Lipids are important biomolecules in all biological systems and serve numerous essential cellular functions. The global analysis of complex lipids is very challenging due to the extreme diversity in lipid structures. Variation in linkages and positions of fatty acyl chain(s) on the lipid backbone, functional group modification, occurrence of the molecular species as isomers or isobars are among some of the greatest challenges to resolve in lipidomics. In this work, we describe a routine analytical approach combining two liquid chromatography platforms: hydrophilic interaction (HILIC) and C30 reversed-phase chromatography (C30RP) coupled to high resolution mass spectrometry (HRMS) as complementary high throughput platforms to analyze complex lipid mixtures. Vascular plants (kale leaves and corn roots), rat brain and soil microbes were used as proxies to evaluate the efficiency of the enhanced approach to resolve traditional, as well as, modified lipids during routine lipidomics analysis. We report for the first time, the observation of a modified class of acylphosphatidylglycerol (acylPG) in corn roots by HILIC, and further resolution of the isomers using C30RP chromatography. We also used this approach to demonstrate the presence of high levels of N-monomethyl phosphatidylethanolamine (MMPE) in soil microbes, as well as to determine the regioisomers of lysophospholipids in kale leaves. Additionally, neutral lipids were demonstrated using C30RP chromatography in positive ion mode to resolve triacylglycerol isomers in rat brain. The work presented here demonstrates how the enhanced approach can more routinely permit novel biomarker discovery, or lipid metabolism in a wide range of biological samples.

Plant pathogens pose a significant threat to the food industry and food security accounting for 10-40% crop losses annually on a global scale. Economic losses from plant diseases are estimated at $300B for major food crops and are associated with reduced food availability and accessibility and also high food costs. Although strategies exist to reduce the impact of diseases in plants, many of these introduce harmful chemicals to our food chain. Therefore, it is important to understand and utilize plants' immune systems to control plant pathogens to enable more sustainable agriculture. Lipids are core components of cell membranes and as such are part of the first line of defense against pathogen attack. Recent developments in omics technologies have advanced our understanding of how plant membrane lipid biosynthesis, remodelling and/or signalling modulate plant responses to infection. Currently, there is limited information available in the scientific literature concerning lipid signalling targets and their biochemical and physiological consequences in response to plant pathogens. This review focusses on the functions of membrane lipid derivatives and their involvement in plant responses to pathogens as biotic stressors. We describe major plant defense systems including systemic-acquired resistance, basal resistance, hypersensitivity and the gene-for-gene concept in this context. 1 | INTRODUCTION The advancement in global agricultural production, the food industry and food security necessitates consideration of the impact of infectious pathogens on plants. This is because pathogens are widely recognized as significant obstacles to important and dependable food systems (Savary et al., 2019). Recent reports have demonstrated that plant diseases pose a significant threat to the food industry and to food security accounting for 10 to 40% crop losses annually on a global scale. Economic losses from plant diseases are estimated at $300B for major food crops, and diseases are associated with reduced food production, availability and accessibility as well as high food costs (Fletcher et al., 2006; Savary et al., 2019). Plants face different biotic stresses during their life cycle. For instance, a variety of diseases are caused by fungi, bacteria, protozoa, nematodes, viruses and phytoplasmas. These pathogens change favourable growing environments for plants into unfavourable conditions, particularly during susceptible growth stages. These cause significant yield losses both in greenhouses and under field conditions. Therefore, it is important to understand and utilize plants' innate immune systems to control plant pathogens to enable more sustainable agriculture (Brackin, Atkinson, Sturrock, & Rasmussen, 2017). Natural defense mechanisms involve a variety of signalling events and responses, which serve to combat intruding pathogens. The defense mechanism is categorized into constitutive and induced defense mechanisms. As the first line of defense, constitutive mechanisms utilize pre-formed chemicals and barriers such as ce...

Currently, there is increased interest in finding appropriate food-grade green extraction systems capable of extracting these bioactive compounds from dietary mushrooms for applications in various food, pharmacological, or nutraceutical formulations. Herein, we evaluated a modified Swiss water process (SWP) method using alkaline and acidic pH at low and high temperature under pressurized conditions as a suitable green food grade solvent to obtained extracts enriched with myco-nutrients (dietary phenolics, total antioxidants (TAA), vitamins, and minerals) from Chaga. Ultra-high performance liquid chromatography coupled to high resolution accurate mass tandem mass spectrometry (UHPLC-HRAMS-MS/MS) was used to assess the phenolic compounds and vitamin levels in the extracts, while inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the mineral contents. Over 20 phenolic compounds were quantitatively evaluated in the extracts and the highest total phenolic content (TPC) and total antioxidant activity (TAA) was observed at pH 11.5 at 100 °C. The most abundant phenolic compounds present in Chaga extracts included phenolic acids such as protocatechuic acid 4-glucoside (0.7–1.08 µg/mL), syringic acid (0.62–1.18 µg/mL), and myricetin (0.68–1.3 µg/mL). Vitamins are being reported for the first time in Chaga. Not only, a strong correlation was found for TPC with TAA (r-0.8, <0.0001), but also, with individual phenolics (i.e., Salicylic acid), lipophilic antioxidant activity (LAA), and total antioxidant minerals (TAM). pH 2.5 at 100 °C treatment shows superior effects in extracting the B vitamins whereas pH 2.5 at 60 and 100 °C treatments were outstanding for extraction of total fat-soluble vitamins. Vitamin E content was the highest for the fat-soluble vitamins in the Chaga extract under acidic pH (2.5) and high temp. (100 °C) and ranges between 50 to 175 µg/100 g Chaga. Antioxidant minerals ranged from 85.94 µg/g (pH7 at 100 °C) to 113.86 µg/g DW (pH2.5 at 100 °C). High temperature 100 °C and a pH of 2.5 or 9.5. The treatment of pH 11.5 at 100 °C was the most useful for recovering phenolics and antioxidants from Chaga including several phenolic compounds reported for the first time in Chaga. SWP is being proposed herein for the first time as a novel, green food-grade solvent system for the extraction of myco-nutrients from Chaga and have potential applications as a suitable approach to extract nutrients from other matrices. Chaga extracts enriched with bioactive myconutrients and antioxidants may be suitable for further use or applications in the food and nutraceutical industries.

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