Identification of a naturally occurring 2, 6-bis (1.1- dimethylethyl)-4-methylphenol from purple leaves of the halophyte plant Mesembryanthemum crystallinum

2, 6-Bis (1.1-dimethylethyl)-4-methylphenol (BHT) is a synthetic antioxidant used generally for food, cosmetics and pharmaceuticals. The leaf extract from the halophyte plant, Mesembryanthemumcrystallinum, was fractionated by using semi-preparative HPLC. The different fractions were tested for their antioxidant activity using DPPH method. One fraction exhibited a high level of antioxidant activity.The molecule responsible for this antioxidant activity was identified as 2, 6-bis (1.1-dimethylethyl)-4-methylphenol) by gas chromatography/mass spectroscopy (GC/MS)

Effect of phosphorus limiting on phytase activity, proton efflux and oxygen consumption by nodulatedroots of common bean (Phaseolus vulgaris)

This work intended to measure the nodulated-roots oxygen consumption, proton efflux and phytase activity in 2 lines of common bean (Phaseolus vulgaris) (115, 147) at 2 levels of P supply. Rooted seedlings were inoculated with Rhizobium tropici CIAT 899 in hydroaeroponic cultivation under glasshouse. Phosphorus was supplied as KH2PO4 at 15 and 250 ìmol pl-1 week-1 (15P and 250P, respectively). Our results showed that plant growth nodulation and symbiotic nitrogen fixation were significantly affected by P limiting (15P) for the both lines, but this adverse effect was more pronounced in 147 than in 115. For the both lines, the phytase activity, higher in roots than in nodules, was significantly increased by P limiting, but 115 maintained higher values as compared to 147 line. Incotyledons, the phytase activity was higher in 115 than in 147. Phosphorus shortage increased the cumulated proton release only in 115, whereas it was lowered for 147. In this line, the proton release was linked to symbiotic nitrogen fixation. Under 15P, the proton efflux per unit of nodulated-root biomass was 25% greater for 115 than 147, suggesting that under P limitation, proton efflux may constitute an efficient way to increase P uptake in the tolerant line (115). 15P increased significantlynodulated-root O2 consumption per g nodule DW and nodule conductance, but to a higher extent in 147. As a whole, bean plants at P-deficient conditions increased the activity of phytases and proton efflux, thus maintaining the oxygen diffusion in nodules. This may represent an adaptive mechanism for N2- fixing legumes to respond to P deficiency, by increasing the utilisation and the uptake of phosphorus for symbiotic nitrogen fixation

Ultrasound-Assisted Extraction: Effect of Extraction Time and Solvent Power on the Levels of Polyphenols and Antioxidant Activity of Mesembryanthemum edule L. Aizoaceae Shoots

Purpose: To investigate the influence of extraction conditions assisted by ultrasound on the quality of extracts obtained from Mesembryanthemum edule shoots.Methods: The extraction procedure was carried out in an ultrasonic bath. The effect of two solvents (methanol and ethanol) and two extraction times (5 and 10 min) were evaluated on the basis of the phenolic content and antioxidant activity of the plant extract.Results: Significant variability in phenolic content and antioxidant activity, depending on the solvent (S), and to a lesser degree, extraction duration (D) and their interaction (S/D) were found. Methanol extract was significantly richer in total polyphenols than ethanol extract, their levels being 104.7 and 74.2 mg GAE.g-1DW, respectively. For the two solvents used, longer extraction duration yielded higher polyphenol content. The ethanol extract exhibited higher antioxidant activity than the methanol extract. Moreover, Also, the longer sonication duration (10 min) yielded extracts with higher antioxidant activities.Conclusion: The antioxidant capacity of M. edule is strongly influenced by the nature of the extracting solvent and the duration of sonication extraction.Keywords: Antioxidant activity, Extraction duration, Mesembryanthemum edule, Polyphenols, Sonicatio

Phenolic nature, occurrence and polymerization degree as marker of environmental adaptation in the edible halophyte Mesembryanthemum edule

