UVA Region Research Articles

Influence of the adsorption effect of graphene quantum dot on the photophysical properties and multiple antioxidant processes of gallic acid

In this work, the influence of graphene quantum dot (GQD) adsorption effect on the multiple antioxidant processes and photophysical properties of gallic acid (GA) has been investigated by density functional theory. Simulated absorption spectra of the GA-GQD covered UVA and UVB regions, and its extremely weak fluorescence intensity means that it is more suitable for use as the sunscreen than GA. Moreover, in the S0 state, the sequence of multiple antioxidant processes of GA (GA-GQD) is: e- → H3+ → e- → H1+ (e- → H2+ → e- → H3+), and the first step of antioxidant processes of GA-GQD is more straightforward to occur than GA according to the specific thermodynamic parameters. Furthermore, the dynamic simulations of GA and GA-GQD reacted with free radical ·OH revealed that their antioxidant processes are spontaneous, verifying their outstanding antioxidant abilities.

Super long ultraviolet-A persistent luminescence and photo-stimulated luminescence from CaMgGeO4: Bi3+

Here, we have developed a novel ultra long ultraviolet-A afterglow material CaMgGeO4: Bi3+, which shows more than 24 h UVA afterglow emission peaked at 346 nm. The crystal structure shows that the prepared sample is a pure phase with an orthogonal system of Pmnb space group. The composition of valence band and conduction band was analyzed by the density of states, which reveals that the bandgap of the CaMgGeO4 matrix is 3.69 eV. The photoluminescence spectrum of the sample consists of a broadband in the 320–400 nm UVA region, which belongs to the 3P1 → 1S0 electron transition of Bi3+. More importantly, under the excitation of ultraviolet lamp for 3 min, CaMgGeO4: Bi3+ exhibited an UVA ultra long persistent luminescence (LPL) with a duration of more than 24 h, which afterglow emission intensity still reaches 1500 cps and is about 6 times of the background intensity. In addition, the UVA emission of CaMgGeO4: Bi3+ after 13 h day can be repeatedly by short periods of low-energy light sources stimulation. The thermoluminescence analysis indicates that the presence of shallow and deep traps is responsible for excellent UVA-LPL and photo-stimulate luminescence (PSL). The excellent LPL and PSL properties can prompt CaMgGeO4: Bi3+ phosphor to be widely used in the field of photodynamic therapy.

A calibration methodology for the novel radioluminescence detector systems

Radioluminescence mapping using well-characterized and optimized optical systems is an effective method for localizing contamination with alpha-emitting radionuclides. To apply this novel approach to radiological emergency management, nuclear safeguards, nuclear decommissioning, and nuclear forensics, an established traceability chain is required. This work presents the development and implementation of a novel calibration methodology to provide valuable information about, and confidence in, the performance of radioluminescence detection systems. The proposed calibration methodology is based on two complementary approaches: (a) application of well-characterized activity standards to establish a traceable relationship between radioluminescence intensity and alpha activity, and (b) use of all optical radiation-based devices that, when calibrated against an alpha activity standard, simulate the radioluminescence induced in nitrogen (N2) and nitric oxide (NO) gases by alpha particles in specific spectral regions. A dedicated 210Po alpha activity standard with a narrow peak of less than 32keV FWHM at 5.3MeV has been developed and used to characterize a lens-based radioluminescence detection system in terms of its sensitivity to alpha-induced radioluminescence in different atmospheres (air, N2, N2 ＋ NO mixture) in the UV-A and UV-C (solar blind) spectral regions. The characterized lens system was then used as an intermediary transfer device to cross-calibrate two portable integrating sphere-based radiance standards designed to simulate radioluminescence in the UV-A and UV-C spectral regions. Both radiance standards can be used as transfer standards simulating up to 510MBq when used in the UV-A and up to 8.7GBq when used in the UV-C spectral regions. They substantially simplify routine quality control of radioluminescence detection systems by eliminating the need for open alpha sources, which are always associated with strict radiation safety precautions. Furthermore, since radiance standards can operate in a wide range of intensities, linearity and detection limits of radioluminescence detectors can be readily determined. The design, construction, radiometric characterization, and calibration of dedicated transfer standards, as well as the development of new calibration procedures for radiometric traceability of radioluminescence detection systems, will enable appropriate accident and post-accident radiation measurements that will lead to more effective countermeasures and better protection of people, wildlife, and the environment.

