Study on the Photodegradation of Salicylic Acid in Different Vehicles in the Absence and in the Presence of TiO2

In this work, the direct photolysis of salicylic acid, generally used as keratolytic agent in many dermatological products and as preservative in cosmetics, was investigated. The photodegradation of the acid under UVB irradiation was evaluated in different vehicles, such as water solutions at different pH, propylene glycol/water, and ethanol/water mixtures, sodium dodecyl sulphate solutions, and O/W emulsions prepared with Montanov 68 and Amphysol K as emulsifiers. The increase of pH enhanced the photodegradation of salicylic acid while the different vehicles protected the acid from the action of UVB radiations. However, the best protection was observed dissolving the acid in the lipid core of O/W emulsions, which probably removes the active from the polar environment that can promote the photolysis. The photocatalytic activity of TiO₂ on the degradation of salicylic acid also was evaluated. TiO₂ frequently is used as sunscreen in many cosmetic preparations. Salicylic acid and the pigment can be contained in the same solar formulation; hence, it can be interesting to study their interaction under UVB. TiO₂ enhanced the photodegradation of salicylic acid in all the media previously reported and its photocatalytic activity was influenced by the pH and by the components of the vehicles.     

Photostability of Ferulic Acid and Its Antioxidant Activity Against Linoleic Acid Peroxidation

Ferulic acid (4‐hydroxy‐3‐methoxycinnamic acid), a phenyl‐propenoid derivative of cinnamic acid, can undergo photolysis upon UV irradiation. The photodegradation kinetics of ferulic acid were thus investigated in different systems. The micellar solutions did not protect the acid from photodegradation. On the contrary, they catalyzed its degradation at a variable extent depending on the surfactant structure. The photodegradation of ferulic acid in microemulsions was slower than in micelles and near to that in water. TiO₂, habitually employed as a physical sunscreen, showed photocatalytic action toward ferulic acid degradation especially at higher initial concentration of ferulic acid. The action of ferulic acid on the peroxidation of linoleic acid in micelles and microemulsions also was evaluated. When the ferulic acid is absent the peroxidation is continuous while when it is present an induction time of 40 minutes or higher was observed. Accordingly, it is likely that linoleic acid acts as photosensitizer for ferulic acid, and that in turn ferulic acid acts as an antioxidant for linoleic acid, reducing the rate of peroxidation.     

ENHANCED MACROPHAGE CYTOTOXICITY AGAINST TUMOR CELLS TREATED WITH PHOTODYNAMIC THERAPY

Abstract— Sulfamethoxazole (SMX) in its nonionized form in aqueous solution has ultraviolet (UV) absorption that is maximal at 268 nm but extends through the ultraviolet-B (UVB) region. It was found to be extremely susceptible to photodegradation when exposed to artificial UV radiation through a Pyrex filter or to unfiltered natural sunlight. The SMX anion was more stable. The quantum yields of the photodegradation of both forms were determined by use of monochromatic light and ferrioxalate chemical actinometry, the values of 0.47 (pH 3.0) and 0.084 (pH 9.0) at the maximum absorption wavelengths (268 and 257 nm, respectively) being obtained. Using literature data on sunlight intensity, the photochemical shelf-life of SMX solutions exposed to direct sunlight was calculated for Sydney (latitude 33.5°S) as a function of season of the year and verified experimentally. A fixed correlation was established between the rate constant for SMX degradation and UVB intensity measured by a radiometer, suggesting the capacity of this chemical system to monitor changes in the UVB region of sunlight.     

Z‐sinapinic acid: the change of the stereochemistry of cinnamic acids as rational synthesis of a new matrix for carbohydrate MALDI‐MS analysis

