Free Phenolic Groups Research Articles

Catechol- and Phenolic Hydroxyl-Functionalized Partially Bio-Based (Co)poly(ether sulfone)s with Multifarious Applicability

A largely bio-based new bisphenol, namely, 4,4′-((3,4-dimethoxyphenyl)methylene)-bis(2-methoxyphenol) (DMBM) was synthesized by the reaction of veratraldehyde with guaiacol. DMBM and varying compositions of DMBM and bisphenol A were polycondensed with bis(4-fluorophenyl) sulfone to afford reasonably high molecular weight film-forming (co)poly(ether sulfone)s possessing built-in methoxyl groups. T10 and Tg values of (co)poly(ether sulfone)s were in the range 382–478 °C and 171–187 °C, respectively indicating their good thermal stability and the values decreased with increase in mol % incorporation of DMBM. The methoxyl groups present in (co)poly (ether sulfone)s were quantitatively de-blocked resulting in the formation of corresponding polymers possessing pendant catechol moieties and free phenolic hydroxyl groups. By virtue of the presence of these functional moieties, (co)poly(ether sulfone)s are amenable for post-polymerization modifications, and exhibited properties such as antimicrobial (23 mm against Staphylococcus aureus and 18 mm against Escherichia coli)), antioxidant (72 % scavenger of free radicals), adhesive (2.24 MPa lap shear strength) and usefulness as redox-active agent in zinc-ion batteries. These data underscore the promise of DMBM as a versatile monomer of wider utility for the synthesis of functional (co)poly(ether sulfone)s capable of expanding their applicability beyond the conventional ones.

Synthesis, bioactivity, and molecular docking of pyrazole bearing Schiff-bases as prospective dual alpha-amylase and alpha-glucosidase inhibitors with antioxidant activity

A series of pyrazole-Schiff base derivatives, 3a-i, were synthesized by reacting arylamines 2a-i with pyrazole aldehyde 1, utilizing two catalysts: ammonium chloride (catalystA) or acetic acid (catalystB). The compounds were analyzed using spectroscopic methods, including 1H and 13C NMR, along with high-resolution mass spectrometry. Their antidiabetic and antioxidant activities were assessed through various in vitro assays, encompassing evaluation of inhibitory effects on α-glucosidase, α-amylase enzymes and determination of reducing power, free radical scavenging activity. The most promising in vitro antidiabetic results were also observed with analogs 3c (α-amylase IC50 = 19.57 ± 0.07 µM, α-glucosidase IC50 = 17.13 ± 0.28 µM) and 3h (α-amylase IC50 = 22.50 ± 0.06 µM, α-glucosidase IC50 = 20.75 ± 0.17 µM). Both products 3c and 3h revealed activity near to the standard acarbose (IC50 (α-amylase) =16.28 ± 0.24 µM, IC50 (α-glucosidase) =13.19 ± 0.26 µM). Among all compounds, 3c and 3h exhibited the highest transition metal reducing activity at levels of 75.27 ± 1.99 and 78.42 ± 0.58 µM Trolox equivalents (TE), respectively, along with the most significant free radical scavenging effects at levels of 73.79 ± 0.11 and 72.98 ± 0.33 µM TE, respectively. The antioxidant results of the current set of pyrazole-Schiff base derivatives 3a–i indicated their potential benefits as free radical scavenging and metal-reducing agents, thus proving their antioxidant capability. Their higher antidiabetic and antioxidant activities compared to other compounds might be explained by the presence of a free phenolic hydroxy group in 3c and a benzothiazole motif in 3h. These findings also lend support to the multifaceted biological functions associated with their antidiabetic activity, including their antioxidant activity. In silico molecular docking studies confirm the antihyperglycemic impact, elucidating the nature of interactions between 3c and 3h and HPA/HLAG catalytic sites.

Molecular Docking Studies of Ortho-Substituted Phenols to Tyrosinase Helps Discern If a Molecule Can Be an Enzyme Substrate.

