A biosensor based on gold nanoparticles,dihexadecylphosphate, and tyrosinase for the determination of catechol in natural water

In this work, a biosensor using a glassy carbon electrode modified with gold nanoparticles (AuNPs) and tyrosinase (Tyr) within a dihexadecylphosphate film is proposed. Cystamine and glutaraldehyde crosslinking agents were used as a support for Tyr immobilization. The proposed biosensor was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and cyclic voltammetry in the presence of catechol. The determination of catechol was carried out by amperometry and presented a linear concentration range from 2.5 × 10⁻⁶ to 9.5 × 10⁻⁵ mol L⁻¹ with a detection limit of 1.7 × 10⁻⁷ mol L⁻¹. The developed biosensor showed good repeatability and stability. Moreover, this novel amperometric method was successfully applied in the determination of catechol in natural water samples. The results were in agreement with a 95% confidence level for those obtained using the official spectrophotometric method.     

An amperometric biosensor based on horseradish peroxidase immobilized onto maize tassel-multi-walled carbon nanotubes modified glassy carbon electrode for determination of heavy metal ions in aqueous solution

A biosensor for trace metal ions based on horseradish peroxidase (HRP) immobilized on maize tassel-multiwalled carbon nanotube (MT-MWCNT) through electrostatic interactions is described herein. The biosensor was characterized using Fourier transform infrared (FTIR), UV–vis spectrometry, voltammetric and amperometric methods. The FTIR and UV–vis results inferred that HRP was not denatured during its immobilization on MT-MWCNT composite. The biosensing principle was based on the determination of the cathodic responses of the immobilized HRP to H₂O₂, before and after incubation in trace metal standard solutions. Under optimum conditions, the inhibition rates of trace metals were proportional to their concentrations in the range of 0.092–0.55 mg L⁻¹, 0.068–2 mg L⁻¹ for Pb²⁺ and Cu²⁺ respectively. The limits of detection were 2.5 μg L⁻¹ for Pb²⁺ and 4.2 μg L⁻¹ for Cu²⁺. Representative Dixon and Cornish-Bowden plots were used to deduce the mode of inhibition induced by the trace metal ions. The inhibition was reversible and mixed for both metal ions. Furthermore, the biosensor showed good stability, selectivity, repeatability and reproducibility.     

Amperometric electrode for determination of urea using electrodeposited rhodium and immobilized urease

An amperometric biosensor was developed for determination of urea using electrodeposited rhodium on a polymer membrane and immobilized urease. The urease catalyzes the hydrolysis of urea to NH₄⁺ and HCO₃⁻ ions and the liberated ammonia is catalytically and electrochemically oxidized by rhodium present in the rhodinized membrane on the Pt working electrode. Three types of rhodinized polymer membranes were prepared by varying the number of electrodeposition cycles: membrane 1 with 10 deposition cycles, membrane 2 with 40 cycles and membrane 3 with 60 cycles. The morphologies of the rhodinized membranes were investigated by scanning electron microscopy and the results showed that the deposition of rhodium was like flowers with cornices-like centers. The influence of the amount of electrodeposited rhodium over the electrode sensitivity to different concentrations of ammonia was examined initially based on the cyclic voltammetric curves using the three rhodium modified electrodes. The obtained results convincingly show that electrode with rhodinized membrane 1, which contain the lowest amount of electrodeposited rhodium is the most active and sensitive regarding ammonia. It was found that the anodic oxidation peak of ammonia to nitrogen occurs at 0.60 V. In order to study the performance of urease amperometric sensor for the determination of urea, experiments at constant potential (0.60 V) were performed. The current–time experiments were carried out with urease rhodinized membrane 1 (10 cycles). The amperometric response increased linearly up to 1.75 mM urea. The detection limit was 0.05 mM. The urea biosensor exhibited a high sensitivity of 1.85 μA mM⁻¹ cm⁻² with a response time 15 s. The Michaelis–Menten constant K_m for the urea biosensor was calculated to be 6.5 mM, indicating that the immobilized enzyme featured a high affinity to urea. The urea sensor showed a good reproducibility and stability. Both components rhodium and urease contribute to the decreasing of the production cost of biosensor by avoiding the use of a second enzyme.     

