Effect of Degradation on the Physicochemical and Mechanical Properties of Extruded Films of Poly(lactic acid) and Chitosan.

This study addresses the fabrication of extruded films using poly(lactic acid) (PLA) and chitosan, with and without maleic anhydride as a compatibilizing agent, for potential applications in disposable food packaging. These films underwent controlled conditions of UV irradiation, water condensation, and temperature variations in an accelerated weathering chamber. The investigation analyzed the effect of different exposure periods on the structural, morphological, mechanical, and thermal properties of the films. It was observed that PLA films exhibited a lower susceptibility to degradation compared to those containing chitosan. Specifically, the pure PLA film showed an increase in elastic modulus and strength during the initial 144 h of exposure, associated with cross-linking induced by UV radiation. On the other hand, film Q2 composed of PLA, chitosan, and maleic anhydride and Q1 without maleic anhydride experienced a tensile strength loss of over 50% after 244 h of exposure. The Q2 film exhibited greater homogeneity, leading to increased resistance to degradation compared to that of Q1. As the degradation time increased, both the Q1 and Q2 films demonstrated a decline in thermal stability. These films also exhibited alterations in crystallinity attributed to the chemo-crystallization process, along with fluctuations in the glass transition temperature and crystallization, particularly at 288 h.

Thiourea-Based Receptors for Anion Recognition and Signaling.

This work reports on two thiourea-based receptors with pyridine and amine units including 1-naphthyl (MT1N) and 4-nytrophenyl (MT4N) as signaling units. For both compounds, their affinity and signaling ability toward various anions of different geometry and basicity in DMSO were studied using UV-vis, fluorescence, and 1H NMR techniques. Anion recognition studies revealed that both MT1N and MT4N have, in general, high affinities toward basic anions. In this regard, a higher acidity of the MT4N receptor was demonstrated. Furthermore, MT4N has a higher affinity for fluoride (log K1 = 5.98) than for the other anions and can effectively detect it through colorimetric changes that can be monitored by the UV-vis technique. The interaction between receptors and anions mainly involves the hydrogens of the amino and thiourea groups of the former. Complementary single-crystal X-ray diffraction studies and molecular modeling at the DFT level were also performed.

Preparation and Characterization of Poly(lactic acid) Membranes and Films Coated with Polyaniline for Potential Use in Environmental Remediation.

This research outlines the fabrication of polymeric membranes and films of poly(lactic acid) (PLA), prepared via electrospinning and extrusion, respectively. These materials were subsequently coated with polyaniline (PANi) by using the in situ chemical polymerization technique. Scanning electron microscopy micrographs revealed that the best coatings were achieved when 3 and 30 min of contact time with the monomeric solution were used for the membrane and film, respectively. Additionally, Fourier transform infrared spectra, thermogravimetric studies, and contact angle measurements demonstrated proper interaction between PLA and PANi. The findings of these studies suggest that PLA membranes and films can serve as suitable substrates for the deposition of PANi, and the composite materials hold potential for use in environmental remediation applications.

Preparation and Characterization of Extruded PLA Films Coated with Polyaniline or Polypyrrole by In Situ Chemical Polymerization.

Conductive polymers, such as polypyrrole and polyaniline, have been extensively studied for their notable intrinsic electronic and ionic conductivities, rendering them suitable for a range of diverse applications. In this study, in situ chemical polymerization was employed to coat extruded PLA films with PPy and PANi. Morphological analysis reveals a uniform and compact deposition of both polyaniline and polypyrrole after polymerization periods of 3 and 1 h, respectively. Furthermore, the PLA-PANi-3h and PLA-PPy-1h composites exhibited the highest electrical conductivity, with values of 0.042 and 0.022 S cm-1, respectively. These findings were in agreement with the XPS results, as the polyaniline-coated film showed a higher proportion of charge carriers compared to the polypyrrole composite. The elastic modulus of the coated films showed an increase compared with that of pure PLA films. Additionally, the inflection temperatures for the PLA-PANi-3h and PLA-PPy-1h composites were 368.7 and 367.2 °C, respectively, while for pure PLA, it reached 341.47 °C. This improvement in mechanical and thermal properties revealed the effective interfacial adhesion between the PLA matrix and the conducting polymer. Therefore, this work demonstrates that coating biopolymeric matrices with PANi or PPy enables the production of functional and environmentally friendly conductive materials suitable for potential use in the removal of heavy metals in water treatment.

