Phytochemical investigation, antioxidant, anti-inflammatory and cytotoxic activities of Tunisian medicinal Tamarix africana Poir.

The current study aimed to evaluate Tunisian Tamarix africana Poir biological activities. In this study, novel biological activities of the shoot extracts related to their phenolics investigated. Secondary metabolite contents, antioxidant, anti-inflammatory and cytotoxic activities of four extracts (hexane, dichloromethane, methanol and water) were investigated. Antioxidant activities were assessed via in vitro and ex vivo assays. Besides, anticancer activity was investigated against human lung carcinoma (A-549) and colon adenocarcinoma (DLD-1) cells. The anti-inflammatory ability was evaluated via inhibition of LPS-induced NO production in RAW 264.7 macrophage cell lines. Methanol and water extracts displayed the highest antioxidant (IC50 = 3.3 and 4.3 µg/mL respectively), which are correlated activities correlated with phenolic contents. Hexane extract exhibited an important anti-inflammatory effect inhibiting NO ability by 100% at 80 µg/mL. Besides, T. africana extracts were found to be active against A-549 lung carcinoma cells with IC50 values ranging from 20 to 34 µg/mL. These results suggested that T. africana is considered as a potential source of readily accessible natural molecules with a promising effect on human health and diseases.

Effects of drought stress induced by D-Mannitol on the germination and early seedling growth traits, physiological parameters and phytochemicals content of Tunisian squash (Cucurbita maximaDuch.) landraces.

Introduction: Drought stress is one of the most devastating environmental stressors, especially in the arid and semi-arid regions of the world. Considering the major constraints that drought stress poses to crop production and the consequent yield losses in food crops, breeding for climate-resilient crops is an efficient means to mitigate stress conditions. Materials and methods: This study aimed at evaluating the response of four squash (Cucurbita maxima Duchesne) landraces to drought stress at germination and at plant stage. Drought stress was induced by different concentrations of D-mannitol (-0.24, -0.47 and -0.73 MPa). The tested parameters at germination stage included germination percentage, seedling vigor index, seed water absorbance and seedling growth potential. At the plant stage, leaf chlorophyll and carotenoids content, chlorophyll fluorescence, evapotranspiration, photosynthesis activity and several biomarkers, namely malondialdehyde, proline, total phenols content, total flavonoids content and DPPH radical scavenging activity were evaluated in both roots and leaves. Results and discussion: Our results indicate a magnitude of drought stress effects reflected via repression of germination and seedling growth as well as adjustments in physiological functions at later growth stages, in a genotype depended manner. Among landraces, "751" and "746" showed better performance, as evidenced by higher seed germination and seedling growth potential even at high stress levels (-0.47 and - 0.73 MPa), whereas "747" was the most sensitive landrace to drought stress at both tested stages. In conclusion, our findings highlight the importance of squash landraces selection for the identification of elite genotypes with increased tolerance to drought stress.

Anti-inflammatory activity of essential oils from Tunisian aromatic and medicinal plants and their major constituents in THP-1 macrophages.

In this study, the capacity of eight essential oils (EOs), sage (Salvia officinalis), coriander (Coriandrum sativum), rosemary (Rosmarinus officinalis), black cumin (Nigella sativa), prickly juniper (Juniperus oxycedrus), geranium (Pelargonium graveolens), oregano (Origanum vulgare) and wormwood (Artemisia herba-alba), on the inhibition of NF-κB activation was screened at concentrations up to 0.25 µL/mL using THP-1 human macrophages bearing a NF-κB reporter. This screening selected coriander, geranium, and wormwood EOs as the most active, which later evidenced the ability to decrease over 50 % IL-6, IL-1ß, TNF-α and COX-2 mRNA expression in LPS-stimulated THP-1 macrophages. The chemical composition of selected EOs was performed by gas chromatography-mass spectrometry (GC-MS). The two major constituents (>50 % of each EO) were tested at the same concentrations presented in each EO. It was demonstrated that the major compound or the binary mixtures of the two major compounds could explain the anti-inflammatory effects reported for the crude EOs. Additionally, the selected EOs also inhibit>50 % caspase-1 activity. However, this effect could not be attributed to the major components (except for ß-citronellol/geranium oil, 40 %/65 % caspase-1 inhibition), suggesting, in addition to potential synergistic effects, the presence of minor compounds with caspase-1 inhibitory activity. These results demonstrated the potential use of the EOs obtained from Tunisian flora as valuable sources of anti-inflammatory agents providing beneficial health effects by reducing the levels of inflammatory mediators involved in the genesis of several diseases.

