Stress Tolerance of the Endemic Antarctic Brown Alga Desmarestia anceps to UV Radiation and Temperature is Mediated by High Concentrations of Phlorotannins

The endemic Antarctic brown macroalga Desmarestia anceps is strongly shade‐adapted, but shows also a high capacity to cope with different environmental stressors, e.g. UV radiation and temperature. Therefore, this species colonizes wide depth gradients, which are characterized by changing environmental conditions. In this study, we examine whether the different physiological abilities allowing D. anceps to grow across a wide depth range is determined by high levels of phlorotannins. Photosynthesis, measured by PAM‐fluorometry, the contents of soluble phlorotannins, antioxidant capacities of field grown were analyzed in response to different conditions of radiation (PAR and PAR + UV) and temperature (2, 7 and 12°C). The results show that maximal quantum of fluorescence (F_v/F_m) decreased with increasing doses of UV radiation, but remained unaffected by temperature. High levels of soluble phlorotannins were detected and confirmed by microscopic observation revealing the abundance of large physodes. Exposure to UV radiation and elevated temperature showed that phlorotannins were not inducible by UV but increased at 12°C. ROS scavenging capacity was positively correlated with the contents of phlorotannins. In general, highest contents of phlorotannins were correlated with the lowest inhibition of F_v/F_m in all experimental treatments, highlighting the UV‐protective role of these compounds in D. anceps.     

Induction of Phlorotannins During UV Exposure Mitigates Inhibition of Photosynthesis and DNA Damage in the Kelp Lessonia nigrescens

Phlorotannins of brown algae are multifunctional compounds with putative roles in herbivore deterrence, antioxidation and as primary cell wall components. Due to their peripheral localization and absorption at short wavelengths, a photoprotective role is suggested. We examined the induction of phlorotannins by artificial UV radiation in the intertidal kelp Lessonia nigrescens and whether they attenuate the inhibition of photosynthesis and DNA damage, two major detrimental effects of UV. The soluble and cell wall-bound fractions of phlorotannins were quantified in blades collected in summer and winter. Major findings were that (1) the synthesis of phlorotannins (both forms) was induced by UV only in summer; (2) the induction was fast (within 3 days); and (3) there was a positive relationship between of the contents of insoluble phlorotannins and the suppression of photoinhibition and DNA damage, measured as formation of cyclobutane pyrimidine dimers and 6-4 photoproducts. Overall, the photoprotective role of phlorotannins appears to respond to an interplay between the external UV stimulus, seasonal acclimation and intrinsic morpho-functional processes. In summer, when algae are naturally exposed to high UV irradiances, soluble phlorotannins are induced, while their transition to insoluble phlorotannins could be related with the growth requirements, as active blade elongation occurs during this season.     

Spatial and Temporal Bioactive Compound Contents and Chlorophyll Fluorescence of Kale (Brassica oleracea L.) Under UV-B Exposure Near Harvest Time in Controlled Environments

UV-B irradiation has been used to enhance the secondary metabolite content in plants, but its spatial effect on plants has not been considered. The objective of this study was to compare spatial photosynthetic traits and bioactive compound accumulation in kale (Brassica oleracea L. var Acephala) according to the distribution and length of UV-B exposure near harvest. Plants were exposed to UV-B of 0–3, 3–6 and 6–9 W m⁻² for 4 h per day at 5 days (Exp. 1) and 4.2 W m⁻² at 5, 4, 3, 2 or 1 days (Exp. 2) before harvest. In spatial distribution, the higher the UV-B intensity, the lower the mean F_v/F_m (maximal photochemical efficiency of PSII) and the higher the concentration of total flavonoid compound (TFC). With UV-B stress, F_v/F_m and fluorescence transient parameters decreased except for DI₀/CS (dissipated energy flux per cross section) and PI_abs (performance index of PSII). When exposed to UV-B radiation for 2 days before harvest, the total phenolic compounds and TFC per plant were highest, not always proportional to the local F_v/F_m but affected by dry weight. Short-term UV-B stress near harvest would be more efficient for the accumulation of bioactive compounds by minimizing the loss of plant weight.     

