Nutraceutical Potential of Leaf Hydro-Ethanolic Extract of the Edible Halophyte Crithmum maritimum L.

Aromatic halophytes represent an exceptional source of natural bioactive compounds for the food industry. Crithmum maritimum L., also known as sea fennel, is a halophyte plant colonizing cliffs and coastal dunes along Mediterranean and Atlantic coasts. It is well known to produce essential oils and polyphenols endowed with antioxidant and biological effects. The present work reports the phytochemical profile, as well as antioxidant, antimicrobial and antimutagenic properties of C. maritimum leaf hydro-alcoholic extract. From LC-ESI-MS analysis, eighteen phenolic compounds were depicted in sea fennel extract and the amount of total phenolic content exceeds 3% DW. Accordingly, C. maritimum extract showed strong antioxidant activities, as evidenced by in vitro (DPPH, ORAC, FRAP) and ex vivo (CAA-RBC and hemolysis) assays. An important antimicrobial activity against pathogenic strains was found as well as a strong capacity to inhibit Staphylococcus aureus (ATCC 35556) biofilm formation. Sea fennel extracts showed a significant decrease of mutagenesis induced by hydrogen peroxide (H2O2) and menadione (ME) in Saccharomyces cerevisiae D7 strain. In conclusion, our results show that C. maritimum is an exceptional source of bioactive components and exert beneficial effects against oxidative or mutagenic mechanisms, and pathogenic bacteria, making it a potential functional food.

Application of Trehalose and Salicylic Acid Mitigates Drought Stress in Sweet Basil and Improves Plant Growth.

Trehalose (Tre) and salicylic acid (SA) are increasingly used to mitigate drought stress in crop plants. In this study, a pot experiment was performed to study the influence of Tre and SA applied individually or in combination on the growth, photosynthesis, and antioxidant responses of sweet basil (Ocimum basilicum L.) exposed to drought stress. Basil plants were watered to 60% or 100% field capacity with or without treatment with 30 mM Tre and/or 1 mM SA. Drought negatively affected growth, physiological parameters, and antioxidant responses. Application of Tre and/or SA resulted in growth recovery, increased photosynthesis, and reduced oxidative stress. Application of Tre mitigated the detrimental effects of drought more than SA. Furthermore, co-application of Tre and SA largely eliminated the negative impact of drought by reducing oxidative stress through increased activities of antioxidant enzymes superoxide dismutase, peroxidase, and catalase, as well as the accumulation of the protective osmolytes proline and glycine betaine. Combined Tre and SA application improved water use efficiency and reduced the amount of malondialdehyde in drought-stressed plants. Our results suggested that combined application of Tre and SA may trigger defense mechanisms of sweet basil to better mitigate oxidative stress induced by drought stress, thereby improving plant growth.

Phytochemical and Biological Activities in Limonium Species Collected in Different Biotopes of Tunisia.

A particular interest is nowadays given to natural antioxidants occurring in foods which can reduce the risk of several diseases through their protective effect. The genus Limonium is widely distributed in different salt regions of Tunisia and known in traditional medicine for the presence of highly effective viral and bacterial replication inhibitors. Limonium leaves have possible beneficial effects on human health for their antioxidant activities and free radical scavenging abilities. To exploit the potential of plants from extreme environments as new sources of natural antioxidants, we studied the extracts from leaves of eight Limonium species growing in extreme environments in Tunisia. Antioxidant molecules (polyphenols, flavonoids, flavonols, ascorbate, tocopherols), in vitro (DPPH, ORAC) and ex vivo antioxidant potential on human erythrocytes, antioxidant enzymes activities (superoxide dismutase, peroxidases, glutathione reductase) were evaluated to identify the species with the best antioxidant capacity. The results showed variability among the species considered in function of the environmental conditions of their natural biotopes, as for the antioxidants measured. In particular, L. vulgare from Oued Rane biotope, characterized by dryness and high temperatures, was the species with the highest enzymatic activity and antioxidant capacity, making it interesting as possible edible halophyte plant or as food complement.