Successful application of matrix‐assisted laser desorption/ionization (MALDI) MS started with the introduction of efficient matrices such as cinnamic acid derivatives (i.e. 3,5‐dimethoxy‐4‐hydroxycinnamic acid, SA; α‐cyano‐4‐hydroxycinnamic acid). Since the empirical founding of these matrices, other commercial available cinnamic acids with different nature and location of substituents at benzene ring were attempted. Rational design and synthesis of new cinnamic acids have been recently described too. Because the presence of a rigid double bond in its molecule structure, cinnamic acids can exist as two different geometric isomers, the E‐form and Z‐form. Commercial available cinnamic acids currently used as matrices are the geometric isomers trans or E (E‐cinnamic and trans‐cinnamic acids). As a new rational design of MALDI matrices, Z‐cinnamic acids were synthesized, and their properties as matrices were studied. Their performance was compared with that of the corresponding E‐isomer and classical crystalline matrices (3,5‐dihydroxybenzoic acid; norharmane) in the analysis of neutral/sulfated carbohydrates. Herein, we demonstrate the outstanding performance for Z‐SA. Sulfated oligosaccharides were detected in negative ion mode, and the dissociation of sulfate groups was almost suppressed. Additionally, to better understand the quite different performance of each geometric isomer as matrix, the physical and morphological properties as well as the photochemical stability in solid state were studied. The influence of the E/Z photoisomerization of the matrix during MALDI was evaluated. Finally, molecular modeling (density functional theory study) of the optimized geometry and stereochemistry of E‐cinnamic and Z‐cinnamic acids revealed some factors governing the analyte–matrix interaction. Copyright © 2013 John Wiley & Sons, Ltd.     

pH-sensitive liposomes composed of phosphatidylethanolamine and fatty acid

pH-induced destabilization, aggregation and fusion of liposomes composed of phosphatidylethanolamine (PE) and various fatty acid were studied. Destabilization was examined as a fluorescent change caused by leakage of coencapsulated aminonaphthalene-3,6,8-trisulfonic acid (ANTS) and N,N-p-xylylenebispyridinium bromide (DPX). Fusion was monitored by two different methods, that is, intermixing assay of internal aqueous contents of liposomes, and lipid dilution assay of liposomes labeled with fluorescent phospholipids. Contents leakage from liposomes was observed by lowering the pH, and pH where the leakage began depended on fatty acid used. Fifty percent leakage of contents from PE liposomes containing alpha-hydroxypalmitic acid or alpha-hydroxy-stearic acid was observed at pH 5.5, that from liposomes containing stearic acid or palmitic acid was observed at pH 6.5-6.7, and that from ricinoleic acid at pH 7.2. Aggregation and fusion of the respective liposomes also occurred at a similar pH region. These results were interpreted by the notion that the protonation of the fatty acid triggers a series of pH-sensitive events. The liposomes developed in this study may be useful as a drug carrier which could release the contents in response to pH changes in their environment.     

Evidences of cyclodextrin-mediated enantioselective photodegradation of rac-nicardipine by capillary electrophoresis

Capillary electrophoresis (CE) was applied to photostability studies on rac-nicardipine, a dihydropyridine chiral drug. CE methods were developed able to provide the enantioresolution of drug and its separation from the photodegradation products. Enantioresolution was achieved using 5% sulfated-beta-cyclodextrin (S-beta-CD) as chiral selector in 20 mM triethanolammonium phosphate solution (pH 3). The photostability studies were carried out on inclusion complexes of rac-nicardipine with beta-cyclodextrin (beta-CD) and (2-hydroxypropyl)-beta-cyclodextrin (HP-beta-CD) in aqueous solutions (pH 7.4 and 5). The CE analysis of the solutions exposed to UV-A and UV-B radiations showed a photoprotective effect by beta-CD; conversely, HP-beta-CD proved to favor the drug photodegradation. Moreover, evidences for CDs-mediated stereoselective photodegradation of rac-nicardipine were obtained. In fact, two distinct photodegradation profiles were observed for the nicardipine enantiomers in the presence of the CDs. The photodegradation was found to follow an apparent first-order kinetics and two different kinetic constants (k) were obtained for the two enantiomers. After exposure to UV-A and UV-B radiations, the solutions contained residual nicardipine with a significant change in the enantiomeric ratio; this effect was depending on the CD used for the inclusion complexation.     

