Purity Of Compounds Research Articles

Synthesis, Crystal Structure, and Physical Properties of Layered LnCrSe2O (Ln = Ce–Nd)

The layered oxyselenides with the formula LnCrSe2O (Ln = Ce-Nd) were synthesized via molten salt methods. The isostructural compounds crystallize in the monoclinic space group of C2/m. The crystal structures feature ∞2[CrSe2O]3- motifs stacked along the a axis, which are separated by Ln3+ ions. The ∞2[CrSe2O]3- layers are composed of [Cr1Se6]9- and [Cr2Se4O2]9- octahedra via corner and edge sharing. Powder X-ray diffraction results confirm the phase purities of the as-synthesized compounds. LnCrSe2O (Ln = Ce-Nd) show typical antiferromagnetic ordering with TN = 125, 120, and 118 K, respectively. Heat capacity measurement for NdCrSe2O indicates that the Debye temperature is 278.4 K. Similar metal-to-semiconductor phase transitions were observed for LnCrSe2O (Ln = Ce-Nd) plates with transition temperatures of 115, 109, and 95 K, respectively. NdCrSe2O also possesses a magnetoresistance effect at low temperature (<25 K) with a significant positive magnetoresistance ∼ 16% at 2 K and 1 T.

Synthesis, characterization and Cytotoxicity Evaluation of New Compounds from Oxazol-5(4H)-ones and Oxazoles Class Containing 4-(4-Bromophenylsulfonyl)phenyl Moiety

Steiger N-acylation of a-alanine with 4-(4-bromophenylsulfonyl)benzoyl chloride led to 2-[4-(4-bromophenylsulfonyl)benzamido]propanoic acid. This compound underwent intramolecular cyclization in the presence of N-methylmorpholine and ethyl chloroformate or acetic anhydride to the corresponding saturated azlactone. Then acylaminoacylation of dry aromatic hydrocarbons with 2-[4-(4-bromophenylsulfonyl)phenyl]-4-methyloxazol-5(4H)-one or 2-[4-(4-bromophenylsulfonyl) benzamido ]propanoyl chloride in the presence of anhydrous aluminum chloride led to corresponding a-acylamino ketones. These new intermediates were heterocyclized under the action of phosphorus oxychloride or concentrated sulfuric acid in the presence of acetic anhydride to the corresponding oxazoles. The newly synthesized compounds were characterized by spectral studies (FT-IR, UV-Vis, MS, 1H- and 13C-NMR) and elemental analysis. The purity of the new compounds was evaluated by RP-HPLC. The experimental research regarding to the in vitro cytotoxic activity of the new compounds were performed using Daphnia magna bioassay.

Computational design, Synthesis of 4,6-dihydroxy-2-phenyl-1-benzofuran-3(2H)-one derivatives as new leads for anti-cancer activity

Benzofuranone is a bicyclic ring where a benzene ring fused with a furanone. Computation chemistry plays a major role in the development of new lead molecules. Computational tools docking, virtual screening, ADMET prediction are utilised in the identification of new lead molecules. Synthetic chemistry plays a major in developing a series of potent anti-cancer agents. Benzofuranone was synthesized by reacting benzene diols, and triols with bromo phenyl acetonitrile yielded an imine derivative are converted to a ketone with treatment with hydrochloric acid then cyclised with sodium acetate. The compounds identity and purity were confirmed by spectral and analytical methods. Benzofuranone derivatives are screened antineoplastic activity was performed against human skin cancer cell line G361 at micro molecular concentrations. The compounds IA, IB, ID, IE, IF, was found to be with potent activity.

Docking, Screening, Synthesis of 4-hydroxy-6-methyl-2-phenyl-1-benzofuran-3(2H)-one derivatives as new leads for anti-cancer activity

Auroneis a bicyclic ring where a benzene ring fused with a furanone. Docking is an efficient tool in the development of new lead molecules. Docking, virtual screening, ADMET prediction are prominent devices in the identification of new lead molecules. Synthetic chemistry plays a major in developing a series of potent anti-cancer agents. Benzofuranone was synthesized by reacting benzene diols, and triols with bromo phenyl acetonitrile yielded an imine derivative are converted to a ketone with treatment with hydrochloric acid then cyclised with sodium acetate. The compounds identity and purity were confirmed by spectral and analytical methods. Benzofuranone derivatives are screened antineoplastic activity was performed against human skin cancer cell line G361 at micro molecular concentrations. The compound IIIA was found to be with potent activity.