Photocatalytic Activity of LaSr2AlO5:Eu Ceramic Powders

The photocatalytic activity, of undoped and Europium‐doped LaSr₂AlO₅ powders, has been investigated by degrading methylene blue dye in water solutions. Those powders were fabricated by a combustion method and an annealing treatment in air. All samples showed a tetragonal single phase according to by X‐ray diffraction measurements (XRD). Scanning electron microscopy (SEM) revealed irregular semi‐oval grains with sizes in the range of 3.5–4.27 μm. Photoluminescence spectrum showed sharp emission peaks at 588 nm and at 617 nm which are associated with ⁷F₁,⁷F₂→ ⁵D₀ Eu³⁺ ion forbidden transitions, respectively, under UV light excitation of 322 nm. The methylene blue (MB) degradation under UV light (254 nm) was studied by monitoring changes in the absorbance peak of MB at 665 nm. Finally, LaSr₂AlO₅:Eu powders were used three times and the efficiency for the degradation of MB decreased from 100 to 61% after the third cycle of use.     

Ultraviolet Radiation Reduces the Photoprotective Capacity of the Marine Diatom Phaeodactylum tricornutum (Bacillariophyceae, Heterokontophyta)

This study demonstrates that UV radiation (UVR) reduces the photoprotective capacity of the diatom Phaeodactylum tricornutum by affecting xanthophyll cycle (XC) activity. The short‐term reduction of photosystem II (PSII) maximum efficiency of charge separation (F_v/F_m) in cells exposed to UVR could be explained mainly by a reduced photoprotective capacity under this condition. Phaeodactylum tricornutum cells acclimated to two different photosynthetically active radiation (PAR) intensities, high light (HL, 200 μmol quanta m^?2 s^?1) and low light (LL, 50 μmol quanta m^?2 s^?1), were exposed to saturating irradiance (1100 μmol quanta m^?2 s^?1) in the presence (PAR + UVR) and absence of UVR (PAR). HL cells exhibited a greater reduction in F_v/F_m in PAR + UVR when compared with the PAR treatment that was related to a reduction in the de‐epoxidation of XC pigments. In contrast, in LL cells, UVR did not considerably affect XC de‐epoxidation even though the reduction in F_v/F_m was greater than in HL cells. The negative effect of UVR on photoprotection was more pronounced in HL cells because they synthesized more XC pigments than LL cells. This was confirmed when XC activity was blocked with dithiothreitol and when PSII repair was inhibited with chloramphenicol (CAP). The differential reduction of F_v/F_m between PAR + UVR and PAR treatments disappeared when XC was blocked in HL cells. A higher reduction and an incomplete recovery of F_v/F_m were observed in cells incubated with CAP in the presence of UVR. Such responses confirm that UVR had a negative effect on photoprotective mechanisms causing an enhancement of damage by PAR, especially in HL‐acclimated cells in which heat dissipation is important for PSII regulation.     

Short‐term UV‐B Dose Stimulates Production of Protective Metabolites in Matricaria chamomilla Leaves

Physiological response of two cultivars of Matricaria chamomilla plants on UV irradiation was studied. The impact of used short‐time UV dose was evaluated in three time points; 2, 24 and 48 h after irradiation. Used UV irradiation immediately resulted in changes in plant oxidative status monitored as increased concentration of H₂O₂. Decrease in chlorophyll a and b indicated the impact on photosynthetic apparatus. For phenolic secondary metabolites, an increase in total soluble phenols and AlCl₃‐reactive flavonols was observed. The activity of main phenolic enzyme, phenylalanine ammonia‐lyase, increased with time after irradiation. Significant changes, mainly decreasing trends, in the content of free coumarins and their glycosidic precursors were observed. Enhanced accumulation in chlorogenic and 1,5‐dicaffeoylquinic acid and in (Z)‐isoform of dicycloethers was detected. From these results, the redirecting precursors of coumarin biosynthesis to biosynthesis of substances with higher antioxidative potential can be assumed. Different reactions in diploid and tetraploid plants were recorded, too.     

Separation and Determination of Nitroguanidine and Guanidine Nitrate by HPTLC

High-performance thin-layer chromatography has been used for separation and quantification of nitroguanidine and guanidine nitrate, for online and off-line quality control of synthesis. The compounds were separated on silica gel 60 F₂₅₄ layers with dioxane–tetrahydrofuran 1:1 (v/v), as mobile phase. UV detection was performed at 210 and 265 nm for guanidine nitrate and nitroguanidine, respectively. Quantitative analysis was performed by absorbance densitometry and use of peak area. Validation was performed taking into consideration the special features of the method.     