Photochemical behavior of sitafloxacin, fluoroquinolone antibiotic, in an aqueous solution

Sitafloxacin (STFX) hydrate, an antimicrobial agent, is photo-labile in aqueous solutions. The photodegradation rates (k) in neutral solutions were higher than those observed in acidic and alkaline solutions and maximum at the maximum absorption wavelength of STFX. The structures of photodegradation products were elucidated as 7-[7-amino-5-azaspiro[2.4]heptan-5-yl]-6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid and 1-(1-amino-2-[16-fluoro-1-(2-fluoro-1-cyclopropyl)-1,4-dihydro-4-oxo-3-quinolin-7-yl]-amino]ethyl)cyclopropanecarbaldehyde. This implies that dechlorination is the key step in the photodegradation of STFX. The effect of halide ions on the photodegradation of STFX was estimated by observing the increments in the photostability of STFX with the addition of chloride ions. In contrast, in the presence of bromide ions, instead of increased photostability of the STFX rate, a new photodegradation product in the presence of bromide ion was observed. The structure of this new photodegradation product was an 8-bromo form of STFX, which was substituted for chlorine at the 8-position, so the dissociation of C-Cl bond at the 8-position of STFX was the rate-limiting step in the initial process of the photodegradation. STFX generated .C (carbon centered radical) and .OH (hydroxyl radical) in the process of photodegradation in a pH 4.0 buffer. On the contrary, STFX did not generate C in the presence of chloride ion in a pH 4.0 buffer. The .C was generated and then degraded into the above degradation products by photoirradiation in the absence of chloride ion, but the .C immediately reacted with chloride when it was present. As a result, the C-Cl bond was recovered leading to a possible increase in the apparent photostability.     

Effects of ultraviolet light on free and peptide-bound pyridinoline and deoxypyridinoline cross-links. Protective effect of acid pH against photolytic degradation

Little is known about the photodegradation of pyridinoline (Pyd) and deoxypyridinoline (Dpd), which are two mature cross-links stabilizing collagen within extracellular matrix. In this study, highly purified free Pyd and Dpd cross-links have been degraded by irradiation with ultraviolet light and we have shown that photolysis varies with the pH value. Assessment of photolysis in basic (pH 9) and neutral (pH 7) solutions by high-performance liquid chromatography as well as by UV absorbance measurement indicates that both cross-links are degraded after a 24 h UV exposure, while in acidic solution (pH 3) only Dpd is photolysed, suggesting that acid pH provides major protection against Pyd photolysis. Photodegradation products have been studied by amino-acid and mass spectral analysis. Both methods confirm the lack of Pyd degradation in acid pH. Furthermore, amino-acid analysis allows us to identify hydroxylysine and lysine as a result of Pyd and Dpd photolysis, respectively, indicating that the mechanism of photodegradation involves the cleavage of the pyridinium ring on each side of the quaternary nitrogen. Finally, we have also studied the photolysis of different molecular species of type I collagen peptides, obtained by digestion with collagenase of demineralized turkey bone. Our results indicate that even when they are part of the structure of collagen peptide, Pyd and Dpd can be photolysed. However, we have shown that the larger the peptide is, the smaller are the effects of UV irradiation.     

Photochemical and antioxidant properties of gamma-oryzanol in beta-cyclodextrin-based nanosponges

Gamma-oryzanol (GO), a mixture of ferulic acid esters, has recently attracted a great interest as natural antioxidant extracted from rice-bran oil, usually employed to stabilize food and pharmaceutical raw materials, moreover as sunscreen in cosmetic formulations. Its usefulness, however, is limited by its fast degradation. A recently proposed approach to increase the stability and effectiveness of antioxidants is based on the inclusion in supramolecular structures (nanoparticles, cyclodextrins, liposomes, etc.). In this work we studied the inclusion of GO in β-cyclodextrin-based nanosponges which in the last few years have been chosen for their ability to encapsulate a great variety of substances to decrease their side-effects and to protect them from degradation. The inclusion complex was prepared in 1:1 w/w ratio and characterized by DSC, XRPD and membrane diffusion runs. The photodegradation of GO upon either UVA or UVB irradiation was found to be slowed down by inclusion in nanosponges. The antioxidant effectiveness of the inclusion complex was also assessed and in vitro experiments on porcine ear skin revealed a certain accumulation of GO also when entrapped in the host structure.     