Efficient and Sustainable Bidentate Amines-Functionalized Resins for Removing Ag+, Cu2+, Pb2+, and Fe3+ from Water.

We evaluate the effectiveness of chelating resins (CR) derived from Merrifield resin (MR) and 1,2-phenylenediamine (PDA), 2,2'-dipyridylamine (DPA), and 2-(aminomethyl)pyridine (AMP) as adsorbent dosimeters for Ag+, Cu2+, Fe3+, and Pb2+ cations from water under competitive and noncompetitive conditions. MR-PDA, MR-DPA, and MR-AMP were obtained in a 95-97% yield and characterized by IR, fluorescence, and SEM. The ability of CRs as adsorbents was determined by batch and flow procedures. MR-PDA showed a batch adsorption capacity order of Fe3+ (29.8 mg/g) > Ag+ (2.7 mg/g) > Pb2+ (2.6 mg/g) at pH 3.4. The flow adsorption showed affinity towards the Ag+ cation at pH 7 (18.4 mg/g) and a reusability of 10 cycles. In MR-DPA, the batch adsorption capacity order was Ag+ (9.1 mg/g) > Pb2+ (8.2 mg/g) > Cu2+ (3.5 mg/g) at pH 5. The flow adsorption showed affinity to the Cu2+ cation at pH 5 (2.2 mg/g) and a reuse of five cycles. In MR-AMP, the batch adsorption capacity was Ag+ (17.1 mg/g) at pH 3.4. The flow adsorption showed affinity to the Fe3+ cation at pH 2 (4.3 mg/g) and a reuse of three cycles. The three synthesized and reusable CRs have potential as adsorbents for Ag+, Cu2+, Fe3+, and Pb2+ cations and showed versatility in metal removal for water treatment.

N-(2-ozoazepan-3-yl)-pyrrolidine-2-carboxamide, a novel Octopus vulgaris ink-derived metabolite, exhibits a pro-apoptotic effect on A549 cancer cell line and inhibits pro-inflammatory markers.

This research aimed to chemically synthesize and evaluate the antiproliferative and anti-inflammatory potential of ozopromide (OPC), a novel compound recently isolated from O. vulgaris ink. After chemical synthesis, OPC structural characterization was confirmed by COSY2D, FTIR, and C-/H-NMR. OPC inhibited the growth of human breast (MDA-MB-231), prostate (22Rv1), cervix (HeLa), and lung (A549) cancerous cells, being the highest effect on the latter (IC50: 53.70 µM). As confirmed by flow cytometry, OPC induced typical apoptosis-derived morphological features on A549 cells, mostly at early and late apoptosis stages. OPC generated a dose-dependent effect inhibiting IL-6 and IL-8 on LPS-stimulated peripheral mononuclear cells (PBMCs). A major affinity of OPC to Akt-1 and Bcl-2 proteins in silico agreed with the observed pro-apoptotic mechanisms. Results suggested that OPC has the potential to alleviate inflammation and be further studied for anticancer activity. Marine-derived food products such as ink contains bioactive metabolites exhibiting potential health benefits.

Tritopic Bis-Urea Receptors for Anion and Ion-Pair Recognition.

This work reports on the synthesis and characterization of three tritopic receptors and their binding properties toward various anions, as their tetrabutylammonium salts, and three alkali metal-acetate salts by UV-vis, fluorescence, 1H, 7Li, 23Na, and 39K NMR in MeCN/dimethyl sulfoxide (DMSO) 9:1 (v/v). Molecular recognition studies showed that the receptors have good affinity for oxyanions. Furthermore, these compounds are capable of ion-pair recognition of the alkali metal-acetate salts studied through a cooperative mechanism. Additionally, molecular modeling at the density functional theory (DFT) level of some lithium and sodium acetate complexes illustrates the ion-pair binding capacity of receptors. The anion is recognized through strong hydrogen bonds of the NH- groups from the two urea sites, while the cation interacts with the oxygen atoms of the polyether spacer. This work demonstrates that these compounds are good receptors for anions and ion pairs.

BADH-NAD+-K+ Complex Interaction Studies Reveal a New Possible Mechanism between Potassium and Glutamic 254 at the Coenzyme Binding Site.

