Oxidative Degradation Products Research Articles

Stability Indicating High‐performance Liquid Chromatography Method for Quantification of Amoxapine and Characterization of Forced Degradation Products Employing Quadrupole‐Time of Flight Mass Spectrometry

ABSTRACTAmoxapine, a tricyclic antidepressant, has been widely used for long‐term treatment of depression along with other psychiatric disorders involving neurosis, agitation, and anxiety. The drug may undergo degradation during manufacturing, transportation, and storage. To ensure drug safety, both identification and characterization of the degradation products (DPs) should be considered. Accordingly, a sensitive and selective stability‐indicating assay method was developed for amoxapine using high‐performance liquid chromatography (HPLC). The amoxapine drug was subjected to acidic hydrolysis, basic hydrolysis, and oxidation separately. The degradation susceptibility of the amoxapine was found to be in the order of Acid hydrolysis > Oxidation > Base hydrolysis. The developed method was validated as per the International Council for Harmonization Q2(R2) guideline. Further, LC‐electrospray ionization‐quadrupole‐time of flight‐tandem mass spectrometry was employed for the identification and characterization of the DPs formed under stress conditions. The study revealed that under accelerated stress conditions, three hydrolytic DPs and one oxidative DP were formed. Three of the four DPs were found to be novel and never reported before. In addition, a plausible mechanism representing the formation of all DPs has also been established.

Degradation of the AMP/PZ-based solvent CESAR1 and effects of solvent management in two longtime pilot plant tests

Two 24/7 longtime testing campaigns at the CO2 capture pilot plant at Niederaussem with an accumulated testing time of more than 40,000 h with the CESAR1 solvent, an aqueous solution of 26.7 wt% 2-amino-2-methylpropan-1-ol (AMP) and 12.9 wt% piperazine (PZ), provide a unique data base for the development of solvent management technologies and the evaluation of hypotheses on amine degradation. In the first campaign with a testing time of 34,000 h without replacement of the solvent inventory, three solvent management strategies with different effect mechanisms were investigated: adsorptive removal of trace elements from the solvent by two kinds of active carbon, removal of ionic contaminants by ion exchange using cation and anion exchange resins, and removal of NO2 from the flue gas by treatment with a thiosulfate/sulfite solution. After replacement of the solvent inventory the second campaign was conducted, in which none of the solvent management technologies mentioned have been applied for 10,000 h. The results of the two campaigns allow a direct comparison of the solvent degradation behavior. It is shown that active carbon does not significantly affect the accumulation rate of degradation products in CESAR1, and that an inappropriate kind of active carbon can cause foaming. Anionic degradation products, metal complexes, trace components and cationic contaminants can be effectively removed from the aged solvent by ion exchange. However, after their removal, accelerated formation of oxidative degradation products by a factor of up to 3 higher than before the anion exchange was observed. Removal of NO2 from the flue gas did not affect the NH3 emissions from the CO2 absorber, but it led to the highest observed increase rate of the accumulation of acidic degradation products for aged CESAR1. The results show that exaggerated efforts for solvent management are contra-productive and that a reassessment of the effect mechanisms of solvent management technologies is necessary.

Development and validation of stability indicating assay method for mitapivat: Identification of novel hydrolytic, photolytic, and oxidative forced degradation products employing quadrupole-time of flight mass spectrometry.

Mitapivat is a novel, first-in-class orally active pyruvate kinase activator approved by the US Food and Drug Administration in 2022 for the treatment of hemolytic anemia. There is no literature available regarding the identification of degradation impurities of mitapivat. The present study deals with the degradation behavior of mitapivat under various stress conditions such as hydrolytic, photolytic, thermal, and oxidative stress. The multivariate analysis found that the independent variables, that is, molarity, temperature, and time, are interacting with each other to affect the degradation of mitapivat. A specific, accurate, and precise high-performance liquid chromatographic (HPLC) method was developed to separate mitapivat from its degradation products. The separation was achieved on the C-18 column (250mm × 4.6mm × 5µm) using the combination of 0.1% formic acid buffer and acetonitrile in gradient elution profile. The method was validated as per the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use Q2(R2) guideline. LC-electrospray ionization-Quadrupole-time of flight was employed to identify degradation products. A total of seven novel degradation products of mitapivat were identified based on tandem mass spectrometry and accurate mass measurement. In-silico toxicity of mitapivat and its degradation products was qualitatively evaluated by the DEREK toxicity prediction tool.