Enhanced Visible Light Absorption in Heteroleptic Cuprous Phenanthrolines.

This work presents a series of Cu(I) heteroleptic 1,10-phenanthroline chromophores featuring enhanced UVA and visible-light-harvesting properties manifested through vectorial control of the copper-to-phenanthroline charge-transfer transitions. The molecules were prepared using the HETPHEN strategy, wherein a sterically congested 2,9-dimesityl-1,10-phenanthrolne (mesPhen) ligand was paired with a second phenanthroline ligand incorporating extended π-systems in their 4,7-positions. The combination of electrochemistry, static and time-resolved electronic spectroscopy, 77 K photoluminescence spectra, and time-dependent density functional theory calculations corroborated all of the experimental findings. The model chromophore, [Cu(mesPhen)(phen)]+ (1), lacking 4,7-substitutions preferentially reduces the mesPhen ligand in the lowest energy metal-to-ligand charge-transfer (MLCT) excited state. The remaining cuprous phenanthrolines (2-4) preferentially reduce their π-conjugated ligands in the low-lying MLCT excited state. The absorption cross sections of 2-4 were enhanced (εMLCTmax = 7430-9980 M-1 cm-1) and significantly broadened across the UVA and visible regions of the spectrum compared to 1 (εMLCTmax = 6494 M-1 cm-1). The excited-state decay mechanism mirrored those of long-lived homoleptic Cu(I) phenanthrolines, yielding three distinguishable time constants in ultrafast transient absorption experiments. These represent pseudo-Jahn-Teller distortion (τ1), singlet-triplet intersystem crossing (τ2), and the relaxed MLCT excited-state lifetime (τ3). Effective light-harvesting from Cu(I)-based chromophores can now be rationalized within the HETPHEN strategy while achieving directionality in their respective MLCT transitions, valuable for integration into more complex donor-acceptor architectures and longer-lived photosensitizers.

Reduction of CO2 in the presence of light via excited-state hydride transfer reaction in a NADPH-inspired derivative.

The photo-catalytic reduction of CO2 into chemical feedstocks using solar energy has attracted vast interest in environmental science because of global warming. Based on our previous study on the CO2 complex with one of the benzimidazoline (BI) derivatives, we explore the photochemical reduction of CO2 in one of the benzimidazoline derivatives (1,3-dimethyl-5,6-diol-2,3-dihydro-1H-benzimidazole) by quantum-chemical methods. Our results reveal that carbon dioxide can be reduced to formate (HCOO-) by a hydride transfer reaction in the excited state of this complex of benzimidazoline derivative and CO2. While the ground-state hydride transfer reaction in this complex exhibits a substantial barrier, a charge-transfer can occur in the first singlet excited state of the complex in the UV-A region (326 nm), and after overcoming a moderate barrier (∼0.4 eV) the system can have access to the products. The interaction with a polar solvent decreases further the barrier such that the reaction in dimethyl sulfoxide can proceed with a negligibly small barrier (∼0.1 eV) or in a nearly barrierless manner. Our results show that this benzimidazoline derivative may act as a catalyst in the photoreduction of CO2.