Synthesis, biological evaluation, and computational studies of novel fused six-membered O-containing heterocycles as potential acetylcholinesterase inhibitors

An efficient, borax-catalyzed protocol for the synthesis of novel 4-aryl-substituted-4H-pyran derivatives fused to α-pyrone ring in a one-pot is described. By this achievement, some novel 4-aryl substituted 4H-pyrans fused to the α-pyrone ring as potential acetylcholinesterase inhibitors (AChEIs) with good to excellent yields are obtained from a one-pot three-component reaction between various aryl aldehydes, 4-hydroxy-6-methyl-2H-pyran-2-one and malononitrile. The method is a facile, inexpensive, practical and highly efficient one to obtain target compounds. The chemical structures of all compounds were characterized by FT-IR, FT-13CNMR and FT-1HNMR, MS spectroscopy and also elemental analyses data. Furthermore, the purity of all novel compounds was checked by HPLC. In addition, both molecular modelling studies and Absorption, Distribution, Metabolism, Excretion and Toxicity (ADMETox) prediction nominated all compounds as good acetylcholinesterase inhibitors to the potential treatment of Alzheimer, Parkinson and Autism diseases that among them compound 4f showed the best activity against acetylcholinesterase enzyme.

Preparation of Salvianolic Acid B Disodium Salt Considering the Water Extract Quality Standard.

A preparation process of salvianolic acid B (SAB) disodium salt from Salvia miltiorrhiza Bunge (Danshen) is provided in this work. A water extract quality standard was also developed to estimate the influences of Danshen quality on SAB disodium salt quality at an early stage of the preparation process. Crude SAB solution was obtained after water extraction, concentration, acidification, 1-butanol extraction, water washing, basification, and water back extraction. Extraction temperature, extraction pH, and back-extraction pH were identified to be key parameters for the preparation of crude SAB solution. These parameters were optimized with Box–Behnken designed experiments. Crude SAB solution was further purified with a chromatography process. AMBERCHROW CG161M resin was selected as the best adsorbent. SAB disodium salt could be obtained by drying the eluate. Considering the quality of Danshen may affect the purity and yield of SAB disodium salt, different batches of Danshen were used to prepare SAB disodium salt with the optimized parameters. Water extract indices of phenolic compound purity and phenolic compound yield were measured. By developing models between SAB disodium salt purity and yield with water extract indices, the quality standard of Danshen water extract was obtained. The application of water extract quality standards can improve the quality consistency of SAB disodium salt. The effects of different batches of Danshen raw materials on the final product could be evaluated at the beginning of production stages. The present method could prepare about five grams of high-purity SAB disodium salt (>95%) in one preparation cycle. The method reported in this work can also be used to develop process intermediate quality standards for other natural products.

Improved one-pot synthetic conditions for synthesis of functionalized fluorescent coumarin-thiophene hybrids: Syntheses, DFT studies, photophysical and thermal properties

We have synthesized coumarin-thiophene hybrids using stepwise and one-pot methods under MWI and CM conditions, and then report the findings and conclusions: one-pot is better than stepwise in terms of high yields and fastness of getting products, and MWI is better than CM in terms of purity of compounds, better yields, and reaction period. Even though both protocols were found to be efficient, the microwave-assisted irradiation reactions were identified to be better, environmentally friendly, cost-effective, mild, more efficient, less time consuming but with high purity. The two protocols were employed for the synthesis of the target coumarin-thiophene hybrids via the Gewald reaction in stepwise and in one-pot three-component. The dyes 3a-j were prepared in good to excellent yields. Although, we recorded better yields via the stepwise protocol (80–96%), for the synthesis of the target molecules, as compared to the one-pot (82–90%), the stepwise condition is fraught with many changes such as long reaction conditions, extra use of solvents for purification of intermediates, and long reaction durations. Photophysical activities of all the target derivatives were investigated using a combination of UV–vis and fluorescence spectroscopies in different solvents. The umbelliferon-like derivative 3g was further investigated for possible use as a pH sensor via deprotonation (using TBAOH) and reverse protonation (using TFA), and was found to be applicable as pH sensor both in organic medium (DMSO) and partial aqueous binary (DMSO/H2O, v/v, 9:1) medium. Again, the ground and the excited state properties of the umbelliferon-like derivative 3g and its deprotonated form were also studied using the quantum chemical calculations. Finally, the thermal properties of all the target compounds were investigated using TGA in order to test their potency and applicability as optical dyes. All the dyes 3a-j have high thermal stability therefore they can be applicable as optical dyes.

