Taieb Tounekti

Improving the Polyphenol Content of Tea

Tea, prepared from the leaves of Camellia species, has one of the highest contents of flavonoids among common food and beverage products. Tea consumption has moved beyond its pleasant flavor and cultural significance since a number of health promoting properties have been ascribed to this widespread beverage (e.g., anticancer, antiobesity and hypotensive effects). The major bioactive compounds in tea are catechins (flavan-3-ols), a group of flavonoids that include, among others, (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin-3-gallate (ECG), and (-)-epigallocatechin-3-gallate (EGCG). These compounds are also the precursors of theaflavins and thearubigins, oxidation products responsible for the taste and colour of certain tea types such as black tea. The composition of the tea leaf, and thus tea quality, is influenced by many pre-harvest factors such as the genetic make-up of the plant, region of production, horticultural and harvesting practices, and environmental conditions. Once harvested, processing, brewing, and storage conditions influence the phenolic composition and quality of tea infusions as well. In the present review we aim at outlining our current knowledge about means to increase the catechin content of teas, a cornerstone for improving the health-promoting properties of this beverage.

Enhanced Phenolic Diterpenes Antioxidant Levels Through Non-transgenic Approaches

Plant-derived antioxidants are essential in our diet, and antioxidant composition is a key determinant of the quality of plant extracts of interest to the pharmaceutical and food industries. By using carnosic acid as an example of a key antioxidant constituent of rosemary and sage extracts, we discuss the importance of studying non-transgenic approaches to enhancing antioxidant levels in plants and improving the antioxidant composition of plant extracts. In contrast to other terpenoids or phenolic compounds, carnosic acid has only been found in some Labiatae species, such as rosemary and sage. Carnosic acid has medicinal properties; it is a potent antioxidant and protects skin cells against UV-A radiation and cancer. Furthermore, it has been used as a preservative in food and non-food products, displaying important antimicrobial effects. However, the key steps involved in its biosynthesis remain largely unknown, and thus non-transgenic approaches are required to increase its level in plant extracts. Dried rosemary or sage leaves can contain between 0.1% and 7% carnosic acid, depending on the species and variety, but also on plant growth conditions, sample treatment and mode of extract preparation. Furthermore, leaf age, salinity and ionic interactions can also have a significant effect on biosynthesis and therefore have a strong impact on the total antioxidant potential of rosemary and sage extracts. Non-transgenic approaches, used in these or other species, can significantly increase antioxidant levels and therefore provide very significant improvements in the quality of several botanical extracts used in industry, and can be applied as either an alternative or a complement to transgenic approaches. FIG. 1 Chemical structure of synthetic and natural plant-derived antioxidants. Note that the hydroxyl groups in the ortho-position at C11 and C12 of the carnosic acid molecule provide high antioxidant properties (color figure available online). FIG. 2 Outline of the non-transgenic approaches presently available to enhance antioxidant levels in plant extracts (color figure available online).

Salicylic Acid Biosynthesis and Role in Modulating Terpenoid and Flavonoid Metabolism in Plant Responses to Abiotic Stress

Salicylic acid (SA) is a simple phenolic acid with hormonal function synthesized from the amino acid phenylalanine or chorismate depending on the plant species, developmental stage and growth conditions. This compound plays a key role in plant growth and development, and in plant responses to abiotic stresses such as salinity and drought stress. Under these environmental constraints, plants synthesize a number of secondary metabolites, including flavonoids and terpenoids, with a defence-related function. Here, we will discuss the role of SA in modulating plant responses to abiotic stress, particularly as an inducer of defence responses against salinity and drought stress. Emphasis will be put on discussing the SA signalling pathways that affect flavonoid and terpenoid metabolism as defense compounds against stress.

NaCl stress-induced changes in the essential oil quality and abietane diterpene yield and composition in common sage -

Aim: The purpose of this study was to evaluate how increasing NaCl salinity in the medium can affects the essential oils (EOs) composition and phenolic diterpene content and yield in leaves of Salvia officinalis L. The protective role of such compounds against NaCl stress was also argued with regard to some physiological characteristics of the plant (water and ionic relations as well as the leaf gas exchanges). Materials and Methods: Potted plants were exposed to increasing NaCl concentrations (0, 50, 75, and 100 mM) for 4 weeks during July 2012. Replicates from each treatment were harvested after 0, 2, 3, and 4 weeks of adding salt to perform physiological measurements and biochemical analysis. Results: Sage EOs were rich in manool, viridiflorol, camphor, and borneol. Irrigation with a solution containing 100 mM NaCl for 4 weeks increased considerably 1.8-cineole, camphor and β-thujone concentrations, whereas lower concentrations (50 and 75 mM) had no effects. On the contrary, borneol and viridiflorol concentrations decreased significantly under the former treatment while manool and total fatty acid concentrations were not affected. Leaf extracts also contained several diterpenes such as carnosic acid (CA), carnosol, and 12-O-methoxy carnosic acid (MCA). The concentrations and total contents of CA and MCA increased after 3 weeks of irrigation with 75 or 100 mM NaCl. The 50 mM NaCl had no effect on these diterpenes. Our results suggest a protective role for CA against salinity stress. Conclusion: This study may provide ways to manipulate the concentration and yield of some phenolic diterpenes and EOs in sage. In fact, soil salinity may favor a directional production of particular components of interest.

Non-thermal dielectric barrier discharge (DBD) plasma affects germination of coffee and grape seeds

Seeds of many plant species often fail to germinate even when moisture and temperature are adequate because they are dormant. Commonly, these seeds need to be exposed to cold temperature or some other forms of stress to release their dormancy. In the nursery, they use strong acids or hot water for the same purpose. Low-temperature plasma has been shown to be effective in improving germination of seeds. In the present study, we have used an atmospheric pressure dielectric barrier discharge (DBD) operated in Helium gas to treat dormant grape and coffee seeds. The seeds were treated at fixed power of 50 W for different durations (control, 30s, 60s, 120s and 240s). Exposure to plasma has affected germination rate and germination vigor of the seeds differently depending on the species. The germination rate of coffee seeds decreased after short exposure to plasma as compared to non-treated seeds. When the seeds were exposed to plasma for 120s germination was advanced but germination rate was the same as that of the control. However, for grape seeds, all plasma treatments increased germination rate as compared to the control treatment. Treating the seeds for 240s advanced germination by 10 days and more than doubled the rate of germination. The effect of plasma seems to be partly due to accelerated water can enhance the vigor of coffee and grape seeds; this should improve seedling establishment and growth.Seeds of many plant species often fail to germinate even when moisture and temperature are adequate because they are dormant. Commonly, these seeds need to be exposed to cold temperature or some other forms of stress to release their dormancy. In the nursery, they use strong acids or hot water for the same purpose. Low-temperature plasma has been shown to be effective in improving germination of seeds. In the present study, we have used an atmospheric pressure dielectric barrier discharge (DBD) operated in Helium gas to treat dormant grape and coffee seeds. The seeds were treated at fixed power of 50 W for different durations (control, 30s, 60s, 120s and 240s). Exposure to plasma has affected germination rate and germination vigor of the seeds differently depending on the species. The germination rate of coffee seeds decreased after short exposure to plasma as compared to non-treated seeds. When the seeds were exposed to plasma for 120s germination was advanced but germination rate was the same as that of...