Effects of Thymbra capitata essential oil on in vitro fermentation end-products and ruminal bacterial communities.

An in vitro trial was carried out to investigate the effects of natural Thymbra capitata essential oil (NEO) and its main compounds [including carvacrol, p-cymene, γ-terpinene given alone or in a synthetic combination (SEO)] on ruminal fermentation and the bacterial community using batch cultures inoculated with ruminal digesta and incubating two different basal diets [high-forage (F) and high-concentrate (C) diet]. After 24 h of incubation, primary fermentation end-products [gas, methane, volatile fatty acids (VFAs) and ammonia] and rumen microbial diversity were determined. NEO reduced the total VFA concentration (P < 0.05) only in the C diet. In contrast, SEO and carvacrol decreased the total VFA concentration (P < 0.05) only in the F diet. Methane production was not affected (P > 0.05) by any of the experimental treatments or diets evaluated. Microbial diversity analysis showed only a moderate effect of carvacrol and SEO on 13 genera, including, mainly, Atopobium and Blautia (involved in subacute ruminal acidosis) or Candidatus Saccharimonas (related to laminitis). In conclusion, T. capitata EO has a limited potential to attain nutritional or environmental benefits, but further research should be carried out to clarify its effects on animal health and microbial food safety.

Nano-Emulsification of Cinnamon and Curcuma Essential Oils for the Quality Improvement of Minced Meat Beef.

This work aims to evaluate cinnamon and curcuma essential oils as natural preservatives in minced beef meat. Essential oil chemical compositions and antibacterial activities were studied, and their encapsulation was optimized into nano-emulsions based on droplet size and distribution assessments. Selected formulas were further explored for their physical stabilities and antibacterial activities. Then, their effects on minced beef meat preservation were evaluated. Results showed significant differences in the chemical compositions and the efficiency of the tested essential oils, with cinnamon having a significant antibacterial efficacy. Formulation results showed that cinnamon nanoemulsion, encapsulated by 7.5% Tween 80, possessed an 89 nm droplet size, while the droplet diameter of curcuma nanoemulsion, encapsulated by 5% Tween 80, was 151 nm. Antimicrobial results depicted a significantly higher activity in nanoemulsions as compared to essential oils. For instance, the inhibition diameter of cinnamon essential oils against S. aureus was equal to 35 mm, while that of its nanoemulsion reached 40 mm. The meat preservation results showed that both bulk and nanoencapsulated essential oils significantly inhibited bacterial growth, as well as the formation of methemoglobin and lipid oxidation in meat. Thus, this work draws attention to the enhanced preservation effects of essential oils on the processing of minced beef meat as well as the great potential of nanoemulsions as carriers for essential oils in food industry applications.

Essential Oil Stabilisation by Response Surface Methodology (RSM): Nanoemulsion Formulation, Physicochemical, Microbiological, and Sensory Investigations.

