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Photodegradation of folic acid is inhibited by 5-MTHF. Folic acid, at 50 M, was exposed in the presence of 25 M 5-MTHF at pH 7.4 to UVA, (lambda max365 nm, 820 W/cm 2 ) for 100 min. Samples analyzed by HPLC showed protection of folic acid (circles) by 5-MTHF (squares) until the latter was almost totally consumed.
Source publication
The known functions of folate are to support one-carbon metabolism and to serve as photoreceptors for cryptochromes and photolyases. We demonstrate that 5-methyltetrahydrofolate (5-MTHF, the predominant folate in plasma) is also a potent, near diffusion limited, scavenger of singlet oxygen and quencher of excited photosensitizers. Both pathways res...
Contexts in source publication
Context 1
... added together with folic acid, 5-MTHF inhib- ited the photolysis of folic acid in a sacrificial way. Folic acid was maintained until 5-MTHF decayed below 1 M concentration (Fig. 2). Thereafter, 6-FP, p-aminoben- zoylglutamate, and PCA were produced as in the ab- sence of ...
Context 2
... at an average concentration of 2 M. Sodium azide at 10 mM also afforded full protec- tion under the same conditions, confirming that the damage is largely mediated by singlet oxygen. DNA damage induced by 50 M folic acid was abrogated by inclusion of 50 M 5-MTHF (added only initially) (Fig. 4B), which decayed in a manner similar to that shown in Fig. ...
Citations
... It also has a positive effect on the prevention of diseases. Vitamins are sensitive to both heat and light [89]. During processing, vitamins are lost due to thermal degradation, photoenzymatic reactions, and oxidation reactions [90]. ...
Microwave technology is used throughout the world to generate heat using energy from the microwave range of the electromagnetic spectrum. It is characterized by uniform energy transfer, low energy consumption, and rapid heating which preserves much of the nutritional value in food products. Microwave technology is widely used to process food such as drying, because food and medicinal plants are the same organisms. Microwave technology is also used to process and extract parts of plants for medicinal purposes; however, the special principle of microwave radiation provide energy to reaction for transforming chemical components, creating a variety of compounds through oxidation, hydrolysis, rearrangement, esterification, condensation and other reactions that transform original components into new ones. In this paper, the principles, influencing factors of microwave technology, and the transformation of natural metabolites using microwave technology are reviewed, with an aim to provide a theoretical basis for the further study of microwave technology in the processing of medicinal materials.
... Moreover, a combination of vitamin C and vitamin E on porcine skin provided improved UVR-photoprotection and reduced thymine dimer formation as compared to either antioxidants alone [29]. While some forms of vitamin B have been suggested to impact human skin photosensitization, folate (vitamin B9) inhibited photosensitization reactions and DNA strand breaks [30,31]. Folate status in the skin was proposed to be major determinant for skin pigmentation and vitamin D production. ...
Chronic exposure of human skin to solar ultraviolet radiation (UVR) induces a range of biological reactions which may directly or indirectly lead to the development of skin cancer. In order to overcome these damaging effects of UVR and to reduce photodamage, the skin's endogenous defence system functions in concert with the various exogenous photoprotectors. Growth factors, particularly insulin-like growth factor-I (IGF-I), produced within the body as a result of cellular interaction in response to UVR demonstrates photoprotective properties in human skin. This review summarises the impact of UVR-induced photolesions on human skin, discusses various endogenous as well as exogenous approaches of photoprotection described to date and explains how IGF-I mediates UVR photoprotective responses at the cellular and mitochondrial level. Further, we describe the current interventions using growth factors and propose how the knowledge of the IGF-I photoprotection signalling cascades may direct the development of improved UVR protection and remedial strategies.
... Bath PUVA therapy is as effective as oral PUVA method without systemic adverse effects of oral psoralen (Pai & Shetty, 2015). UV radiation could disintegrate serum folate in vitro, but there are not enough experiences to support similar results in vivo (Der-Petrossian, Födinger, Knobler, Hönigsmann, & Trautinger, 2007;Off et al., 2005;Offer et al., 2007). ...
... On the other hand, phototherapy by itself may be associated with cutaneous cancers. Therefore, simultaneous folate deficiency and phototherapy may increase risk of skin cancers (Duthie, 1999;Juzeniene, Stokke, Thune, & Moan, 2010;Malerba et al., 2006;Offer et al., 2007). Some studies have been done in vitro and in vivo to evaluate photolytic effects of UV rays on the serum folate level with therapy and 8 weeks posttreatment, and cumulative dosage of UVA during 8 weeks of treatment were collected for all patients. ...
