STUDIA CHEMIA - Issue no.4 / 2016 - Table of contents

The article reports the radiocarbon investigation results of the Humani Bedford baobab, an old African baobab from Savé Valley, Zimbabwe. Two wood samples were collected from the large inner cavity. Several segments were extracted from these samples and analysed by AMS (accelerator mass spectrometry) radiocarbon dating. We found that the age values of segments increase with the distance into the wood. This major anomaly is characteristic to multi-stemmed baobabs with a closed ring-shaped structure and a false cavity inside. The investigation of the Humani Bedford baobab evinced that the baobab consists of three fused stems. The fourth stem of the ring is missing. The oldest dated segment was found to have a radiocarbon date of 1655 ± 14 BP, which corresponds to a calibrated age of 1575 ± 30 yr. The dating results show that the stems which build the ring stopped growing toward the false cavity more than 600 yr ago. By considering the position of the oldest segment in the investigated stem, we concluded that the Humani Bedford baobab is around 1800 yr old. According to our dating results, the Humani Bedford baobab becomes the oldest living African baobab.

Keywords: AMS radiocarbon dating, Adansonia digitata, tropical trees, dendrochronology, age determination.

The article discloses the results of radiocarbon investigation of the baobab of Golconda Fort, Hyderābād, India, which is the largest African baobab outside Africa. Two wood samples were collected from the large inner cavity; of these we extracted several segments for AMS (accelerator mass spectrometry) radiocarbon dating. The oldest sample segment had a radiocarbon date of 342 ± 22 BP, which corresponds to a calibrated age of 430 ± 20 yr. We estimate that the oldest part of the baobab has an age of 475 ± 50 yr. The investigation of the baobab of Golconda Fort revealed that it consists of 6 + 2 fused stems. Six stems build two rings that close two distinct false cavities, while two additional stems are located outside the rings. We called this new type of architecture double closed ring-shaped structure with two separate false cavities.

Keywords: AMS radiocarbon dating, Adansonia digitata, tropical trees, age determination, inner cavity, multiple stems.

In this paper, three species of aromatic herbs (Petroselinum crispum, Ocimum basilicum, and Origanum vulgare) were investigated, by mean of stable isotopes (deuterium, oxygen and carbon) and total phenol content, in order to study the influence of irrigation water. The results revealed the fact that there is a strong correlation between the isotopic compositions of irrigation water (deuterium enriched water or tap water) and D, δ18O, 13C values and total polyphenol content of studied plants. Multielemental content was subjected to analysis of variance (ANOVA). It was found that Ocimum basilicum plant was characterized by a higher level of As and Co as compared to other two species, while Origanum vulgare had the highest content of Cu. Also, a correlation between the irrigation water content and toxic metal uptake had shown that the Pb concentration is influenced by the water isotopic composition.

Keywords: irrigation water, aromatic herbs, stable isotopes, total polyphenols, chemometrics.

Objective: To evaluate the bleaching effect and the changing in the surface roughness of one experimental natural-based bleaching gel and of three commercial bleaching gels, namely: Opalescence PF 16%, Ultradent, Opalescence Quick PF 45%, Ultradent (based on carbamide peroxide CP) and Philips Zoom DayWhite 6% HP light activated (based on hydrogen peroxide HP) upon A3 body shade Filtek Supreme, 3M Espe nanocomposite. Material and methods: Thirty disks of the A3 body shade Filtek Supreme, 3M Espe, were immersed in a coffee solution and further divided into 6 groups: group 1 was kept as control, while groups 2-6 underwent a certain bleaching protocol, with different materials and exposure time, as follows: group 2: experimental gel, five sessions, 6 hours each; group 3: Opalescence PF 16 % (Ultradent), five sessions 6 hours each; group 4: Opalescence Quick PF 45% (Ultradent), 2 sessions, 30 min each; group 5: Opalescence Quick PF 45% - 2 applications/30 min and Opalescence PF 16% - 5 applications/6h and group 6 was bleached using an in office gel containing HP 6% (Philips Zoom DayWhite 6% HP light-activated 2 applications/30min). CIE L*a*b* parameters and surface roughness were recorded before and after bleaching. Data were analyzed using one-way repeated measures ANOVA, and multiple comparisons were adjusted using the Bonferroni method (p<0.05). Results: The average colour differences at the end of the bleaching protocols were as follows: 1:ΔE*=1.40, 2:ΔE*=3.76, 3:ΔE*=5.13, 4:ΔE*=4.79, 5:ΔE*=5.44, and 6:ΔE*=6.83. Overall, a significant statistical difference was found between the groups (p<0.05). However, multiple comparisons showed no significant difference among the groups based on carbamide peroxide (CP) (3, 4, and 5) (p>0.05). The results of the statistical test indicated a significant effect of the bleaching gels only for groups 5 and 6 (p<0.05). For these groups, surface roughness significantly decreased after the bleaching protocol. For the experimental group, no significant modifications of the surface were observed. Conclusions: The most effective protocol was the “in office” bleaching method based on hydrogen peroxide (HP) with light activation. The natural extract-based gel was less efficient than CP and HP groups; however, ΔE* was above the acceptability threshold. The natural extract-based experimental bleaching gel showed no significant change upon surface roughness.

