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-1β, 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 β-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.

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.

[Evaluation of different procedures for the extraction of phenolic compounds from a medicinal plant: 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.

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.

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.

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.

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 β-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.

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.

Anti-aging activities of extracts from Tunisian medicinal halophytes and their aromatic constituents

Six medicinal halophytes widely represented in North Africa and commonly used in traditional medicine were screened for pharmacological properties to set out new promising sources of natural ingredients for cosmetic or nutraceutical applications. Thus, Citrullus colocynthis, Cleome arabica, Daemia cordata, Haloxylon articulatum, Pituranthos scoparius and Scorzonera undulata were examined for their in vitro antioxidant (DPPH scavenging and superoxide anion-scavenging, β-carotene bleaching inhibition and iron-reducing tests), antibacterial (microdilution method, against four human pathogenic bacteria) and anti-tyrosinase activities. Besides, their aromatic composition was determined by RP-HPLC. H. articulatum shoot extracts exhibited the strongest antioxidant activity and inhibited efficiently the growth of Salmonella enterica and Escherichia coli. P. scoparius and C. arabica inhibited slightly monophenolase, whereas H. articulatum was the most efficient inhibitor of diphenolase activity. Furthermore, H. articulatum exhibited the highest aromatic content (3.4 % DW), with dopamine as the major compound. These observations suggest that shoot extract of H. articulatum, and to a lesser extent of C. arabica, could be used as antioxidant, antibiotic as well as new natural skin lightening agents. Also, possible implication of aromatic compounds in anti-tyrosinase activity is discussed.

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.

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.

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.

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 β-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.

Antioxidant and antimicrobial activities of the edible medicinal halophyte Tamarix gallica L. and related polyphenolic constituents

Tamarix gallica is a halophytic species having hepatotonic and stimulant properties, as it was traditionally used in the treatment of various liver disorders. Leaf and flower infusion have anti-inflammatory and anti-diarrheic properties. In this work, we have investigated antioxidant and antimicrobial activities of leaf and flower extracts and their phenolic composition. Results showed that flowers exhibit a higher antioxidant activity as compared to the leaves, IC(50) values of the flower extracts are being 1.3 (beta-carotene bleaching) to 19 times (lipid peroxidation inhibition) lower than those for leaves. Accordingly, flower extracts exhibited the highest total phenolic content (135.35 mgGAE/gDW) and RP-HPLC analysis showed that syringic acid, isoquercitin as well as catechin were the major phenolics. Furthermore, Tamarix extracts showed appreciable antibacterial properties against human pathogen strains. The mean inhibition zone was from 0 to 6.5mm when the concentration increased from 2 to 100mg/l. The strongest activity was recorded against Micrococcus luteus and the lowest activity was observed against Escherichia coli. Moreover, organ extracts show a weakly to moderate activity against the tested Candida. These findings suggest that Tamarix may be considered as an interesting source of antioxidants for therapeutic or nutraceutical industries and for food manufactures.

Salinity effects on polyphenol content and antioxidant activities in leaves of the halophyte Cakile maritima

Cakile maritima is a local oilseed halophyte exhibiting potential for secondary metabolite production. In the present study, plant growth, leaf polyphenol content and antioxidant activity were comparatively analyzed in two C. maritima Tunisian accessions (Jerba and Tabarka, respectively sampled from arid and humid bioclimatic stages) under salt constraint. Three-week-old plants were subjected to 0, 100, and 400 mM NaCl for 28 days under glasshouse conditions. A significant variability in salt response was found between both accessions: while Tabarka growth (shoot biomass, leaf expansion) was significantly restricted at 100 and 400 mM NaCl, compared to the control, Jerba growth increased at 100mM before declining at 400 mM NaCl. The better behaviour of Jerba salt-challenged plants, compared to those of Tabarka, may be related to their higher polyphenol content (1.56- and 1.3-fold the control, at 100 and 400 mM NaCl respectively) and antioxidant activity (smaller IC(50) values for both 1,1-diphenyl-2-picrylhydrazyl and superoxide scavenging), associated with lower leaf MDA accumulation (ca. -66% of the control at 100mM NaCl). Taken together, our findings suggest that halophytes may be interesting for production of antioxidant compounds, and that the accession-dependent capacity to induce antioxidative mechanisms in response to salt, may result in a corresponding variability for growth sustainability.