Influence of hydroxypropyl-β-cyclodextrin on the photostability and antiradical activity of Trolox

Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), a derivative of vitamin E, can undergo photolysis upon UV irradiation. In the present study the photodegradation kinetics of Trolox were thus investigated in different systems in the absence and in the presence of titanium dioxide, a physical sunscreen present in several cosmetic products, that can act as photocatalyst. In all the considered media Trolox degraded under UVB light following pseudo-zero order kinetics, probably by a mechanism of photooxidation. The rate of Trolox photodegradation was lower in O/W emulsions than in aqueous solution and in gel; furthermore it was significantly influenced by the presence of TiO₂. Aiming to increase Trolox stability, it was complexed with hydroxypropyl-β-cyclodextrin: the inclusion complex was characterized by phase solubility studies, spectrophotometry and differential scanning calorimetry. The irradiation experiments indicated that complexation with hydroxypropyl-β-cyclodextrin was effective in reducing the photodegradation rate of Trolox. Moreover the host molecule favored the uptake of Trolox into the porcine skin, as shown by in vitro permeation studies. Nevertheless the assay of peroxidation, based on the reaction of malondialdehyde with thiobarbituric acid, indicated that the antioxidant activity of Trolox was maintained even after inclusion in cyclodextrin.     

Polydopamine‐coated magnetic molecularly imprinted polymer for the selective solid‐phase extraction of cinnamic acid,ferulic acid and caffeic acid from radix scrophulariae sample

We describe novel cinnamic acid polydopamine‐coated magnetic imprinted polymers for the simultaneous selective extraction of cinnamic acid, ferulic acid and caffeic acid from radix scrophulariae sample. The novel magnetic imprinted polymers were synthesized by surface imprinting polymerization using magnetic multi‐walled carbon nanotubes as the support material, cinnamic acid as the template and dopamine as the functional monomer. The magnetic imprinted polymers were characterized by transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and vibrating sample magnetometry. The results revealed that the magnetic imprinted polymers had outstanding magnetic properties, high adsorption capacity, selectivity and fast kinetic binding toward cinnamic acid, ferulic acid and caffeic acid. Coupled with high‐performance liquid chromatography, the extraction conditions of the magnetic imprinted polymers as a magnetic solid‐phase extraction sorbent were investigated in detail. The proposed imprinted magnetic solid phase extraction procedure has been used for the purification and enrichment of cinnamic acid, ferulic acid and caffeic acid successfully from radix scrophulariae extraction sample with recoveries of 92.4–115.0% for cinnamic acid, 89.4–103.0% for ferulic acid and 86.6–96.0% for caffeic acid.     

On the complexation of Trolox with methyl-β-cyclodextrin: characterization, molecular modelling and photostabilizing properties

Exposure to UV radiations could reduce the efficiency of some antioxidants like Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), a water-soluble vitamin E analogue largely employed in cosmetic products. Accordingly, in this paper we examined the possibility of increasing the stability of Trolox towards UVB irradiation by its complexation with methyl-β-cyclodextrin. Formation of the inclusion complex was confirmed by solubility diagrams, differential scanning calorimetry (DSC), and diffusion study through hydrophilic membrane. The stability constants and docking results suggested that the complexation phenomenon was related to the pH of the medium. The photodegradation studies were carried out in different topical formulations (gel, O/W emulsion, and W/O/W emulsion) containing Trolox free or complexed with methyl-β-cyclodextrin. Results showed that in all the cases Trolox degraded following pseudo-zero order kinetics. Moreover, the host molecule increased Trolox photostability also in the presence of TiO₂, a physical sunscreen well-known as photocatalyzer.     

Topically applied eicosapentaenoic acid protects against local immunosuppression induced by UVB irradiation, cis-urocanic acid and thymidine dinucleotides

UVB-induced immunosuppression, a promoter of photocarcinogenesis, involves the formation of pyrimidine dimers and cis-urocanic acid (cis-UCA), but reactive oxygen species (ROS) also plays an important role. Eicosapentaenoic acid (EPA) can inhibit photocarcinogenesis, but due to its polyunsaturated nature it is susceptible to oxidative damage by ROS. The antioxidant defense system may therefore be challenged upon ultraviolet-B (UVB) irradiation in the presence of EPA. We investigated whether topically applied EPA in mice could protect against local immunosuppression (contact hypersensitivity response to dinitrofluorobenzene) induced by UVB radiation (1.5 J/cm2), or topically applied cis-UCA (150 nmol/cm2) or thymidine dinucleotides (pTpT) (5 nmol/cm2). The influence of EPA on epidermal lipid peroxidation and antioxidant status was also measured. UVB irradiation, cis-UCA and pTpT all caused 70% immunosuppression. Topical pretreatment of mice with EPA partially protected against immunosuppression; the EPA dose needed to accomplish this was 10 nmol/cm2 for UVB irradiation, 100 nmol/cm2 for cis-UCA and 1000 nmol/cm2 for pTpT. Higher EPA doses caused higher UVB-induced lipid peroxidation and lower vitamin C levels. Glutathione only decreased with the highest EPA dose whereas vitamin E was not decreased after UVB irradiation. In conclusion, topically applied EPA protects against UVB-, cis-UCA- and pTpT-induced immunosuppression and maintenance of an adequate antioxidant defense seems to be an important prerequisite for the protective action by EPA.     