... It has been reported that UV radiation may cause neural tube defects in embryos of exposed mothers probably due to folate deficiency. On the other hand, UV rays increases vitamin D production (Cicarma et al., 2010;Offer et al., 2007). Folic acid and its derivatives are essential micronutrients for DNA and amino acids biosynthesis (Off et al., 2005;Offer et al., 2007). ...
Background:
Ultraviolet (UV) radiation could disintegrate folate molecule, so phototherapy may reduce folate levels in the patients. The effect of phototherapy on serum folate in human body is questionable. We investigated the effect of Bath PUVA therapy on serum folate level.
Materials and methods:
This study was designed as a before-after study. Thirty-two patients completed study during two years. Our variables were demographic data, folate levels before and eight weeks after treatment and cumulative dosage of UVA during 8 weeks of treatment. Serum folate was evaluated with chemiluminescence immunoassay technique. All data were analyzed using SPSS 18 software.
Results:
Folate level changes were statistically significant before and after Bath PUVA therapy. There was no significant difference in folate levels in psoriasis patients compared to non-psoriasis patients. In psoriasis patients, folate levels had no significant correlation with psoriasis activity index before treatment. Decrease in folate levels was more significant in fair-skinned patients. There was no association between folate status and cumulative dosage of UVA.
Conclusion:
Bath PUVA therapy reduced serum folate level in our patients although none of them were folate deficient. Folate deficiency should be evaluated and corrected especially in fair-skinned cases, as it may be aggravated by phototherapy. This article is protected by copyright. All rights reserved.
... As photosensitizers, it was reported that UV-A excitation of pterins induces DNA damage (9,23,24). In the context of our studies on the photosensitizing properties of these heterocycles, we have previously demonstrated that Ptr, the parent unsubstituted compound of oxidized pterins, and the vitiligo-related pterin derivatives (Bip, formylpterin and carboxypterin) are able to photoinduce the degradation of purine nucleotides [2 0 -deoxyguanosine 5 0 -monophosphate (dGMP) (10,(25)(26)(27) and 2 0 -deoxyadenosine 5 0 -monophosphate (dAMP) (28,29)] in aqueous solutions. ...
Pterin derivatives are heterocyclic compounds which are present in different biological systems. Neutral aqueous solutions of pterins presents acid‐base and keto‐enol equilibria. These compounds under UV‐A radiation fluoresce, undergo photooxidation, generate reactive oxygen species, and photoinduce the oxidation of biological substrates. As photosensitizers, they may act through different mechanisms; mainly through an electron‐transfer initiated process (type I mechanism), but they also produce singlet molecular oxygen (¹O2) upon irradiation (type II mechanism). In general, upon UV‐A excitation two triplet states, corresponding to the lactim and lactam tautomers, are formed, but only the last one is the responsible for the photosensitized reactions of biomolecules. We present a study of the photochemical properties of 3‐methylpterin (3‐Mep) which, in contrast to most pterin derivatives, exists only in the lactam form. Also an improvement in the synthesis of 3‐Mep is reported. The spectroscopic properties 3‐Mep in aqueous solution were similar to those of the unsubstituted pterin derivative (Ptr) in its acid form, such as absorption, fluorescent and phosphorescent emission spectra. Experiments using 2′‐deoxyguanosine 5′‐monophosphate (dGMP) as oxidizable target, demonstrated that methylation at C‐3 position of the pterin moiety does not affect significantly the efficiency of photosensitization, but results in a more photostable sensitizer.
This article is protected by copyright. All rights reserved.
... In the late 1990s it was reported that oxidized pterins are efficient 1 O 2 photosensitizers [33,34], and that UV-A excitation of pterins induces DNA damage [35]. Later studies provided additional evidence on the photosensitizing capability of pterins to degrade DNA, but contradictory mechanisms were proposed [36,37]. In the context of our investigations on the photosensitizing properties of pterins in aqueous solutions, we have previously demonstrated that pterin (Ptr), the parent unsubstituted compound of oxidized pterins (Fig. 1), and the vitiligo-related pterin derivatives (biopterin, formylpterin and carboxypterin) are efficient photosensitizers inducing the degradation of purine nucleotides (2′-deoxyguanosine 5′-monophosphate (dGMP) [38][39][40] and 2′-deoxyadenosine 5′-monophosphate (dAMP) [41,42]). ...