Phenolic compounds with a position ortho to the free phenolic hydroxyl group occupied can be tyrosinase substrates. However, ortho-substituted compounds are usually described as inhibitors. The mechanism of action of tyrosinase on monophenols is complex, and if they are ortho-substituted, it is more complicated. It can be shown that many of these molecules can become substrates of the enzyme in the presence of catalytic o-diphenol, MBTH, or in the presence of hydrogen peroxide. Docking studies can help discern whether a molecule can behave as a substrate or inhibitor of the enzyme. Specifically, phenols such as thymol, carvacrol, guaiacol, eugenol, isoeugenol, and ferulic acid are substrates of tyrosinase, and docking simulations to the active center of the enzyme predict this since the distance of the peroxide oxygen from the oxy-tyrosinase form to the ortho position of the phenolic hydroxyl is adequate for the electrophilic attack reaction that gives rise to hydroxylation occurring.

Cyclic diarylheptanoids from Myrica javanica: isolation, transformation, and bioactivity evaluation

Three cyclic diarylheptanoids, myricanol (1), myricanone (2), and porson (3), were isolated from Myrica javanica (Myricaceae). As a major component, myricanol (1) was obtained from dry powdered bark and twigs (up to 1.6%). Transformation of myricanol (1) afforded 5-prenylmyricanol (4) and 5-benzylmyricanol (5) in 84.5% and 65% yields, respectively. The bioactivities of the isolated cyclic diarylheptanoids and their derivatives were investigated to determine their cytotoxicity and DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging activities. The cytotoxicity assay against murine leukaemia P-388 cells demonstrated that compounds 4 and 5 showed an almost two-fold increase in the activity of their parent molecule (1), with an IC50 value of 12 µM. Furthermore, the free radical scavenging assay showed that myricanol (1) had the highest radical scavenging activity, revealing the importance of the free phenolic group (IC50 39.3 µM).

Preparation of high antioxidant nanolignin and its application in cosmetics

Lignin, as a natural polyphenol, displays anti-oxidant activity by trapping and binding free radicals through its free phenolic hydroxyl groups. However, the most accessible form, industrial lignins, generally has low phenolic hydroxyl content, which severely limits their application value and scenarios. Herein, we showed that potassium-glycerate deep eutectic solvent (PG-DES) treatment can be combined with laccase oxidation to afford prepared high antioxidant lignin nanoparticles (HA-LNPs) with notably improved anti-oxidant activities benefiting from both the enhanced phenolic hydroxyl content 170.8 % and reduced average particle size (59.0 nm). At concentrations as low as 60 μg/mL, HA-LNPs showed favorable effects in promoting collagen formation. When HA-LNPs were used as an active ingredient in the anti-aging mask formulation, the reactive oxygen species (ROS) scavenging activity of mask samples containing 0.4 % HA-LNPs reached 37.2 %. The data suggest great promise of HA-LNPs as a natural antioxidant for formulating in anti-aging skin care products.

Facile synthesis of multifunctional magnetic porous organic polymers with high catalytic performance and dye adsorption capacity

Multifunctional magnetic porous organic polymers (MOPs) rich in sulfide and free phenolic hydroxyl groups were synthesized. The MOPs exhibit a large surface area and can interact strongly with metal ions and cationic dyes, including methylene blue.

Mechanism insights into enol ether intermediate formation during β-O-4-type lignin pyrolysis

Enol ether (EE) is considered to be one of the important intermediates in lignin pyrolysis, but its formation process is still unclear. In this study, the generation of EE structure from the pyrolysis of β-O-4 linkages under vairous structural environments was studied systematically with simplified lignin models, covering phenyl dimers, phenolic dimers, and phenolic polymers, and its formation mechanism and inducing factors were summarily proposed. Results showed that EE intermediates were difficult to generate in β-O-4-type phenyl structures, but the activation of α/β-substituted side chains promoted the EE formation, confirming that elimination reactions in pyrolysis was the main driving force for EE generation. Free phenolic hydroxyl groups and corresponding phenoxy radicals were very effective EE formation activators, as they can both induce the production of quinone intermediates, which were easily converted to EE structure. These conclusions provided a new connotation for the pyrolysis of lignin β-aryl ether linkages.

