Photophysics and photochemistry of aflatoxins B1 and B2

Netto‐Ferreira, José Carlos; Heyne, Belinda; Scaiano, Juan C.

doi:10.1039/c1pp05103b

Cited by 12 publications

(8 citation statements)

References 67 publications

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“…In order to ascertain the nature of the transient species observed, several quenching experiments were performed . Usually the presence of a triplet state is confirmed by the use of a low energy triplet quencher such as β ‐carotene . Unfortunately, this quencher could not be used in this study due to the overlap of its absorption spectrum with that of NBD‐hexane.…”

Section: Resultsmentioning

confidence: 99%

“…Quenching rate constant for the triplet state of NBD‐hexane by 4‐hydroxy‐TEMPO was obtained from a Stern–Volmer plot according to Eq. :

k_{normalobs} = k_{o} + k_{q} false[Q false]

where k o is the triplet decay rate constant in the absence of quencher; k q is the triplet decay rate constant in the presence of the quencher and [Q] is the quencher concentration in mol L −1 .…”

Section: Methodsmentioning

confidence: 99%

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Unveiling the Triplet State of a 4‐Amino‐7‐Nitrobenzofurazan Derivative in Cyclohexane

Sveen

Macia

Zaremberg

et al. 2015

Photochem & Photobiology

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The nitrobenzofurazan (NBD) moiety has gained tremendous popularity over the last decades due to its fluorogenic nature. Indeed, upon interaction with aliphatic amines, it generates a stable fluorescent adduct, which has been used for protein and lipid labeling. In fact the 4-amino substituted NBD belongs to the broad family of intramolecular charge transfer molecules, with the amino group acting as an electron donor upon photoexcitation, and the nitro group as an electron acceptor. Although the singlet excited state of 4-amino NBD derivatives has been abundantly studied, investigation of its triplet manifold is scarce and even the absence of intersystem crossing for this type of molecules has been suggested. However, intramolecular charge transfer molecules are known to undergo intersystem crossing and high phosphorescence quantum yields have been reported in a nonpolar solvent. In the present paper, we have investigated the photophysical and photochemical properties of N-hexyl-7-nitrobenzo[c][1,2,5]xadiazole-4-amine. We have shown the existence of a triplet state for this molecule in cyclohexane via nanosecond laser flash photolysis. Interestingly, deactivation of the triplet state leads to photoproducts formation, which are only present in the absence of oxygen.

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Section: Resultsmentioning

confidence: 99%

“…Quenching rate constant for the triplet state of NBD‐hexane by 4‐hydroxy‐TEMPO was obtained from a Stern–Volmer plot according to Eq. :

k_{normalobs} = k_{o} + k_{q} false[Q false]

Section: Methodsmentioning

confidence: 99%

Unveiling the Triplet State of a 4‐Amino‐7‐Nitrobenzofurazan Derivative in Cyclohexane

Sveen

Macia

Zaremberg

et al. 2015

Photochem & Photobiology

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“…In Type II mechanism, energy is transferred from triplet aflatoxin to molecular oxygen leading to singlet oxygen formation. These reactive species react with the aflatoxins and form oxidized products 36 . Various authors have studied the degradation kinetics of aflatoxins.…”

Section: Uv-a Degradation Kinetics Of Afb 1 and Afmmentioning

confidence: 99%

Performance of a UV-A LED system for degradation of aflatoxins B1 and M1 in pure water: kinetics and cytotoxicity study

