Optimisation of phytochemical characteristics and antioxidative properties of Foeniculum vulgare Mill. seeds and Ocimum basilicum L. leaves superfine powders using new parting process.

INTRODUCTION: Fennel (Foeniculum vulgare Mill.) and basil (Ocimum basilicum L.) are two aromatic medicinal plants. Recently, a new parting process which is named CDS "Comminution and to control Diffraction Sieving" is taken into consideration and its positive effect on the extraction of bioactive compounds from the plants, without any solvent, is reported. OBJECTIVE: Study the effect of CDS on phytochemical properties of superfine powders of fennel seeds and basil leaves. METHODS: Fennel seeds and basil leaves superfine powders were fractionated as follows: 100-180 µm, 180-315 µm, 315-500 µm, > 500 µm and unsieved superfine powders. Extraction of polyphenols was carried out using hydromethanolic maceration. The essential oils were extracted by maceration with dichloromethane. The antioxidant activities were evaluated by DPPH (2,2-diphenyl-1-picrylhydrazyl) assay. Using liquid chromatography ultraviolet electrospray ionisation mass spectrometry (LC-UV-ESI-MS), concentrations of characterised phenolic compounds were measured. The essential oils compositions were characterised using gas chromatography mass spectrometry (GC-MS). RESULTS: In fennel seeds, the 100-180 µm fraction had maximum antioxidant activity and LC-UV-ESI-MS analyses proved that the best extraction of certain polyphenols was obtained in the 100-180 µm fraction. In basil leaves, the best antioxidant activity corresponded to the 315-500 µm fraction and LC-UV-ESI-MS analyses showed that the polyphenols were concentrated in the < 315 µm fractions. For both plants, GC-MS presented that the essential oils were concentrated in the 315-500 µm fraction. CONCLUSION: CDS as a new green parting process leads to improve the phytochemical properties of these two superfine plant powders in the specific granulometric classes.

Correlative Analysis of Fluorescent Phytoalexins by Mass Spectrometry Imaging and Fluorescence Microscopy in Grapevine Leaves.

Plant response to their environment stresses is a complex mechanism involving secondary metabolites. Stilbene phytoalexins, namely resveratrol, pterostilbene, piceids and viniferins play a key role in grapevine (Vitis vinifera) leaf defense. Despite their well-established qualities, conventional analyses such as HPLC-DAD or LC-MS lose valuable information on metabolite localization during the extraction process. To overcome this issue, a correlative analysis combining mass spectroscopy imaging (MSI) and fluorescence imaging was developed to localize in situ stilbenes on the same stressed grapevine leaves. High-resolution images of the stilbene fluorescence provided by macroscopy were supplemented by specific distributions and structural information concerning resveratrol, pterostilbene, and piceids obtained by MSI. The two imaging techniques led to consistent and complementary data on the stilbene spatial distribution for the two stresses addressed: UV-C irradiation and infection by Plasmopara viticola. Results emphasize that grapevine leaves react differently depending on the stress. A rather uniform synthesis of stilbenes is induced after UV-C irradiation, whereas a more localized synthesis of stilbenes in stomata guard cells and cell walls is induced by P. viticola infection. Finally, this combined imaging approach could be extended to map phytoalexins of various plant tissues with resolution approaching the cellular level.

Effect of particle size on antioxidant activity and catechin content of green tea powders.

This work evaluated the effect of grinding and sieving process of green tea leaves on particle size distribution and antioxidant activity. Granulometric classes ranging from 20 µm to 500 µm were studied. Hydroalcoholic extracts of green tea powders (GTPs) were analysed for total phenolic, total flavonoid, and catechin contents. The fraction of 100-180 µm ground at 6000 rpm showed the maximum catechin content with 33.5 mg/g dry matter (DM) and, the best antioxidant activity with IC50 values of 0.28 µg/mL and 0.13 µg/mL using DPPH and ABTS radical scavenging assays, respectively. However, antioxidant properties and catechin content decreased for particle of sizes less than 50 µm. Catechin content was higher for those ground at 6000 rpm as compared to at 18,000 rpm. The best grinding conditions and particle size were 6000 rpm and 100-180 µm.

MALDI mass spectrometry imaging for the simultaneous location of resveratrol, pterostilbene and viniferins on grapevine leaves.

To investigate the in-situ response to a stress, grapevine leaves have been subjected to mass spectrometry imaging (MSI) experiments. The Matrix Assisted Laser Desorption/Ionisation (MALDI) approach using different matrices has been evaluated. Among all the tested matrices, the 2,5-dihydroxybenzoic acid (DHB) was found to be the most efficient matrix allowing a broader range of detected stilbene phytoalexins. Resveratrol, but also more toxic compounds against fungi such as pterostilbene and viniferins, were identified and mapped. Their spatial distributions on grapevine leaves irradiated by UV show their specific colocation around the veins. Moreover, MALDI MSI reveals that resveratrol (and piceids) and viniferins are not specifically located on the same area when leaves are infected by Plasmopara viticola. Results obtained by MALDI mass spectrometry imaging demonstrate that this technique would be essential to improve the level of knowledge concerning the role of the stilbene phytoalexins involved in a stress event.

Metabolic study of grapevine leaves infected by downy mildew using negative ion electrospray--Fourier transform ion cyclotron resonance mass spectrometry.

Grapevine is of worldwide economic importance due to wine production. However, this culture is often affected by pathogens causing severe harvest losses. Understanding host-pathogen relationships may be a key to solve this problem. In this paper, we evaluate the direct flow injection by electrospray - Fourier transform ion cyclotron resonance mass spectrometry (MS) of leaf extracts as a rapid method for the study of grapevine response to downy mildew (Plasmopara viticola) attack. The comparison of MS profiles obtained from control and infected leaves of different levels of resistant grapevines highlights several classes of metabolites (mainly saccharides, acyl lipids, hydroxycinnamic acids derivatives and flavonoids) which are identified using high resolution MS and tandem MS (MS/MS). Statistical analyses of 19 markers show a clear segregation between inoculated and healthy samples. This study points out relative high levels of disaccharides, acyl lipids and glycerophosphoinositol in inoculated samples. Sulfoquinovosyl diacylglycerols also emerge as possible metabolites involved in plant defense.