ONE-POT DIASTEREOSELECTIVE SYNTHESIS OF CHIRAL TRICYCLIC l-CYSTEINE AND d-PENICILLAMINE DERIVATIVES: A LABORATORY EXPERIMENT

A one-pot diastereoselective synthesis of thiazolidine-ring fused systems derived from enantiomerically pure amino acids, L-cysteine or D-penicillamine, and achiral succindialdehyde is described as an experiment to be carried out by upper-division undergraduate students in a laboratory classroom. Reactions were performed under mild conditions, the products were isolated through simple experimental procedures and fully characterized. This study combines organic synthesis, determination of the purity of compounds (TLC analysis and melting point measurements), optical activity measurements as well as structural analysis (interpretation of 1D NMR and 2D NMR spectra). It offers a platform for the discussion of important organic chemistry concepts such as diastereoselectivity, kinetic control vs thermodynamic control and cyclization reactions via nucleophilic addition to imines/iminium cations.

Integrative natural medicine inspired graphene nanovehicle-benzoxazine derivatives as potent therapy for cancer.

Natural products from medicinal plants have always attracted a lot of attention due to their diverse and interesting therapeutic properties. We have employed the principles of green chemistry involving isomerization, coupling and condensation reaction to synthesize a class of compounds derived from eugenol, a naturally occurring bioactive phytophenol. The compounds were characterized structurally by 1H-, 13C-NMR, FT-IR spectroscopy and mass spectrometry analysis. The purity of compounds was detected by HPLC. The synthesized compounds exhibited anti-cancer activity. A 10-12-fold enhancement in efficiency of drug molecules (~ 1µM) was observed when delivered with graphene oxide (GO) as a nanovehicle. Our data suggest cell death via apoptosis in a dose-dependent manner due to increase in calcium levels in specific cancer cell lines. Interestingly, the benzoxazine derivatives of eugenol with GO nanoparticle exhibited enhanced therapeutic potential in cancer cells. In addition to anti-cancer effect, we also observed significant role of these derivatives on parasite suggesting its multi-pharmacological capability.

Bioactive Constituents of Lamium album L. as Inhibitors of Cytokine Secretion in Human Neutrophils.

The traditional role of Lamium album L. (white dead nettle, Lamiaceae) in providing relief from pain in rheumatism as well as vaginal and cervical inflammation was described. The aim of the study was to screen for the anti-inflammatory bioactivity of compounds isolated from aqueous-methanolic extract of Lamium album herb in human neutrophils (PMNs). The effect of the compounds on the inhibition of selected inflammatory markers released by neutrophils, such as cytokines (IL-8, TNF-α), was studied. The molecular masses and the purity of compounds were determined using high-performance liquid chromatography coupled with diode array detection and mass spectrometry (HPLC-DAD-MSn). The level of cytokines production after incubation with the compounds (1–25 µM) was measured by ELISA. Two derivatives of quercetin, not previously described, were isolated in this study. Phenylpropanoids (verbascoside and phlinoside D), as well as iridoids (lamalbid, and shanzhiside methyl ester), and flavonoids revealed to be more significant inhibitors of IL-8 secretion than TNF-α. The compounds at a concentration of 25 µM, except for shanzhiside methyl ester (6), inhibited secretion of IL-8 in the range from 29.1 to 50.0%. In conclusion, L. album might be a valuable source of bioactive compounds and may provide constituents to limit noninfectious inflammation associated with the aforementioned diseases.

Influence of alloy engineering on structural and photo detection properties of SbXSn1-XSe2 ternary alloys

In order to exploit effect of Sb incorporation on properties of SnSe2, alloy engineering is performed in SbxSn1-xSe2 (x = 0, 0.1, 0.2, 0.3) ternary compounds. The single crystals are grown by direct vapour transport technique. The elemental composition and purity of as-grown compounds are characterized by EDAX. The optical microscopy and scanning electron microscopy show characteristic morphological features like helical spiral, layered structure, clean surface, etc. on surface of grown crystals. The powder X-ray diffraction shows that the pristine and Sb incorporated samples possess 2H-Hexahonal lattice structure. However, lattice parameters and unitcell volume are changed on incorporation of Sb in SnSe2 structure due to increase in microstrain. The Raman spectroscopy reveals SnSe2-type A1g vibrational mode and the corresponding peak is shifted on lower wavenumber side on increasing Sb content. The results confirm substitution of Sb(+5) on Sn(+4) lattice site in host network. The influence of alloy engineering on photo response is studied. The highest photocurrent of 1.88 μA, responsivity of 43.45 mAW−1, detectivity of 18.25 × 1011 Jones and EQE (%) of 47.28% are observed for X = 0.1 sample.

