Characteristics of the Polyphenolic Profile and Antioxidant Activity of Cone Extracts from Conifers Determined Using Electrochemical and Spectrophotometric Methods

The aim of the study was to analyze the polyphenolic profile of cone extracts of Douglas fir, Scots pine and Korean fir, and to study their antioxidant activity. The mechanism of electro-oxidation of polyphenols (such as procyanidins and catechins) from cone extracts was investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), as well as spectrophotometric methods—ABTS (2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate)), DPPH (2,2-diphenyl-1-picrylhydrazyl), FRAP (Ferric Reducing Antioxidant Power ) and CUPRAC (CUPric Reducing Antioxidant Capacity). The scientific novelty of the research is the comprehensive analysis of cone extracts in terms of antioxidant properties. Due to the high polyphenol content, the extracts showed significant ability to reduce oxidative reactions, as well as the ability to scavenge free radicals and transition metal ions. Douglas fir, Scots pine and Korean fir cone extracts can potentially be used as natural stabilizers, preservatives and antimicrobial substances in the food industry and in medications

Environmentally Friendly Polymer Compositions with Natural Amber Acid

Few scientific reports have suggested the possibility of using natural phenolic acids as functional substances, such as stabilizers for polymeric materials. The replacement of commercial stabilizers in the polymer industry can be beneficial to human health and the environment. The aim of this study was to obtain biodegradable composition of polylactide (PLA) and polyhydroxyalkanoate (PHA) with natural amber (succinic) acid. The materials were subjected to controlled thermooxidation and solar aging. The research methodology included thermal analysis, examination of surface energy, mechanical properties and spectrophotometric analysis of the color change after aging. The samples of aliphatic polyesters containing from 1 to 2 parts by weight of succinic acid were characterized by increased resistance to oxidation (DSC analysis). Natural acid, preferably at a concentration of 1–1.5 parts by weight, acted as a stabilizer in the polymer compositions. On the other hand, materials that had amber acid above 2 parts by weight added were more susceptible to oxidation (DSC). They also showed the lowest aging coefficients (K). The addition of acid at 2.5–4 parts by weight caused a pro-oxidative effect and accelerated aging. By adding amber acid to PLA and PHA, it is possible to design their time in service and their overall lifetime

The Application of (+)-Catechin and Polydatin as Functional Additives for Biodegradable Polyesters

Plant polyphenols are a huge group of compounds with a wide spectrum of applications. Substances from this group have been used in polymer materials such as stabilizers, dyes, indicators, fungicides, and bactericides, especially in new generation packaging materials. The aim of this study is to obtain environmentally friendly materials based on the biodegradable aliphatic polyesters, polylactide (PLA) and polyhydroxyalkanoate (PHA), with plant functional additives, (+)-catechin and polydatin. These natural polyphenols (polydatin and (+)-catechin) have not been used so far in polymer materials (especially in biodegradable polyesters) as stabilizers, dyes, and indicators of aging. The application of polydatin and (+)-catechin as multifunctional additives for biodegradable polymers is a scientific novelty. This paper presents the following analyses of polyester materials: SEM microscopy, wide angle x-ray diffraction, mechanical properties, thermal analysis, surface free energy analysis, and determination of change of color after controlled UV exposure, thermal oxidation and weathering. Both PLA and PHA polyesters were characterized by higher resistance to oxidation and greater resistance to degradation under the influence of UV radiation. In addition, (+)-catechin was used simultaneously as a dye and an indicator of the aging time of polymeric materials. In contrast, polydatin did not dye polymers, but was a very good indicator of their lifetime, changing color under the influence of various external factors. Both polyphenols can be successfully used as natural additives for pro-ecological polyesters

Environmentally Friendly Polymer Compositions with Natural Amber Acid

Few scientific reports have suggested the possibility of using natural phenolic acids as functional substances, such as stabilizers for polymeric materials. The replacement of commercial stabilizers in the polymer industry can be beneficial to human health and the environment. The aim of this study was to obtain biodegradable composition of polylactide (PLA) and polyhydroxyalkanoate (PHA) with natural amber (succinic) acid. The materials were subjected to controlled thermooxidation and solar aging. The research methodology included thermal analysis, examination of surface energy, mechanical properties and spectrophotometric analysis of the color change after aging. The samples of aliphatic polyesters containing from 1 to 2 parts by weight of succinic acid were characterized by increased resistance to oxidation (DSC analysis). Natural acid, preferably at a concentration of 1–1.5 parts by weight, acted as a stabilizer in the polymer compositions. On the other hand, materials that had amber acid above 2 parts by weight added were more susceptible to oxidation (DSC). They also showed the lowest aging coefficients (K). The addition of acid at 2.5–4 parts by weight caused a pro-oxidative effect and accelerated aging. By adding amber acid to PLA and PHA, it is possible to design their time in service and their overall lifetime

