Encapsulation of Cinnamic Acid by Cucurbit[7]uril for Enhancing Photoisomerization

Abstract

Cis- or Z-configuration is required for the plant growth-promoting activity of cinnamic acid (CA), whereas the E-form is inactive. Herein, we describe the encapsulation of E-CA by cucurbit[7]uril (CB7) and show that photoisomerization reactions can be more efficiently controlled in aqueous solutions by utilizing this supramolecular approach. Measurements of UV–visible absorption and proton NMR spectra at different pH values confirm that E-CA and its methyl ester, methyl-E-cinnamate (MC), form stronger 1:1 host–guest complexes with CB7 compared to cucurbit[8]uril (CB8) or three cyclodextrins (α-, β-, and γ-CD). Irradiation of (300 nm) UV light to an aqueous solution of the CB7-bound E isomers induces E to Z photoisomerization and the dissociation of the complex. When the same solution is irradiated by (254 nm) UV light, Z to E conformational changes of the unbound Z isomers are observed and are accompanied by restoring the host–guest complex formation.

Antimicrobial Biomaterial on Sutures, Bandages and Face Masks with Potential for Infection Control

“…Iodine is a iodophor, which is most stable in form of “smart” triiodide species [ 34 , 36 , 41 , 42 , 100 , 101 , 102 , 103 , 104 ]. TCA, its derivatives and related AV bioconstituents, especially cinnamic acid, aloin, acemannan, aloe-emodin, pyrogallol, hesperidine, aloesin, 10-O-β-d-glucopyranosyl-aloenin and rhein increased biological activities due to their synergistic mechanisms [ 36 , 39 , 41 , 42 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 98 , 99 ]. TCA and its hydroxycinnamic derivates in AV have abilities to permeate cell membranes of Gram-positive pathogens, resulting in cell membrane disruptions and changes [ 46 ].…”

“…According to Hanai et al, the Raman spectrum for cis-CA and TCA shows Raman shifts at 1632 and 1637 cm −1 related to the C=C-stretching vibration [ 59 ]. TCA is easily changed due to UV photoisomerization to cis-CA [ 58 , 59 , 107 ]. We propose the existence of a mixture between cis-CA and TCA in our title compound AV-PVP-TCA-I 2 due to shifts at 1643 and 1645 cm −1 [ 58 , 59 , 107 ].…”

“…TCA is easily changed due to UV photoisomerization to cis-CA [ 58 , 59 , 107 ]. We propose the existence of a mixture between cis-CA and TCA in our title compound AV-PVP-TCA-I 2 due to shifts at 1643 and 1645 cm −1 [ 58 , 59 , 107 ].…”

“…The UV-vis spectrum contains broad and high intensity absorptions in the regions around 200 to 230 nm and 240 to 310 nm ( Figure 6 ). These broad absorption bands are the result of overlapping AV, TCA, PVP and iodine moieties [ 22 , 23 , 41 , 42 , 58 , 59 , 60 ]. The absorption of PVP-I 2 (black curve) determines the regions related to PVP clearly in a broad band from 200 to 250 nm with a λ max at 209 nm and a shoulder at 305 nm ( Figure 6 ) [ 22 , 23 , 41 , 42 ].…”

“…Hydroxycinnamic acids are phytochemicals, which exert inhibitory action on a wide range of pathogens [ 46 , 47 , 55 , 56 ]. Trans-cinnamic acid (TCA) is a potent inhibitor of microbial proliferation [ 39 , 46 , 47 , 55 , 56 , 57 , 58 , 59 , 60 ]. TCA is abundantly available in the plant kingdom [ 46 , 47 ].…”