A re-circulating horizontal flow constructed wetland for the treatment of synthetic azo dye at high concentrations.

A re-circulating horizontal flow constructed wetland (RHFCW) system was developed in a greenhouse. This system was operated with Typha domingensis to study the phytoremediation capacity of this macrophyte species in different developing stages for synthetic textile wastewater with the pollutant type, the amaranth (AM) azo dye. Experiments were applied with a fixed flow rate Q = 10 L/h corresponding to a theoretical residence time of 3 h. The synthetic feeding to the RHFCW container was re-circulated back until the required water quality was achieved. The performance of this pilot-scale system was compared to an unplanted RHFCW. The effect of the initial dye concentration was studied using four dye concentrations (10, 15, 20, and 25 mg/L). The following parameters pH, color, COD, BOD5, NO3-, NO2-, and NH4+ were monitored during treatment. The maximum efficiencies obtained for discoloration, COD, NO3-, and NH4+ were 92 ± 0.14%, 56 ± 1.12%, 92 ± 0.34%, and 97 ± 0.17% respectively. Experiences demonstrate a decrease of removal efficiencies of studied parameters with the increase of dye concentrations, leading to an increase of the duration of treatment. Changes in activities of antioxidant enzymes (superoxide dismutase (SOD), guaiacol peroxidase (GPX), catalase (CAT), ascorbic peroxidase (APX), and glutathione reductase (GR)) and their relation to plant defense system against stress were studied. Enzymes were evaluated in leaves of T. domingensis during the remediation of the azo dye (amaranth). During treatment, an increase of enzymes activities was observed in accordance with the high removal efficiency.

A stress-associated protein, LmSAP, from the halophyte Lobularia maritima provides tolerance to heavy metals in tobacco through increased ROS scavenging and metal detoxification processes.

Agricultural soil pollution by heavy metals is a severe global ecological problem. We recently showed that overexpression of LmSAP, a member of the stress-associated protein (SAP) gene family isolated from Lobularia maritima, in transgenic tobacco led to enhanced tolerance to abiotic stress. In this study, we characterised the response of LmSAP transgenic tobacco plants to metal stresses (cadmium (Cd), copper (Cu), manganese (Mn), and zinc (Zn)). In L. maritima, LmSAP expression increased after 12 h of treatment with these metals, suggesting its involvement in the plant response to heavy metal stress. LmSAP transgenic tobacco plants subjected to these stress conditions were healthy, experienced higher seedling survival rates, and had longer roots than non-transgenic plants (NT). However, they exhibited higher tolerance towards cadmium and manganese than towards copper and zinc. LmSAP-overexpressing tobacco seedlings accumulated more cadmium, copper, and manganese compared with NT plants, but displayed markedly decreased hydrogen peroxide (H2O2) and lipid peroxidation levels after metal treatment. Activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) were significantly higher in transgenic plants than in NT plants after exposure to metal stress. LmSAP overexpression also enhanced the transcription of several genes encoding metallothioneins (Met1, Met2, Met3, Met4, and Met5), a copper transport protein CCH, a Cys and His-rich domain-containing protein RAR1 (Rar1), and a ubiquitin-like protein 5 (PUB1), which are involved in metal tolerance in tobacco. Our findings indicate that LmSAP overexpression in tobacco enhanced tolerance to heavy metal stress by protecting the plant cells against oxidative stress, scavenging reactive oxygen species (ROS), and decreasing the intracellular concentration of free heavy metals through its effect on metal-binding proteins in the cytosol.

Increased sensitivity to salt stress in tocopherol-deficient Arabidopsis mutants growing in a hydroponic system.