Betaine aldehyde dehydrogenase (BADH EC 1.2.1.8) catalyzes the irreversible oxidation of betaine aldehyde to glycine betaine using NAD+ as a coenzyme. Incubation of porcine kidney BADH (pkBADH) with NAD+ decreases the catalytic cysteine (C288) reactivity. Potassium ion increases the pkBADH affinity by the coenzyme. This work aimed to analyze pkBADH and NAD+ interaction in the presence and absence of K+ using 1H NMR to identify the amino acids that interact with NAD+ and/or K+ to understand the regulation process of pkBADH-NAD+ complex formation mediated by the K+ ion and their impact on the substrate binding and catalysis. Nuclear magnetic resonance spectra of pkBADH were obtained in the presence and absence of NAD+ and K+. The results show a chemical shift of the signals corresponding to the catalytic glutamic that participates in the transfer of H+ in the reaction of the pkBADH-NAD+-K+ complex formation. Furthermore, there is a widening of the signal that belongs to the catalytic cysteine indicating higher rigidity or less grade of rotation of the structure, which is consistent with the possible conformations of C288 in the catalytic process; in addition, there is evidence of changes in the chemical environment that surrounds NAD+.

Optical Anion Receptors with Urea/Thiourea Subunits on a TentaGel Support.

Two simple chemosensors with urea (L1) and thiourea (L2) groups were synthesized and studied by different spectroscopic techniques. Both receptors can sense acetate (Ac-), dihydrogen phosphate (H2PO4 -), and fluoride (F-) anions, accompanied by changes in UV-vis and 1H NMR spectra, and an optical response is observed as a color change of the solutions due to deprotonation and hydrogen-bonding processes. Also, L1 and L2 were supported on TentaGel resins (R1 and R2), and their fluoride-sensing properties in DMSO and water solutions were studied. Interestingly, R2 can sense fluoride ions in sample solutions of 100% water.

Octopus vulgaris ink extracts exhibit antioxidant, antimutagenic, cytoprotective, antiproliferative, and proapoptotic effects in selected human cancer cell lines.

Cancer is a noncommunicable disease of rising worldwide concern. Marine food products such as Octopus vulgaris ink (OI) could be sources of compounds addressing these concerns. This study aimed to evaluate the antimutagenic, cytoprotective, antiproliferative, proapoptotic, and antioxidant capacity of OI extracts on human cancer cell lines (22Rv1, HeLa, A549). The ARPE-19 cell line was used as a reference human cell line to evaluate the ink's cytotoxicity. The water extract exhibited the highest antimutagenic and cytoprotective effect, but the dichloromethane extract (DM) showed the lowest half lethal concentration against 22Rv1 cells. Structural elucidation of purified DM fractions (F1, F2, F3) identified an unreported compound, N-(2-ozoazepan-3-yl)-pyrrolidine-2-carboxamide (OPC). DM-F2 showed high antiproliferative effect (LC50 = 27.6 µg/mL), reactive species modulation, early-apoptosis induction (42.9%), and nuclei disruption in 22Rv1 cells. In silico analysis predicted high OPC affinity with Cyclin D1 (-6.70 kcal/mol), suggesting its potential impact on cell cycle arrest. These results highlight the antimutagenic, cytoprotective, and antiproliferative potential health benefits derived from underutilized marine food products such as OI. Further investigations at in vitro or in vivo levels are required to elucidate mechanisms and health benefits from OI. PRACTICAL APPLICATION: O. vulgaris ink is an underutilized marine natural product that could be a source of biological compounds with potential health benefits such as antioxidant activity and cancer prevention.

Xanthommatin is Behind the Antioxidant Activity of the Skin of Dosidicus gigas.