Keywords: nanocomposite, colour stability, bleaching, surface roughness, natural extract

The aim of this study is to investigate the active compounds of an experimental gel and to evaluate its antimicrobial and antifungal effects. This gel consists of a mix extract of Arctium lappa L. root powder and Aloe vera (L.) Burm.f. gel and is used in endodontic procedures. With the help of HPLC/ESI(+)-MS method, various active compounds were identified in the experimental extract. For the evaluation of the antimicrobial and antifungal activity, microorganisms commonly found in endodontic infections were used. The agar-diffusion method was performed for each plant formula and the microdilution method was used to obtain the minimum inhibitory concentration and also the minimum bactericidal concentration. Clear inhibition zones around discs indicated the presence of antimicrobial and antifungal activity for the disc diffusion assay. The minimum inhibitory and bactericidal concentration obtained were compared to the antibiotics or antifungals, specific for each microorganism.

Keywords: antimicrobial, antifungal, HPLC/ESI(+)-MS, agar-diffusion, microdilution, Arctium lappa, Aloe vera

Starting from commercial 4-aminopiperidine, three new amino-striazines, seen as potential dendritic building-blocks, were synthesised by chemoselective SN2-Ar amination of cyanuric chloride. A three steps synthetic sequence, (i) Boc-chemoselective N-protection of 4-aminopiperidine  (ii) amination of cyanuric chloride  (iii) deprotection, yielded a novel potential dendritic central unit, 2,4,6-tris[(piperidin-4-yl)amino]-s-triazine.

Keywords: 4-aminopiperidine, SN2-Ar amination, dendritic cores, melamines

Superoxide dismutases (SOD) are a group of metallo-enzymes, containing one or two coordinated metals, and their main role in the organism is protection against superoxide radicals, one of the reactive oxygen species (ROS). Among these Cu(II)-Zn(II) SOD is present in cytoplasm and acts as a scavenger of superoxide radicals. Cu(II)-complexes may act as low-molecule analogue of Cu-Zn SOD and therefore are being studied as antiradical agents. In this study a series of Cu(II) complexes were synthesizes, containing ligands prepared from salicyl aldehyde and amino acids: L-asparagine, L-glutamine and L-aspartic acid. Complexes prepared from L-asparagine and L-glutamine are novel and were compared with the already reported complex Cu(HSal-L-Asp) hydrate (6e). An assay based on the ability to inhibit reduction of iodonitrotetrazolium dye (INT) by superoxide anion-radicals was used to determine antiradical activity of these complex. The prepared complexes - Cu(HSal-L-Asn) acetate (6a), Cu(HSal-L-Asn) hydrate (6b) and Cu(HSal-L-Gln) acetate (6c) proved to be good antiradical agents compared to complex 6e. The IC50 values of the radical transport were 19.2 ± 1.2 μM for 6a, 53.9 ± 9.4 μM for 6b and 4.11 ± 0.37 mM for 6c.