A method for determination of xanthine in meat by amperometric biosensor based on silver nanoparticles/cysteine modified Au electrode

A method is described for construction of an amperometric xanthine biosensor based on covalent Immobilization of xanthine oxidase (XOD) onto citrate capped silver nanoparticles deposited on Au electrode surface through cysteine self assembled monolayers (SAM). The biosensor showed optimum response within 5 s at pH 7.0 and 35 °C, when polarized at 0.5 V vs. Ag/AgCl. The linear working range of biosensor for xanthine was from 2 to 16 μM, with a detection limit of 0.15 μM and sensitivity of 0.17 mA/μM/cm². The mean analytical recovery of exogenously added xanthine in fish meat extract (5 g/l and 10 g/l) was 96.2 ± 2.3% and 95.2 ± 3.4%, respectively. Within and between batches coefficients of variation were <2.6% and <3.4%, respectively. The biosensor measured xanthine in fish, chicken, pork, and beef meat. The enzyme electrode lost 20% of its initial activity after its regular 180 uses over a period of 60 days, when stored at 4 °C in dry state.     

Screen printed graphite biosensors based on bacterial cells

A microbial biosensor was developed for the determination of phenolic compounds and the measurement was based on oxygen consumption in relation to analyte oxidation. Induced cells of Pseudomonas putida DSM 50026 were immobilised on the surface of SPG electrodes covered with cellulose acetate membrane by means of gelatine which was then cross linked with glutaraldehyde. The systems were calibrated for different phenolic substances. Detection ranges were 0.1–1.0 μM for phenol and 0.05–1.0 μM for l-tyrosine and l-DOPA, respectively, with a response time of 3 min. Furthermore, phenol detection was performed in the presence of synthetic wastewater samples.     

A nylon membrane based amperometric biosensor for polyphenol determination

A nylon membrane based amperometric biosensor employing banana fruit polyphenol oxidase (PPO) is presented for polyphenol detection. Nylon membrane was first activated and then coupled with chitosan. PPO was covalently attached to this membrane through glutaraldehyde coupling. The membrane bioconjugate was characterized by scanning electron microscopy (SEM) and Fourier Transform Infrared (FTIR) study and then mounted onto Au electrode using parafilm to construct a working electrode. Once assembled along with Ag/AgCl as reference and Pt as auxiliary electrode, the biosensor gave optimum response within 15 s at pH 7.5 and 30 °C, when polarized at +0.4 V. The response (in mA) was directly proportional to polyphenol concentration in the range 0.2–400 μM. The lower detection limit of the biosensor was 0.2 μM. The biosensor was employed for determination of polyphenols in tea, beverages and water samples. The enzyme electrode showed 25% decrease in initial activity after 150 reuses over 6 months, when stored at 4 °C.     

Amperometric biosensor based on a site-specific immobilization of acetylcholinesterase via affinity bonds on a nanostructured polymer membrane with integrated multiwall carbon nanotubes

Acetylcholinesterase (AChE) was immobilized on chemically modified poly-(acrylonitrile-methyl-methacrylate-sodium vinylsulfonate) membranes in accordance with three different methods, the first of which involved random enzyme immobilization via glutaraldehyde, the second one—site-specific enzyme immobilization via glutaraldehyde and Concanavalin A (Con A) and the third method—modified site-specific enzyme immobilization via glutaraldehyde in the presence of a mixture of multiwall carbon nanotubes and albumin (MWCNs + BSA), glutaraldehyde and Con A. Preliminary tests for the activity of immobilized AChE were carried out using these three methods. The third method was selected as the most efficient one for the immobilization of AChE and the prepared enzyme carriers were used for the construction of amperometric biosensors for the detection of acetylthiocholine (ATCh).A five level three factorial central composite design was chosen to determine the optimal conditions for the enzyme immobilization with three critical variables: concentration of enzyme, Concanavalin A and MWCNs. The design illustrated that the optimum values of the factors influencing the amperometric current were C_E: 70 U mL⁻¹; C_{Con A}: 1.5 mg mL⁻¹ and C_MWCN: 11 mg mL⁻¹, with an amperometric current 0.418 μA. The basic amperometric characteristics of the constructed biosensor were investigated. A calibration plot was obtained for a series of ATCh concentrations ranging from 5 to 400 μM. A linear interval was detected along the calibration curve from 5 to 200 μM. The correlation coefficient for this concentration range was 0.995. The biosensor sensitivity was calculated to be 0.065 μA μM⁻¹ cm⁻². The detection limit with regard to ATCh was calculated to be 0.34 μM. The potential application of the biosensor for detection and quantification of organophosphate pesticides was investigated as well. It was tested against sample solutions of Paraoxon. The biosensor detection limit was determined to be 1.39 × 10⁻¹² g L⁻¹ of Paraoxon, as well as the interval (10⁻¹¹ to 10⁻⁸ g L⁻¹) within which the biosensor response was linearly dependant on the Paraoxon concentration. Finally the storage stability of the enzyme carrier was traced for a period of 120 days. After 30-day storage the sensor retained 76% of its initial current response, after 60 days—68% and after 120 days—61%.     