This manuscript aimed to optimise the encapsulation of Thymus capitatus essential oil into nanoemulsion. Response Surface Methodology results were best fitted into polynomial models with regression coefficient values of more than 0.95. The optimal nanoemulsion showed nanometer-sized droplets (380 nm), a polydispersity index less than 0.5, and a suitable Zeta potential (-10.3 mV). Stability results showed that nanoemulsions stored at 4 °C were stable with the lowest d3,2, PolyDispersity Index (PDI), and pH (day 11). Significant ameliorations in the capacity to neutralise DPPH radical after the encapsulation of the antimicrobial efficacy of thyme essential oil were recorded. S. typhimurium growth inhibition generated by nanoencapsulated thyme essential oil was 17 times higher than by bulk essential oil. The sensory analysis highlighted that the encapsulation of thyme essential oil improved enriched milk's sensory appreciation. Indeed, 20% of the total population attributed a score of 4 and 5 on the scale used for milk enriched with nanoemulsion. In comparison, only 11% attributed the same score to milk enriched with bulk essential oil. The novel nanometric delivery system presents significant interest for agroalimentary industries.

The Effects of Salt Stress on Germination, Seedling Growth and Biochemical Responses of Tunisian Squash (Cucurbita maxima Duchesne) Germplasm.

Salt stress is considered as one of the most common abiotic stresses reducing the productivity and fruit quality of crop plants. The present study was carried out to assess the salt tolerance among 15 local squash (Cucurbita maxima Duchesne) landraces. Different salt (NaCl) concentrations of 0, 100, 200 and 300 mM were selected in order to evaluate the response of the study germplasm to salt stress based on 12 agronomic parameters and 3 biochemical traits, proline, malondialdehyde (MDA) and chlorophylls. A varied effect of the salt stress level was observed among the studied landraces based on germination potential, as well as on growth and biochemical parameters at seedling stage. Results showed that all landraces were drastically affected at high stress level with a significant variation in their stress response, indicating the existence of considerable genetic variability. Landraces "746" and "747" were the best performing cultivars across stress levels, whereas "1007", "1008" and "1009" were the most negatively affected. Based on the tested landrace performance, four landraceswere selected and further evaluated at biochemical level, focusing on the determination of compounds that play a key role in the ability to withstand salt stress. The mean MDA content across landraces was generally increased in stressed plants, as compared to the control treatment; the increase was attributed to a peak in MDA content at specific stress levels. In particular, "746" and "1007" showed the maximum content at 100 mM NaCl, while in landrace "751", MDA content reached its peak at 300 mM NaCl. In addition, the response of most landraces to salt stress involved an increase in free proline content, with the exception of "746", with the maximum content being observed either at 200 mM ("748" and "751" landraces) or at 300 mM NaCl, where only "747" expressed the highest content. These findings can be extrapolated into efforts to develop more salt-tolerant squash landraces and exhaust the possibilities of using saline water or soils under changing climate conditions.

Formulation, physicochemical characterization, and anti- E. coli activity of food-grade nanoemulsions incorporating clove, cinnamon, and lavender essential oils.

This research studies the application of a specific nanoemulsion as anti-Escherichia coli agent. The specific mixture was generated by a simplex-centroid design. Physicochemical parameters such as droplet average diameter, pH, viscosity, density, turbidity, whitening index, refractive index, stability (thermal, physical, and osmotic stability), and antibacterial activity kinetic, have been assessed. The mixture nanoemulsions had droplet diameters significantly smaller than those of clove or cinnamon nanoemulsions. Individual and mixture essential oils nanoemulsion exhibited appropriate stability under pH, thermal, and ionic stress as well as after mid-term storage. Antibacterial activity kinetic revealed the fast and pronounced efficacy of mixture nanoemulsions on E. coli (reach 98% of growth inhibition), especially for the nanoemulsion composed of 50% essential oil in the dispersed phase upon 20 days of storage. All data considered, the actual work evidences the promising advantages of using specific nanoemulsions as delivery systems of antibacterial agents in the beverage and food industry.

[Evaluation of different procedures for the extraction of phenolic compounds from a medicinal plant: Verbena officinalis]. / Évaluation de différents procédés d'extraction des composés phénoliques d'une plante médicinale : Verbena officinalis.

