Caractérisation des constituants antioxydants de Phagnalon saxatile subsp saxatile par CLHP-ESI-MSn

International audienc

Analyse des phytonutriments naturels de Phagnalon saxatile subsp saxatile par LC-ESI-MS

International audienc

Identification par HPLC-ESI-MS d’un extrait d’aiguille de Juniperus oxycedrus subsp oxycedrus obtenu par extraction par soxhlet

International audienc

Le potentiel antioxydant de Haloxylon articulatum et l’identification de l’extrait actif par LC-ESI-Mn

International audienc

Identification of phytonutriments responsible for haemolytic and anti-radical effect from Cade

International audienc

Isolation and functional characterization of CYP71AJ4 encoding for the first P450 monooxygenase of angular furanocoumarin biosynthesis

The biosynthesis of linear and angular furanocoumarins is still poorly understood at the molecular level, with only psoralen synthase (CYP71AJ1) identified from Ammi majus. Using cDNA probes inferred from CYP71AJ1, three orthologs were isolated from Apium graveolens (CYP71AJ2) and Pastinaca sativa (CYP71AJ3 and -4) and functionally expressed in yeast cells. CYP71AJ2 and CYP71AJ3 displayed psoralen synthase activity, whereas CYP71AJ4 only catalyzed the conversion of (+)-columbianetin to angelicin and negligible amounts of a hydroxylated columbianetin by-product. CYP71AJ4 thus constitutes the first fully characterized P450 monooxygenase specific for the angular furanocoumarin pathway. The angelicin synthase exhibited an apparent K-m of 2.1 +/- 0.4 mu M for (+)-columbianetin and a k(cat) of 112 +/- 14 min(-1). Moreover, the use of 3'-deuterated (+)-columbianetin as substrate led to an almost complete "metabolic switch," resulting in the synthesis of anti-3'-hydroxy-3'-deuterated (+)-columbianetin. This confirms that angelicin synthase attacks columbianetin by syn-elimination of hydrogen from C-3'. Sequence comparison between psoralen synthase (CYP71AJ3) and angelicin synthase (CYP71AJ4) showed 70% identity, whereas the identity dropped to 40% in those regions thought to provide the substrate recognition sites. Accordingly, CYP71AJ3 and CYP71AJ4 might be derived from a common ancestor of unknown functionality by gene duplication and subsequent molecular evolution

Host plant nitrogen enrichment has both positive and negative effects on the larval growth of a specialist butterfly : Larval growth and nitrogen enrichment

1. The nitrogen limitation hypothesis posits that phytophagous insects benefit from nitrogen enrichment of their host plants through a reduction of the concentration of toxic compounds and an increase of free amino acids and proteins. However, species' response to nitrogen enrichment varies substantially and high nitrogen levels are associated with population decline, suggesting there are major costs to feeding on nitrogen‐rich host plants. 2. To test the hypothesis that larval growth performance is maximal at intermediate nitrogen enrichment, nitrogen levels were measured in 18 populations of the host plant of Lycaena helle, a specialist butterfly inhabiting nutrient‐poor wet meadows. The nitrogen content of host plants was then modified to mirror average natural nitrogen levels (C), highest field‐recorded levels (T1), and levels higher than those observed across our study populations (T2). 3. Caterpillars fed with T1 leaves had a greater maximum body mass than caterpillars of the C group because of their improved food assimilation during the early stages of their development. Caterpillars of C and T2 groups had similar growth patterns but high nitrogen content had detrimental effects, as caterpillars fed with T2 leaves had a slower ingestion rate than C and T1 groups. 4. Quantifying the fitness consequences of these changes in growth performance is necessary to fully understand the implications of nitrogen enrichment for L. helle (rapid growth may result in fitness costs). However, conservation plans for this emblematic glacial relict species should also consider the preservation of its host plant quality to ensure its persistence