Green Tea Makes Polyphenol Nanoparticles with Radical‐Scavenging Activities

Abstract

lactide, tannin, tea polyphenols (TP), and many others. [5a,6] Among them, TP are of particular interest as monomers for broadening the scope of functional nanomaterials with interesting physicochemical properties and biological activities. [7] TP, also referred as catechins, represent a typical class of polyphenol mixtures directly extracted from green tea. The unique molecular structures (i.e., catechol and pyrogallol units) and biofunctions (i.e., antioxidation and metal chelation) of TP offer ideal scenarios in establishing a series of polymeric nanomaterials with virtually new possibilities for structural and functional variation. [8] For example, Li's group used Cu 2+ to mediate oxidative coupling assembly of TP molecules for the development of porous and hollow nanoparticles as controlled delivery platforms; [8a] Fei et al. reported the rapid one-pot preparation of autofluorescent TP-based core-shell nanocomposites via Ag + oxidation-inducing self-assembly process under microwave irradiation; [8b] Markova et al. employed the oxidationreduction reaction between TP and Fe 3+ to synthesize the TP-Fe nano-hybrids with significant ecotoxicological impact. [8c] Generally speaking, current approaches for the fabrication of polyphenol nanomaterials mainly involve the oxidation of TP building blocks by using foreign metal ion additives. Despite the proliferation of work via similar strategy, all those established methods have met with profound challenges yet to be resolved. Issues including additional toxicity introduced by foreign additives, as well as the spontaneous metal-catechol/pyrogallol complexation process, might hinder the formation of pure organic polyphenol nanomaterials (note that only metal-organic hybrid materials can be obtained by conventional methods). [5b] Therefore, an environmentally friendly synthetic strategy via greener processes is still highly desirable toward functional polyphenol nanoparticles (PNs) without using any foreign toxic additives.To address this issue, herein we employ theophylline, [9] another kind of biomass compound also extracted from green tea leaves, to copolymerize with TP monomers for the construction of pure organic materials in the presence of air (Scheme 1). This one-pot green method provides a facile access to functional PNs with controlled sizes and desired biofunctions. Results and Discussion Synthesis of Polyphenol NanoparticlesIt was anticipated that the TP molecules could undergo oxidation-mediated self-polymerization under alkaline conditions AntioxidantsThe constant demand for functional nanomaterials from natural biomass polymers usually requires new "green" synthetic strategies without using any foreign additives. Here, the green fabrication of a series of polyphenol nanoparticles (PNs) only from green tea extraction compounds is reported (i.e., tea polyphenols and theophylline). It is found that the nanoparticle formation process involves covalent copolymerization of monomers, as well as noncovalent self-assembly pathways. Additionally, the re...

Advances and Impact of Antioxidant Hydrogel in Chronic Wound Healing

“…Antioxidants have been shown to be effective against excessive ROS. Among them, polyphenols which are mainly found in plant‐derived foods have been extensively studied because of their excellent antioxidant properties . Plant polyphenols are a kind of secondary metabolites with polyphenol structure widely existing in plants.…”

“…At present, antioxidant hydrogels mainly include hydrogels loaded with antioxidants and self‐antioxidant hydrogels. The loaded antioxidants can be divided into natural antioxidants (such as natural polyphenols or red jujube extract), and modified antioxidants (such as modified polyphenols) . Most of self‐antioxidant hydrogel matrixes are modified polyphenols.…”

<p>The Influence of Nanoparticle Properties on Oral Bioavailability of Drugs</p>

“…of PTX in the complex nanoparticles, which was helpful to improve bioavailability. 75 In addition, TA has been verified to exhibit high biological activities, 76,77 such as inhibited effect of P-gp. It is all known that P-gp-mediated efflux is one of the major absorptive barriers in vivo.…”

Antioxidant Polymers via the Kabachnik‐Fields Reaction to Control Cellular Oxidative Stress

“…Examples of external antioxidants include vitamins (A, C, and E), catechins, and tea polyphenols. [ 4–7 ] However, these small molecular antioxidants have little therapeutic effect in clinical trials. This is mainly attributed to the natural features of the small molecules, that is, high instability, poor water‐solubility, and fast clearance rate from the body.…”