Since ancient times, plants have been the main source of bioactive molecules, such as phenolic compounds, capable of remedying various diseases. However, polyphenols' content and efficiency vary greatly as a function of several intrinsic and extrinsic factors. To optimize the procedure for the extraction of active molecules from the medicinal plant Verbena officinalis, effects of the plant origin, selected solvent, and extraction method were assessed. V. officinalis aerial parts were collected in two different regions of Tunisia (Bizerte and Ain Draham), and their bioactive molecules were extracted by maceration, decoction, and by the Soxhlet apparatus, either with water or with ethanol. Significant variability in the extracts' contents of phenolic compounds as well as their antioxidant and antimicrobial capacities were noted depending on the different studied factors. In particular, ethanol extracts were found to generally contain higher concentrations of phenolic compounds and more potent antioxidant capacities than water extracts. However, when tested against various pathogenic bacteria, water extracts were most often at least as active as ethanol extracts to inhibit bacteria growth in vitro. Finally, differences were also observed between V. officinalis samples from Bizerte compared to Ain Draham area. All of these results emphasize the need of adapting various parameters for the optimal extraction of bioactive molecules from a medicinal plant such as V. officinalis.

Title: Évaluation de différents procédés d'extraction des composés phénoliques d'une plante médicinale : Verbena officinalis. Abstract: Depuis la nuit des temps, les plantes ont été la source principale de molécules bioactives, tels les composés phénoliques, capables de remédier à diverses maladies. Cependant, le contenu et l'activité des polyphénols dépendent d'un certain nombre de facteurs intrinsèques et extrinsèques. Dans le but d'optimiser les procédés d'obtention des principes actifs de la verveine (Verbena officinalis), les effets de la provenance de la plante, du solvant et de la méthode d'extraction ont été évalués. Ainsi, la partie aérienne de V. officinalis a été collectée dans deux régions différentes de la Tunisie (Bizerte et Ain Draham). L'extraction a été réalisée par macération, décoction et par l'appareil de Soxhlet tantôt avec de l'eau tantôt avec de l'éthanol pur. Une variabilité significative des teneurs en composés phénoliques ainsi que des capacités antioxydantes et antimicrobiennes des extraits a été observée en fonction des facteurs étudiés. De manière générale, les extraits éthanoliques sont plus riches en composés phénoliques et présentent des activités antioxydantes plus fortes que les extraits aqueux. Cependant, vis-à-vis de différentes souches pathogènes, les extraits aqueux sont souvent au moins aussi puissants que les extraits éthanoliques pour inhiber la croissance bactérienne in vitro. De plus des différences notables sont observées selon que V. officinalis provient de la région de Bizerte ou d'Ain Draham. Ces résultats montrent que la prise en compte de plusieurs paramètres est nécessaire pour optimiser l'efficacité des procédures d'extraction des molécules bioactives de V. officinalis.

Essential oils: A promising eco-friendly food preservative.

Essential oils (EOs) are natural, volatile and aromatic liquids extracted from special plants. EOs are complex mixture of secondary metabolites (terpenes, phenolic compounds, alcohol). EOs possess a wide range of biological activities including antioxidant, antimicrobial and anti-inflammatory ones. Particularly, EOs exhibit pronounced antibacterial and food preservative properties that represent a real potential for the food industry. Numerous EOs have the potential to be used as a food preservative for meat and meat products, vegetables and fruits as well as for dairy products. The main obstacles for using EOs as food preservatives are their safety limits, marked organoleptic effects and possible contamination by chemical products such as pesticides. This review aims to provide an overview of current knowledge about EOs food preservative properties with special emphasis on their antibacterial activities and to support their uses as natural, eco-friendly, safe and easily biodegradable agents for food preservation.

Plant Growth Modulates Metabolites and Biological Activities in Retama raetam (Forssk.) Webb.