Evaluation of knowledge, attitudes, and practices of estate managers on food safety of black tea manufacturing in the Uva region of Sri Lanka

Sri Lankan black tea is renowned for its high quality and regarded as a brand that is chemically safe, ozone-friendly, and ethically acceptable with accountable stakeholders in the supply chain. Meantime, food safety has become one of the mandated food attributes that is heavily concern by stakeholders even at the estate level. Hence, this study aimed to determine the level of knowledge, attitudes, and practice (KAP) of managers at black tea manufacturing in the Uva region of Sri Lanka regarding basic food safety concerns. Data were collected from 30 respondents at 30 black tea manufacturing factories in the Uva region using a stratified random sampling technique. A pre-tested interviewer-administered questionnaire based on KAP of basic food safety was utilized and collected data were analyzed using descriptive analysis and correlation analysis. The study indicated that the mean percentage of knowledge was satisfactory (93.1%), and the mean score for attitudes and practices of food safety was 4.7±0.4 (X±SD) and 4.6±0.5 (X±SD), respectively. However, this study depicted that the knowledge of food safety influenced managers’ attitudes (0.421, P<0.05) but not their food safety behaviour. Further, they believed that food safety management systems would be a means of directing their black tea to the international market (76.7%), while pledging the concerns of food safety (70%). However, it was depicted that constraints with food handlers (100%) and financial difficulties (73.3%) hugely affected the implementation of food safety management systems at the black tea manufacturing factories in the Uva region of Sri Lanka. Hence, this study suggests continuous, periodical but short training to sustain the practice of handling teas safely in the Uva region of Sri Lanka.

Hyaluronic acid/polyphenol sunscreens with broad-spectrum UV protection properties from tannic acid and quercetin

Currently, commercial sunscreens cause a number of biotoxicity and environmental issues, making it imperative to develop biocompatible alternatives. In this study, we aimed to develop an alternative sunscreen from two ecofriendly and biocompatible natural polyphenolic compounds, tannic acid (TA) and quercetin (Que). The sunscreen was prepared through a simple process using an oil-in-water emulsion as the medium and hyaluronic acid (HA) as the base polymer to improve biocompatibility. The HA/TA/Que. sunscreen prepared in this study exhibits 0 % transmittance in the UVB region and <15 % transmittance in the UVA region, resulting in excellent sun-protection properties (SPF 30). Remarkably, the as-prepared HA/TA/Que. sunscreen has a suitable viscosity and similar UV protection properties to those of commercial sunscreens. The HA/TA/Que. sunscreen also exhibits 90.4 % antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl, demonstrating an ability to effectively capture reactive oxygen species that directly affect the skin. In addition, the cell viability was >90 % at a concentration of 50 μg/mL after 7 days, indicating excellent cytocompatibility. Owing to its various advantageous features, the HA/TA/Que. sunscreen with excellent sun protection properties and multiple functionalities is expected to resolve many environmental and biological issues caused by commercial sunscreens.

Construction of photo-responsive lignin as a broad-spectrum sunscreen agent

Lignin has potential to serve as promising sunscreen agents as it has good ultraviolet (UV) absorption and antioxidant properties. However, the weak absorption capacity of lignin in the long-wave UV region (UVA, 320–400 nm) limits its further development. In this work, a spiropyran-modified lignin (DLSP) with photo-responsive property was prepared by in-situ construction of spiropyran (SP) structure in the demethylated lignin (DL). Due to the presence of SP moiety, the absorption of DLSP in the UVA region was significantly improved. Under UV irradiation, its absorption peak was redshifted as unconjugated SP form isomerized to conjugated merocyanine (MC) form, and the UVA/UVB ratio increased from 0.62 to 0.74. The free-radical scavenging ability of lignin could protect SP from photodegradation, which provided DLSP excellent fatigue resistance. DLSP were blended into creams to investigate its sunscreen performance. Results indicated that DLSP exhibited radiation-enhanced sunscreen performance, the sun protection factor (SPF) of cream containing 10 wt% of DLSP improved from 20 to 67 after 8 h of UV irradiation. Moreover, DLSP showed low skin penetration and good biocompatibility. These results provide a useful guideline for the rational design of sunscreens with special functionalities.