Keywords: copper complexes, reduced Schiff bases, antiradical activity, SOD mimetics, INT method, amino acid derived ligands

The chiral HPLC separation parameters of a series of fourteen β-blockers previously performed on four polysaccharide-based chiral stationary phases (CSPs) was evaluated through computational techniques, using a set of 340 molecular descriptors (MD), calculated with the Molecular Operating Environment (MOE) software. Several semi-empirical mathematical models were built and refined by PLS, O2PLS multivariate data analysis and by PLS-Tree® clustering, correlating chromatographic data with the descriptors. The resulting models revealed the importance of certain analyze descriptors shaping chromatographic behaviour of the studied enantiomers. The chiral selector backbone as well as the presence of halogen atom(s) in the structure of the used stationary phase appears to exert an influence on the type of descriptors that significantly contribute either positively or negatively on the prediction power of the developed models. The influence of additive on the predictive power of models was also briefly analysed. This QSPR study generated models with a good predictive power. However, these results could be substantially improved in the future by including the descriptors for the chiral selectors and additives in the model and by performing docking studies.

Keywords: Molecular descriptors, MOE, β-blockers, clustering, chiral HPLC

In this study, ternary complexes of four nonsteroidal antiinflammatory drugs (ibuprofen, ketoprofen, flufenamic acid and mefenamic acid) with hydroxypropyl-β-cyclodextrin were studied using a molecular modeling technique. As third component in the complexes, different types of small molecules were chosen – regarding the acid-base character, molecular volume, etc. The binding energy, surface area contraction and volume contraction of these binary and ternary complexes were calculated. The results show that, by adding auxiliary substance to the active ingredient-cyclodextrin binary system, more stable complexes are formed. The ternary complexes are stabilised by hydrogen bonds and van der Waals interactions.

Keywords: cyclodextrin, ternary complex, molecular modeling, NSAID

The hypothesis of the study was that linear chained polymers have a natural chance to stabilize as a helix. Ten linear chained polymers, poly(ethylene glycol), polyethyleneimine, poly(lactic acid), poly(N-vinyl-pyrrolidone), poly(trans-1-butenylene), poly(1-chloro-trans-1-butenylene), poly(1-methyltrans- 1-butenylene), poly(1,4,4-trifluoro-trans-1-butenylene), polyacrylonitrile, polychlorotrifluoroethylene, were investigated. The structure of polymers was drawn and then optimized at Hartree-Fock, 6-31G* level of theory. The helix parameter was extracted from the optimized geometries using a home-made program. Seven out of ten polymers are likely to have a helical structure; the polymers with oxygen shown the highest residual error. The helix coefficient and rotation step per monomer were also calculated. The top three polymers according to rotation step per monomer behaved same as the one according to the helix coefficient. The top three non-increasing order was: polychlorotrifluoroethylene-Cl, polyacrylonitrile-N, and poly(lactic acid)-C-methyl. The smallest rotation step per monomer was associated with the smallest value of the helix coefficient (this being linearly related to rotation step per monomer). The highest helix radius was identified for poly(1-chloro-trans-1-butenylene), followed by poly(1-methyl-trans-1-butenylene) and poly(1,4,4-trifluoro-trans-1-butenylene).

Keywords: linear chained polymer, helix radius, computational study

Bond dissociation enthalpies (DEs) relevant to thermal dissociation of brominated diphenyl ethers were investigated in a computational approach at the density functional theory (DFT) level. In a preliminary assessment of eight of the most popular exchange-correlation functionals (including B3P86, PBE1PBE, mPW1PW91, wB97xD and two of each of the M05 and M06 families) the M06 meta-hybrid is shown to perform the best in reproducing two experimental C-O and C-Br BDEs, with errors bellow 1 kcal/mol and less dependent on basis set. The M06/cc-pVDZ is chosen as a good compromise between cost and accuracy for computing DEs of seven brominated diphenyl ethers. In the case of decabromodiphenyl ether we report a DE of 68.7 kcal/mol for the homolysis of the ether group and 74 to 77 kcal/mol for bromine cleavage. Compared to the corresponding values of the fully brominated compound, in lower brominated congeners we predict a substantial increase of both DEs with the decrease of bromine content.

Keywords: brominated flame retardants, decabromodiphenyl ether, density functional theory, bond dissociation energies

In this paper, magnetic iron oxides were synthesized by using a modified Ueda method starting from ferrous sulfate as iron precursor and different substitued organic amines as precipitants. The evolution of the obtained iron oxides with the annealing temperatures was monitored by thermal analysis, FTIR spectroscopy and X-ray diffractometry. The magnetic powders obtained have been characterized by SEM microscopy and magnetic measurements.