Recent studies suggest that tocopherols could play physiological roles in salt tolerance but the mechanisms are still unknown. In this study, we analyzed changes in growth, mineral and oxidative status in vte1 and vte4 Arabidopsis thaliana mutants exposed to salt stress. vte1 and vte4 mutants lack α-tocopherol, but only the vte1 mutant is additionally deficient in γ-tocopherol. Results showed that a deficiency in vitamin E leads to reduced growth and increased oxidative stress in hydroponically-grown plants. This effect was observed at early stages, not only in rosettes but also in roots. The vte1 mutant was more sensitive to salt-induced oxidative stress than the wild type and the vte4 mutant. Salt sensitivity was associated with (i) high contents of Na(+), (ii) reduced efficiency of PSII photochemistry (Fv/Fm ratio) and (iii) more pronounced oxidative stress as indicated by increased hydrogen peroxide and malondialdeyde levels. The vte 4 mutant, which accumulates γ- instead of α-tocopherol showed an intermediate sensitivity to salt stress between the wild type and the vte1 mutant. Contents of abscisic acid, jasmonic acid and the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid were higher in the vte1 mutant than the vte4 mutant and wild type. It is concluded that vitamin E-deficient plants show an increased sensitivity to salt stress both in rosettes and roots, therefore indicating the positive role of tocopherols in stress tolerance, not only by minimizing oxidative stress, but also controlling Na(+)/K(+) homeostasis and hormonal balance.

Physiological response of halophytes to multiple stresses.

As halophytes grow vigorously in saline soils, they serve as extraordinary resources for the identification and development of new crop systems. Understanding the mechanisms of tolerance of halophytes to salinity in combination with other co-occurring constraints such as drought, flooding, heavy metals and nutrient deficiencies, would facilitate efforts to use halophytes for saline land revegetation, as well as provide new insights that might be considered in future breeding of plants for salt-affected agricultural lands. Recent results suggest that salinity may improve the response of halophytes to other stresses. Some physiological and biochemical mechanisms of tolerance to salinity are common to many halophytes when plants are subjected to salinity, whereas others are specifically amplified under a combination of stresses. Therefore, the response of halophytes to multiple stresses may not reflect an additive effect of these constraints, but rather, constitute specific response to a new situation where many constraints are operating simultaneously. Comparative studies between halophytes and glycophytes have shown that halophytes are better equipped with the mechanisms of cross-stress tolerance and are constitutively prepared for stress. Moreover, other data has shown that the pre-treatment of halophytes with salinity or other constraints in the early stages of development improves their subsequent response to salinity, which suggests the capacity of these plants to 'memorise' a previous stress allows them respond positively to subsequent stress.

Early effects of salt stress on the physiological and oxidative status of Cakile maritima (halophyte) and Arabidopsis thaliana (glycophyte).

Early changes in physiological and oxidative status induced by salt stress were monitored in two Brassicaceae plants differing in their tolerance to salinity, Cakile maritima (halophyte) and Arabidopsis thaliana (glycophyte). Growth response and antioxidant defense of C. maritima under 400 mM NaCl were compared with those of A. thaliana exposed to 100 mM NaCl. Salinity induced early growth reduction that is less pronounced in C. maritima than in A. thaliana. Maximum hydrogen peroxide (H2O2) level occurred in the leaves of both species 4 h after the onset of salt treatment. A rapid decline in H2O2 concentration was observed thereafter in C. maritima, whereas it remained high in A. thaliana. Correlatively, superoxide dismutase, catalase and peroxidase activities increased at 4 h of treatment in C. maritima and decreased thereafter. However, the activity of these enzymes remained higher in treated plants than that in controls, regardless of the duration of treatment, in A. thaliana. The concentrations of malondialdehyde (MDA) reached maximum values at 24 h of salt stress in both species. Again, MDA levels decreased later in C. maritima, but remained high in A. thaliana. The contents of α-tocopherol remained constant during salt stress in C. maritima and decreased during the first 24 h of salt stress and then remained low in A. thaliana. The results clearly showed that C. maritima, in contrast to A. thaliana, can rapidly evolve physiological and antioxidant mechanisms to adapt to salt and manage the oxidative stress. This may explain, at least partially, the difference in salt tolerance between halophytes and glycophytes.