Assessment of the PARP inhibitor talazoparib photosafety profile

Talazoparib (TLZ) is a poly(adenosine diphosphate [ADP]-ribose) polymerase inhibitor employed for the treatment of breast cancer. This drug displays an absorption band in the UVA region, and therefore investigation of the possible phototoxic side-effects associated to its administration results of enormous relevance. In this context, we describe here a photochemical and photobiological study to ascertain the photosafety profile of TLZ. Concerning transient species, the singlet and triplet excited states of TLZ were detected by fluorescence (λmax em = 440 nm) and laser flash photolysis experiments (λmax abs = 400 nm), respectively. Remarkably, TLZ irradiation with UVA light in aqueous solution resulted in formation of a stable photooxidated product, TLZ-P, whose absorption band is extended until the visible region. From in vitro experiments, phototoxicity was revealed for the parent drug by neutral red uptake (NRU) assays, with a PIF value of ca 7; besides, TLZ induced formation of reactive oxygen species (ROS) and produced significant damage to both proteins and DNA. By contrast, the singlet and triplet excited states of TLZ-P were not detected, and no photodamage was observed in the NRU experiments. Overall, the results indicate that TLZ induces phototoxicity, whereas its photoproduct exhibits photosafety.

Lymnaea stagnalis and Ophryotrocha diadema as Model Organisms for Studying Genotoxicological and Physiological Effects of Benzophenone-3.

Benzophenone-3 (BP-3) is a lipophilic organic compound that occurs naturally in flower pigments. Since it adsorbs ultraviolet (UV) radiation in the UVA and UVB regions, it is one of the most common UV filters found in sunscreen and cosmetic products. We explored by in vivo micronuclei (MNi) assay the genotoxic effects of BP-3 on hemocytes from the freshwater gastropod Lymnaea stagnalis. We also studied its possible toxic effects on life-history traits: body growth in L. stagnalis and egg production of both L. stagnalis and the marine polychaete worm Ophryotrocha diadema. Adult individuals were exposed to increasing concentrations of BP-3 (0.025, 0.050, 0.100, and 0.200 mg/L) once a week for 4 weeks. In L. stagnalis, exposure to BP-3 at concentrations of both 0.2 and 0.1 mg/L produced genotoxic effects on the micronuclei frequencies, but only concentrations of 0.2 mg/L affected the NBUDs frequencies. Similarly, negative effects on body growth were observed at the concentrations of 0.2 and 0.1 mg/L and a significant reduction of egg production at 0.2 mg/L. In O. diadema, a negative correlation between egg production and increasing BP-3 concentrations was observed. Our findings suggest the need for more stringent measures to reduce the presence of BP-3 in the environment.

Synthesis of CaNb2O6 with a Rynersonite-like Structure: Morphology, Rietveld Refinement, Optical, and Vibrational Properties.

In this study, we report the easy and low-cost synthesis of calcium niobate (CaNb2O6) with the isomorphic structure of the Rynersonite mineral for CaTa2O6. The samples were prepared by the ball milling method at room temperature at a synthesis time of 0.5, 1, 2, 3, and 4 h. The structural analysis by XRD, Rietveld refinement, and vibrational Raman spectroscopy confirms all diffraction peaks and active mode characteristics of the pure phase of CaNb2O6 for the 3-h and 4-h samples, with a crystallite size of 22.5 and 23.2 nm, respectively. The optical band gap obtained was 3.18(2) eV (3-h sample), lower than the optical band gap for niobium oxide, characteristic of materials with strong photon absorption in the UVA region of the spectrum. The surface analysis by scanning electron microscopy reveals the obtention of several agglomerates of irregular particles ranging in the submicro and micro scales. Therefore, the present approach successfully obtained calcium niobate with the formula CaNb2O6 at a short synthesis time and room temperature.