New Bis-Pyrazolones as Potential Leads for ROS Inhibition; Environment Friendly Green Synthesis, Structural Characterization, and In Vitro Studies.

Pyrazolones have identified as significant antioxidant agents and many marketed and clinically prescribed NSAIDs have pyrazolone ring as main scaffold. Keeping in consideration the antioxidant potential of pyrazolone scaffold, new bispyrazolones 3-30 were synthesized by a green and enviroment friendly reaction route, in which two equivalents of 1-(4-chlorophenyl)-3-methyl-1H-pyrazol-5-ol were treated with one equivalent of benzaldehyde derivatives without any catalyst. All compounds were structurally characterzied by 1H-NMR and FAB analysis. 13C-NMR of selected compounds was also recorded. All compounds gave satisfactory elemental analyses and found in good agreement with calculated values. Synthetic bis-pyrazolones 3-30 were evaluated for their oxidative burst inhibitory effect of zymosan stimulated whole blood phagocytes by using luminol enhanced chemilluminescence technique. All molecules demonstrated the potent ROS inhibition activity in the range of IC50 = 1.2 ± 0.1-48.8 ± 3.9 µM as compared to the standard ibuprofen (IC50 = 54.2 ± 9.2 μM). The purity of active compounds was checked by HPLC. This study has identified a number of non-acidic lead molecules for future research on ROS inhibitors.

Targeting PPAR-γ to design and synthesize antidiabetic thiazolidines.

A series of thiazolidine derivatives were designed by docking into PPAR-γ active site. The structure of target was obtained from the protein data bank (PDB ID P37231). A library of 200 molecules was prepared on random basis. Molecular docking studies were performed using VLife MDS 4.3 software. After molecular docking studies, the 4-substituted-6-methyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylic acid N-[4-(2,4-dioxo-thiazolidin-5-ylidenemethyl)-phenyl]-hydrazides (4a-4h) were selected for synthesis. The progress of reaction and purity of the synthesized compounds were monitored by TLC and melting point. Structures of title compounds were confirmed by elemental analysis, IR, 1H NMR and mass spectral data. The antidiabetic activity of title compounds was performed using the Wistar rats by alloxan-induced method. The compounds have shown antidiabetic activity comparable with the standard drug pioglitazone. These findings suggest that potent antidiabetics can be generated by substituting nonpolar, electron withdrawing substituents at the fourth position of pyrimidine skeleton and hydrogen bond acceptor at the nitrogen of the thiazolidine nucleus, to inhibit peroxisome proliferator-activated receptor-γ.

Identification of Anticandidal Cyclic Trisaccharide from Alhagi pseudalhagi Plant

Background: Alhagi pseudoalhagi (Camel thorn) is a herbaceous perennial plant. Recently, several investigations have been conducted for its medical and pharmaceutical applications. Methods: The aerial part of the plant was air dried and extracted by different solvents with increasing polarity. The residue from each extract was in-vitro tested against C. albicans that has been previously isolated from vaginal candidiasis patients. The ethyl acetate extract showed anti-candidial activity and showed presence of two compounds on the TLC plate eluted with methanol. This extract was further purified by silica gel column eluted with methanol. The obtained two compounds were tested against C. albiacns and the purity of the active compound was confirmed by reversed phase HPLC with methanol as a mobile phase and detected at 240nm. The chemical structure of the active pure compound was elucidated by mass spectrometry, 1D and 2D-NMR and IR analysis. Result: The NMR analyses characterized three sugar molecules cross-linked in a cyclic structure. These three building units are: (4,6-dideoxy,6-methyne, α,D,glucopyranose), (β, D,1-deoxy, 1-methyne, fructofuranose), and (2-deoxy, 3-methyne, 4,6-epoxy, fructofuran). The three units are cross-linked through the methyne group that bind with C6 of 4,6-dideoxy, 6-methyne, α,D-glucopyranose, C1 of 1-deoxy, 1- methyne, fructofuranose and with C3 of 2-deoxy, 4,6-epoxy, 3-methyne, fructofuran moieties. The COSY, HSQC, HMBC and TOCSY analyses confirmed the elucidated structure with a molecular formula C19H26C11 and MW = 430.4. Conclusion: The result from this research identified for the first time the cyclic trisaccharide glycoside from Alhagi pseudoalhagi with antifungal activity against C. albicans. Keywords: Alhagi pseudoalhagi, anticandidal, glycoside, C. albicans, mass spectrometry, NMR.