Stanley

Patras

Pendyala

et al. 2020

Sci Rep

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The efficacy of a UV-A light emitting diode system (LED) to reduce the concentrations of aflatoxin B 1 , aflatoxin M 1 (AFB 1 , AfM 1) in pure water was studied. This work investigates and reveals the kinetics and main mechanism(s) responsible for the destruction of aflatoxins in pure water and assesses the cytotoxicity in liver hepatocellular cells. Irradiation experiments were conducted using an LED system operating at 365 nm (monochromatic wavelength). Known concentrations of aflatoxins were spiked in water and irradiated at UV-A doses ranging from 0 to 1,200 mJ/cm 2. The concentration of AFB 1 and AfM 1 was determined by HPLC with fluorescence detection. LC-MS/MS product ion scans were used to identify and semi-quantify degraded products of AFB 1 and AfM 1. It was observed that UV-A irradiation significantly reduced aflatoxins in pure water. In comparison to control, at dose of 1,200 mJ/cm 2 UV-A irradiation reduced AFB 1 and AfM 1 concentrations by 70 ± 0.27 and 84 ± 1.95%, respectively. We hypothesize that the formation of reactive species initiated by UV-A light may have caused photolysis of AFB 1 and AfM 1 molecules in water. In cell culture studies, our results demonstrated that the increase of UV-A dosage decreased the aflatoxins-induced cytotoxicity in HepG2 cells, and no significant aflatoxin-induced cytotoxicity was observed at UV-A dose of 1,200 mJ/cm 2. Further results from this study will be used to compare aflatoxins detoxification kinetics and mechanisms involved in liquid foods such as milk and vegetable oils. Filamentous fungi invading various feed crops produces toxic secondary metabolites called mycotoxins which possess a serious threat to consumer health 1. Aflatoxins are highly cytotoxic and carcinogenic secondary metabolites, produced predominantly by Aspergillus flavus and Aspergillus paraciticus, especially in the tropical and subtropical regions as hot and humid climatic conditions are optimal for mold growth and toxin production 2,3. Aflatoxins are difuranocoumarin derivatives formed from the polyketide pathway and include a group of 17 aflatoxins, among which AFB 1 is the predominant and is highly toxic 4. Aflatoxin contamination in animal feed results in their carry-over in foods of animal origin such as eggs and milk. The major AFB 1 metabolite in milk, AFM 1, is formed due to the action of hepatic cytochrome P450-dependent polysubstrate monoxygenase enzyme superfamily as a result of the hydroxylation of the fourth carbon of the terminal furan ring. In dairy cows, the biotransformation rate of AFB 1 to AFM 1 ranges from 0.3 to 6.2% 5,6. Aflatoxins are detrimental upon ingestion, inhalation, and skin contact; and the consequences of aflatoxin infection are collectively called aflatoxicosis. The biotransformation of AFB 1 in liver results in the production of AFB 1-8,9-epoxide which is highly related to the incidence of hepatocellular carcinoma 6,7. The carcinogenicity of AFM 1 is approximately one-tenth of that of AFB 1 The International Agency for Research on Cancer in 1993 classif...

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“…In addition, most studies were carried out on the Ames test and cytotoxicity of HepG2 cells of AFB 1 products after irradiation [10,13,16,17]. The toxicities of the photodegradation products of AFB 1 in water and peanut oil on HepG2 cells were investigated, and it was found that the cytotoxicity of products of AFB 1 in water decreased 40%, while that of products of AFB 1 in peanut oil reduced about 100% [13].…”

Section: Introductionmentioning

confidence: 99%

A Structure Identification and Toxicity Assessment of the Degradation Products of Aflatoxin B1 in Peanut Oil under UV Irradiation

Mao

Zhang

et al. 2016

Toxins

122

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Aflatoxins, a group of extremely hazardous compounds because of their genotoxicity and carcinogenicity to human and animals, are commonly found in many tropical and subtropical regions. Ultraviolet (UV) irradiation is proven to be an effective method to reduce or detoxify aflatoxins. However, the degradation products of aflatoxins under UV irradiation and their safety or toxicity have not been clear in practical production such as edible oil industry. In this study, the degradation products of aflatoxin B1 (AFB1) in peanut oil were analyzed by Ultra Performance Liquid Chromatograph-Thermo Quadrupole Exactive Focus mass spectrometry/mass spectrometry (UPLC-TQEF-MS/MS). The high-resolution mass spectra reflected that two main products were formed after the modification of a double bond in the terminal furan ring and the fracture of the lactone ring, while the small molecules especially nitrogen-containing compound may have participated in the photochemical reaction. According to the above results, the possible photodegradation pathway of AFB1 in peanut oil is proposed. Moreover, the human embryo hepatocytes viability assay indicated that the cell toxicity of degradation products after UV irradiation was much lower than that of AFB1, which could be attributed to the breakage of toxicological sites. These findings can provide new information for metabolic pathways and the hazard assessment of AFB1 using UV detoxification.

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Photophysics and photochemistry of aflatoxins B1 and B2

Cited by 12 publications

References 67 publications

Unveiling the Triplet State of a 4‐Amino‐7‐Nitrobenzofurazan Derivative in Cyclohexane

Unveiling the Triplet State of a 4‐Amino‐7‐Nitrobenzofurazan Derivative in Cyclohexane

Performance of a UV-A LED system for degradation of aflatoxins B1 and M1 in pure water: kinetics and cytotoxicity study

A Structure Identification and Toxicity Assessment of the Degradation Products of Aflatoxin B1 in Peanut Oil under UV Irradiation

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