The Effect of a Hydrophobic Coating on the Photodegradation of Dyed Nylon 6 Yarns

Nylon 6 is one of the most widely used polymers in the world. For some nylon products, hydrophobic coatings are used for impregnation. However, it has been suggested in the literature that coating could accelerate aging. Therefore, in this paper, we focused on the degradation process of dyed nylon yarns with and without perfluorinated coating under accelerated weathering conditions. To monitor the degradation process, we used methods such as tensile test, molecular weight analysis, ultraviolet–visible spectroscopy, Fourier-transform infrared spectroscopy, differential scanning calorimetry, energy dispersive X-ray analysis, and scanning electron microscopy. We found that the hydrophobic coating is unlikely to have a negative effect on the degradation process. However, the coating decomposes during weathering, and its concentration on the fiber's surface decreases. The type of dye used was identified as the most significant factor influencing the degradation rate. This was explained by the screening effect of dyes in the UVA region of the light spectrum. Manufacturers of nylon products, which require a pleasant appearance and safety, should, therefore, consider a careful selection of dyes.

Stability improvement of UV-filter between methoxy cinnamic acid derivatives and cyclodextrins inclusion complexes based on DFT and TD-DFT investigations

Structures and UV–vis absorption spectra of the host-guest interaction of the methoxy cinnamic acid (MCA) derivatives and cyclodextrins (CDs) were performed by using the density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. All geometries of MCA derivatives (4-MCA, 245-MCA, 246-MCA), three types of CD (αCD, βCD, γCD), and five host-guest inclusion complexes between MCA and CD consisting of 4-MCA/αCD (1), 4-MCA/βCD (2), 245-MCA/βCD (3), 246-MCA/βCD (4), and 246-MCA/γCD (5) were fully optimized by using the M06-2X/6-31G (d,p) levels of theory. Two orientations (A and B) of the MCA guest molecule were considered. Upon examining the optimized geometry, five complexes of the methoxy cinnamic acid molecules are located inside the cavity of CD. Orientation B was more stable than orientation A because of the stronger intermolecular hydrogen bonds between the hydroxyl group of CD and the carboxylic group of MCA. The results indicated that the intermolecular hydrogen bond is mainly the driving force of formation between methoxy cinnamic acid and cyclodextrins. To reveal the host-guest interaction that is relevant to UV-filter compounds, the UV–vis absorption spectra were performed using TD-DFT calculations. The obtained results confirmed that orientation B is the most stable orientation and can absorb in both UVB and UVA regions which is similar to the parent MCA. Therefore, this knowledge will bring to understand the host-guest interaction between methoxy cinnamic acid and cyclodextrin complexes. The theoretical results are expected to provide valuable information for improving the stability of further UV-filter compounds.

Photocatalytic and structure evaluation of g-C3N4/carbon microspheres and melam/dimelem intermediates under white LED and UVA-Vis irradiation

Despite the polymeric metal-free graphitic carbon nitride (g-C3N4) has been extensively studied for photodegradation, intermediate oligomers (melam/dimelem) can be generated during the polymerization process and it is a subject matter. The melem compounds feature active amino groups (-NH2) partially linked to one another, facilitating intermolecular reactions and alteration of the compound's structure. This study evaluated the synergic effect of carbon matrix on the physicochemical and electronic characteristics of g-C3N4 (CN) and melam/dimelem intermediates compounds by synthesis in situ of chitosan and CN precursors. The g-C3N4 were obtained using urea (U) and melamine (M), denoted as CN/U and CN/M, and the carbon microspheres, denoted as CN/CU and CN/CM. The characterizations suggest C–N sp2-hybridized bonds between the carbon ring from chitosan and the melam/dimelem unit, which may be highly activated either in the visible or UVA regions. An increase of 16% in photocatalytic efficiency for CN/CM material was observed by incorporating chitosan in the g-C3N4 using withe LED light. The carbon microspheres interact synergistically with the bulk g-C3N4 to form two-dimensional planes in which the charge carriers can move freely along the carbon ring structure. The carbon microspheres are an excellent option to separate the photocatalyst easily from the reaction mixture. Additionally, the photocatalytic degradation mechanism of RhB by carbon microspheres was also proposed.