Controlling the reactivity of hydrophilic bark extractives as biopolyols in urethane-formation reactions using various catalysts

The composition, functionality, and reactivity of black alder (Alnus glutinosa) bark extractives as a biopolyol with polymeric diphenyl methane diisocyanate (PMDI) have been studied using a variety of methods, including HPLC, GPC, GC, wet chemistry, and isothermal calorimetry. The Black alder (BA) bark extractives were identified as a prospective polyol consisting mainly of the oregonin-xyloside form of diarylheptanoid, which contains OH groups that are almost equally represented by phenolic and aliphatic origins. To identify catalysts that effectively increase the reactivity of low-active phenolic OH groups in urethane formation reactions, the kinetics of extractives and model compounds' interaction with PMDI catalyzed with tin organic, dibutyl tin dilaurate (DBTDL) and tertiary amine, 1,4-diazabicyclo[2.2.2]octane (DABCO) catalyst in dimethylsulfoxide (DMSO) solution were studied. The results showed that DABCO resulted in a fourfold higher reactivity of phenolic groups with PMDI compared to DBTDL catalyzed reactions. Furthermore, the reactivity of phenolic groups with PMDI catalyzed by DABCO was almost twofold greater than that of aliphatic OH catalyzed by DBTDL. The second-order constants of 31.9 × 10−4 mol·L−1·s−1 and 53.7 × 10−4 mol·L−1·s−1 were determined for the interaction of extractives with PMDI in the presence of DBTDL and DABCO, respectively. The disappearance of the radical scavenging effect of phenolic compounds in extractives derived PU elastomers obtained with DABCO catalyst indicates complete reactions of phenolic groups with isocyanate, while these groups remain partly free in the case of DBTDL catalysis. It is assumed that a combination of DBTDL and DABCO catalysts will be necessary to achieve high crosslinking while leaving a small portion of free phenolic groups in the bio-based PU network, thus obtaining material with high mechanical properties and thermal oxidative stability.

Collagen/poly(acrylic acid)/MXene hydrogels with tissue‐adhesive, biosensing, and photothermal antibacterial properties

AbstractThe application of collagen‐based hydrogel is severely restricted due to its poor mechanical strength and functional singleness. In this paper, two‐dimensional MXene nanosheets were introduced into collagen/acrylic acid (AA) system, which was polymerized in situ to produce versatile hydrogel (GCol‐MX‐PAA). The tensile stress and compressive stress values of the resultant hydrogel at the MXene concentration of 5 mg/mL reached 211.5 kPa and 7.8 MPa, respectively, which were approximately 4.0 and 1.4 times higher than those of GCol‐PAA. The bonding strength of the hydrogel reached 30.7 kPa in the porcine skin‐adhesive model owing to the large number of free phenolic hydroxyl groups on GCol. Furthermore, GCol‐MX‐PAA could be applied to monitor large and subtle activities of human body due to the excellent electrical conductivity of MXene. Thanks to the outstanding photothermal conversion performance of MXene, the hydrogel could kill E. coli and S. aureus effectively under NIR irradiation. In addition, in vitro cytotoxicity test performed on L929 fibroblasts demonstrated the desirable biocompatibility of GCol‐MX‐PAA. The design strategy in this work gives guidance for the development of multifunctional collagen‐based hydrogel in a wide range of applications.Highlights Versatile hydrogel constructed from GA‐modified collagen, PAA, and MXene. The composite hydrogel displays improved mechanical properties. This hydrogel possesses superior tissue adhesion and strain sensitivity. This hydrogel shows desired photothermal antibacterial property and biocompatibility.

