzymatic performance, desired features include a correct specificity for the target, combined with high stability. Poor specificity towards a specific substituent is thus a major drawback for enzymes in particular applications. Efforts to develop the enzymes as conversion tools are reviewed.
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| 2. |
- Nordberg, Gunnar F., et al.
(författare)
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Interactions and mixtures in metal toxicology
- 2021
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Ingår i: Handbook on the Toxicology of Metals: Volume I: General Considerations. - London : Elsevier. - 9780128232927 ; , s. 319-347
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Human exposures to metals, metalloids, and their compounds frequently occur as mixtures; therefore, the joint action of these elements should be considered with respect to mechanisms of action and risk assessment. When present at the same time in a system, multiple chemicals can influence toxicity. The joint action of metallic elements may produce additive, synergistic/potentiating, or antagonistic effects manifesting in an overall toxicity, differing from that of individual components of the mixture. Dose-response relationships may be further influenced by constitutive factors such as age, sex, and the expression of specific proteins. Mechanisms of importance for the development of potentiated or antagonistic toxicity include the expression of metal-binding proteins (metallothioneins or lead-binding proteins) and interference with metal transporters such as Divalent Metal Transporter (DMT-1) and the ZIP family of zinc transporting proteins. Compared to men, women of childbearing age generally absorb more Cd from the gastrointestinal tract because they typically have lower iron stores than men. Another example of synergism that occurs in humans is when inorganic arsenic and cadmium together induce kidney toxicity. In many cases, however, direct primary data on the joint action of toxic or essential elements are lacking, and so innovative derivative methods such as the binary weight-of-evidence method have been used to predict potential interactions among groups of metals and metalloids. Using this method, broad recommendations can be made for assessing the potential impact of interactions on the public health assessment of environmental mixtures. At present, there is much to be learned about the joint action of both toxic and essential elements, and this is clearly a critical area of research.
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