An eco-friendly first and second derivative synchronous spectrofluorimetry for quantification of florfenicol in presence of its different degradation products. Application to kinetic stability study.

Two rapid, simple, sensitive and selective derivative spectrofluorimetric methods (first and second derivative synchronous spectrofluorimetric (FDSFS and SDSFS) procedures) have been developed for the analysis of florfenicol in the presence of its various degradation products. FDSFS was applied to assay the drug in the presence of its alkaline, oxidative and photolytic degradation products while SDSFS was used to quantify it in the presence of its acidic degradation product. These methods permitted quantification of florfenicol at corresponding λ Em of 288, 287, 279 and 284 nm without interferences from any of its degradation products. Full validation procedures were applied to the suggested method according to International Conference of Harmonization guidelines. Moreover, different degradation kinetic parameters were calculated such as half-life (t 1/2), degradation rate constant (K) and activation energy (E a). Using the analytical eco-scale, green analytical procedure index and analytical greenness metric approach AGREE as greenness assessment tools, the proposed method was found to be environmentally friendly.

Evaluation of beneficial effects of dexpanthenol on hypoxic-ischemic encephalopathy

ABSTRACT Hypoxic-ischemic encephalopathy (HIE) is a cause of serious morbidity and mortality in newborns. Dexpanthenol, which is metabolized into D-pantothenic acid, has antioxidant and other potentially therapeutic properties. We examined some effects of dexpanthenol on the brains of week-old rat pups with HIE induced by obstruction of the right carotid artery followed by keeping in 8% O2 for 2 hours. Dexpanthenol (500 mg/kg) was administered intraperitoneally to 16 of 32 pups with HIE. Protein, DNA, and lipid oxidation degradation products were assayed and hippocampal and cortical cell apoptosis and neuronal cell numbers were evaluated in stained sections. Dexpanthenol application reduced oxidative stress and inflammation. TNF-α and IL-6 cytokine levels in HIE also decreased with dexpanthenol treatment. The numbers of caspase-3 positive cells in the dentate gyrus and CA1/CA2/CA3 regions of the hippocampus was lower, and apoptosis was decreased in the dexpanthenol-treated animals. These findings suggest possible clinical applications of dexpanthenol in human HIE.

Purification and Structural Analyses of Sulfated Polysaccharides from Low-Value Sea Cucumber Stichopus naso and Anticoagulant Activities of Its Oligosaccharides.

Three polysaccharides (SnNG, SnFS and SnFG) were purified from the body wall of Stichopus naso. The physicochemical properties, including monosaccharide composition, molecular weight, sulfate content, and optical rotation, were analyzed, confirming that SnFS and SnFG are sulfated polysaccharides commonly found in sea cucumbers. The highly regular structure {3)-L-Fuc2S-(α1,}n of SnFS was determined via a detailed NMR analysis of its oxidative degradation product. By employing β-elimination depolymerization of SnFG, tri-, penta-, octa-, hendeca-, tetradeca-, and heptadeca-saccharides were obtained from the low-molecular-weight product. Their well-defined structures confirmed that SnFG possessed the backbone of {D-GalNAc4S6S-β(1,4)-D-GlcA}, and each GlcA residue was branched with Fuc2S4S. SnFS and SnFG are both structurally the simplest version of natural fucan sulfate and fucosylated glycosaminoglycan, facilitating the application of low-value sea cucumbers S. naso. Bioactivity assays showed that SnFG and its derived oligosaccharides exhibited potent anticoagulation and intrinsic factor Xase (iXase) inhibition. Moreover, a comparative analysis with the series of oligosaccharides solely branched with Fuc3S4S showed that in oligosaccharides with lower degrees of polymerization, such as octasaccharides, Fuc2S4S led to a greater increase in APTT prolongation and iXase inhibition. As the degree of polymerization increases, the influence from the sulfation pattern diminishes, until it is overshadowed by the effects of molecular weight.

