Floret Biofortification of Broccoli Using Amino Acids Coupled with Selenium under Different Surfactants: A Case Study of Cultivating Functional Foods.

Broccoli serves as a functional food because it can accumulate selenium (Se), well-known bioactive amino-acid-derived secondary metabolites, and polyphenols. The chemical and physical properties of Se are very similar to those of sulfur (S), and competition between sulfate and selenate for uptake and assimilation has been demonstrated. Towards an efficient agronomic fortification of broccoli florets, the working questions were whether we could overcome this competition by exogenously applying the S-containing amino acids cysteine (Cys) or/and methionine (Met), or/and the precursors of Glucosinolate (GSL) types along with Se application. Broccoli plants were cultivated in a greenhouse and at the beginning of floret growth, we exogenously applied sodium selenate in the concentration gradient of 0, 0.2, 1.5, and 3.0 mM to study the impact of increased Se concentration on the organic S (Sorg) content of the floret. The Se concentration of 0.2 mM (Se0.2) was coupled with the application of Cys, Met, their combination, or a mixture of phenylalanine, tryptophane, and Met. The application took place through fertigation or foliar application (FA) by adding isodecyl alcohol ethoxylate (IAE) or a silicon ethoxylate (SiE) surfactant. Fresh biomass, dry mass, and Se accumulation in florets were evaluated, along with their contents of Sorg, chlorophylls (Chl), carotenoids (Car), glucoraphanin (GlRa), glucobrassicin (GlBra), glucoiberin (GlIb), and polyphenols (PPs), for the biofortification efficiency of the three application modes. From the studied selenium concentration gradient, the foliar application of 0.2 mM Se using silicon ethoxylate (SiE) as a surfactant provided the lowest commercially acceptable Se content in florets (239 µg or 0.3 µmol g-1 DM); it reduced Sorg (-45%), GlIb (-31%), and GlBr (-27%); and it increased Car (21%) and GlRa (27%). Coupled with amino acids, 0.2 mM Se provided commercially acceptable Se contents per floret only via foliar application. From the studied combinations, that of Met,Se0.2/FA,IAE provided the lowest Se content per floret (183 µg or 0.2 µmol g-1 DM) and increased Sorg (35%), Car (45%), and total Chl (27%), with no effect on PPs or GSLs. Cys,Met,Se0.2/FA,IAE and amino acid mix,Se0.2/FA,IAE increased Sorg content, too, by 36% and 16%, respectively. Thus, the foliar application with the IAE surfactant was able to increase Sorg, and methionine was the amino acid in common in these treatments, with varying positive effects on carotenoids and chlorophylls. Only the Cys,Met,Se0.2 combination presented positive effects on GSLs, especially GlRa, but it reduced the fresh mass of the floret. The foliar application with SiE as a surfactant failed to positively affect the organic S content. However, in all studied combinations of Se 0.2 mM with amino acids, the Se content per floret was commercially acceptable, the yield was not affected, the content of GSLs was increased (especially that of GlRa and GlIb), and PPs were not affected. The content of GlBr decreased except for the treatment with methionine (Met,Se0.2/FA,SiE) where GlBr remained unaffected. Hence, the combination of Se with the used amino acids and surfactants can provide enhanced biofortification efficiency in broccoli by providing florets as functional foods with enhanced functional properties.

Larvicidal activity of naturally occurring naphthoquinones and derivatives against the West Nile virus vector Culex pipiens.

Concentration-dependent mortality effects were observed for three pure synthetic natural products (alkannin, shikonin, and shikalkin) and three acetylated derivatives of shikonin against Culex pipiens (Culicidae: Diptera) for the first time. The larvicidal properties of all naphthoquinones were evaluated under laboratory conditions against the larvae of the mosquito species C. pipiens biotype molestus, the anthropophilic biotype of the C. pipiens mosquito species. Experimental data of the tested toxicity of quinones revealed generally high efficacy where shikonin (3.9 mg/L) was the most active followed by shikalkin (8.73 mg/L) and alkannin (12.35 mg/L). The insecticidal performance of shikonin-acetylated derivatives was also investigated, aiming at the same time in the establishment of the relationships between the structure and the activity of shikonin-type compounds with larvicidal activity against C. pipiens. Results indicated that naphthoquinones, compared with other natural compounds with larvicidal activity, are very toxic against mosquito larvae and could be a potential source of natural larvicidal substances. Finally, bioassays with shikonin derivatives also revealed that although hydroxylic groups seem to play a secondary role in efficacy, the quinone moiety is essential.

First total synthesis of trans- and cis-resorcylide: remarkable hydrogen-bond-controlled, stereospecific ring-closing metathesis.

[reaction: see text] Stereospecific synthesis of the pair of natural macrolides, trans- and cis-resorcylide, was performed using ring-closing metathesis on dienes 3 and 4, which lack or feature an intramolecular H-bond, respectively. An effective Stille carbonylative coupling of benzyl chlorides 11 and 15 was employed for their preparation. The influence of intramolecular H-bonding on the interconversions of resorcylides was also studied.