Wheat Oxylipins in Response to Aphids, CO2 and Nitrogen Regimes

Wheat is critical for food security, and is challenged by biotic stresses, chiefly aphids and the viruses they transmit. The objective of this study was to determine whether aphids feeding on wheat could trigger a defensive plant reaction to oxidative stress that involved plant oxylipins. Plants were grown in chambers with a factorial combination of two nitrogen rates (100% N vs. 20% N in Hoagland solution), and two concentrations of CO₂ (400 vs. 700 ppm). The seedlings were challenged with Rhopalosiphum padi or Sitobion avenae for 8 h. Wheat leaves produced phytoprostanes (PhytoPs) of the F₁ series, and three types of phytofurans (PhytoFs): ent-16(RS)-13-epi-ST-Δ¹⁴-9-PhytoF, ent-16(RS)-9-epi-ST-Δ¹⁴-10-PhytoF and ent-9(RS)-12-epi-ST-Δ¹⁰-13-PhytoF. The oxylipin levels varied with aphids, but not with other experimental sources of variation. Both Rhopalosiphum padi and Sitobion avenae reduced the concentrations of ent-16(RS)-13-epi-ST-Δ¹⁴-9-PhytoF and ent-16(RS)-9-epi-ST-Δ¹⁴-10-PhytoF in relation to controls, but had little or no effect on PhytoPs. Our results are consistent with aphids affecting the levels of PUFAs (oxylipin precursors), which decreased the levels of PhytoFs in wheat leaves. Therefore, PhytoFs could be postulated as an early indicator of aphid hosting for this plant species. This is the first report on the quantification of non-enzymatic PhytoFs and PhytoPs in wheat leaves in response to aphids.

Predictive Multi Experiment Approach for the Determination of Conjugated Phenolic Compounds in Vegetal Matrices by Means of LC-MS/MS

Polyphenols (PCs) are a numerous class of bioactive molecules and are known for their antioxidant activity. In this work, the potential of the quadrupole/linear ion trap hybrid mass spectrometer (LIT-QqQ) was exploited to develop a semi-untargeted method for the identification of polyphenols in different food matrices: green coffee, Crocus sativus L. (saffron) and Humulus lupulus L. (hop). Several conjugate forms of flavonoids and hydroxycinnamic acid were detected using neutral loss (NL) as a survey scan coupled with dependent scans with enhanced product ion (EPI) based on information-dependent acquisition (IDA) criteria. The presented approach is focused on a specific class of molecules and provides comprehensive information on the different conjugation models that are related to specific base molecules, thus allowing a quick and effective identification of all possible combinations, such as mono-, di-, or tri-glycosylation or another type of conjugation such as quinic acid esters.

Cannabinoid Profile in Cannabis sativa L. Samples by Means of LC-MRM/IDA/EPI Analysis: A New Approach for Cultivar Classification

A new multitarget screening procedure for 36 cannabinoids in 12 Cannabis sativa L. cultivars (hemp) was developed using multiple reaction monitoring (MRM) coupled with an enhanced product ion (EPI) scan in an information-dependent acquisition (IDA) experiment, which can be performed by means of high-performance liquid chromatography-mass spectrometry (HPLC-MS)/MS analysis. The MRM-IDA-EPI experiment was used for the analysis of hemp samples and the identification of the compounds of interest. It was performed through the comparison of EPI spectra with literature data and with the in-house library. The results, processed by multivariate statistical analysis, showed an accurate classification of the 12 C. sativa cultivars, emphasizing the synergic contribution of the new cannabinoids recently discovered and showing how the traditional classification based on a common cannabinoid is limiting.

Chemical characterization and evaluation of antioxidant activity from different cultivars of Cannabis sativa L. of Abruzzo's region

In this work, the chemical composition and the antioxidant evaluation of the inflorescences from 12 Cannabis sativa L. monoecious cultivars (Carmagnola Lemon CL, Ferimon F, Gran Sasso Kush GSK, Antal A, Carmagnola C, Kompolti K, Futura 75 F75, Villanova V, Tiborzallasi T, Finola FL, Kc Virtus KV and Pineapple P) cultivated at the same condition, were investigated. GC-MS analysis was carried out to evaluate the volatile fraction, while HPLC-MS/MS was used for cannabinoids and polyphenolic compounds. The evaluation of antioxidant activity was carried out using ABTS^*+, Trolox equivalence antioxidant capacity (TEAC), ferric reducing antioxidant property (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH*) assays in vitro. The obtained data, demonstrated that each cultivar has a characteristic chemical profile, with highest antioxidant capacity for CL, F75, GSK and F. Based on the in vitro antioxidant activity the plant extracts can be considered as promising candidates for different applications in food field.

Targeted and semi-untargeted determination of phenolic compounds in plant matrices by high performance liquid chromatography-tandem mass spectrometry

In this work two different acquisition approaches were used for the quantification and/or tentative identification of phenolic compounds (PCs) in plant matrices by HPLC-MS/MS. A targeted approach, based on MRM acquisition mode, was used for the identification and quantification of a list of target analytes by comparison with standards; a semi-targeted approach was also developed by the precursor ion scan and neutral loss for the tentative identification of compounds not included in the target list. Analysis of phenolic content in three different plant matrices (curry leaves, hemp and blueberry) was carried out. The extraction and clean-up steps were set up according to the characteristics of the sample allowing to minimize the interfering compounds present in such complex matrices, as proved by the low matrix effect obtained (<16%) and recovery values ranging from 45% to 98% for all the analytes. This approach provided a sensitive and robust quantitative analysis of the target compounds with LOQs between 0.0002 and 0.05 ng mg^-1, which allowed the identification and quantification of several hydroxycinnamic and hydroxybenzoic acids, in addition to numerous flavonoids in all three matrices. Furthermore, different moieties were considered as neutral losses or as precursor ions in semi-targeted MS/MS approach, providing the putative identification of different glycosylated forms of flavonoids, such as luteolin-galactoside and diosmin in all three matrices, while apigenin-glucuronide was detected in hemp and quercetin-glucuronide in blueberry. A further study was carried out by MS³, allowing the discrimination of compounds with similar aglycones, such as luteolin and kaempferol.