Photosynthetic,Biochemical and Secondary Metabolite Changes in a Medicinal Plant Chlorophytum borivillianum (Safed musli) against Low and High Doses of UV-B Radiation

Plants are inevitably grown in presence of sunlight, therefore bound to be exposed to natural UV-B radiation. Several studies have already been conducted with UV-B and medicinal plants and only few studies showed dose dependent variation. The present study aims to find out the variations and adaptation in Chlorophytum borivillianum under two different doses of UV-B radiation; ambient + low (3.2 kJm⁻² d⁻¹) and high (7.2 kJm⁻² d⁻¹) UV-B dose, denoted as LD and HD, respectively. Reduction in photosynthetic rate was higher at HD, while plants receiving LD displayed nonsignificant variation. During vegetative and reproductive stage, significant reduction (P ≤ 0.001) in stomatal conductance was obtained when exposed to HD-eUV-B. F_v/F_m showed more reductions in HD-eUV-B (12.6%) followed by LD-eUV-B (7.9%). Low and high doses of UV-B enhanced the anthocyanin content but the increase was significant in HD, indicates epidermal protection strategy by the plants. Under LD-eUV-B, the content of saponin, a major phytochemical constituent was enhanced by 26%. Phytochemical analysis of roots revealed reduction mostly in fatty acid components whereas the steroidal components (stigmasterol and sarsasapogenin) showed enhancement in response to LD. The study suggests the importance of LD-eUV-B in the stimulation of medicinal compounds in C. borivillianum.     

Reflectance and Cyclic Electron Flow as an Indicator of Drought Stress in Cotton (Gossypium hirsutum)

The response and the functioning of the photosynthetic machinery of cotton, Gossypium hirsutum during water stress was studied by leaf optical properties, linear (ETRII) and cyclic electron flow (CEF) and chlorophyll a fluorescence. We observed that in G. hirsutum, during water limitation, Chlorophyll b showed the best correlation with reflectance at 731 nm and is a better indicator of drought. F_v/F_m was observed to be very insensitive to mild water stress. However, during severe water stress the leaves exhibit considerable inhibition in F_v/F_m and an increase in anthocyanin levels by about 20‐fold. CEF was very responsive to mild water stress. The mild drought stress caused large decrease in the ability of the leaves to utilize the light energy. Photosystem I and photosystem II is protected from photoinhibition by high CEF and nonphotochemical quenching under mild water stress. While during severe drought stress, linear electron flow showed a sharp decrease in comparison to CEF. CEF play a major role in G. hirsutum leaves during mild as well as under severe water stress condition and is thus a good indicator of water stress.     

Extraction of <Emphasis Type="Italic">p</Emphasis>-hydroxyacetophenone and catechin from Norway spruce needles. Comparison of different extraction solvents

The phenolic compounds p-hydroxyacetophenone and catechin have been extracted from Norway spruce needles with pure methanol, 80 and 50% (v/v) aqueous methanol, pure acetonitrile, 80% (v/v) aqueous acetonitrile, and pure water. Extraction efficiency of the individual solvents was compared. Although 80% aqueous methanol is the solvent most frequently used for extraction of soluble phenolic compounds from needles, it was found that pure methanol is a more suitable extraction solvent. Surprisingly, a two-step procedure based on the extraction of crushed needles with water then re-extraction with methanol proved a good alternative to direct extraction with methanol. Extraction of uncrushed spruce needles might indicate that relatively more p-hydroxyacetophenone than catechin was located in the surface layer of the needle.     

HPTLC–densitometric and HPTLC–MS methods for analysis of flavonoids

HPTLC silica gel plates without and with fluorescence indicator F₂₅₄ in combination with n-hexane–ethyl acetate–formic acid (20:19:1, v/v/v) as a developing solvent were explored for the HPTLC–densitometric and HPTLC–MS/(MSⁿ) analyses of flavonoids. Pre-development of the plates with chloroform–methanol (1:1, v/v) was needed for reliable HPTLC–densitometric analyses of flavonoid aglycones in the whole R_F range, while 2-step pre-development (1^st methanol–formic acid (10:1, v/v), 2^nd methanol), that decreased background signals of formic acid adducts, was required for HPTLC–MS analyses. Optimization with conditioning of the adsorbent layer with water before development and saturation of the twin trough chamber resulted in required decrease of the R_F values of studied flavonoids (flavone, apigenin, luteolin, chrysin, quercetin dihydrate, myricetin, kaempferide, kaempferol, naringenin, pinocembrin).