UV-A radiation (320-400 nm), recognized as a class I carcinogen, induces damage to the DNA molecule and its components through different mechanisms. Pterin derivatives are involved in various biological functions, including enzymatic processes, and it has been demonstrated that oxidized pterins may act as photosensitizers. In particular, they accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder. We have investigated the ability of pterin (Ptr), the parent compound of oxidized pterins, to photosensitize the degradation of the pyrimidine nucleotide thymidine 5’-monophosphate (dTMP) in aqueous solutions under UV-A irradiation. Although thymine is less reactive than purine nucleobases, our results showed that Ptr is able to photoinduce the degradation of dTMP and that the process is initiated by an electron transfer from the nucleotide to the triplet excited state of Ptr. In the presence of molecular oxygen, the photochemical process leads to the oxidation of dTMP, whereas Ptr is not consumed. In the absence of oxygen, both compounds are consumed to yield a product in which the pterin moiety is covalently linked to the thymine. This compound retains some of the spectroscopic properties of Ptr, such as absorbance in the UV-A region and fluorescence properties.
... Low concentrations of FA (b1 μM) may be photocarcinogenic, because it does not photodegrade so fast as higher concentrations (Fig. 4), and may induce high levels of ROS for the longer time (Fig. 3). The maximal concentration of PCA was observed at around 80 J/cm 2 for 1 μM FA, at 25 J/cm 2 for 5 μM FA, at 20 J/cm 2 for 10 μM FA (Fig. 2), and at 2 J/cm 2 for 85 μM FA [29]. The photodegradation of FA at much higher concentrations (N80 μM) was investigated in the literature earlier [9,29]. ...
... The maximal concentration of PCA was observed at around 80 J/cm 2 for 1 μM FA, at 25 J/cm 2 for 5 μM FA, at 20 J/cm 2 for 10 μM FA (Fig. 2), and at 2 J/cm 2 for 85 μM FA [29]. The photodegradation of FA at much higher concentrations (N80 μM) was investigated in the literature earlier [9,29]. ...
... These dimers distort the conformation of the double helix and interfere with normal DNA replication, which can produce mutations [4,12,15,16] and chromosomal fragmentation [5]. UV-A light also indirectly affects DNA by promoting the formation of reactive species, mainly reactive oxygen species (ROS) [1,4,12,17]. These entities oxidize the bases within DNA, which can lead to the fragmentation of DNA strands [1,17,18] and may lead to the formation of micronuclei [5,10,19,20]. ...
... UV-A light also indirectly affects DNA by promoting the formation of reactive species, mainly reactive oxygen species (ROS) [1,4,12,17]. These entities oxidize the bases within DNA, which can lead to the fragmentation of DNA strands [1,17,18] and may lead to the formation of micronuclei [5,10,19,20]. The UV-B in sunlight is a causative agent of skin cancer [21]. ...
... The UV-A light is capable of producing pyrimidine dimers [4], this meaning that the DNA molecule in these conditions are more susceptible to strand breakage [20] and can give rise to micronuclei. The UV-A lamp can also cause damage by induction of ROS [1,4,12,17,27,48], which may also produce chromosome breaks [10,19] and micronuclei, as was observed in the present. ...
Ultraviolet-A Light Induces Micronucleated Erythrocytes in Newborn Rats
Ultraviolet-A (UV-A) light induce DNA damage by creating pyrimidine dimers, or indirectly affects DNA by the formation of reactive oxygen species. The objective was to determine DNA damage by micronucleus test in neonatal rats exposed to UV-A light. Rat neonates were exposed to light from a LED lamp (control group), to UV-C light 254 nm (control group to desquamation skin) or UV-A light 365 nm and in one group the dams were supplemented with folic acid (FA), to determine micronucleated erythrocytes (MNE) and micronucleated polychromatic erythrocytes (MNPCE) in peripheral blood of offspring.
... It is therefore very stable under the majority of conditions (i.e, temperature and pH), and is the vitamer used for supplements and food fortification (30). However, when PteGlu is exposed to UV radiation, it breaks down into the photo-scission products p-aminobenzoylglutamate (p-ABG) and 6-formylpterin (6-FP), the latter of which eventually oxidizes to form pterin-6-carboxylic acid (PCA) (31,32). ...