Keywords: iron oxides, magnetic, substitutes amines, thermal analysis

Guided by theoretical (sulphoaluminate belitic) SAB clinker chemical compositions, raw materials of known chemical composition (locally sourced from the Carpathian orocline), were mixed and tested by burning in laboratory conditions at different temperatures 1220, 1240 and 1260°C. The resulting materials were analyzed by optical transmission and reflection microscopy (using HF etching) and completed with XRD analyses. In this paper we describe chemical and mineralogical characterization of clinker belitic components manufactured in laboratory conditions. Belite nests and clusters with complex zoned structure are observed optically in interstitial material of the clinker that is composed of sulfoaluminate, ferrite and anhydrite. These structures display all three morphological types of belite, corresponding to the different polymorphs of belite, depending on the burning and quenching conditions of the clinker. The XRD patterns are interpreted to show that the appearance of β- and α’-belite and different α’β transition forms are due to cooling to room temperatures and presence of the belite polymorph stabilizing ions SO3, Al3+, Fe3+ and alkali. The conclusions of the study were that belites were formed in various mixtures of raw materials treated at low burning temperatures, relatively slow cooling rates (resulting in different proportions of impurity absorption) and with some experiments run under reducing conditions during firing. Chemically, the lime saturation factor of clinkers is low (LSF= 0.74 - 0.84), such compositions favoring the clinker belite component; the silica ratio is low (SR < 1.5), which can improve the burnability of the clinker; the alumina ratio is medium (AR= 1.5 - 2.5), chemically restricting the solid solution of mineral phases, and the hydraulic modulus (HM) is under 1.7, enhancing resistance to chemical attack.

Keywords: SAB clinker, belite polymorphs, mineralogy, XRD

This paper assesses the efficiency of twelve spherical codes in CW EPR powder simulations. The spherical codes are either regular or are generated using optimisation methods. The EPR simulations are performed for spin systems with axial and rhombic symmetry. The spherical codes are compared using Voronoi tessellation-based homogeneity and EPR properties.

Keywords: CW EPR powder simulations, spherical code, uniformity degree, EPR metrics

Coagulation is one of the most important stages of the oil wastewaters pre-treatment. Oil wastewaters coagulation that we have studied and which had a content of 95.9-270.6mg Total Petroleum Hydrocarbon (TPH)•L-1 required optimal doses of polyaluminum chloride (PAC) coagulant between 12.0-16.4mgAl•L-1. In the PAC coagulation, the use of various coagulants aids with absorbent properties, such as: indigenous volcanic tuff, charcoal, anaerobic biologic sludge led to: 1. The PAC dose reduction with 30-50%; 2. Turbidity, Total Organic Carbon (TOC), TPH and absorbance at wavelength 254 nm, A254, of treated samples in the presence of aids and reduced PAC doses were similar vs. samples treated with non-reduced PAC doses in aids absence. The use of indigenous volcanic tuff as coagulation aid led to coagulation sludge which are able to sediment with faster than the sludge obtained with PAC coagulation but without aid. More the volume of the coagulation sludge obtained is reduced with 50% vs. one obtained in other variants. By adding coagulation aids there was a reduction of coagulation reagent costs up to 50%. The correlation between A254 and TPH parameters can be useful in establishing on-line relationships that could ease the operators’ activity in wastewater treatment plants.

Keywords: Total Petroleum Hydrocarbons, wastewater coagulation, polyaluminum chloride, coagulant aids, costs

Recently, indoor air quality (IAQ) has become a serious concern. More and more people are facing health problems due to the poor air quality at the workplace; most of them are exposed to pollutants without even realizing it. Therefore, it is important to monitor the indoor air quality to prevent an unsafe environment. In the shoe making process, various volatile compounds – like toluene, found especially in adhesives – are used. These chemicals tend to slowly desorb from the final products and to accumulate ultimately inside the shoe shops. We report here the total volatile organic compounds (tVOCs) that are prone to be ionized by the UV radiation; measurements were performed over eight weeks inside six shoe shops located in Cluj-Napoca, Romania, with a ppbRAE Plus instrument manufactured by RAE Systems Inc. USA. We found with this ultra-sensitive photoionization detector (PID) maximum concentrations up to 7 ppmv of tVOCs (isobutene units) in air for each shoe shop investigated. The obtained results demonstrate that people working in the selected shoe stores may be exposed to significant tVOCs concentrations during a working day. Thus, PID devices are useful tools for quickly surveying the indoor air quality.

