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Combined experimental and computational investigation of the absorption spectra of E- and Z-cinnamic acids in solution: The peculiarity of Z-cinnamics

Paper ID Volume ID Publish Year Pages File Format Full-Text
29698 44431 2015 8 PDF Available
Title
Combined experimental and computational investigation of the absorption spectra of E- and Z-cinnamic acids in solution: The peculiarity of Z-cinnamics
Abstract

•UV-abs spectra show the different solvent E- and Z-cinnamics interactions.•Quite different absorption spectra were obtained in water.•The interaction is analyzed by high-level quantum mechanical computations.•The non-planar, largely distorted Z-structure is stabilized by three water molecules.•A basis for the study of their functional and biotechnological roles is provided.

Cinnamic acids are present in all kinds of plant tissues and hence in herbs and derived medicines, cosmetics and foods. The interest in their role in plants and their therapeutic applications has grown exponentially. Because of their molecular structure they can exist in E- and Z-forms, which are both found in plants. However, since only the E-forms are commercially available, very few in vitro and in vivo studies of the Z-form have been reported. In this work the physico-chemical properties of Z-cinnamic acids in solution have been examined by means of UV-absorption spectroscopy and high-level quantum mechanical computations. For each isomer similar absorption spectra were obtained in methanol and acetonitrile. However, distinct trends were found for Z- and E forms of cinnamic acids in water, where a higher hypsochromic shift of the Z-isomer relative to the E-form was observed. In general the wavelength of maximal absorption of the Z-form is dramatically blue shifted (−30 to −40 nm) to λ < 280 nm, while a slightly blue shift of the absorption maxima for the corresponding E-form (+3 to −4 nm) was observed. This difference is associated with the non-planar, largely distorted, Z-structure and to the almost complete flat structure of the E-form. The results provide a basis for the study of functional and biotechnological roles of cinnamic acids and for the analysis of samples containing mixture of both geometric isomers.

Graphical abstractNon-planar, largely distorted, Z-structure specially stabilized by interaction with a chain of water molecules accounts for the hypsochromic shift in aqueous media. High-level quantum mechanical computations describes this effect too (figure: Z-sinapinic acid in water (red line; carboxylate anionic form), in methanol (black line; neutral form).Figure optionsDownload full-size imageDownload as PowerPoint slide

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Combined experimental and computational investigation of the absorption spectra of E- and Z-cinnamic acids in solution: The peculiarity of Z-cinnamics
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology B: Biology - Volume 148, July 2015, Pages 128–135
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us