Eelgrass slabs, a soilless culture substrate that inhibits adhesion of fungi and oomycetes and enhances antioxidant activity in tomato.

Composed of a marine plant, Zostera sp., eelgrass slabs are a novel organic substrate for soilless cultures used in tomato production. The benefit of using eelgrass slabs for growing tomatoes was assessed by comparing it with coconut fiber slabs in regard to contamination by Pythium spp. and to the antioxidant properties of tomato fruits. First, tomato root contamination by Pythium spp. was studied by direct plate counting, and a molecular comparison of fungal and oomycete communities was conducted using PCR-DHPLC. Second, the antioxidant properties of tomato fruits were analyzed by measuring total phenol and carotenoid contents and by evaluating radical scavenging activity. Compared to plants grown on coconut fiber slabs, those on eelgrass slabs presented a lower rate of Pythium spp. root contamination. Moreover, culture on eelgrass slabs produced fruits with better radical scavenging activity and higher total phenol content compared to controls. Carotenoid content was not affected by the type of substrate. This study highlights the value of detrital leaves of Zostera sp. as a substrate for soilless culture that reduces root contamination and also promotes the production of tomato fruits with better nutritional value.

New antibacterial and cytotoxic activities of falcarindiol isolated in Crithmum maritimum L. leaf extract.

Bioassay-guided fractionation of a chloroformic extract obtained from Crithmum maritimum leaves led to the chemical isolation of falcarindiol, a polyacetylene widely distributed within the Apiaceae family. Structure of this compound was confirmed by NMR and activity was tracked using a screening microplate bioassay. Falcarindiol strongly inhibited the growth of Micrococcus luteus and Bacillus cereus, with a minimum inhibitory concentration (MIC) value of 50 microg ml(-1). Moreover, this compound showed cytotoxicity against IEC-6 cells with an IC50 value of 20 microM after 48 h of exposition. These results suggest that Crithmum maritimum could be potentially used in food manufactures and cosmetology as preservative agents and biopesticides, or in medicine as new antibiotics, confirming the interest in studying halophytic species as sources of bioactive compounds.

Antioxidant activity and phenol content of Crithmum maritimum L. leaves.

Sea fennel (Crithmum maritimum L.) is an edible halophyte with various economical interests because of its high secondary metabolite content. However, little is known about water-soluble compounds in that species. Here, we have studied major solutes in C. maritimum leaves. Among these solutes, carbohydrates (sucrose, glucose) were the most abundant, followed by organic acids (malate and quinate) and a phenolic compound never described in a halophyte before: chlorogenic acid (CGA). Total phenols and chlorogenic acid contents were followed throughout one year, as well as antioxidant activity, in two populations of C. maritimum growing in contrasting habitats: sand hills and cliffs. Sea fennel leaves appeared to be rich in phenolic compounds, particularly in chlorogenic acid. On that point, differences between the two populations were found, sand hill plants accumulating more CGA than those growing on cliffs. Moreover, the former presented a higher radical-scavenging activity, and the two observations were positively correlated. These results indicate that sea fennel can be considered as a valuable source of antioxidant products, especially of chlorogenic acid.

Radical scavenging, antioxidant and antimicrobial activities of halophytic species.

For the first time, both antioxidant and antimicrobial activities are simultaneously reported in halophytic plants, particularly on polar fractions. Chloroformic and methanolic extracts of the halophytes Eryngium maritimum L., Crithmum maritimum L. and Cakile maritima Scop. were tested for their antimicrobial activities against 12 bacterial and yeast strains. In addition, radical scavenging and antioxidant activities were assessed, as well as total phenol contents. Only one bacterial strain (Listeria monocytogenes) was not inhibited by plants extracts, and apolar (chloroformic) fractions were generally more active than polar (methanolic) ones. Eryngium maritimum presented the weakest radical scavenging activity (ABTS IC(50)=0.28 mg ml(-1)), as well as the lowest total phenol content (16.4 mg GAE g(-1) DW). However, the three halophytic species had relatively strong total antioxidant activities (from 32.7 to 48.6 mg ascorbate equivalents g (-1) DW). Consequences on the potential use of these plants in food or cosmetic industry are discussed.