Study on the luminescence properties of the Eu3+ and Tb3+ dual-doped fluorophosphate glasses for UV sensitization detection

In this article, NaPO3-BaF2-AlF3-CaF2 glasses doped with Eu3+ and Tb3+ were manufactured by conventional melt-quenching method, and they showed good physical properties throughout various measurements: density, refractive index, Raman scattering, and X-ray diffraction (XRD). Basing on Judd-Ofelt theory, the Ω2/4/6 values were calculated. The higher Ω2 values of the Eu3+-doped fluorophosphate glasses indicate a highly polarized environment around Eu3+ ions. Accompanying with the Eu3+ and Tb3+ dual-doped glass, it showed that the response of excitation absorption extended by whole UVA region. This phenomenon was explained by the energy transferring between Eu3+ and Tb3+. Combining the dual-doped glass with silicon-based photodetectors, the spectral response of the detectors in the UVA region was improved up to 20%.

In situ tailoring of Ag-doped-TiO2/TPMP/cotton nanocomposite with UV-protective, self-sterilizing and flame-retardant performance for advanced technical textiles

Herein, we present a novel approach to the development of a multifunctional, UV-protective, photocatalytic, antimicrobial and flame-retardant nanocomposite fabric surface. Using a sol–gel/hydrothermal approach, a phosphorus-based flame-retardant 3-(trihydroxysilyl)propyl methylphosphonate (TPMP) in combination with Ag-doped TiO2 was applied to the surface of cotton fibers for the first time, using an aqueous AgNO3 solution as the dopant. The modified cotton fabrics were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDS) and X-ray diffraction spectroscopy (XRD) to confirm the successful application of Ag-TiO2 and TPMP on the cotton fabric by analyzing the surface morphology, chemical composition, chemical bonding and crystal structure. The functional properties of the modified cotton fabric were determined by measuring the UV protection factor (UPF), burning behavior and thermo-oxidative stability, as well as antibacterial activity against Escherichia coli and Staphylococcus aureus. The results show the formation of a unique nanocomposite matrix of TPMP–polysiloxane on the surface of cotton fibers with well-distributed Ag-TiO2. The formation of TiO2/Ag2O particles on the surface of cellulose fibers was also confirmed. The synergism between all components of the nanocomposite resulted in excellent UV protection in the UVA and UVB region, with a UPF of 50+, self-sterilizing activity against both tested bacteria and enhanced thermo-oxidative stability. Therefore, the novel approach proposed herein is promising for the development of multifunctional, protective surfaces for advanced technical textiles.

Plasmon-Driven Photochemical Reduction Reaction on Silver Nanostructures for Green Fabrication of Superhydrophobic Surface.

Green fabrication of superhydrophobic surface by water-based processing is still challenging, because introduction of the substances with hydrophilic moieties compromises its superhydrophobicity. Herein, a plasmon-driven photochemical reduction reaction under ultraviolet light (UVA) irradiation is first discovered and is applied to deoxygenation of hydrophilic organic adsorbates on rough nano-Ag coating for the formation of stable superhydrophobic surface. A nano-Ag coating with strong localized surface plasmon resonance in the UVA region is prepared by a water-based silver mirror reaction and results in a unique chemical reduction reaction on its surface. Consequently, the low residual hydrophilic functionalities and the formed cross-linked structure of the adsorbate on Ag nanoparticles (NPs) enables the coating to exhibit stable superhydrophobicity against to both air and water. The superhydrophobic Ag NP-coated sandpaper can also be used as a surface-enhanced Raman scattering (SERS) substrate to concentrate aqueous analytes for trace detection.