PEPPSI-Type Pd(II)—NHC Complexes on the Base of p-tert-Butylthiacalix[4]arene: Synthesis and Catalytic Activities

The creation of effective catalytic systems for cross-coupling reactions, reduction, etc., capable of working in water-organic or pure aqueous media is in great demand. The article presents the synthesis of NHC-palladium complexes of the PEPPSI type based on monoimidazolium derivatives of thiacalix[4]arene. The structure of the imidazolium precursors, obtained in 81–88% yields and the complexes themselves, obtained in 40–50% yields, is established using modern methods, including X-ray structural analysis and high-resolution mass spectrometry. It is shown that the obtained complex with bulk substituents near the palladium atom is not inferior to the well-known PEPPSI-type Organ’s catalyst in the catalysis of Suzuki-Miyaura coupling and is four times superior to the latter in the p-nitrophenol reduction reaction. Given the presence of free phenolic hydroxyl groups in the macrocycle, the obtained complexes are of interest for further post-modification or for immobilization on a carrier.

Demethyleneberberine alleviated the inflammatory response by targeting MD-2 to inhibit the TLR4 signaling.

The colitis induced by trinitrobenzenesulfonic acid (TNBS) is a chronic and systemic inflammatory disease that leads to intestinal barrier dysfunction and autoimmunedisorders. However, the existing treatments of colitis are associated with poor outcomes, and the current strategies remain deep and long-time remission and the prevention of complications. Recently, demethyleneberberine (DMB) has been reported to be a potential candidate for the treatment of inflammatory response that relied on multiple pharmacological activities, including anti-oxidation and antiinflammation. However, the target and potential mechanism of DMB in inflammatory response have not been fully elucidated. This study employed a TNBS-induced colitis model and acute sepsis mice to screen and identify the potential targets and molecular mechanisms of DMB in vitro and in vivo. The purity and structure of DMB were quantitatively analyzed by high-performance liquid chromatography (HPLC), mass spectrometry (MS), Hydrogen nuclear magnetic resonance spectroscopy (1H-NMR), and infrared spectroscopy (IR), respectively. The rats were induced by a rubber hose inserted approximately 8 cm through their anus to be injected with TNBS. Acute sepsis was induced by injection with LPS via the tail vein for 60 h. These animals with inflammation were orally administrated with DMB, berberine (BBR), or curcumin (Curc), respectively. The eukaryotic and prokaryotic expression system of myeloid differentiation protein-2 (MD-2) and its mutants were used to evaluate the target of DMB in inflammatory response. DMB had two free phenolic hydroxyl groups, and the purity exceeded 99% in HPLC. DMB alleviated colitis and suppressed the activation of TLR4 signaling in TNBS-induced colitis rats and LPS-induced RAW264.7 cells. DMB significantly blocked TLR4 signaling in both an MyD88-dependent and an MyD88-independent manner by embedding into the hydrophobic pocket of the MD-2 protein with non-covalent bonding to phenylalanine at position 76 in a pi-pi T-shaped interaction. DMB rescued mice from sepsis shock induced by LPS through targeting the TLR4-MD-2 complex. Taken together, DMB is a promising inhibitor of the MD-2 protein to suppress the hyperactivated TLR4 signaling in inflammatory response.

Stabilized Lignin Nanoparticles for Versatile Hybrid and Functional Nanomaterials.