Difference comparison of characteristic aroma compounds between braised pork cooked by traditional open-fire and induction cooker and the potential formation cause under electromagnetic cooking

The characteristic aroma compounds of braised pork were identified through molecular sensory science and PLSR analysis, and the difference between two cooking methods, traditional open-fire (BPF) and induction cooker (BPC), was compared. Seventeen aroma compounds with odor activity values (OAVs) > 1 were identified in both samples. BPF revealed higher OAVs for most of the aroma compounds compared to BPC, and the higher aroma quality. Aroma recombination and omission experiments confirmed that twelve aroma compounds significantly contributed to the characteristic aroma of braised pork, and eight compounds such as hexanal, (E)-2-octenal, and methanethiol were further confirmed as important contributors by PLSR analysis. Furthermore, PLSR analysis clarified the role of aldehydes such as hexanal, (E)-2-octenal, and (E,E)-2,4-decadienal in contributing to fatty attribute, whereas methanethiol was responsible for the meaty aroma. These characteristic aroma compounds mainly derived from lean meat due to its high content of phospholipids, and the exogenous seasonings contributed to the balanced characteristic aroma profile of braised pork by altering the distribution of these characteristic aroma compounds. Variations in heating parameters affected the formation of lipid oxidation and Strecker degradation products, which might explain aroma discrepancy between braised pork cooked by two methods with different heat transfer efficiencies.

Photoaged polystyrene nanoplastics exposure results in reproductive toxicity due to oxidative damage in Caenorhabditis elegans

The increase of plastic production together with the incipient reuse/recycling system has resulted in massive discards into the environment. This has facilitated the formation of micro- and nanoplastics (MNPs) which poses major risk for environmental health. Although some studies have investigated the effects of pristine MNPs on reproductive health, the effects of weathered MNPs have been poorly investigated. Here we show in Caenorhabditis elegans that exposure to photoaged polystyrene nanoplastics (PSNP-UV) results in worse reproductive performance than pristine PSNP (i.e., embryonic/larval lethality plus a decrease in the brood size, accompanied by a high number of unfertilized eggs), besides it affects size and locomotion behavior. Those effects were potentially generated by reactive products formed during UV-irradiation, since we found higher levels of reactive oxygen species and increased expression of GST-4 in worms exposed to PSNP-UV. Those results are supported by physical-chemical characterization analyses which indicate significant formation of oxidative degradation products from PSNP under UV-C irradiation. Our study also demonstrates that PSNP accumulate predominantly in the gastrointestinal tract of C. elegans (with no accumulation in the gonads), being completely eliminated at 96 h post-exposure. We complemented the toxicological analysis of PSNP/PSNP-UV by showing that the activation of the stress response via DAF-16 is dependent of the nanoplastics accumulation. Our data suggest that exposure to the wild PSNP, i.e., polystyrene nanoplastics more similar to those actually found in the environment, results in more important reprotoxic effects. This is associated with the presence of degradation products formed during UV-C irradiation and their interaction with biological targets.

Potential Residual Toxicity of the Ibuprofen Oxidative Degradation Products by HPLC–MS and Principal Component Analysis

Potential Residual Toxicity of the Ibuprofen Oxidative Degradation Products by HPLC–MS and Principal Component Analysis

The protein phosphorylation landscape in photosystem I of the desert algae Chlorella sp.

The phosphorylation of photosystem II (PSII) and its antenna (LHCII) proteins has been studied, and its involvement in state transitions and PSII repair is known. Yet, little is known about the phosphorylation of photosystem I (PSI) and its antenna (LHCI) proteins. Here, we applied proteomics analysis to generate a map of the phosphorylation sites of the PSI-LHCI proteins in Chlorella ohadii cells that were grown under low or extreme high-light intensities (LL and HL). Furthermore, we analyzed the content of oxidized tryptophans and PSI-LHCI protein degradation products in these cells, to estimate the light-induced damage to PSI-LHCI. Our work revealed the phosphorylation of 17 of 22 PSI-LHCI subunits. The analyses detected the extensive phosphorylation of the LHCI subunits Lhca6 and Lhca7, which is modulated by growth light intensity. Other PSI-LHCI subunits were phosphorylated to a lesser extent, including PsaE, where molecular dynamic simulation proposed that a phosphoserine stabilizes ferredoxin binding. Additionally, we show that HL-grown cells accumulate less oxidative damage and degradation products of PSI-LHCI proteins, compared with LL-grown cells. The significant phosphorylation of Lhca6 and Lhca7 at the interface with other LHCI subunits suggests a physiological role during photosynthesis, possibly by altering light-harvesting characteristics and binding of other subunits.

Detailed profiling of polysorbate 80 oxidative degradation products and hydrolysates using liquid chromatography-tandem mass spectrometry analysis.