Detection was performed based on fluorescence quenching (on the plates with F₂₅₄), natural fluorescence and after post-chromatographic derivatization with natural product reagent without or with further enhancement and stabilization of fluorescent zones with polyethylene glycol (PEG 400 or PEG 4000) or paraffin–n-hexane reagents. For all three reagents, drying temperature and time passed after drying influenced the intensity, which was increasing the first 20?min, and the stability (less than 2?h for PEGs and at least 24?h for paraffin–n-hexane) of the standards’ zones.

Optimal wavelengths for densitometric evaluation were selected based on in-situ absorption spectra scanned before and after derivatization and after stabilization. The developed method was tested via analyses of propolis, roasted coffee, rose hip, hibiscus, rosemary and sage crude extracts. To further increase the reliability of the obtained densitometric results HPTLC–MS/(MSⁿ) analyses of all crude extracts were performed. Several phenolic and non-phenolic compounds were tentatively identified.

Some possible interferences with phenolic acids (chlorogenic acid, rosmarinic acid, protocatechuic acid, gallic acid, syringic acid, ellagic acid, trans-cinnamic acid, o-coumaric acid, m-coumaric acid, p-coumaric acid, caffeic acid, ferulic acid, sinapic acid) that are often present in the extracts together with flavonoids were also examined.     

Effect of the structure of latex particles on adhesion. Part II: Analogy between peel adhesion and rheological properties of acrylic copolymers

This article, the second part of this series, concerns the development of an analogy between the peel behavior of pressure-sensitive adhesives and the dynamic mechanical properties of the corresponding copolymers. The adhesive copolymers used were synthesized by emulsion polymerization processes. Their physical and dynamic mechanical properties were characterized and presented in Part I of this series. In this study, an analogy was built up between the force in a peel test as a function of peel velocity, F_p(v_p), and the loss modulus of the adhesive as a function of the angular frequency in a dynamic mechanical experiment, G″(ω). This was done by superimposing the curves of F_p versus v_p and those of G″ versus ωβ₀/β, where β₀/β is a shift factor with β being a parameter in the Kaelble theory and β₀ being some reference value of the Kaelble parameter. When the curves of F_p ～ v_p and those of G″ ～ ωβ₀ were plotted together, they followed the same trend of variation. This analogy between G″(ωβ₀/β) and F_p(v_p) was further confirmed by the fact that the apparent activation energies of the primary glass transition for G″(ω) and F_p(v_p) are virtually the same, suggesting that the analogy between G″(ω) and F_p(v_p) is dictated by the glass transition. The existence of the above-mentioned analogy between G″(ω) and F_p(v_p) shows that the performance of an adhesive can be evaluated or predicted from the dynamical loss modulus of the corresponding (co)polymer. ©1995 John Wiley & Sons, Inc.     

Production and Characteristics of the Whole-Cell Lipase from Organic Solvent Tolerant <Emphasis Type="BoldItalic">Burkholderia</Emphasis> sp. ZYB002

The thermostable and organic solvent tolerant whole-cell lipase (WCL) was produced by Burkholderia sp. ZYB002 with broad spectrum organic solvent tolerance. The production medium of the WCL was primarily optimized, which resulted in the maximum activity of 22.8 U/mL and the 5.1-fold increase of the WCL yield. The optimized culture medium was as follows (% w/v or v/v): soybean meal 2, soybean oil 0.5, manganese sulfate 0.1, K₂HPO₄ 0.1, olive oil 0.5, initial pH 6.0, inoculum density 2, liquid volume 35 mL in 250-mL Erlenmeyer flask, and incubation time 24 h. The biochemical characterization of the WCL from Burkholderia sp. ZYB002 was determined, and the results showed that the optimal pH and temperature for lipolytic activity of the WCL was 8.0 and 65°C, respectively. The WCL was stable at temperature up to 70°C for 1 h and retained 79.2% of its original activity. The WCL was highly stable in the pH range from 3.0 to 8.5 for 6 h. Ca²⁺, K⁺, Na⁺, NO₃⁻, etc. ions stimulated its lipolytic activity, whereas Zn²⁺ ion caused inhibition effect. The WCL was also relatively stable in n-butanol at a final concentration of 50% (v/v) for 24 h. However, the WCL was strongly inhibited in Triton X-100 at a final concentration of 10% (v/v). The WCL with thermal resistance and organic solvent tolerance showed its great potential in various green industrial chemical processes.     