This work focuses on the variability of Retama raetam (Forssk.) Webb bioactive compounds as a function of the plant cycle. The main results showed that it exhibited the highest percentage of polyunsaturated fatty acids, along with superior levels of vitamin C and total phenolic compounds (66.49%, 645.6 mg·100 g-¹ FW and 23.9 mg GAE·g-¹, respectively) at the vegetative stage. Instead, at the flowering and mature fruiting stages, R. raetam (Forssk.) Webb exhibited notable contents of proline (25.4 µmol·g-¹ DW) and carotenoids (27.2 µg·g-¹ FW), respectively. The gathered data concerning the antioxidant activity highlighted the effectiveness of the vegetative stage in comparison to the other periods. Actually, IC50 and EC50 values of the hydromethanolic extract obtained from the plant shoots at the vegetative stage were of 23, 380, 410, 1160 and 960 µg·mL-1 (DPPH• and ABTS•+ radicals scavenging activity, reducing power, chelating power and ß-carotene bleaching activity, respectively). Furthermore, the four studied stages showed appreciable antibacterial capacities against human pathogens with a higher efficiency of the vegetative stage extract. Finally, the LC-DAD-ESI/MSn analysis revealed the predominance of isoflavonoids as main class of phenolic compounds and demonstrates that individual phenolic biosynthesis was clearly different as a function of plant growth. These findings highlight that reaching the optimum efficiency of R. raetam (Forssk.) Webb is closely linked to the physiological stage.

Thymus capitatus essential oil ameliorates pasteurization efficiency.

This work aims to characterize Thymus capitatus essential oil and to investigate its preservative effects on raw milk quality alone or combined to pasteurization heat treatment. To study its preservative effect, 1 mg l-1 of T. capitatus essential oil, characterized by GC-MS, was added to pasteurized or raw milk. The evaluation of milk quality was made by consulting samples total acidities, peroxide values and their total microbial counts, as compared to control milks. Assays were made immediately and after every 48 h of incubation at room temperature throughout 6 days. Results showed that the incorporation of T. capitatus EO to pasteurized milk was the most efficient treatment that inhibited milk deterioration. Combining pasteurization to EO incorporation into raw milk inhibited completely the contaminant bacterial growth to the second day of incubation. Moreover, until the fourth day, no statistical differences have been recorded on the total acidity of incorporated and pasteurized milk samples, while raw milk acidity exceeded 55 g of lactic acid equivalent l-1. Considering milk fat oxidation, adding T. capitatus EO to pasteurized milk has significantly retarded milk peroxide production to day 4. In conclusion, Thymus capitatus essential oil, combined to pasteurization, presents an interesting potency to act as milk stabilizer.

Potassium deficiency alters growth, photosynthetic performance, secondary metabolites content, and related antioxidant capacity in Sulla carnosa grown under moderate salinity.

Salinity and K+ deficiency are two environmental constraints that generally occur simultaneously under field conditions, resulting in severe limitation of plant growth and productivity. The present study aimed at investigating the effects of salinity, either separately applied or in combination with K+ deficiency, on growth, photosynthetic performance, secondary metabolites content, and related antioxidant capacity in Sulla carnosa. Seedlings were grown hydroponically under sufficient (6000 µM) or low (60 µM) K+ supply with 100 mM NaCl (C + S and D + S treatments, respectively). Either alone or combined with K+ deficiency, salinity significantly restricted the plant growth. K+ deficiency further increased salt impact on the photosynthetic activity of S. carnosa, but this species displayed mechanisms that play a role in protecting photosynthetic machinery (including non photochemical quenching and antioxidant activity). In contrast to plants subjected to salt stress alone, higher accumulation of phenolic compounds was likely related to antioxidative defence mechanism in plants grown under combined effects of two stresses. As a whole, these data suggest that K+ deficiency increases the deleterious effects of salt stress. The quantitative and qualitative alteration of phenolic composition and the enhancement of related antioxidant capacity may be of crucial significance for S. carnosa plants growing under salinity and K+ deficient conditions.

Quality preservation of deliberately contaminated milk using thyme free and nanoemulsified essential oils.