Spherical lignin nanoparticles are emerging biobased nanomaterials, but instability and dissolution in organic solvents and aqueous alkali restrict their applicability. Here, we report the synthesis of hydroxymethylated lignin nanoparticles and their hydrothermal curing to stabilize the particles by internal cross-linking reactions. These colloidally stable particles contain a high biobased content of 97% with a tunable particle size distribution and structural stability in aqueous media (pH 3 to 12) and organic solvents such as acetone, ethanol, dimethylformamide, and tetrahydrofuran. We demonstrate that the free phenolic hydroxyl groups that are preserved in the cured particles function as efficient reducing sites for silver ions, giving rise to hybrid lignin-silver nanoparticles that can be used for quick and facile sensing of hydrogen peroxide. The stabilized lignin particles can also be directly modified using base-catalyzed reactions such as the ring-opening of cationic epoxides that render the particles with pH-dependent agglomeration and redispersion properties. Combining scalable synthesis, solvent stability, and reusability, this new class of lignin nanoparticles shows potential for its use in circular biobased nanomaterials.

Multifunctional lignin-poly (lactic acid) biocomposites for packaging applications.

Lignin is the most abundant aromatic biopolymer with many promising features but also shortcomings as a filler in polymer blends. The main objective of this work was to improve the processability and compatibility of lignin with poly (lactic acid) (PLA) through etherification of lignin. Commercial kraft lignin (KL) and oxypropylated kraft lignin (OPKL) were blended with PLA at different weight percentages (1, 5, 10, 20, and 40%) followed by injection molding. Low lignin contents between 1 and 10% generally had a favorable impact on mechanical strength and moduli as well as functional properties of the PLA-based composites. Unmodified lignin with free phenolic hydroxyl groups rendered the composites with antioxidant activity, as measured by radical scavenging and lipid peroxidation tests. Incorporating 5–10% of KL or OPKL improved the thermal stability of the composites within the 300–350°C region. DSC analysis showed that the glass transition temperature values were systematically decreased upon addition of KL and OPKL into PLA polymer. However, low lignin contents of 1 and 5% decreased the cold crystallization temperature of PLA. The composites of KL and OPKL with PLA exhibited good stabilities in the migration test, with values of 17 mg kg−1 and 23 mg kg−1 even at higher lignin content 40%, i.e., well below the limit defined in a European standard (60 mg kg−1). These results suggest oxypropylated lignin as a functional filler in PLA for safe and functional food packaging and antioxidant applications.

Synthesis and characterization of novel potentially biodegradable aromatic polyesters consisting of divanillic acids with free phenolic hydroxyl groups

Potentially biodegradable bio-based polyesters (P6DVAs) were synthesized from 1,6-hexanediol and divanillic acid (DVA) with free hydroxyl groups. Four DVA-based monomers with different silyl protecting groups were synthesized. Each silyl protected monomer was polymerized with 1,6-hexanediol by bulk transesterification using tetraisopropyl orthotitanate as a catalyst at 140–180 °C (first step), and 200–220 °C under vacuum (second step). Triisopropylsilyl (TIPS) -protected DVA polymerization proceeded without the elimination of TIPS groups, and a TIPS-protected DVA polyester was obtained. After deprotection of the TIPS groups, a P6DVA (weight-average molecular weight; Mw = 3.9 × 104, polydispersity; 1.4) was obtained. The P6DVA was an amorphous polymer with a glass transition point of 108 °C. Environmental degradability was assessed by a biochemical oxygen demand (BOD) test using a mixture of fresh water and soil collected from a pond. The BOD degradability of the P6DVA was 8% over 40 days, indicating its potential as a degradable polymer.

A prodrug of 3-(ferrocenylaminocarbonyloxymethyl)phenol activated by reactive oxygen species in cancer cells

Hybrid drugs containing ferrocene and phenol residues, whose π systems are not conjugated with each other, exhibit potent anticancer activity as previously reported. Few important open questions are remaining before practical application of these drugs becomes possible. First, their mode of action is not fully clarified. Second, it is not known whether these drugs exhibit cancer cell specificity. Third, due to the presence of the phenol moiety, these drugs can potentially be oxidatively deactivated and eliminated via phase II metabolism when applied in vivo. In this paper we report on synthesis of three prodrugs of aminoferrocene-phenol hybrids, where the phenolic OH group is masked as a boronic acid pinacol ester. We confirmed that the best prodrug in this small series p5 is activated in human ovarian cancer A2780 and Burkitt's lypmphoma BL-2 cells, but remains inactive in representative normal SBLF9 cells. Since p5 does not contain free phenolic OH groups, it will not be metabolized as phenols in vivo. We confirmed that the mechanism of anticancer activity of aminoferrocene-phenol prodrug p5 relies on generation of reactive oxygen species in cells.