Simultaneous determination of hydrochlorothiazide and losartan potassium in tablets by high-performance low-pressure chromatography using a multi-syringe burette coupled to a monolithic column

This contribution describes use of a separation method based on on-line coupling of a multisyringe flow system with a chromatographic monolithic column for simultaneous determination of hydrochlorothiazide and losartan potassium in tablets. The system comprised a multisyringe module, three low-pressure solenoid valves, a monolithic C₁₈ column (25 mm × 4.6 mm i.d.), and a diode-array detector. The mobile phase was 10 mmol L⁻¹ potassium dihydrogen phosphate (pH 3.1)-acetonitrile-methanol (65:33:2 v/v/v) at a flow rate 0.8 mL min⁻¹. UV detection was carried out at 226 nm. The multi-syringe chromatographic (MSC) method with UV spectrophotometric detection was optimized and validated. Results from validation were very good. The analysis time was about 400 s. The method was found to be applicable to routine analysis of both compounds in tablets. The coupling of the monolithic columns with a multi-syringe flow-injection analysis manifold provides an excellent and inexpensive tool to solve the separation problems without use of HPLC instrumentation.     

A New <Emphasis Type="Italic">Stenotrophomonas maltophilia</Emphasis> Strain Producing Laccase. Use in Decolorization of Synthetics Dyes

Laccase activity was detected in a soil bacterium Stenotrophomonas maltophilia AAP56 identified by biochemical and molecular methods. It was produced in cells at the stationary growth phase in Luria Bertani (LB) medium added by 0.4 mM copper sulfate. The addition of CuSO₄ in culture medium improved production of laccase activity. However, one laccase enzyme was detected by native polyacrylamide gel electrophoresis. The enzyme showed syringaldazine (K _m = 53 μM), 2,2’-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (K _m = 700 μM), and pyrocatechol (K _m = 25 μM) oxidase activity and was activated by addition of 0.1% (v/v) Triton-X-100 in the reaction mixture. Moreover, the laccase activity was increased 2.6-fold by the addition of 10 mM copper sulfate; the enzyme was totally inhibited by ethylenediaminetetraacetic acid (5 mM), suggesting that this laccase is a metal-dependant one. Decolorization activity of some synthetic dyes (methylene blue, methyl green, toluidine blue, Congo red, methyl orange, and pink) and the industrial effluent (SITEX Black) was achieved by the bacteria S. maltophilia AAP56 in the LB growth medium under shaking conditions.     

A reversed-phase ion-interaction chromatographic method for in-vitro estimation of the percutaneous absorption of water-soluble UV filters

An analytical method based on ion-interaction chromatography with UV detection for simultaneous in-vitro estimation of the percutaneous absorption of the most used water-soluble UV filters in sunscreen cosmetics is proposed. These UV filters were phenylbenzimidazole sulfonic acid, disodium phenyl dibenzimidazole tetrasulfonate, benzophenone-4, and terephthalylidene dicamphor sulfonic acid. The methodology is based on applying the sunscreen containing the target UV filters to human epidermis in a diffusion cell. Analytes are determined in the receptor solution. To ensure skin integrity, screening of the cells was carried out by analytical determination of a marker. Analytical variables such as percentage ethanol, concentration of ion-pairing agent, pH of the mobile phase, and temperature were studied in order to achieve high resolution of the chromatographic peaks in the lowest possible time of analysis. The conditions selected consisted of a mobile phase composed of 35:65 (v/v) ethanol–ammonium acetate buffer solution (pH 4, containing 50 mmol L⁻¹ tetra-n-butylammonium bromide). The chromatographic determination was carried out with the analytical column at 50 °C. UV detection was carried out at the maximum absorption wavelength for each analyte. The limit of detection (3s _y/x /b) ranged from 16 to 65 ng mL⁻¹, depending on the analyte.     

Bithiophene triarylborane dyad: An efficient material for the selective detection of CN− and F− ions

A new fluorescent chemosensor based on bithiophene coupled dimesitylborane (BMB-1) was synthesized and characterized. BMB-1 was used for colorimetric and turn-on fluorescent sensing of cyanide (CN⁻) and fluoride (F⁻) ions, in the presence of other competitive anions in an aqueous (CH₃CN–H₂O) medium. BMB-1 showed a hypsochromic shift (blue shift) with addition of CN⁻ and F⁻ ions in absorption studies. The lower detection level of CN⁻ and F⁻ ions is 1.37 × 10⁻⁹ and 1.75 × 10⁻⁹ M, respectively. The BMB-1 binding mechanism is based on the nucleophilic addition of CN⁻ and F⁻ ions in the internal charge transfer transition of bithio moiety to the boranylmesitylene unit, and the color changes were observed under UV light. This result is further confirmed by Fourier transform infrared spectroscopy, mass spectrometry and density functional theory calculations. Also, the BMB-1 probe is found to be a good adsorbent for the removal of F⁻ ions in real water samples using the adsorption technique.     