Marine bioactive compounds have been found in very different sources and exert a very vast array of activities. Squid skin, normally considered a discard, is a source of bioactive compounds such as pigments. Recovering these compounds is a potential means of valorizing seafood byproducts. Until now, the structure and molecular properties of the bioactive pigments in jumbo squid skin (JSS) have not been established. In this study, methanol-HCl (1%) pigment extracts from JSS were fractionated by open column chromatography and grouped by thin-layer chromatography in order to isolate antioxidant pigments. Antioxidant activity was determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH●) and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS●+) radical scavenging assays and ferric reducing power (FRAP) assay. Fractions 11-34 were separated and grouped according to flow rate values (F1-F8). Fractions F1, F3, and F7 had the lowest IC50 against ABTS●+ per milligram, and fractions F3 and F7 showed the lowest IC50 in the FRAP assay. Finally, fraction F7 had the highest DPPH● scavenging activity. The chemical structure of the F7 fraction was characterized by infrared spectroscopy, 1H nuclear magnetic resonance, and electrospray ionization-mass spectrometry. One of the compounds identified in the fraction was xanthommatin (11-(3-amino-3-carboxypropanoyl)-1-hydroxy-5-oxo-5H-pyrido[3,2-a]phenoxazine-3-carboxylic acid) and their derivatives (hydro- and dihydroxanthommatin). The results show that JSS pigments contain ommochrome molecules like xanthommatin, to which the antioxidant activity can be attributed.

Effect of temperature on the actomyosin-paramyosin structure from giant squid mantle (Dosidicus gigas).

BACKGROUND: The secondary structure of a protein determines its functional properties, such as its gelling capacity. The α-helix and ß-sheet comprise its main structures. Myofibrillar proteins from jumbo squid are composed mainly of the actomyosin-paramyosin complex; this complex contains a high percentage of α-helix, because actin, paramyosin, and myosin constitute 30%, 100%, and 55% of the α-helix, respectively. It is important to elucidate the role of the secondary structures in the gelation of giant squid proteins as they form gel. The role of the secondary structures in the gelation of giant squid proteins is therefore very important. For this reason, the objective of this work was to evaluate the effect of temperature on the structural behavior of actomyosin-paramyosin isolate (API) from Dosidicus gigas. RESULTS: The unfolding of the API system, which is composed of the actomyosin-paramyosin complex, was clarified by studying surface hydrophobicity and viscosity. Three characteristic peaks were found, associated with myosin, paramyosin, and actin. Infrared and circular dichroism corroborated the view that API undergoes major structural changes, because it proceeds from mostly an α-helix structure to 100% ß-sheet. CONCLUSION: The structural rearrangement favors gelation by cross-linking, generating new protein-protein and water-protein interactions, which create a more stable structure compared to mantle proteins (MP). Likewise, the presence of sarcoplasmic and stromal proteins in D. gigas muscle prevents the unfolding of myofibrillar proteins, favoring gelation by agglomeration, decreasing the ability to trap water and thus its gelling capacity. © 2019 Society of Chemical Industry.

Effect of Temperature and pH on the Secondary Structure and Denaturation Process of Jumbo Squid Hepatopancreas Cathepsin D.

BACKGROUND: Cathepsin D is a lysosomal enzyme that is found in all organisms acting in protein turnover, in humans it is present in some types of carcinomas, and it has a high activity in Parkinson's disease and a low activity in Alzheimer disease. In marine organisms, most of the research has been limited to corroborate the presence of this enzyme. It is known that cathepsin D of some marine organisms has a low thermostability and that it has the ability to have activity at very acidic pH. Cathepsin D of the Jumbo squid (Dosidicus gigas) hepatopancreas was purified and partially characterized. The secondary structure of these enzymes is highly conserved so the role of temperature and pH in the secondary structure and in protein denaturation is of great importance in the study of enzymes. The secondary structure of cathepsin D from jumbo squid hepatopancreas was determined by means of circular dichroism spectroscopy. OBJECTIVE: In this article, our purpose was to determine the secondary structure of the enzyme and how it is affected by subjecting it to different temperature and pH conditions. METHODS: Circular dichroism technique was used to measure the modifications of the secondary structure of cathepsin D when subjected to different treatments. The methodology consisted in dissecting the hepatopancreas of squid and freeze drying it. Then a crude extract was prepared by mixing 1: 1 hepatopancreas with assay buffer, the purification was in two steps; the first step consisted of using an ultrafiltration membrane with a molecular cut of 50 kDa, and the second step, a pepstatin agarose resin was used to purification the enzyme. Once the enzyme was purified, the purity was corroborated with SDS PAGE electrophoresis, isoelectric point and zymogram. Circular dichroism is carried out by placing the sample with a concentration of 0.125 mg / mL in a 3 mL quartz cell. The results were obtained in mdeg (millidegrees) and transformed to mean ellipticity per residue, using 111 g/mol molecular weight/residue as average. Secondary-structure estimation from the far-UV CD spectra was calculated using K2D Dichroweb software. RESULTS: It was found that α helix decreases at temperatures above 50 °C and above pH 4. Heating the enzyme above 70°C maintains a low percentage of α helix and increases ß sheet. Far-UV CD measurements of cathepsin D showed irreversible thermal denaturation. The process was strongly dependent on the heating rate, accompanied by a process of oligomerization of the protein that appears when the sample is heated, and maintained a certain time at this temperature. An amount typically between 3 and 4% α helix of their secondary structure remains unchanged. It is consistent with an unfolding process kinetically controlled due to the presence of an irreversible reaction. The secondary structure depends on pH, and a pH above 4 causes α helix structures to be modified. CONCLUSION: In conclusion, cathepsin D from jumbo squid hepatopancreas showed retaining up to 4% α helix at 80°C. The thermal denaturation of cathepsin D at pH 3.5 is under kinetic control and follows an irreversible model.