Catalyst‐free reprocessable crosslinked biobased polybenzoxazine‐polyurethane based on dynamic carbamate chemistry

AbstractThe introduction of dynamic covalent chemistry into the field of polymer chemistry has resulted in a new class of network polymer materials named covalent adaptable networks (CANs). These new materials have effectively bridged two antagonistic materials, that is, conventional thermoplastic and thermoset polymers together, thanks to these dynamic exchangeable covalent bonds, making them recyclable. In this work, we report a catalyst‐free reprocessable polybenzoxazine‐polyurethane thermosetting system with activation of carbamate dynamic bond exchange. The curing characteristics and properties of this biobased polybenzoxazine‐polyurethane network have been determined by Fourier transform infra‐red (FTIR), differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMA). Moreover, the tests of the recyclability of the material were successfully achieved under mild reprocess conditions (130°C, 10 min) thanks to the formation of abundant free phenolic hydroxyl groups. This work provides a promising potential for industrial applications as a new recyclable and reprocessable thermosetting polybenzoxazine material.

Synthesis, Characterization and Antioxidant Activity of Two Novel Oxovanadium (IV) Curcuminoids

The reaction of bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (curcumin) and two novel ligands of bis[4- tetrabenzylglucose-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (bis(tetrabenzylglucose)curcumin) (BTBGC) and bis[4-tetraacetylglucose- 3-methoxyphenyl]-1,6-heptadiene-3,5-dione (bis(tetraacetylglucose)curcumin) (BTAGC) with vanadium in methanol, in a 2:1 molar ratio, which yield the complexes of ML2 where M is [VO]2+, have been synthesized and characterized by FT-IR, mass spectrometry, 1H NMR spectroscopy and elemental analysis. These novel compounds were also examined for their antioxidant activity (using Trolox Equivalent Antioxidant Capacity (TEAC) antioxidant assay as a measure of their overall ability to scavenge free radicals compared to antioxidant standards such as Trolox); compounds with free hydroxyl groups were more active than those one whose locking such and also the metal complexes showed more activity than Trolox. The antioxidant capacity was decreased in BTBGC, BTAGC and their complexes compared to curcumin and its oxovanadium (IV) complex, corroborating the importance of curcumin’s free phenolic OH groups for scavenging oxidants potential. Also, the presence of the methoxy group increases the activity.

Low-Dimensional Architectures in Isomeric cis-PtCl2{Ph2PCH2N(Ar)CH2PPh2} Complexes Using Regioselective-N(Aryl)-Group Manipulation.