Dimers of Ag2+ Ions – Synthesis and Characterization of the Quaternary Silver Fluoride Ag2ZnZr2F14 with [Ag2F7]3– Units

Deep blue‐violet colored powder samples of Ag₂ZnZr₂F₁₄ were synthesized by heating Zn(NO₃)₂·4H₂O, Ag and ZrOCl₂·8H₂O at 300 °C under fluorine atmosphere. The crystal structure of Ag₂ZnZr₂F₁₄ was refined from X‐ray powder diffraction data using the Rietveld method (C2/m, a = 9.0206(1) Å, b = 6.6373(1) Å, c = 9.0563(1) Å, β = 90.44(1)°, Z = 2). The structure is derived from the isotypic Ag₃Zr₂F₁₄ by replacing only one of the two crystallographically different Ag²⁺ ions with Zn²⁺ ions, thus leading to discrete Ag₂F₇ dimers. These dimers are connected via nearly linear Ag–F···F–Ag bridges with short F···F distances of 2.33 Å to form two‐legged ladders. Magnetic susceptibility measurements and density functional calculations show that the two Ag²⁺ ions in each Ag₂F₇ dimer are strongly coupled antiferromagnetically.     

Synthesis and In Vitro Photodynamic Activities of an Integrin‐Targeting cRGD‐Conjugated Zinc(II) Phthalocyanine

A 1,4‐disubstituted zinc(II) phthalocyanine conjugated with a cyclic Arg‐Gly‐Asp‐D ‐Phe‐Lys (cRGDfK) moiety through a triazole linker was prepared and characterized by UV/Vis spectroscopy and high‐resolution ESI‐MS. The conjugate showed a relatively weak fluorescence emission in N,N‐dimethylformamide (Φ_F=0.08), but it was a very efficient singlet oxygen generator (Φ_Δ=0.80) as a result of the di‐α‐substituted structure. Owing to the presence of the cyclic peptide sequence cRGDfK, which is a well‐known α_vβ₃‐integrin antagonist, this conjugate exhibited significantly higher cellular uptake toward the α_vβ₃⁺ U87‐MG cells compared with the α_vβ₃^? MCF‐7 cells, as determined by flow cytometry and fluorescence microscopy. The photocytotoxicity of this compound against these two cell lines, however, was comparable owing to the similar efficiency of intracellular reactive oxygen species generation. Confocal microscopic studies also revealed that this conjugate localized preferentially in the lysosomes, but not in the nucleus, endoplasmic reticulum, and mitochondria of the U87‐MG cells.     

Increased Antioxidant Activity and Changes in Phenolic Profile of Kalanchoe pinnata (Lamarck) Persoon (Crassulaceae) Specimens Grown Under Supplemental Blue Light

Antioxidant compounds protect plants against oxidative stress caused by environmental conditions. Different light qualities, such as UV‐A radiation and blue light, have shown positive effects on the production of phenols in plants. Kalanchoe pinnata (Lamarck) Persoon (Crassulaceae) is used for treating wounds and inflammations. Some of these beneficial effects are attributed to the antioxidant activity of plant components. We investigated the effects of blue light and UV‐A radiation supplementation on the total phenol content, antioxidant activity and chromatographic profile of aqueous extracts from leaves of K. pinnata. Monoclonal plants were grown under white light, white plus blue light and white plus UV‐A radiation. Supplemental blue light improved the antioxidant activity and changed the phenolic profile of the extracts. Analysis by HPLC of supplemental blue‐light plant extracts revealed a higher proportion of the major flavonoid quercetin 3‐O‐α‐l ‐arabinopyranosyl (1→2) α‐l ‐rhamnopyranoside, as well as the presence of a wide variety of other phenolic substances. These findings may explain the higher antioxidant activity observed for this extract. Blue light is proposed as a supplemental light source in the cultivation of K. pinnata, to improve its antioxidant activity.