Polysorbate 80 (PS80) is an amphipathic, nonionic surfactant that is commonly used to stabilize proteins in biopharmaceutical formulations. PS80 undergoes oxidative and/or enzymatic degradation. However, because PS80 is a complex mixture consisting of many constituents, comprehensive evaluations of its oxidative degradation products are difficult and insufficient. Our previously reported comprehensive liquid chromatography-tandem mass spectrometry (LC/MS/MS)-based method for PS80 effectively provides an overall profile of PS80 components under simple LC conditions. In this study, we attempted to shorten the analysis time. Furthermore, PS80 was oxidatively degraded in a solution containing histidine and iron, and the oxidative degradation products were evaluated using a modified LC/MS/MS method. In addition, enzymatically hydrolyzed PS80 samples were analyzed. We succeeded in shortening the analysis time from 70 to 20 min while maintaining the resolution of the PS80 components of the same selected reaction monitoring transition. Both the previously reported oxidative degradation products and the newly discovered products were successfully detected, and their composition ratios and changes over time were observed. Changes in the hydrolysates over time are shown in the analysis of the hydrolyzed PS80 samples. This study clearly showed the presence of changes in PS80 oxidative and/or enzymatic degradation products, including those previously unreported. These results demonstrate that a detailed profiling of PS80 degradation products can be performed using LC/MS/MS, which is less expensive and more generally adopted than high-resolution MS.

A unique revolutionary eco-friendly spectrophotometric technique for solving the spectral overlap in the determination of carvedilol and ivabradine in their binary combination: stability study

BackgroundCarivalan® dosage form containing carvedilol and ivabradine is widely indicated for patients with stable angina. Three precise, eco-friendly and reproducible spectrophotometric techniques were created for resolving the researched drugs in their mixtures using zero and/or ratio spectra. Technique I is a factorized dual wavelength coupled with spectrum subtraction (FDW-SS), technique II is a ratio difference, and technique III is a constant center coupled with spectrum subtraction (CC-SS). Moreover, CAR and IVA were simultaneously determined in the existence of their oxidative degradation products exploiting the newly developed induced tripartite amplitude difference coupled with ratio subtraction (ITAD-RS) technique.ResultsThe calibration curves for CAR and IVA showed linearity within 3.0–30.0 µg/ml, each. Techniques' precision, accuracy, and linearity ranges were resolved and validated in harmony with ICH guidelines. Additionally, the specificity was examined by examining created combinations of the proposed drugs with LOD of 0.258 and 0.290 for CAR, while for IVA 0.272 and 0.204.ConclusionThese techniques were used to determine the presence of the provided drugs in Carivalan® tablets. There is statistical comparison between the found results of the offered spectrophotometric techniques and the previously reported ones with no discernible variance in the acquired results.

Reaction Pathways of Oxidative Transformation of the Radioprotector Quercetin

Quercetin is one of the most promising natural polyphenolic radioprotective compounds. This property is based on its radical-scavenging activity and high antioxidant capacity, in the manifestation of which the products of oxidative degradation of quercetin play a significant role. The formation of specific metabolites during the oxidation of quercetin can determine not only its radioprotective properties, but also toxic manifestations. The purpose of this article is to summarize previously obtained data regarding the reaction pathways of oxidative transformation of quercetin. Materials and methods. We used publicly available scientific publications dedicated to the study of quercetin transformation processes. The method of analysis is descriptive. The discussion of the results. A review of scientific works dedicated to oxygen oxidation, radical-initiated oxidation, electrochemical and enzymatic oxidation is presented, possible transformation products of quercetin and the mechanisms of their formation are given. The most characteristic oxidation pathways of quercetin are determined by the chemical structure of the rings, which exhibit specific reactivity. The influence of the solvent composition on the oxidation products during the autoxidation of quercetin was revealed, while the radical and electrochemical models of oxidation differ in the presence of polymer adducts. Once in a living organism, quercetin can bind free radicals, thereby preventing the harmful effects of radiation, that is, it has the properties of a radioprotector. Conclusions. Quercetin can be considered as a potential radioprotector due to its ability to bind free radicals formed in the biological fluids of living organisms exposed to radiation.