AbstractMesembryanthemum edule is an edible medicinal halophyte traditionally used to treat several human diseases. In this study, particular importance was attached to the influence of environmental conditions on phenolic composition and antioxidant activities of two M. edule provenances from contrasting climatic regions (Djerba and Monastir sampled from arid and superior semi-arid bioclimatic stages, respectively). Shoot phenolic content was evaluated using colorimetric method and its composition was identified by HPLC analysis with or without thiolysis. Antioxidant activities were assessed by five in vitro antioxidant systems. Results showed that the two M. edule provenances were significantly different according to their antioxidant activity as well as their polyphenol profiles. Indeed, plants from Djerba (lack of rainfall and long light hour periods) exhibited stronger antioxidant activity together with higher phenolic content. For instance, Djerba provenance shoots showed much lower IC50 (4.8μgml−1) and EC50 (80μgml−1) values for DPPH and Fe-reducing tests, respectively. In addition, the superiority of this provenance (Djerba) was more marked as compared to positive controls (BHT, BHA, and VitC). HPLC identification revealed also an important difference between the two provenances on major flavonoid components. This difference was confirmed by the mean degrees of tannin polymerization (DPn) which was higher in Djerba plants. These data suggest that M. edule adaptation to environmental stresses proceeds through induced particular phenol quality and DPn for the improvement of their antioxidant capacities to protect plant tissues against oxidative stress

Localization and composition of seed oils of Crithmum maritimum L. (Apiaceae)

The use of some halophytes for rehabilitation of salt affected area has been reported. Crithmum maritimum L. halophyte and apiaceae can tolerate high levels of salt. Their seed was endospermic and had a suitable size for oil extraction. The aim of this report is to localize the lipids in the seed and determine their oils composition. The results showed that the lipids were accumulated in endosperm tissue as oil globoids. The percentage of oils was 44.4% dry weight basis. The C. maritimum L. seed oil was rich with oleic acid (78.6%), low level of palmitic acid (4.8%) and non negligible amount of linoleic acid (15.4%). This composition is similar to olive oil and canola oil. These results confirmed the good quality of C. maritimum L. seed oils.Keys word: Halophytes; Crithmum maritimum L.; seed oils

Long-term mannitol-induced osmotic stress leads to stomatal closure, carbohydrate accumulation and changes in leaf elasticity in Phaselous vulgaris leaves

The effect of long-term osmotic stress was investigated in leaves of two common bean lines, with contrasting tolerance: Flamingo (tolerant) and coco blanc (sensitive). Water relations, organic solute, ion accumulation and amino acids content as well as osmotic adjustment (OA) were studied during an extended exposure to osmotic stress. Osmotic stress was applied by means of 50 mM mannitol for 15 days. At the end of the stress period, both osmotic potential at full turgor (Ψ100) and at turgor loss point (Ψ0) decreased significantly in stressed plants compared with the control. The decrease being greater in the sensitive line, showed a greater OA compared with flamingo. Sugars contents increased in stressed plants and seem to be the major components of osmotic adjustment in stressed common bean leaves. The increase was more marked in coco blanc. Osmotic stress tolerance could thus not be associated with higher OA. The possible role of decreased leaf cell elasticity (εmax) is discussed in relation to osmotic stress tolerance in this species.Key words: Common bean, carbohydrate accumulation, growth, osmotic stress, osmotic adjustment, P-V curve, water relations

Anatomy of the fruit of the halophyte Crithmum maritimum L. with emphasis on the endosperm structure and histochemistry

The halophytes are plants that can survive and reproduce under high salinity. They show high potentiality as new crops plant for biosaline agriculture. Crithmum maritimum L. (Apiaceae) is one of the promising halophytes. In this paper, the endosperm structure of the fruit of this oilseeds halophyte was investigated using scanning electrons microscopy (SEM), light microscopy (LM) and fluorescence microscopy (FM). The fruit was composed of a spongy outer coat, a secretory envelope, a thin endocarp reduced to a unicellular layer delimiting the endosperm and an embryo. The endosperm cell appeared limited by thick cell wall and filled with numerous reserve globoids. The histochemical test showed that the cell wall of the endosperm was rich of carbohydrates as revealed by PAS (periodic acid-schiffs). Within the endosperm cells, there were mainly lipid bodies and protein bodies. The starch grains were less abundant. The protein bodies enclose crystal globoids. The x-ray microanalysis revealed that the reserve globoids accumulated mostly Mg, K, Ca, S and P. Taken together, these results highlight the structural features, the biochemical composition and confirm the nutritional quality of C. maritimum L. fruit.Keys words: C. maritimum L., crystal globoids, the endosperm cells, histochemical test, protein bodies, x-ray microanalysis