Photodegradation of Caffeic Acid in W/O/W Emulsions in the Absence and in the Presence of TiO2

Caffeic acid, a natural phenol with antioxidant and sunscreen activity, can undergo photooxidation upon UV irradiation. The photodegradation of caffeic acid at different concentrations was assessed in water, at pH 4.0 and 6.0, without and with TiO₂. The study was then carried out on W/O/W emulsions entrapping the phenolic acid either in the inner or in the outer aqueous phase in the absence and in the presence of TiO₂, added in the external phase (pH 6.0 or 7.0). The degradation of caffeic acid followed a pseudo-zero order kinetic with an inverse dependence from its initial concentration; at increasing pH of the medium caffeic acid degraded faster. The addition of TiO₂ increased the initial photodegradation rate. Compared with water, W/O/W emulsions protected the phenol towards both the photodegradation and the photocatalytic activity of TiO₂. Multiple systems allowed to incorporate caffeic acid and TiO₂ in the same formulation avoiding any catalytic interactions.     

Chromatographic determination of itopride hydrochloride in the presence of its degradation products

Two sensitive and reproducible methods are described for the quantitative determination of itopride hydrochloride (IH) in the presence of its degradation products. The first method is based on HPLC separation on a reversed phase Kromasil column [C18 (5-microm, 25 cm x 4.6 mm, ID)] at ambient temperature using a mobile phase consisting of methanol and water (70:30, v/v) adjusted to pH 4.0 with orthophosphoric acid with UV detection at 258 nm. The flow rate was 1.0 mL per min with an average operating pressure of 180 kg/cm2. The second method is based on HPTLC separation on silica gel 60 F254 using toluene:methanol:chloroform:10% ammonia (5.0:3.0:6.0:0.1, v/v/v/v) as mobile phase at 270 nm. The analysis of variance (ANOVA) and Student's t-test were applied to correlate the results of IH determination in dosage form by means of HPLC and HPTLC methods. The drug was subjected to acid and alkali hydrolysis, oxidation, dry heat, wet heat treatment, UV, and photodegradation. The proposed HPLC method was utilized to investigate the kinetics of the acidic, alkaline, and oxidative degradation processes at different temperatures and the apparent pseudo-first-order rate constant, half-life, and activation energy were calculated. In addition the pH-rate profile of degradation of IH in constant ionic strength buffer solutions in the pH range 2-11 was studied.     

Mutants of Arabidopsis as Tools to Understand the Regulation of Phenylpropanoid Pathway and UVB Protection Mechanisms

Abstract— Plants accumulate certain phenylpropanoid compounds in the vacuoles of their epidermal and subepidermal cell layers thereby protecting the underlying tissue against UVB-induced damage. However, a number of mutants of Arabidopsis thaliana are known that fail to synthesize these protective pigments, thereby allowing harmful UVB radiation to penetrate into their dermal layers. Study of several of these nonlethal mutants, defective in various aspects of flavonoid and lignin biosynthesis, has led to a better understanding of the coordinate regulation and expression of important genes as well as of mechanisms involved in plant defense against UVB radiation. The characteristics of the various phenylpropanoid mutants of Arabidopsis, viz. flavonoid mutants (banyuls [ baity , increased chalcone synthase expression 1 [ icx1 ]; transparent testa [ tt ] and ultraviolet sensitive [ uvs ]) and hydroxycinnamic acid ester mutants (ferulic acid hydroxylase 1 [ fahl ] and sinapoylglucose accumulator 1 [ sng1 ]) are discussed in detail. We have briefly touched upon, wherever relevant, the unique aspects in other plant species too.     