Fractionation of polyphenols from thermomechanical pulp mill process water by flotation and membrane integrated process

ABSTRACTFractionation of phenolic compounds in thermomechanical pulp mills was performed with a coupling of a prior treatment realized by flotation and a ceramic membrane process. Two lines of membranes filtration were tested. After a common 150 kDa clarification, 1 kDa filtration was performed with or without previous 5 kDa filtration. Flotation was shown to be inevitable to retain lipophilic compounds which cause severe membrane fouling. 150 kDa permeate flux was 20% higher when process water was firstly floated and was around 260 L h−1 m−2. 1 kDa membrane was fouled with 31% of irreversible fouling without previous 5 kDa filtration and phenolic compounds purity reached only 26% in this 1 kDa permeate. Phenolic compounds as lignin-like substances which might be attached to hemicelluloses were recovered in 5 kDa retentate. Retentate of 1 kDa might contain a major fraction of lignin derivatives with molecular weights around 1 kDa free or linked with phenolic acids. Permeate of 1 kDa contained 14% of phenolic compounds such as lignans and free phenolic acids purified at 50%.

Liver enzymes improve drug leads

Medicinal chemists know all too well the pain of running dozens of syntheses when diversifying drug leads. Researchers at Pfizer now report they’ve saved time, reagents, and expense by using mishmashes of enzymes contained in liver microsomes—vesicles collected from liver tissue in animals and humans—in multiple drug discovery programs. When medicinal chemists have a promising compound, they sometimes look for analogs with more druglike properties, says R. Scott Obach, the Pfizer drug metabolism researcher who led the project. Traditionally, chemists come up with synthetic routes to each of the many analogs. High yield and compound purity are paramount for these routes, Obach says. Pfizer’s technology is different. The team biosynthesizes mixtures of products with liver microsomes, which contain a melange of cytochrome P450 enzymes that can modify molecules in myriad ways. Team members test microsomes from various species, including rabbit, monkey, and human, to determine which are best at making

Synthesis, pharmacological activity, and chromatographic enantioseparation of new heterocyclic compounds of the aryloxyaminopropanol type derived from 4-hydroxyphenylalkanones

In the paper, a series of six pharmacologically active compounds (β-adrenolytics) derived from 4-hydroxyphenylethanone and 4-hydroxyphenylpropan-1-one are reported. The compounds incorporate pyrrolidin-1-yl and 4-methylpiperazin-1-yl substituents in the hydrophilic part of the molecule and ethoxymethyl and methoxyethoxymethyl side chains on the aromatic ring in the lipophilic moiety. They were prepared by a four-step synthesis from 4-hydroxyalkanones via chloromethyl, alkoxymethyl, and oxirane intermediates. The purity of the target compounds was checked by TLC and their structures were confirmed by the interpretation of the IR, UV, 1H NMR, and 13C NMR spectra. The pharmacological evaluation of the obtained compounds confirmed their vasodilatory and specific antiisoprenaline activities. All evaluated compounds at conc. 10−6 mol dm−3 inhibited vasoconstrictory effect of phenylephrine (8.22–33.7%) on isolated rat aorta. The ability to inhibit positive chronotropic effect of isoprenaline was observed on isolated spontaneously beating rat’s atria after pre-treatment with the evaluated compounds at conc. 10−7 and 10−6 mol dm−3. The calculated pA2 values of specific antagonistic effect against isoprenaline, related to their apparent β-adrenolytic activity, ranged between 6.54 and 7.57. The value for the standard compound carvedilol was 8.15 ± 0.22. The majority of the evaluated compounds at conc. 10−6–10−7 mol dm−3 also showed negative chronotropic effect on the basic heart rate of atria. Enantioseparation of the prepared compounds was performed by chiral HPLC on an amylose tris(3,5-dimethylphenylcarbamate) column (Chiralpak AD) and a native teicoplanin column (Chirobiotic T). The chromatographic characteristics as retention, separation, and resolution factors were reported.