Impregnacja poli(kwasu mlekowego) (PLA) polifenolami pochodzenia roślinnego

The aim of the research was the solvent-based impregnation of poly(lactic acid) (PLA) with polyphenols of plant origin. The process is a scientific novelty because quercetin, rutin, xanthone and green tea extract had not been previously used to stabilise PLA as a result of the solvent-based impregnation of a polymer. As part of the work, the extruded poly(lactic acid) was impregnated with ethanol solutions of polyphenols. Samples after impregnation were subjected to tests: determination of mechanical properties, differential scanning calorimetry, melt flow index and SEM microscopy. In addition, the properties of the samples, such as the Vicat softening temperature and change in colour, before and after controlled weathering as well as thermal and UV aging were investigated. On the basis of the results presented, the effectiveness of the impregnation of poly(lactic acid) with natural compounds was confirmed as a new method of stabilisation of the biodegradable polyester selected.Celem badań była rozpuszczalnikowa impregnacja poli(kwasu mlekowego) (PLA) z zastosowaniem polifenoli pochodzenia roślinnego. Proces jest nowością naukową, ponieważ kwercetyna, rutyna, ksanton i ekstrakt zielonej herbaty nie były wcześniej stosowane do stabilizacji PLA w procesie impregnacji polimeru. W ramach pracy wytłoczyny poli(kwasu mlekowego) impregnowano etanolowymi roztworami polifenoli. Próbki po impregnacji poddano badaniom: określeniu właściwości mechanicznych, różnicowej kalorymetrii skaningowej, wskaźnikowi szybkości płynięcia i mikroskopii SEM. Ponadto zbadano właściwości próbek, takie jak temperatura mięknienia Vicata i zmiana koloru, przed i po kontrolowanym starzeniu klimatycznym, termicznym i wywołanym promieniowaniem UV. Na podstawie przedstawionych wyników potwierdzono skuteczność impregnacji poli (kwasu mlekowego) związkami naturalnymi jako nową metodę stabilizacji wybranego biodegradowalnego poliestru

Effect of Impregnation of Biodegradable Polyesters with Polyphenols from <i>Cistus linnaeus</i> and <i>Juglans regia Linnaeus</i> Walnut Green Husk

The publication describes a process combining the extraction of plant material and impregnation of biodegradable polymers (polylactide (PLA) and polyhydroxyalkanoate (PHA)). As raw plant materials for making extracts, Cistus and green walnut husk were selected due to their high content of active phytochemicals, including antioxidants. The extracts used to impregnate polymers contained valuable polyphenolic compounds, as confirmed by FTIR and UV&#8211;Vis spectroscopy. After impregnation, the polymer samples showed greater thermal stability, determined by the differential scanning calorimetry (DSC) method. In addition, despite the presence of natural antibacterial and antifungal substances in the extracts, the polyester samples remained biodegradable. The manuscript also describes the effect of UV aging on the change of surface free energy and the color of polymers. UV aging has been selected for testing due to the high susceptibility of plant compounds to this degrading factor. The combination of the extraction of plant material and polymer impregnation in one process proved to be an effective and functional method, as both the obtained plant extracts and impregnated polymers showed the expected properties

The Effect of Substances of Plant Origin on the Thermal and Thermo-Oxidative Ageing of Aliphatic Polyesters (PLA, PHA)

The stabilization efficiency of flavonoids (rutin and hesperidin) in polyester (polylactide (PLA) and polyhydroxyalkaonate (PHA)) composites under oxygen at high temperature was investigated. The polymer was homogenized with three antioxidants then processed by extrusion. The effects of stabilizers on the following physicochemical properties were investigated: melt flow, Vicat softening temperature, surface energy, and color change (Cie-Lab space). The aim of this study was to improve the stability of aliphatic polyesters by extending and controlling their lifetime. Differential Scanning Calorimetry DSC and Thermogravimetric analysis DTG methods were used to confirm the stabilizing effects (the inhibition of oxidation) of flavonoids (rutin and hesperidin) on the ageing process of biodegradable polymers. The levels of migration of plant antioxidants from PLA and PHA were determined and compared to the industrial stabilizer (Chimassorb 944 UV absorber). Based on this study, a comparable-to-higher efficiency of the proposed flavonoids for the stabilization of polyesters was found when compared to the commercial stabilizers. Thus, in the future, natural plant-derived substances may replace toxic hindered amines, which are commonly used as light stabilizers (HALS&#8212;Hindered Amine Light Stabilizers) in the polymer industry