Protective Effect of Magnesium-L-Ascorbyl-2 Phosphate Against Skin Damage Induced by UVB Irradiation

The protective effect of magnesium-L-ascorbyl-2-phosphate (MAP) on cutaneous photodamage such as lipid peroxidation and inflammation induced by ultraviolet B (UVB) exposure (290–320nm, max. 312 nm) was investigated using hairless mice. When MAP was administered intraperitoneally to mice at a dose of 100 mg of ascorbic acid (AS) per kg body weight base immediately before irradiation (15 kJ/m²), the expected increases in thiobarbituric acid reactive substance (TBARS) formation in skin and serum sialic acid, indices of lipid peroxidation and inflammatory reaction, respectively, were significantly reduced. However, the expected decrease in the level of cutaneous AS was unchanged. Similar results were observed for animals given 100 mg of AS-Na per kg body weight before UVB irradiation. When MAP was administered intracutaneously immediately before irradiation, the expected UVB-induced increases in TBARS and sialic acid were again significantly prevented. Ascorbic acid-Na had a less protective effect than intracutaneous MAP administration. The cutaneous AS level was significantly higher in the MAP-treated mice than in the controls, and the UVB-induced decrease in tissue AS was prevented by intracutaneous MAP administration. These results suggest that MAP protects against UVB irradiation-induced lipid peroxidation and inflammation in cutaneous tissue, regardless of the drug administration route. We found, in an in vitro experiment, that MAP was converted to AS as it crossed the epidermis, but that AS-Na did not pass through the epidermis. Furthermore, MAP was also converted to AS in serum. These results suggest that the protective effect of MAP on UVB-induced cutaneous damage is due to conversion of MAP to AS.     

Influence of human serum albumin on photodegradation of folic acid in solution

It has been proposed that photodegradation of folates may be the reason for the pigmentation of races living under high fluence rates of ultraviolet radiation. The photodegradation of folic acid (FA) induced by ultraviolet-A (UV-A) radiation, in solution and in the presence of human serum albumin (HSA), was studied with absorption and fluorescence spectroscopy. FA photodegradation, with formation of p-aminobenzoyl-l-glutamic acid, 6-formylpterin and pterin-6-carboxylic acid, was found to follow an exponential trend. A scheme of FA photodegradation, which involves photosensitization of FA degradation by its photoproducts, was proposed. The rate of FA photodegradation decreased drastically in the presence of HSA, whereas the spectral characteristics of the photoproducts remained constant. The reduction of the FA photodegradation rate by HSA was accompanied by degradation of tryptophan in HSA. Tryptophan, when added to solutions of FA, had a similar effect as HSA. In solutions of FA and HSA the FA photoproducts cause photodamage mainly to HSA rather than to FA itself. The oxygen dependence of FA photodegradation and the inhibition of this process by sodium azide indicate that singlet oxygen may participate in the photosensitizing activity of FA photoproducts.     

Application of ZnO‐Al2O3 Nanocomposite as Nanocatalyst for Photodegradation of Acid Violet 5B

ZnO‐Al₂O₃ nanocomposite (ZANC) is used as nanocatalyst for photodegradation of acid violet 5B (AV5B) as an industrial dye. The experimental data shows that the degradation of AV5B is accelerated by ZANC and UV light. The effects of various parameters such as pH, hydrogen peroxide and ethanol are investigated on the photodegradation efficiency. Photocatalytic degradation rate of AV5B is increased by ethanol and hydrogen peroxide. Based on the kinetic studies, the rate constant of the photodegradation reaction is estimated 2.829 × 10^‐1 min^‐1.     

Electrochemical Reduction of a Conjugated Cinnamic Acid Diazonium Salt as an Immobilization Matrix for Glucose Biosensor

Initial results on the synthesis of a new conjugated diazonium salt of trans‐4‐cinnamic acid diazonium fluoroborate, which is used for the chemical modification of the glassy carbon (GC) electrode with trans‐4‐cinnamic acid groups through electrochemical reduction, and direct covalent immobilization of glucose oxidase (GOD) on the cinnamic acid groups are presented. The chemically modified GC electrode exhibits a good selectivity relative to the bare GC electrode for the various possible interfering compounds in glucose analysis: namely ascorbic acid and 4‐acetamidophenol. Covalent immobilization of GOD on the chemically modified GC electrode produces a biosensor which responds to glucose concentration changes in the presence of a soluble redox mediator (ferrocenemethanol). The chemical modification of GC by cinnamic acid groups is potentially useful for the attachment of other enzymes and biochemical reagents.