Synthesis and anion recognition studies of new oligomethylene bis(nitrophenylureylbenzamide) receptors.

A new series of oligomethylene bis(nitrophenylureylbenzamide) receptors were synthesized varying the relative position of the urea and amide groups (ortho4 and meta8) and the length of the oligomethylene chain (C2 to C8). An anion recognition study was performed with TBAX salts (X = AcO-, BzO-, F-, H2PO4 -, and HP2O7 3-) by UV-vis and 1H NMR. The flexibility of these receptors allows a cooperative effect of both ureylbenzamide units in the receptors. Noteworthy, the ortho position favored the 1 : 1 stoichiometry in the complexes with the carboxylates. The formation of 2 : 1 receptor-anion complexes with both types of receptors 4 and 8 and with hydrogen pyrophosphate and high log K values obtained were very significant in this work. The NMR studies evidenced the formation of supramolecular complexes, even in a competitive solvent, such as DMSO.

Comparative Studies of Structures and Peroxidase-like Activities of Copper(II) and Iron(III) Complexes with an EDTA-Based Phenylene-Macrocycle and Its Acyclic Analogue.

With the objective of studying the conformational and macrocyclic effects of selected metal chelates on their peroxidase activities, Cu2+ and Fe3+ complexes were synthesized with a macrocyclic derivative of ethylenediaminetetraacetic acid and o-phenylenediamine (abbreviated as edtaodH2) and its new open-chain analogue (edtabzH2). The Fe3+ complex of edtaodH2 has a peroxidase-like activity, whereas the complex of edtabzH2 does not. The X-ray study of the former shows the formation of a dimeric molecule {[Fe(edtaod)]2O} in which each metal with an octahedral coordination is overposed over the macrocyclic cavity, as a result of rigid macrocyclic frame, to form an Fe-O-Fe bridge; the exposure of the central metal to the environment facilitates the capture of oxygen to drive the biomimetic activity. The peroxidase-inactive Fe3+ complex consists of a mononuclear complex ion [Fe(edtabz)(H2O)]+, the metal ion of which is suited in a distorted pentagonal bipyramid to be protected from environmental oxygen. The copper(II) complexes, which have mononuclear structures with high thermodynamic stability compared with the iron(III) complexes, show no peroxidase activity. The steric effects play a fundamental role in the biomimetic activity.

Muscle lysyl oxidase activity and structural/thermal properties of highly cross-linked collagen in jumbo squid (Dosidicus gigas) mantle, fins and arms.

Muscle from mantle, fins and arms of squid (Dosidicus gigas) were compared based on lysyl oxidase activity (LOX), chemical/structural and thermodynamic properties of highly cross-linked collagen. The arms collagen presented the highest temperature (Tp) and enthalpy of transition. The arms collagen thermic properties may be explained by the higher imino amino acid content, proline and lysine hydroxylation degrees. Moreover, among the regions, the collagen from the arms had a more intense ß band chain, hydroxymerodesmosine peak in the resonance magnetic nuclear spectra and pyridinoline peak in the Raman spectra. Fins showed the highest LOX activity. The LOX activity was associated with the Tp, proline and lysine hydroxylation degrees. These results implied that the collagen in the arms was more intermolecularly ordered than the mantle and fins, and may provide a theoretical basis for a better understanding of the thermal behaviour of squid tissues during management and processing.