An amperometric H2O2 biosensor based on cytochrome c immobilized onto nickel oxide nanoparticles/carboxylated multiwalled carbon nanotubes/polyaniline modified gold electrode

Cytochrome c was immobilized covalently onto nickel oxide nanoparticles/carboxylated multiwalled carbon nanotubes/polyaniline composite (NiO-NPs/cMWCNT/PANI) electrodeposited on gold (Au) electrode. An amperometric H₂O₂ biosensor was constructed by connecting this modified Au electrode along Ag/AgCl as reference and Pt wire as counter electrode to the galvanostat. The modified Au electrode was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and Fourier transform infra-red spectroscopy (FTIR). Cyclic voltammetric (CV) studies of the electrode at different stages demonstrated that the modified Au electrode had enhanced electrochemical oxidation of H₂O₂, which offered a number of attractive features to develop an amperometric biosensor based on split of H₂O₂. There was a good linear relationship between the current (mA) and H₂O₂ concentration in the range 3–700 μM. The sensor had a detection limit of 0.2 μM (S/N = 3) with a high sensitivity of 3.3 mA μM^?1 cm^?2. The sensor gave accurate and satisfactory results, when employed for determination of H₂O₂ in different fruit juices.     

Electrochemical detection of xanthine in fish meat by xanthine oxidase immobilized on carboxylated multiwalled carbon nanotubes/polyaniline composite film

A commercial xanthine oxidase (XOD) was immobilized covalently onto carboxylated multiwalled carbon nanotubes (c-MWCNT) and polyaniline (PANI) composite film electrodeposited on the surface of a Pt electrode, using N-ethyl-N′-(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) chemistry. A xanthine biosensor was fabricated using XOD/c-MWCNT/PANI/Pt electrode as a working electrode, Ag/AgCl (3 M KCl) as standard electrode and Pt wire as auxiliary electrode connected through a potentiostat. The enzyme electrode was characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectrophotometry and electrochemical impedance spectroscopy (EIS). The biosensor showed optimum response within 4 s at pH 7.0 and 35 °C, when polarized at 0.4 V. The optimized xanthine biosensor showed linear response range of 0.6–58 μM, with a detection limit of 0.6 μM (S/N = 3), and a correlation coefficient of 0.98. The biosensor was applied to determine xanthine in fish meat. The biosensor lost 50% of its initial activity after its 200 uses over a period of 100 days.     

Zirconia-poly(propylene imine) dendrimer nanocomposite based electrochemical urea biosensor

In this article we report a selective urea electrochemical biosensor based on electro-co-deposited zirconia-polypropylene imine dendrimer (ZrO₂-PPI) nanocomposite modified screen printed carbon electrode (SPCE). ZrO₂ nanoparticles, prepared by modified sol–gel method were dispersed in PPI solution, and electro-co-deposited by cyclic voltammetry onto a SPCE surface. The material and the modified electrodes were characterised using FTIR, electron microscopy and electrochemistry. The synergistic effect of the high active surface area of both materials, i.e. PPI and ZrO₂ nanoparticles, gave rise to a remarkable improvement in the electrocatalytic properties of the biosensor and aided the immobilisation of the urease enzyme. The biosensor has an ampereometric response time of ∼4 s in urea concentration ranging from 0.01 mM to 2.99 mM with a correlation coefficient of 0.9985 and sensitivity of 3.89 μA mM⁻¹ cm⁻². The biosensor was selective in the presence of interferences. Photochemical study of the immobilised enzyme revealed high stability and reactivity.     

Development of glucose biosensor based on reconstitution of glucose oxidase onto polymeric redox mediator coated pencil graphite electrodes

In this study, a novel glucose biosensor was fabricated by reconstitutional immobilization of glucose oxidase (GOx) onto a poly(glycidyl methacrylate-co-vinylferrocene) (poly(GMA-co-VFc)) film coated pencil graphite electrode (PGE). The amperometric current response of poly(GMA-co-VFc)-GOx to glucose is linear in the concentration range between 1 and 16 mM (correlation coefficient of 0.9998) with a detection limit of 2.7 μM (S/N = 3). Experimental parameters were studied in detail and optimized, including the pH and temperature governing the analytical performance of the biosensor. The stability and reusability of the biosensor as well as its kinetic parameters have also been studied.     