Demonstration of iodide-dependent UVA-triggered growth inhibition in Saccharomyces cerevisiae cells and identification of its suppressive molecules

Upon white light illumination, the growth of the budding yeast Saccharomyces cerevisiae was extremely impaired only in the presence of iodide ions, but not fluoride, chloride and bromide ions. Action spectroscopy revealed that the maximum wavelength of the light is around at 373 nm, corresponding to the UVA region. Using a genetic approach, several genes, including OPY1, HEM1, and PAU11, were identified as suppressors of this growth inhibition. This iodide-dependent UVA-triggered growth inhibition method, along with its suppressive molecules, would be beneficial for understanding cell growth processes in eukaryotes and can be utilized for medium sterilization using UVA light.

A Novel UV Barrier Poly(lactic acid)/Poly(butylene succinate) Composite Biodegradable Film Enhanced by Cellulose Extracted from Coconut Shell.

Cellulose was extracted from coconut shell powder (CSP) as a renewable biomass resource and utilized as a reinforcing material in poly(lactic acid)/poly(butylene succinate) (PLA/PBS) solvent casting films. The extraction process involved delignification and mercerization of CSP. Microscopic investigation of the extracted microfibers demonstrated a reduction in diameter and a rougher surface characteristic compared to the raw CSP. The cellulose prepared in this study exhibited improved thermal stability and higher crystallinity (54.3%) compared to CSP. The morphology of the cycrofractured surface, thermal analysis, mechanical property, and UV transmittance of films were measured and compared. Agglomeration of 3 wt.% of cellulose was observed in PLA/PBS films. The presence of cellulose higher than 1 wt.% in the PLA/PBS decreased the onset decomposition temperature and maximum decomposition temperature of films. However, the films loading 3 wt.% of cellulose had a higher char formation (5.47%) compared to neat PLA/PBS films. The presence of cellulose promoted the formation of non-uniform crystals, while cellulose had a slightly negative impact on crystallinity due to the disruption of polymer chains at lower cellulose content (0.3, 0.5 wt.%). The mechanical strength of PLA/PBS films decreased as the cellulose content increased. Moreover, PLA/PBS film with 3 wt.% of cellulose appeared to show a 3% and 7.5% decrease in transmittance in UVC (275 nm) and UVA (335 nm) regions compared to neat PLA/PBS films while maintaining a certain transparency.

Therapeutic value of organic and conventional teas in Sri Lanka against microbial agents

Due to its naturally occurring medicinal ingredients known as polyphenols, tea attracts the interest of the pharmaceutical and scientific disciplines. Besides the established antioxidant activity, many phenolic compounds in tea exhibit significant antimicrobial activity. Environmental factors and crop management substantially influence the amount and activity of polyphenols available in tea leaves. In Sri Lanka, there are six main agro-ecological regions where tea is grown using either conventional or organic management. Present study focused to determine the effects of tea production system and their growing region on polyphenol content and antimicrobial properties of made tea. Fresh leaf samples were collected from randomly selected tea estates each for organically certified and conventional from major tea growing regions in Sri Lanka. They were manufactured into CTC black tea using a miniature system. Polyphenol content was assessed by ISO standard method, while the anti-bacterial and anti-fungal properties were evaluated using disk diffusion technique against Escherichia coli ATCC 25922 and clinical pathogen of Aspergillus niger. Polyphenol content, anti-bacterial and anti-fungal properties were significantly different (P&lt;0.05) between the tea production systems and among the growing regions, where organic tea had higher polyphenol content, anti-bacterial and anti-fungal properties than conventional teas. The Southern region tea had greater anti-bacterial and anti-fungal properties probably due to the high polyphenol content, while it was the lowest in Uva region. In conclusion, this research presents preliminary evidence that Sri Lankan teas grown and managed organically have superior antimicrobial properties over conventional teas. To confirm the findings, more investigation using time series measurement in all tea-growing regions is suggested.