Toxicity of products of thermal oxidative degradation of nitrogen-containing building polymer materials

Introduction. In the event of fires in residential premises in which nitrogen-containing thermal insulation materials (foam rubber, polyisocyanurate foam) are used, the victims will be exposed to toxic thermal degradation products. Data on long-term disorders caused by intoxication by thermal degradation products of these materials could not be found in the available literature. The aim of the study was to assess the toxicity of the products of thermal oxidative degradation of nitrogen-containing thermal insulation materials, both in the early and long-term post-intoxication period. 
 Material and methods. Static inhalation intoxication of rats with products of thermooxidative destruction of polyfoam and polyisocyanurate foam (at a concentration of 0,8HLC50) was simulated. The concentration of carboxyhemoglobin in the blood of rats, indicators of vital functions were determined immediately before and on days 1, 7 and 28 after exposure. To assess learning disabilities in rats, a conditioned reflex of active avoidance by swimming was developed. To assess spatial memory in rats, the method of developing and reproducing the conditioned reflex of searching for food was used.
 Results and discussion. The intoxication of rats with products of thermooxidative destruction of the studied materials of moderate severity was simulated. Violations of the functions of the respiratory and cardiovascular system of rats in the early (7 days) and long-term (28 days) post-intoxication period were not detected. In the long-term (28 days) post-intoxication period, an increase in the duration of the latent period of active avoidance by swimming of rats was determined (compared with the control), an increase in the number of spatial memory errors in rats and the time of testing (compared with the control) was revealed.
 Limitation of the study. Limitations are due to the methodology of the research being conducted. A quantitative analysis of only some gaseous products of thermal oxidative destruction was perfomed.
 Conclusion. It was found that intoxication of rats with products of thermooxidative destruction of foam rubber and foam polyiysocyanurate (at a concentration of 0,8HLC50) led to impaired learning and spatial memory of rats in the long-term post-intoxication period.

Influence of Crystal Disorder on the Forced Oxidative Degradation of Vortioxetine HBr

The present study investigates the impact of the solid-state disorder of vortioxetine hydrobromide (HBr) on oxidative degradation under accelerated conditions. A range of solid-state disorders was generated via cryogenic ball milling. The solid-state properties were evaluated by calorimetry, infrared-, and Raman spectroscopies. While salt disproportionation occurred upon milling, no chemical degradation occurred by milling. The amorphous fraction remained physically intact under ambient storage conditions. Subsequently, samples with representative disordered fractions were mixed with a solid oxidative stressor (PVP-H2O2 complex) and were compressed to compacts. The compacts were exposed to 40°C/75% RH for up to 6 h. The sample was periodically withdrawn and analyzed for the physical transformations and degradation. Two oxidative degradation products (DPs) were found to be formed, for which dissimilar relations to the degree of disorder and kinetics of formation were observed. The degradation rate of the major DP formation obtained by fitting the exponential model to the experimental data was found to increase up to a certain degree of disorder and decrease with a further increase in the disordered fraction. In contrast, the minor DP formation kinetics was found to increase monotonically with the increase in the disorder content. For the similar crystallinity level, the degradation trend (rate and extent) differed between the single-phase disorder generated by milling and physically mixed two-phase systems. Overall, the study demonstrates the importance of evaluating the physical and chemical (in)stabilities of the disordered solid state of a salt form of a drug substance, generated through mechano-activation.Graphical

Green sustainable assessment of stability indicating first derivative synchronous fluorimetry for determination of anti-diabetic drug with its toxic impurity

Canagliflozin is prescribed with proper diet and exercise for the treatment of type 2 diabetes mellites. In this work, simple and sensitive synchronous fluorescence spectroscopic method coupled with the first derivative was proposed for the quantitative determination of canagliflozin in the presence of its oxidative degradation product. Canagliflozin and its oxidative degradation product have native fluorescence at 353 nm and 364 nm after excitation at 294 nm and 289 nm, respectively. The application of synchronous fluorescence mode gave a sharp peak but failed to resolve canagliflozin and its potential toxic degradation product. First-order derivatization of synchronous spectra resolved the overlap and allowed the determination of canagliflozin in the presence of its oxidative degradation product at 324 nm using Δλ = 20 nm. The method showed linearity with excellent correlation in the concentration range of 1–20 μg/mL for canagliflozin. The method was successfully applied for the determination of canagliflozin in pharmaceutical formulation and laboratory-prepared mixtures with mean percent recovery of 99.95 ± 1.14 and 99.81 ± 1.06, respectively. The greenness of the proposed method was assessed and approved by different tools such as analytical eco-scale, green analytical procedure index GAPI and AGREE.