Flavonoid and stilbenoid production in callus cultures of Artocarpus lakoocha

Callus cultures of Artocarpus lakoocha Roxb., established from seedling explants and maintained on woody plant medium containing 1 mg/l 2,4-dichlorophenoxyacetic acid and 1 mg/l benzyladenine, were studied for their chemical constituents and biosynthetic potential of secondary metabolites. Four prenylflavones and prenylated stilbenes, along with nine known polyphenolic compounds, were isolated and elucidated for their structures through extensive analysis of their NMR and MS data. Among the 13 isolates, it appeared that seven of them are prenylated derivatives of 5,7,2′,4′-tetrahydroxyflavones, and four are prenylated derivatives of 2,4,3′,5′-tetrahydroxystilbene (oxyresveratrol), suggesting that the biosynthetic pathways of these two polyphenolic groups and their prenylating enzymes are highly expressed in A. lakoocha callus cultures. A study on the growth-product relationship of the callus cultures showed that the secondary metabolites were all formed simultaneously during the rapid growth phase of the culture cycle, with various prenylflavones, and a prenylated stilbene as major constituents. In assays for DPPH free radical scavenging activity and tyrosinase inhibitory potential, the stilbenoids appeared to possess moderate effects, whereas the flavonoids showed only weak activity.     

Direct electrochemistry of hemoglobin based on chitosan–ionic liquid–ferrocene/graphene composite film

This paper described an ingenious approach for the fabrication of a promising biosensor, hemoglobin (Hb)/chitosan (Chit)–ionic liquid (IL)–ferrocene (Fc)/graphene (Gr)/glassy carbon electrode (GCE), that exploited the synergistic beneficial characteristics of Fc, Gr and IL for Hb. The proposed biosensor showed a strong electrocatalytic activity toward the reduction of H₂O₂, which could be attributed to the favored orientation of Hb in the well-confined surface as well as the high electrical conductivity of the resulting Chit–IL–Fc/Gr inorganic hybrid composite. The developed biosensor exhibited a fast amperometric response (2 s), a good linear response toward H₂O₂ over a wide range of concentration from 50 μM to 1200 μM, and a low detection limit of 3.8 μM. The apparent Michaelis–Menten constant (K_m) of Hb on the composite medium was 0.16 mM, showing high bioelectrocatalytic activity of immobilized protein toward H₂O₂ reduction. High sensitivity and stability, technically simple and possibility of preparation at short period of time are of great advantages of the developed biosensors.     

Amperometric acetylthiocholine sensor based on acetylcholinesterase immobilized on nanostructured polymer membrane containing gold nanoparticles

Poly(acrylonitrile-methylmethacrylate-sodium vinylsulfonate) membranes were chemically modified and loaded with gold nanoparticles. Acetylcholinesterase was immobilized on the prepared membranes in accordance with two distinctive procedures, the first of which involved immobilization of the enzyme by convection, and the other by diffusion. The prepared enzyme carriers were used for the construction of amperometric biosensors for detection of acetylthiocholine.Two sets of experiments were carried out. The first set was designed so that to evaluate the effects of the gold nanoparticle deployment and the immobilization procedures over the biosensor effectiveness. The other set of experiments was conducted in order to determine the influence of the individual components of the enzyme mixture, containing gold nanoparticles, acetylcholinesterase, bovine serum albumin and glutaraldehyde, over the current output of the constructed acetylthiocholine biosensors. The optimum composition of the mixture was determined to be as follows: enzyme, 0.1 U ml^?1; gold nanoparticles, 0.50 ml (per 1 ml enzyme mixture); albumin, 0.5% and glutaraldehyde, 0.7%.On the basis of the experimental results, the most efficient enzyme membrane was selected and used for the preparation of an acetylthiocholine biosensor. Its basic amperometric characteristics were investigated. A calibration plot was obtained for ATCh concentration ranging from 10 to 400 μM. A linear interval was detected along the calibration curve from 10 to 170 μM. The sensitivity of the constructed biosensor was calculated to be 0.066 μA μM^?1 cm^?2. The correlation coefficient for this concentration range was 0.996. The detection limit with regard to ATCh was calculated to be 1.80 μM.The potential application of the biosensor for detection and quantification of organophosphate pesticides was investigated as well. It was tested against sample solutions of Paraoxon. The biosensor detection limit for Paraoxon was determined, 7.39 × 10^?11 g l^?1, as well as the concentration interval (10^?10 to 10^?7 g l^?1) within which the biosensor response was linearly dependant on Paraoxon concentration.Finally the storage stability of the enzyme carrier was traced for a period of 50 days. After storage for 20 days the sensor retained 75% of its initial current response and after 30 days ?25%.     