Keywords: photoionization detection PID, indoor air quality IAQ, volatile organic compounds VOCs, toluene.

This paper presents the synthesis of CoFe2O4 nanoparticles via a sol-gel combustion method. Nanoparticles with the grain size in the range of 20-70 nm were synthesized using hydrated nitrates of cobalt and iron, sucrose and pectin. Sucrose was used as a polycondensation agent for the formation of the gel. The reaction mechanism for the gel formation is discussed in the paper. The addition of pectin facilitated the formation of a hard gel through the drying of the precursor solution at 200oC. Through a thermogravimetric analysis on the gel, the temperature at which the entire organic part has decomposed is concluded. The fine black nanopowder was obtained after a thermal treatment of the gel at a temperature of 700oC. Infrared spectroscopy (FT-IR) highlighted the presence, respectively the absence of organic compounds before and after the thermal treatment. Structural, morphological and magnetic measurements were conducted using X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM).

Keywords: CoFe2O4, Sol-gel, nanoparticles, magnetic, ferrite

Glass ceramics samples with chemical composition (Fe2O3)x·(P2O5)40·(ZnO)(60-x) (0 ≤ x ≤ 20 mol%) were prepared by meltquenching technique, followed by a thermal treatment at two different temperatures for two hours. Structural properties were studied by DTA, XRD, and FTIR measurements. From DTA measurements can be observed that, with increasing in concentration of the dopant (Fe2O3), the transition and crystallization temperatures increase. The XRD data show, the presence of two or three crystalline phases, and the FTIR data confirm the existence of ZnO4 structural units in our samples. So the thermal treatment applied to the samples lead to changes in the structural properties and also to some modification in the glass ceramic network.

Keywords: zinc phosphate glass ceramics, DTA, XRD, transitional metals doped glass ceramics

The fabrication of a planar micro electrochemical cell is presented. The simplicity and the relative low cost of this kind of cells make them very interesting and promising in the development of chemical and biochemical sensors. The utilization of microelectrodes as working electrodes in planar electrochemical cells is preferred to the conventional macro electrodes because microelectrodes can be used in highly resistive media, have short response time, and excellent signal to noise ratio. In electrochemical sensor applications, the microelectrode surfaces are commonly modified with multiple layers to boost selectivity, control sensitivity, or to provide a biocompatible interface between the sensor and its environment. In this work, the fabricated set of bundled electrodes is covered with a hydrogel as an example of its potential use as electrochemical gas sensor. All micro electrochemical cells were characterized by cyclic voltammetry (CV) and the results were analyzed with different statistical methods.

Keywords: Electrochemical gas sensor, microelectrode, planar micro electrochemical cell, cyclic voltammetry

Zeolitic volcanic tuff was tested as a potential adsorbent for malachite green (MG) dye removal from aqueous solutions. The influences of contact time, temperature, dye initial concentration, solid:liquid ratio, and adsorbent grain size over the adsorption capacity and efficiency were considered. Removal efficiencies up to 99% and a monolayer capacity (Langmuir) of 4.05 mg MG/g were calculated. The equilibrium and kinetic study showed that the experimental data were best fitted on the Temkin model and that the intra-particle diffusion could be the rate determining step. Thermodynamic analysis showed that MG adsorption onto ZVT is an endothermic, non-spontaneous process.

Keywords: natural zeolite, malachite green, adsorption, efficiency, equilibrium, kinetic, thermodynamic

A series of commercially available lipases in various solvents using several alcohols as nucleophiles were studied for the stereoselective esterification of ibuprofen and alcoholysis of ibuprofen esters respectively. Novel methods were developed for the stereoselective synthesis of both enantiomers of the target compound. The (S)-selective alcoholysis and (R)- selective hydrolysis in a parallel kinetic resolution procedure in presence of lipase from Mucor miehei as catalyst were performed.