Natural Polymeric Compound Based on High Thermal Stability Catechin from Green Tea

Catechin is a plant polyphenol with valuable antioxidant and health-promoting properties. Polymerization is one way to stabilize flavonoids and may cause changes in their specific properties. The aim of this study is to obtain a polymeric complex catechin compound with high thermal stability. As a result of polymerization, a condensed and cross-linked catechin structure was obtained, which guaranteed high thermal resistance and, moreover, the phosphorus groups added in the second step of polymerization ensured that the compound obtained had thermal stability higher than natural condensed tannins. The first step of self-polymerization of (+)-catechin may be an easy way to obtain proanthocyanidins with greater antioxidant activity. The second step of the polymerization obtained a polymeric complex catechin compound that showed better thermal stability than catechin. This compound can potentially be used as a new pro-ecological thermal stabilizer

Polymeric Forms of Plant Flavonoids Obtained by Enzymatic Reactions

Naringenin is one of the flavonoids originating from citrus fruit. This polyphenol is mainly found in grapefruit, orange and lemon. The antioxidant and antimicrobial properties of flavonoids depend on their structure, including the polymeric form. The aim of this research was to achieve enzymatic polymerization of naringenin and to study the properties of poly(naringenin). The polymerization was performed by methods using two different enzymes, i.e., laccase and horseradish peroxidase (HRP). According to the literature data, naringenin had not been polymerized previously using the enzymatic polymerization method. Therefore, obtaining polymeric naringenin by reaction with enzymes is a scientific novelty. The research methodology included analysis of the structure of poly(naringenin) by NMR, GPC, FTIR and UV-Vis and its morphology by SEM, as well as analysis of its properties, i.e., thermal stability (DSC and TGA), antioxidant activity (ABTS, DPPH, FRAP and CUPRAC) and antimicrobial properties. Naringenin oligomers were obtained as a result of polymerization with two types of enzymes. The polymeric forms of naringenin were more resistant to thermo-oxidation; the final oxidation temperature To of naringenin catalyzed by laccase (poly(naringenin)-laccase) was 28.2 &deg;C higher, and poly(naringenin)-HRP 23.6 &deg;C higher than that of the basic flavonoid. Additionally, due to the higher molar mass and associated increase in OH groups in the structure, naringenin catalyzed by laccase (poly(naringenin)-laccase) showed better activity for scavenging ABTS+&bull; radicals than naringenin catalyzed by HRP (poly(naringenin)-HRP) and naringenin. In addition, poly(naringenin)-laccase at a concentration of 5 mg/mL exhibited better microbial activity against E. coli than monomeric naringenin

Novel Polymeric Biomaterial Based on Naringenin

Biomaterials prepared based on raw plant materials are becoming more and more popular due to their specific properties and environmental friendliness. Naringenin is a flavonoid naturally occurring in citrus fruit with antioxidant and pharmacological activity. Polymeric materials based on flavonoids may have favorable properties in comparison to monomeric polyphenols, such as stronger antioxidant and antimicrobial properties. One of the methods of obtaining the polymeric form of flavonoids is polymerization with a cross-linking compound. This method has already been used to obtain poly(quercetin) and poly(rutin) from a flavonol group as well as poly(catechin) from the flavan-3-ol group of flavonoids. However, to date, no polymeric forms of flavanones have been prepared in a cross-linking reaction; the aim of this study was to obtain poly(naringenin) by reaction with a cross-linking compound using glycerol diglycide ether GDE. The degree of conversion of naringenin to poly(naringenin) determined by FTIR spectroscopy was 85%. In addition, the thermal, antioxidant and antimicrobial properties of poly(naringenin) were analyzed. Poly(naringenin) was characterized by greater resistance to oxidation and better thermal stability than monomeric naringenin. Moreover, polymeric naringenin also had a better ability to scavenge ABTS and DPPH free-radicals. In contrast to monomeric form, poly(naringenin) had antimicrobial activity against Candida albicans. Polymeric biomaterial based on naringenin could potentially be used as a natural stabilizer and antimicrobial additive for polymer compositions, as well as pro-ecological materials