A copper based metal-organic framework: Synthesis, modification and VOCs adsorption

A new copper (II) metal-organic framework Cu-MOF based on the ligand of 5-aminoisophthalic acid (AIPA) has been synthesized. Single-crystal X-ray structural analysis confirmed the formation of this compound, namely [Cu(AIPA)·DMF]n. The crystal structure exhibits a 2D sheet, which generate a 3D framework through non-classical hydrogen bond interactions. TGA, IR and VT-PXRD have been carried out to characterize the compound's thermal stability and purity. The as-synthesized sample was activated by removal of the coordination DMF solvent to afford porous framework Cu-MOF (1) without degradation of the original crystallinity. As the model of volatile organic compounds (VOCs), formaldehyde capture studies have shown that Cu-MOF (1) exhibits a versatile behavior for toxic gas accumulation.

Generation of spin currents from one-dimensional quantum spin liquid

Spin-Seebeck effects (SSEs) in a one-dimensional quantum spin liquid (QSL) system have been investigated in a Sr2CuO3/Pt hybrid structure. Sr2CuO3 contains one-dimensional spin-12 chains in which typical spinons in QSL have been confirmed. Heat-induced voltage measured in a clean Pt/Sr2CuO3 exhibits anomalous sign reversal with decreasing temperature, the negative component of which can be attributed to the spinon-induced SSE. However, the SSE was found to be critically decreased upon the exposure of Sr2CuO3 to air, which can be associated with the chemical degradation of the interface of Sr2CuO3. Despite the drastic change in the SSE signals, properties of the one-dimensional QSL are little changed in the spin susceptibility as well as the thermal conductivity of Sr2CuO3. The SSE signal is also sensitive to the purity of Sr2CuO3; it is suppressed with a decrease in the purity of the primary compounds of the Sr2CuO3. The result indicates that the spinon-induced SSE in Sr2CuO3 is sensitive to the bulk condition due to the one-dimensional atomic channel for spin transport in Sr2CuO3. In a carefully prepared Sr2CuO3/Pt sample, we found that the spinon-induced SSE signal is tolerant to magnetic fields; it increases linearly with the field even up to 9 T. In contrast, SSEs are suppressed under such a high field in ferrimagnetic insulators Y3Fe5O12 or paramagnetic insulators Gd3Ga5O12, which is caused by the Zeeman gap in the spin-wave or paramagnetic spin excitations. The robustness of the spinon-induced SSE is consistent with the Tomonaga-Luttinger liquid theories.

2‐Hydroxypyridine‐N‐oxide (HOPO): Equivocal in the ames assay

2-Hydroxypyridine-N-oxide (HOPO) is a useful coupling reagent for synthesis of active pharmaceutical ingredients. It has been reported to be weakly mutagenic in the Ames assay (Ding W et al. []: J Chromatogr A 1386:47-52). According to the ICH M7 guidance (2014) regarding control of mutagenic impurities to limit potential carcinogenic risk, mutagens require control in drug substances such that exposure not exceeds the threshold of toxicological concern. Given the weak response observed in the Ames assay and the lack of any obvious structural features that could confer DNA reactivity we were interested to determine if the results were reproducible and investigate the role of potentially confounding experimental parameters. Specifically, Ames tests were conducted to assess the influence of compound purity, solvent choice, dose spacing, toxicity, type of S9 (aroclor vs phenobarbital/β-napthoflavone), and lot variability on the frequency of HOPO induced revertant colonies. Initial extensive testing using one lot of HOPO produced no evidence of mutagenic potential in the Ames assays. Subsequent studies with four additional lots produced conflicting results, with an ∼2.0-fold increase in revertant colonies observed. Given the rigor of the current investigation, lack of reproducibility between lots, and the weak increase in revertants, it is concluded that HOPO is equivocal in the bacterial reverse mutation assay. It is highly unlikely that HOPO poses a mutagenic risk in vivo; therefore, when it is used as a reagent in pharmaceutical synthesis, it should not be regarded as a mutagenic impurity, but rather a normal process related impurity. Environ. Mol. Mutagen. 59:312-321, 2018. © 2018 Wiley Periodicals, Inc.