Photosynthetic responses to salinity in two obligate halophytes: Sesuvium portulacastrum and Tecticornia indica

Abstract Seedlings of the obligate halophytes Sesuvium portulacastrum L. and Tecticornia indica (Willd.) subsp. indica were grown with 0, 200, or 400 mM NaCl for 13 weeks to investigate whether salt tolerance was related to maintenance of adequate photosynthetic activity and pigment equipment. Both species showed growth optimum at 200 mM NaCl and better tissue hydration under salinity but different photosynthetic response to salinity. CO2 assimilation rate and stomatal conductance of S. portulacastrum were highest at 200 mM NaCl, while in T. indica they decreased with salinity. Pigment content increased under salinity in both species. The de-epoxidation state in S. portulacastrum suggests the need for energy dissipation at 400 mM NaCl, while its salt-induced decline in T. indica, despite the reduced photochemistry, suggests the involvement of adaptive mechanisms other than the xanthophyll cycle

Differential performance of two forage species, Medicago truncatula and Sulla carnosa, under water-deficit stress and recovery

The response patterns during water deficit stress and subsequent recovery of two forage species, Medicago truncatula and Sulla carnosa, were studied. After germination and pre-treatment, seedlings were individually cultivated for two months under two irrigation modes: 100% and 33% of field capacity. Measured parameters were plant growth, water relations, leaf osmotic potential, lipid peroxidation, and leaf inorganic (Na+ and K+) and organic (proline and soluble sugars) solute contents, as well as delta-1-pyrroline-5-carboxylate synthase (P5CS) and proline dehydrogenase (PDH) activities. Our results showed that under control conditions, and in contrast to roots, no significant differences were observed in shoot biomass production between the two species. However, when subjected to water-deficit stress, M. truncatula appeared to be more tolerant than S. carnosa (reduction by 50 and 70%, respectively). In the two studied species, water-deficit stress led to an increase in root/shoot ratio and leaf proline and soluble sugar contents, and a decrease in leaf osmotic potential. Enzymatic assay revealed that in the two species, P5CS activity was stimulated whereas that of PDH was inhibited under stress conditions. Despite greater accumulation of proline, sugar, and potassium in leaves of S. carnosa, M. truncatula was more tolerant to water deficit. This was essentially due to its capacity to control tissue hydration and water-use efficiency, in addition to its greater ability to protect membrane integrity. Following stress relief, M. truncatula and S. carnosa showed partial re-establishment of growth capacity

Analysis of cadmium translocation, partitioning and tolerance in six barley (Hordeum vulgare L.) cultivars as a function of thiol metabolism

Six barley cultivars widely differing for cadmium (Cd) tolerance, partitioning, and translocation were analyzed in relation to their thiol metabolism. Results indicated that Cd tolerance was not clearly related to the total amount of Cd absorbed by plants, resulting instead closely dependent on the capacity of the cultivars to trap the metal into the roots. Such behaviors suggested the existence of root mechanisms preserving shoots from Cd-induced oxidative damages, as indicated by the analysis of thiobarbituric acid-reactive substances \u2014diagnostic indicators of oxidative stress\u2014whose increases in the shoots were negatively related to Cd root retention and tolerance. Cd exposure differentially affected glutathione (GSH) and phytochelatin (PC) levels in the tissues of each barley cultivar. The capacity to produce PCs appeared as a specific characteristic of each barley cultivar, since it did not depend on Cd concentration in the roots and resulted negatively related to the concentration of the metal in the shoots, indicating the existence of a cultivar-specific interference of Cd on GSH biosynthesis, as confirmed by the existence of close positive linear relationships between the effect of Cd on GSH levels and PC accumulation in both roots and shoots. The six barley cultivars also differed for their capacity to load Cd ions into the xylem, which was negatively related to PC content in the roots. Taken as a whole, these data indicated that the different capacity of each cultivar to maintain GSH homeostasis under Cd stress may strongly affect PC accumulation and, thus, Cd tolerance and translocation