... Additionally, photo-degradation of PteGlu is accelerated by other photosensitizers such as other unconjugated pterin moieties (142) and riboflavin (149), and the interaction with other nutrients is still unknown. It is, therefore, a putative concern in skin and other cancers in the post-fortification era (31,145). ...
The impact of folate on health and disease, particularly pregnancy complications and congenital malformations, has been extensively studied. Mandatory folic acid fortification therefore has been implemented in multiple countries, resulting in a reduction in the occurrence of neural tube defects. However, emerging evidence suggests increased folate intake may also be associated with unexpected adverse effects. This literature review focuses on contemporary issues of concern, and possible underlying mechanisms as well as giving consideration the future direction of mandatory folic acid fortification. Folate fortification has been associated with the presence of unmetabolized folic acid (PteGlu) in blood, masking of vitamin B12 deficiency, increased dosage for anti-cancer medication, photo-catalysis of PteGlu leading to potential genotoxicity, and a role in the pathoaetiology of colorectal cancer. Increased folate intake has also been associated with twin birth and insulin resistance in offspring, and altered epigenetic mechanisms of inheritance. Although limited data exists to elucidate potential mechanisms underlying these issues, elevated blood folate level due to the excess use of PteGlu without consideration of an individual's specific phenotypic traits (e.g. genetic background and undiagnosed disease) may be relevant. Additionally, the accumulation of unmetabolized PteGlu may lead to inhibition of dihydrofolate reductase and other enzymes. Concerns notwithstanding, folic acid fortification has achieved enormous advances in public health. It therefore seems prudent to target and carefully monitor high risk groups, and to conduct well focused further research to better understand and to minimize any risk of mandatory folic acid fortification.
... It was demonstrated for the first time in 1997 by Ito and Kawanishi (17) that UV-A excitation of pterins induces DNA damage. Later studies provided additional evidence on the photosensitizing capability of pterins to degrade DNA, but contradictory mechanisms were proposed (18,19). In previous studies performed with single nucleotides as substrates (20,21), we have demonstrated that pterin (Ptr), the parent unsubstituted compound of oxidized pterins (Scheme 1), can act as a photosensitizer through both type I and type II mechanisms. ...
Biopterin (Bip) and its photoproducts 6-formylpterin (Fop) and 6-carboxypterin (Cap) accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder where the protection against UV radiation fails because of the lack of melanin. These compounds absorb in the UV-A inducing a potential photosensitizing action that can cause damage to DNA and other biomolecules. In this work, we have investigated the capability of these pterin derivatives (Pt) to act as photosensitizers under UV-A irradiation for the degradation of 2'-deoxyadenosine 5'-monophosphate (5'-dAMP) in aqueous solutions, as model DNA target. Steady-state and time-resolved experiments were performed and the effect of pH was evaluated. The results showed that photosensitized degradation of 5'-dAMP was only observed under acidic conditions, and a mechanistic analysis revealed the participation of the triplet excited state of the pterin derivatives ((3) Pt*) by electron transfer yielding the corresponding pair of radical ions (Pt(•-) and 5'-dAMP(•+) ), with successive photosensitizer recovery by electron transfer from Pt(•-) to O2 . Finally 5'-dAMP(•+) participates in subsequent reactions to yield degradation products. This article is protected by copyright. All rights reserved.
... No apparent changes were observed in the absorption spectra of 0.26 and 1 lM FA after UV exposure (data not shown). Not more than 5% of FA was photooxidized during given UV exposures [5,20]. ...
... Due to the biological importance of FA, many scientists have studied its photodegradation mechanism in aqueous solutions [4,5,7,16,[20][21][22]. The photolysis of FA has been studied mostly under broadband UVA, UVC (which is absorbed by the ozone layer and does not reach the Earth's surface) or visible light exposure [4,5,7,23,24]. ...
... Their formation is dominant in the beginning of the photolysis of FA, while later their degradation becomes dominant. Additionally, FPT and CPT, but not PABA-Glu, act as photosensitizers [5,7,17,20,23]. Furthermore, they act differently at different wavelengths, due to differences in their absorption characteristics (Fig. 2): PABA-Glu absorbs mostly in the UVB region, while FPT and CPT absorb both in the UVB and in the UVA regions [5]. All these factors influence the photobleaching rates at different wavelengths [26][27][28]. ...