Melanogenesis inhibitory activity of a 7-O-9′-linked neolignan from Alpinia galanga fruit

An aqueous acetone extract from the fruit of Alpinia galanga (Zingiberaceae) demonstrated inhibitory effects on melanogenesis in theophylline-stimulated murine B16 melanoma 4A5 cells (IC₅₀ = 7.3 μg/mL). Through bioassay-guided separation of the extract, a new 7-O-9′-linked neolignan, named galanganol D diacetate (1), was isolated along with 16 known compounds including 14 phenylpropanoids (2–15). The structure of 1, including its absolute stereochemistry in the C-7 position, was elucidated by means of extensive NMR analysis and total synthesis. Among the isolates, 1 (IC₅₀ = 2.5 μM), 1′S-1′-acetoxychavicol acetate (2, 5.0 μM), and 1′S-1′-acetoxyeugenol acetate (3, 5.6 μM) exhibited a relatively potent inhibitory effect without notable cytotoxicity at effective concentrations. The following structural requirements were suggested to enhance the inhibitory activity of phenylpropanoids on melanogenesis: (i) compounds with 4-acetoxy group exhibit higher activity than those with 4-hydroxy group; (ii) 3-methoxy group dose not affect the activity; (iii) acetylation of the 1′-hydroxy moiety enhances the activity; and (iv) phenylpropanoid dimers with the 7-O-9′-linked neolignan skeleton exhibited higher activity than those with the corresponding monomer. Their respective enantiomers [1′ (IC₅₀ = 1.9 μM) and 2′ (4.5 μM)] and racemic mixtures [(±)-1 (2.2 μM) and (±)-2 (4.4 μM)] were found to exhibit melanogenesis inhibitory activities equivalent to those of the naturally occurring optical active compounds (1 and 2). Furthermore, the active compounds 1–3 inhibited tyrosinase, tyrosine-related protein (TRP)-1, and TRP-2 mRNA expressions, which could be the mechanism of melanogenesis inhibitory activity.     

An immobilized Thiobacillus thioparus biosensing system for monitoring sulfide hydrogen; optimized parameters in a bioreactor

A microbial biosensing system for detection of hydrogen sulfide has been developed by using immobilized Thiobacillus thioparus TK-m in poly vinyl alcohol matrix, together with a dissolved oxygen sensor. Parameters of immobilization (poly vinyl alcohol concentration and amount of wet cell) were optimized by using statistical software. The obtained values for concentration of poly vinyl alcohol and wet cell weight were 11.3% (w/v) and 45 mg, respectively, where the response time of biosensor was 80 s. Calibration of oxygen concentration based on hydrogen sulfide concentration was investigated between 1 mg/L and 20 mg/L. The effect of pH and temperature were investigated in specific range of experimental conditions as well. Some parameters including operational stability and detection limit were studied in detail for characterization of biosensing system. In order to determine the operational stability, bio-sensing system at optimized working conditions was used to distinguish viability of microorganisms in polymer beads in period of time.     

Glucose biosensor based on glucose oxidase immobilized at gold nanoparticles decorated graphene-carbon nanotubes

Biopolymer pectin stabilized gold nanoparticles were prepared at graphene and multiwalled carbon nanotubes (GR-MWNTs/AuNPs) and employed for the determination of glucose. The formation of GR-MWNTs/AuNPs was confirmed by scanning electron microscopy, X-ray diffraction, UV–vis and FTIR spectroscopy methods. Glucose oxidase (GOx) was successfully immobilized on GR-MWNTs/AuNPs film and direct electron transfer of GOx was investigated. GOx exhibits highly enhanced redox peaks with formal potential of −0.40 V (vs. Ag/AgCl). The amount of electroactive GOx and electron transfer rate constant were found to be 10.5 × 10⁻¹⁰ mol cm⁻² and 3.36 s⁻¹, respectively, which were significantly larger than the previous reports. The fabricated amperometric glucose biosensor sensitively detects glucose and showed two linear ranges: (1) 10 μM – 2 mM with LOD of 4.1 μM, (2) 2 mM – 5.2 mM with LOD of 0.95 mM. The comparison of the biosensor performance with reported sensors reveals the significant improvement in overall sensor performance. Moreover, the biosensor exhibited appreciable stability, repeatability, reproducibility and practicality. The other advantages of the fabricated biosensor are simple and green fabrication approach, roughed and stable electrode surface, fast in sensing and highly reproducible.     