The objective of this study is to evaluate the effect of either a solution of Thymus capitatus essential oil or its nanoemulsion on the quality of milk contaminated by bacteria. After 24h of S. aureus inoculation, bacterial growth reached 202×10(3)CFU/ml in the presence of the essential oil while it was limited to 132×10(3)CFU/ml when treated with nanoemulsion. The reduction of antioxidant capacity of milk treated with essential oil was higher when treated with nanoemulsion. Moreover, free essential oil was more efficient in protecting proteins from degradation than the nanoemulsion. For instance, after 24h of E. hirae contamination, 26% of the total proteins were consumed in the presence of nano-encapsulated essential oil, while only 14% of the initial content was consumed when free essential oil was added. Concerning milk acidity increase and the inhibition of peroxide production, no statistical differences have been recorded between the use of free essential oil or its nano-emulsion. In conclusion, bulk or nano-encapsulated T. capitatus essential oil preserve milk quality and can extend its shelf life.

Antioxidant, anti-inflammatory and anticancer activities of the medicinal halophyte Reaumuria vermiculata.

Reaumuria vermiculata is a xero-halophytic specie widely distributed in the south of Tunisia. In the current study, antioxidant, anti-inflammatory and anticancer activities of Reaumuria vermiculata shoot extracts as well as its phenolic compounds were investigated in different solvent extracts (hexane, dichloromethane, methanol and water). Results showed a strong antioxidant activity, using the ORAC method and a cell based-assay, in methanol extract as well as an important phenolic composition (117.12 mg GAE/g). Hexane and dichloromethane proved an interesting anticancer activity against A-549 lung carcinoma cells, with IC50 values of 17 and 23 µg/ml, respectively. Besides, dichloromethane extract displayed the utmost anti-inflammatory activity, inhibiting NO release over 100 % at 80 µg/ml in LPS-stimulated RAW 264.7. Taken together, these finding suggest that R. vermiculata exhibited an interesting biological activities which may be related to the phenolic composition of this plant. Moreover, the identification of phenolic compounds in R. vermiculata dichloromethane extract using RP-HPLC revealed that myricetin was the major molecule. These results allow us to propose R. vermiculata as a valuable source for bioactive and natural compounds exhibiting interesting biological capacities.

Evaluation of antioxidant activities of the edible and medicinal Acacia albida organs related to phenolic compounds.

This study compared phenolic contents and antioxidant activity in different organs of Acacia albida (leaves and bark) and focuses on identification of phenolic compounds of leaves by HPLC-DAD. The analysed organs exhibited differences in total polyphenol contents (100 and 59.5 mg GAE g(-1) DW). Phenolic contents of leaves were two times higher than those in bark. Ethanolic extracts exhibited good antioxidant activities with IC50 = 26 µg mL(-1) for DPPH and EC50 = 50 µg mL(-1) for FRAP. Identification by HPLC-DAD revealed the presence of nine phenolic compounds known for their high antioxidant activity. The results suggested that this species can be used as source of natural antioxidants.

Isolation of powerful antioxidants from the medicinal halophyte Limoniastrum guyonianum.

The antioxidant capacities of the crude extract, aqueous and ethyl acetate partitions of Limoniastrum guyonianum Boiss. (Zita) were investigated in this study. The ethyl acetate phase exhibited a significant antioxidant activity as judged by total antioxidant activity, DPPH test and reducing power. Fractionation of this extract by centrifugal partition chromatography (CPC) using quaternary Arizona solvent systems composed of n-heptane/ethyl acetate/methanol/water led to ten fractions. The antioxidant capacities of these fractions were assessed using the same previous tests. Fraction 8 showed the highest antioxidant capacity (1291.1mg GAE/g DR), the power ability to quench DPPH radical (IC(50)=2µg/ml) and to reduce Fe(3+) (EC(50)=65µg/ml). From this fraction, three powerful flavonoids were isolated (1-3): gallocatechin (1), epigallocatechin (2) and epigallocatechin-3-O-gallate (3). These findings suggest that the antioxidative property of L. guynianum is may be related to the presence of these flavonoids, which can be used in various industrial fields.

Effect of salt treatment on phenolic compounds and antioxidant activity of two Mesembryanthemum edule provenances.