Keywords: lipase, Ibuprofen, enzymatic kinetic resolution, stereoselectivity

The aim of this study is to assess and present the contamination with some environmental toxic parameters of water samples of Sitnica River, Kosovo. Sitnica River is one of the main rivers in Kosovo. The river is located in the area with high anthropogenic pressure, were the contamination of river with different pollutants presents a complex long-term environmental problem. The water samples from Sitnica River were collected from five stations every three months. These stations are covering the upstream and downstream sites of major industrial area of Obiliq city close to Thermo Power Plant (TPP) Kosovo “B” as the main power plant in the country. This Thermo Power Plant apart from air and soil pollution is considered as main source of contamination for the river water as well due to the direct discharged of waste water without any prior treatment. International permissible limits (75/440/EEC) and Kosovo National limits (UA13/2008) were applied to assess the river water contamination. Physico-chemical parameters in water samples from Sitnica River were determined to assess the level of contamination. The concentrations of some toxic parameters such: Fe2+, Mn2+, Al3+, Cr3+, NO2--N, NO3--N, NH3-N, PO43--P were measured using UV-VIS spectrophotometry in accordance with standard method US EPA 6010C.The results showed that the Sitnica River is heavily polluted. The results were summarized using the program Statistica 6.0 descriptive statistical method. In order to protect the river water from further contamination, the remediation options in order to reduce the anthropogenic discharges are suggested.

Keywords: Physico-chemical, Sitnica River contamination, UV-VIS Spectrophotometry

The effect of ablation environment on the characteristics of graphene sheets produced by the laser ablation method in liquid medium has been studied experimentally and reported here. Graphene sheets were synthesized by using Q-switch Nd-YAG laser at 532 nm wavelength and 7 ns pulse width and laser fluence of 0.5 J/cm2 in liquid nitrogen and distilled water environments. The structure and morphology of the ablation products are characterized by X-ray diffraction method, UV-Visible absorption spectroscopy, transmission electron microscopy (TEM), Raman and Fourier transform infrared spectroscopy (FTIR). Results indicate that the graphene nanosheets synthesized by the laser ablation method in liquid nitrogen environment have larger sp2 carbon domains and minor structural defects. Therefore, in our experimental conditions, the liquid nitrogen environment seems to be a better medium for producing graphene sheets with high quality, in comparison with the water.

Keywords: Pulsed laser ablation, Graphene, Carbon nanostructures, liquid nitrogen, TEM

The main extract used by the youngest branch of phytotherapy, named meristemotherapy, is obtained from the freshly processed Blackcurrant buds. Due by the lack of information regarding the optimal harvesting time of the buds and buds chemical composition it was begun a larger study, the results presented in this paper being the preliminary screening of the possible active compounds that can be contained by this vegetal material. The apical and axillar buds from Ribes nigrum L shrubs were collected in three different development phases. The bioactive compounds composition screening was performed using monodimensional double development TLC on extracts obtained in ethanol, glycerol and their mixture, according to EPh. The analysis results show that the lipophilic compounds are increased in the maximum development stage and are decreasing when the buds begin to open. In the opened stage are increasing the hydrophilic compounds, like the polyphenols that are secondary metabolites of the plants. These changing in chemical composition indicate also the tissues differentiation. In conclusion of this study can decide that the optimal harvesting time of the buds is before the opening and tissues differentiation, period that is according also with the traditional harvesting time of these type of plant materials.

Keywords: Ribes nigrum L. buds, meristemotherapy, monodimensional double development TLC, optimal chemical composition.

A study during 36 months, was conducted in a conventional greenhouse (open type) and a geothermal (closed type) of TEI Thessaly to determine the productivity, total phenols content, antioxidant activity and certain qualitative characteristics of hydroponic tomatoes and peppers. At geothermal greenhouse the concentration of total phenols in tomatoes ranged from 151 to 324.5 μg (GAE) /g fresh weight and the antioxidant activity ranged from 3.54 to 3.90 μM (AA) /g fresh weight, while in peppers the total phenols ranged from 597 to 815 μg (GAE) /g fresh weight and the antioxidant activity ranged from 6.3 to 7.2 μM (AA) /g fresh weight. At conventional greenhouse the concentration of total phenols in tomatoes ranged from 163 to 195 μg (GAE) /g fresh weight and the antioxidant activity ranged from 3.3 to 3.9 μM (AA) /g fresh weight, while in peppers the total phenols ranged from 527 to 729 μg (GAE) /g fresh weight and the antioxidant activity ranged from 5.7 to 6.8 μM (AA) /g fresh weight. In tomatoes the yield of the production was higher in the geothermal greenhouse as compared to the conventional greenhouse, while in peppers the yield of the production between of geothermal greenhouse and of conventional greenhouse showed no statistically significant differences.

Keywords: Antioxidant activity FRAP; Hydroponic systems; Peppers; Tomatoes; Total phenols