Oxidation of cyanobenzocycloheptatrienes: Synthesis,photooxygenation reaction and carbonic anhydrase isoenzymes inhibition properties of some new benzotropone derivatives

The oxidation of some cyanocycloheptatrienes with CrO₃ and pyridine was investigated and a few new nitrile functionalised benzotropone derivatives were obtained. Photooxygenation reaction of these products was also studied. The structures of the formed products were determined on the basis of NMR spectroscopy and the formation mechanism of unusual products was discussed. Human carbonic anhydrase isoenzymes I, and II (hCA I and hCA II) inhibition properties of nitrile functionalized new benzotropone derivatives were also studied. Both CA isozymes were inhibited in the low micromolar range by these nitrile functionalized benzotropone analogues. The newly synthesized benzotropone derivatives showed inhibition constants in the sub-micromolar range (2.51–4.06 μM). The best hCA I inhibition was observed in 5H-benzocycloheptene-7-carbonitrile (K_i: 2.88 ± 0.86 μM). On the other hand, 5-oxo-5H-benzocycloheptatriene-7-carbonitrile showed the powerful inhibitory effect against hCA II (K_i: 2.51 ± 0.34 μM).     

Activation of nylon net and its application to a biosensor for determination of glucose in human serum

A glucose biosensor using a glucose oxidase (GO_x)-immobilized nylon net with glutaraldehyde as cross-linking reagent and an oxygen (O₂) electrode for the determination of glucose has been fabricated. The detection scheme was based on the utilization of dissolved O₂ in oxidation of glucose by the membrane bound GO_x. Crucial factors including O-alkylation temperature, reaction times of nylon net with dimethyl sulfate, l-lysine, and glutaraldehyde, and enzyme loading were examined to determine the optimal enzyme immobilization conditions for the best sensitivity of the developed glucose biosensor. In addition, the effects of pH and concentration of phosphate buffer on the response of the biosensor were studied. The glucose biosensor had a linear range of 18 μM to 1.10 mM with the detection limit of 9.0 μM (S/N = 3) and response time of 80 s. The biosensor exhibited both good operational stability with over 200 measurements and long-term storage stability. The results from this biosensor compared well with those of a commercial glucose assay kit in analyzing human serum glucose samples.     

Flavanoids from Dalea elegans: Chemical reassignment and determination of kinetics parameters related to their anti-tyrosinase activity

In the first chemical investigation developed on the species Dalea elegans twenty years ago, the occurrence of two prenylated derivatives of pinocembrin was reported: 2′,4′-dihydroxy-5′-(1‴,1‴-dimethylallyl)-6-prenylpinocembrin (6PP) given as a new structure in this family of compounds, and another derivative of already known structure, 6-prenylpinocembrin (6P). In the present paper, their structures were again analyzed by using spectroscopic techniques, especially 2D NMR. Based on the evidence obtained it is proposed the reassignment of both flavanones as: 2′,4′-dihydroxy-5′-(1‴,1‴-dimethylallyl)-8-prenylpinocembrin (8PP) for the first and 8-prenylpinocembrin (8P) for the last. Additionally, triangularin, demethoxymatteucinol, comptonin and 7-hydroxy-5-methoxy-6,8-dimethylflavanone were isolated from aerial parts of D. elegans and informed by the first time for this species. All of these compounds were evaluated in vitro in relation to the antityrosinase effect by using a spectrophotometric method. Compound 8PP (IC₅₀ 2.32 ± 0.01 μM) exhibited the most potency and was two times more active than Kojic acid (IC₅₀ 4.93 ± 0.01 μM) used as a positive control. Triangularin also has shown an important inhibitory activity. Kinetic studies were performed for both compounds. Hence, new tyrosinase inhibitors with potential applications in pharmacy and cosmetic industry are presented.