Mesembryanthemum edule L. is an edible and medicinal halophyte widespread in Tunisia seashore. In this study, parameters of oxidative stress, phenolic compounds and antioxidant activities were comparatively investigated in two M. edule provenances (Jerba and Bizerte, respectively sampled from arid and humid bioclimatic stages). Plants were subjected to 0, 300 and 600mM NaCl treatment under glasshouse conditions. Results showed that M. edule response to salinity depends on provenance (P), salt treatment (T) and their interaction (P×T). (T) affected more significantly the oxidative stress parameters and antioxidant activities than (P) and (P×T). Conversely, (P) was much affluent for tannin polymerization degree and interaction between the two factors (P×T) was more determinants for analyzed antioxidant parameters. The higher salt tolerance of Jerba plants was associated with low levels of malondialdehyde and of electrolyte leakage mainly at 600mM NaCl. Besides, antioxidant activities of Jerba provenance, were more efficient than Bizerte. In addition, avicularin was the major phenolic in both provenances. This compound concentration increased with salinity in Jerba shoots, while it was reduced in Bizerte especially at 600mM NaCl. Overall, the higher salt tolerance of plants from Jerba provenance, and to a lower extent of those from Bizerte, may be partly related to their better capacity to limit oxidative damage when salt-challenged, and this is likely the result of redistribution in phenolic composition. Besides, abiotic factors such as salinity could be determinant in antioxidant potentiality of this medicinal plant.

Municipal solid waste compost application improves productivity, polyphenol content, and antioxidant capacity of Mesembryanthemum edule.

Organic wastes were successfully used as soil amendment to improve agrosystems productivity. Yet, the effectiveness of this practice to enhance plant antioxidant capacities has received little attention. Here, we assess the effect of municipal solid waste (MSW) compost (at 40 t ha(-1)) on growth, polyphenol contents and antioxidant activities of Mesembryanthemum edule. MSW compost application significantly increased the soil contents of carbon, nitrogen, calcium, phosphorus and potassium. This was associated with higher nutrient (N, P, and K) uptake, which likely led to the significant improvement of the plant biomass and relative growth rate (RGR) (+93% on average) as compared to the control. In the same way, the fertilizing effect of the added organic matter significantly enhanced the antioxidant potential M. edule, assessed by radical scavenging activity, iron reducing power and ß-carotene bleaching capacity. This was associated with significantly higher antioxidant contents, mainly total phenols and flavonoids. Heavy metal (Pb, Cd, Cu, and Zn) concentrations were slightly increased upon compost application, but remained lower than phytotoxic values. Overall, our results point out that short-term MSW compost application at 40 t ha(-1) is efficient in enhancing the productivity together with the antioxidant potentiality of M. edule without any adverse environmental impact.

OPTIMIZATION OF SALT CONCENTRATIONS FOR A HIGHER CAROTENOID PRODUCTION IN DUNALIELLA SALINA (CHLOROPHYCEAE)(1).

Dunaliella salina (Dunal) Teodor, when treated over 25 d with a wide range of NaCl salinities (0.6-4.5 M), showed its maximal growth potentialities at 1.5-3.0 M NaCl and was able to survive even at 4.5 M NaCl. Sodium concentrations increased significantly at the supraoptimal salinities, reaching up to 5 mmol · g(-1) dry weight (dwt) at 4.5 M NaCl. Interestingly, ability of D. salina to take up essential mineral nutrients was not impaired by increased salinity. As for growth, chl concentrations were maximal in the 1.5-3.0 M NaCl range. Interestingly, carotenoid concentrations increased with the increasing salinity. The highest values of total antioxidant activity (5.2-6.9 mg gallic acid equivalents [GAE] · g(-1) dwt), antiradical activity, and reducing power were measured at 1.5-3.0 M NaCl. As a whole, these results showed that at 1.5-3.0 M NaCl, D. salina produce appreciable antioxidant level. But, once it reaches its growth maximum, a salt addition up to 4.5 M could enhance its carotenoid yield.