Physicochemical characterization of actomyosin-paramyosin from giant squid mantle (Dosidicus gigas).

BACKGROUND: The giant squid (Dosidicus gigas) has been proposed as raw material to obtain myofibrillar protein concentrates. However, it has been observed that colloidal systems formed from squid proteins have limited stability. Therefore, the isolation and characterization of the actomyosin-paramyosin isolated (API) complex were performed, because they are the main proteins to which functionality has been attributed. RESULTS: Densitogram analysis revealed 45% of actin, 38% of myosin and 17% of paramyosin. The amino acid profile indicates a higher proportion of acidic amino acids, which gives a higher negative charge; this was supported by the zeta potential. Total sulfhydryl (TSH) content was lower compared with proteins of other aquatic species. CONCLUSION: The higher percentage of actin in relation to myosin, the presence of paramyosin, as well as the low content of sulfhydryl groups, could comprise the main causes of the low technological functional property of proteins from D. gigas mantle. © 2017 Society of Chemical Industry.

Preparation and Characterization of Extruded Composites Based on Polypropylene and Chitosan Compatibilized with Polypropylene-Graft-Maleic Anhydride.

The preparation of composites of synthetic and natural polymers represent an interesting option to combine properties; in this manner, polypropylene and chitosan extruded films using a different proportion of components and polypropylene-graft-maleic anhydride (PPgMA) as compatibilizer were prepared. The effect of the content of the biopolymer in the polypropylene (PP) matrix, the addition of compatibilizer, and the particle size on the properties of the composites was analyzed using characterization by fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), tensile strength, and contact angle, finding that in general, the addition of the compatibilizer and reducing the particle size of the chitosan, favored the physicochemical and morphological properties of the films.

Synthesis, Characterization, and Cu(2+) Coordination Studies of a 3-Hydroxy-4-pyridinone Aza Scorpiand Derivative.

The synthesis, acid-base behavior, and Cu(2+) coordination chemistry of a new ligand (L1) consisting of an azamacrocyclic core appended with a lateral chain containing a 3-hydroxy-2-methyl-4(1H)-pyridinone group have been studied by potentiometry, cyclic voltammetry, and NMR and UV-vis spectroscopy. UV-vis and NMR studies showed that phenolate group was protonated at the highest pH values [log K = 9.72(1)]. Potentiometric studies point out the formation of Cu(2+) complexes of 1:2, 2:2, 4:3, 1:1, and 2:1 Cu(2+)/L1 stoichiometries. UV-vis analysis and electrochemical studies evidence the implication of the pyridinone moieties in the metal coordination of the 1:2 Cu(2+)/L1 complexes. L1 shows a stronger chelating ability than the reference chelating ligand deferiprone. While L1 shows no cytotoxicity in HeLa and ARPE-19 human cell lines (3.1-25.0 µg/mL), it has significant antioxidant activity, as denoted by TEAC assays at physiological pH. The addition of Cu(2+) diminishes the antioxidant activity because of its coordination to the pyridinone moiety phenolic group.

A ¹H NMR Investigation of the Interaction between Phenolic Acids Found in Mango (Manguifera indica cv Ataulfo) and Papaya (Carica papaya cv Maradol) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) Free Radicals.

The benefits of phenolic acids on human health are very often ascribed to their potential to counteract free radicals to provide antioxidant protection. This potential has been attributed to their acidic chemical structure, which possesses hydroxyl groups in different positions. Phenolic acids can interact between themselves and exhibit an additive, antagonistic or synergistic effect. In this paper, we used 1H NMR to analyze the interactions and mechanisms that are present in major phenolic acids found in mango (gallic, protocatechuic, chlorogenic and vanillic acids) and papaya (caffeic, ferulic and p-coumaric acids), and the DPPH radical was used to evaluate the effect of the antioxidant mixtures. The interactions were found to occur via hydrogen bonds between the -OH and -COOH groups. Moreover, the phenolic acids exhibit two types of mechanisms for the neutralization of the DPPH radical. According to the results, these two mechanisms are Hydrogen Atom Transfer (HAT) and Single Electron Transfer (SET). The ability of the phenolic acid to neutralize the DPPH radical decreases in the following order in mango: gallic > chlorogenic > protocatechuic > vanillic. Moreover, within the acids found in papaya, the order was as follows: caffeic > p-coumaric > ferulic.