The solid-state behaviour of two series of isomeric, phenol-substituted, aminomethylphosphines, as the free ligands and bound to PtII, have been extensively studied using single crystal X-ray crystallography. In the first library, isomeric diphosphines of the type Ph2PCH2N(Ar)CH2PPh2 [1a–e; Ar = C6H3(Me)(OH)] and, in the second library, amide-functionalised, isomeric ligands Ph2PCH2N{CH2C(O)NH(Ar)}CH2PPh2 [2a–e; Ar = C6H3(Me)(OH)], were synthesised by reaction of Ph2PCH2OH and the appropriate amine in CH3OH, and isolated as colourless solids or oils in good yield. The non-methyl, substituted diphosphines Ph2PCH2N{CH2C(O)NH(Ar)}CH2PPh2 [2f, Ar = 3-C6H4(OH); 2g, Ar = 4-C6H4(OH)] and Ph2PCH2N(Ar)CH2PPh2 [3, Ar = 3-C6H4(OH)] were also prepared for comparative purposes. Reactions of 1a–e, 2a–g, or 3 with PtCl2(η4-cod) afforded the corresponding square-planar complexes 4a–e, 5a–g, and 6 in good to high isolated yields. All new compounds were characterised using a range of spectroscopic (1H, 31P{1H}, FT–IR) and analytical techniques. Single crystal X-ray structures have been determined for 1a, 1b∙CH3OH, 2f∙CH3OH, 2g, 3, 4b∙(CH3)2SO, 4c∙CHCl3, 4d∙½Et2O, 4e∙½CHCl3∙½CH3OH, 5a∙½Et2O, 5b, 5c∙¼H2O, 5d∙Et2O, and 6∙(CH3)2SO. The free phenolic group in 1b∙CH3OH, 2f∙CH3OH, 2g, 4b∙(CH3)2SO, 5a∙½Et2O, 5c∙¼H2O, and 6∙(CH3)2SO exhibits various intra- or intermolecular O–H∙∙∙X (X = O, N, P, Cl) hydrogen contacts leading to different packing arrangements.

The ethoxycarbonyl group as both activating and protective group in N-acyl-Pictet-Spengler reactions using methoxystyrenes. A short approach to racemic 1-benzyltetrahydroisoquinoline alkaloids.

We present a systematic investigation on an improved variant of the N-acyl-Pictet–Spengler condensation for the synthesis of 1-benzyltetrahydroisoquinolines, based on our recently published synthesis of N-methylcoclaurine, exemplified by the total syntheses of 10 alkaloids in racemic form. Major advantages are a) using ω-methoxystyrenes as convenient alternatives to arylacetaldehydes, and b) using the ethoxycarbonyl residue for both activating the arylethylamine precursors for the cyclization reaction, and, as a significant extension, also as protective group for phenolic residues. After ring closure, the ethoxycarbonyl-protected phenols are deprotected simultaneously with the further processing of the carbamate group, either following route A (lithium alanate reduction) to give N-methylated phenolic products, or following route B (treatment with excess methyllithium) to give the corresponding alkaloids with free N–H function. This dual use of the ethoxycarbonyl group shortens the synthetic routes to hydroxylated 1-benzyltetrahydroisoquinolines significantly. Not surprisingly, these ten alkaloids did not show noteworthy effects on TPC2 cation channels and the tumor cell line VCR-R CEM, and did not exhibit P-glycoprotein blocking activity. But due to their free phenolic groups they can serve as valuable intermediates for novel derivatives addressing all of these targets, based on previous evidence for structure–activity relationships in this chemotype.

Improving antioxidant ability of functional emulsifiers by conjugating polyphenols to sodium caseinate

Sodium caseinate (NaCas), a commonly used food emulsifier, is prone to oxidation, resulting in decreased emulsion quality and stability. This study aims to understand the effect of polyphenol structures on protein's antioxidant activity and develop protein-polyphenol complexes (PPCs) with better physical and oxidation stabilities. NaCas' antioxidant abilities with or without polyphenols were examined by DPPH, FRAP, and β-carotene blenching test. The binding mechanism between protein and polyphenols was also investigated using multispectral technology and molecular docking. The results show that the addition of kaempferol, phloretin, catechin, resveratrol, and hydroxytyrosol improved NaCas' free radicals scavenging ability, reducing power and lipid protection effect. In contrast, adding apigenin, coumarin, p-hydroxybenzoic acid, and p-coumaric acid caused unsatisfactory results. The number and location of free phenolic hydroxyl groups, the binding affinity between protein and polyphenol, and protein conformation are the criteria dictating the antioxidant properties of PPCs. Finally, four novel antioxidant emulsifiers were obtained, including NaCas-catechin, NaCas-resveratrol, NaCas-phloretin, and NaCas-hydroxytyrosol complexes. Our results explored the potential application of nano-delivering functional oil using PPCs as antioxidant emulsifiers.