Validated Stability Indicating Spectrophotometric Methods for Quantitative Determination of Anticonvulsant Drug Zonisamide in the Presence of Its Oxidative Degradation Product

Validated Stability Indicating Spectrophotometric Methods for Quantitative Determination of Anticonvulsant Drug Zonisamide in the Presence of Its Oxidative Degradation Product

Lipidomics and volatilomics reveal the changes in lipids and their volatile oxidative degradation products of brown rice during accelerated aging.

Brown rice exhibits higher nutritional value and attracts more and more attentions; however, lipid alteration in brown rice during aging is poorly understood. In this study, lipidomics and volatilomics were employed to investigate free fatty acids, triglycerides, and volatile oxidative degradation products of lipids in brown rice during accelerated aging for 70days. The results showed that the total free fatty acids in brown rice increased significantly (2.90-4.14 times) while triglycerides decreased remarkably at the initial stage of aging. Monounsaturated and polyunsaturated aldehydes, ketones, and acids increased obviously in brown rice during accelerated aging for 70days. The screening of significantly different compounds indicated that the enzymatic hydrolysis of triglycerides (EHT) and enzymatic oxidation of lipids (EOL) were the main biochemical behaviors at the initial stage of aging (0-28day) while automatic oxidation of lipids (AOL) was the primary chemical reaction for 28-70days aging.

Understanding the Mechanism of Light-Induced Age-Related Decrease in Melanin Concentration in Retinal Pigment Epithelium Cells.

It is known that during the process of aging, there is a significant decrease in the number of melanosomes in the retinal pigment epithelium (RPE) cells in the human eye. Melanosomes act as screening pigments in RPE cells and are fundamentally important for protection against the free radicals generated by light. A loss or change in the quality of melanin in melanosomes can lead to the development of senile pathologies and aggravation in the development of various retinal diseases. We have previously shown that the interaction between melanin melanosomes and superoxide radicals results in oxidative degradation with the formation of water-soluble fluorescent products. In the present study, we show, using fluorescence analysis, HPLC, and mass spectrometry, that visible light irradiation on melanolipofuscin granules isolated from RPE cells in the human eye results in the formation of water-soluble fluorescent products from oxidative degradation of melanin, which was in contrast to lipofuscin granules and melanosomes irradiation. The formation of these products occurs as a result of the oxidative degradation of melanin by superoxide radicals, which are generated by the lipofuscin part of the melanolipofuscin granule. We identified these products both in the composition of melanolipofuscin granules irradiated with visible light and in the composition of melanosomes that were not irradiated but were, instead, oxidized by superoxide radicals. In the melanolipofuscin granules irradiated by visible light, ions that could be associated with melanin oxidative degradation products were identified by applying the principal component analysis of the time-of-flight secondary ion mass spectrometry (ToF-SIMS) data. Degradation of the intact melanosomes by visible light is also possible; however, this requires significantly higher irradiation intensities than for melanolipofuscin granules. It is concluded that the decrease in the concentration of melanin in RPE cells in the human eye with age is due to its oxidative degradation by reactive oxygen species generated by lipofuscin, as part of the melanolipofuscin granules, under the action of light.

The degradation of p-nitrophenol by biochar is dominated by its electron donating capacity

The typical aromatic and phenolic pollutant, p-nitrophenol (PNP), is extensively used in the industry and can seriously threaten the environmental health. Biochar, as a solid carbon-rich material, can directly degrade PNP. It has been reported that the PNP degradation by biochar is closely related to the electron exchange capacity of biochar (the sum of electron donating and accepting capacities). However, the roles of electron donating and accepting capacity of biochar in PNP degradation have not been distinguished before. In this study, the biochar samples were chemically modified to manipulate the electron donating and accepting capacities of biochar samples. Compared with pristine biochar (3.67 %), modified biochar had higher degradation efficiencies of PNP (>7.81 %). The strictly positive correlation between the electron donating capacities and the PNP degradation rates of biochar samples (r = 0.98, p < 0.05) indicated that the PNP degradation process by biochar is dominated by the reduction process. Although both the oxidation and reduction degradation products were found in the degradation system, the quenching experiment of OH, a key radical in the process of oxidation degradation, further proved that the oxidation process just played a minor role (<10 %) in the PNP degradation by biochar. This study shed light on the degradation mechanism of PNP by biochar and could promote the application of biochar in the pollution remediation.