Extraction and Natural Bioactive Molecules Characterization in Spinach, Kale and Purslane: A Comparative Study

Oxalate in Foods: Extraction Conditions, Analytical Methods, Occurrence, and Health Implications

Oxalate is an antinutrient present in a wide range of foods, with plant products, especially green leafy vegetables, being the main sources of dietary oxalates. This compound has been largely associated with hyperoxaluria, kidney stone formation, and, in more severe cases, systematic oxalosis. Due to its impact on human health, it is extremely important to control the amount of oxalate present in foods, particularly for patients with kidney stone issues. In this review, a summary and discussion of the current knowledge on oxalate analysis, its extraction conditions, specific features of analytical methods, reported occurrence in foods, and its health implications are presented. In addition, a brief conclusion and further perspectives on whether high-oxalate foods are truly problematic and can be seen as health threats are shown.

Systems-level proteomics and metabolomics reveals the diel molecular landscape of diverse kale cultivars

Kale is a group of diverse Brassicaceae species that are nutritious leafy greens consumed for their abundance of vitamins and micronutrients. Typified by their curly, serrated and/or wavy leaves, kale varieties have been primarily defined based on their leaf morphology and geographic origin, despite having complex genetic backgrounds. Kale is a very promising crop for vertical farming due to its high nutritional content; however, being a non-model organism, foundational, systems-level analyses of kale are lacking. Previous studies in kale have shown that time-of-day harvesting can affect its nutritional composition. Therefore, to gain a systems-level diel understanding of kale across its wide-ranging and diverse genetic landscape, we selected nine publicly available and commercially grown kale cultivars for growth under near-sunlight LED light conditions ideal for vertical farming. We then analyzed changes in morphology, growth and nutrition using a combination of plant phenotyping, proteomics and metabolomics. As the diel molecular activities of plants drive their daily growth and development, ultimately determining their productivity as a crop, we harvested kale leaf tissue at both end-of-day (ED) and end-of-night (EN) time-points for all molecular analyses. Our results reveal that diel proteome and metabolome signatures divide the selected kale cultivars into two groups defined by their amino acid and sugar content, along with significant proteome differences involving carbon and nitrogen metabolism, mRNA splicing, protein translation and light harvesting. Together, our multi-cultivar, multi-omic analysis provides new insights into the molecular underpinnings of the diel growth and development landscape of kale, advancing our fundamental understanding of this nutritious leafy green super-food for horticulture/vertical farming applications.

Extraction, Purification, Structural Characteristics, Biological Activity and Application of Polysaccharides from Portulaca oleracea L. (Purslane): A Review

Portulaca oleracea L. (purslane) is a widely distributed plant with a long history of cultivation and consumption. Notably, polysaccharides obtained from purslane exhibit surprising and satisfactory biological activities, which explain the various benefits of purslane on human health, including anti-inflammatory, antidiabetic, antitumor, antifatigue, antiviral and immunomodulatory effects. This article systematically reviews the extraction and purification methods, chemical structure, chemical modification, biological activity and other aspects of polysaccharides from purslane collected in the Chinese Pharmacopoeia, Flora of China, Web of Science, PubMed, Baidu Scholar, Google Scholar and CNKI databases in the last 14 years, using the keywords "Portulaca oleracea L. polysaccharides" and "purslane polysaccharides". The application of purslane polysaccharides in different fields is also summarized, and its application prospects are also discussed. This paper provides an updated and deeper understanding of purslane polysaccharides, which will provide useful guidance for the further optimization of polysaccharide structures and the development of purslane polysaccharides as a novel functional material, as well as a theoretical basis for its further research and application in human health and manufacturing development.

The Effect of Fresh Kale (Brassica oleracea var. sabellica) Addition and Processing Conditions on Selected Biological, Physical, and Chemical Properties of Extruded Snack Pellets

The purpose of this study was to determine the effect of the addition of fresh kale and processing conditions on extruded pellet antioxidant activity and selected physicochemical properties. The results of the applied DPPH, FRAP, and TPC methods indicated that, for both 60 and 100 rpm screw speeds, snack pellet antioxidant activity and phenolic content were strongly linked to the fresh kale content, and these properties increased with the addition of this plant. The amount of fresh kale and the applied processing variables (extruder screw speed and the moisture content of the raw material blends) were also found to significantly affect the water absorption index, water solubility index, fat absorption index, fatty acid profile, and basic chemical composition of the obtained extrudates. The sample with the highest phenolic content (72.8 μg GAE/g d.w.), the most advantageous chemical composition (protein, ash, fat, carbohydrates, and fiber content), and high antioxidant properties was produced at a fresh kale content of 30%, a 36% moisture content, and a 100 rpm screw speed. The following phenolic acids were identified in this sample: protocatechuic, 4-OH-benzoic, vanillic, syringic, salicylic, caffeic, coumaric, ferulic, and sinapic. Sinapic acid was the prevailing phenolic acid.

Effects of Wet and Dry Micronization on the GC-MS Identification of the Phenolic Compounds and Antioxidant Properties of Freeze-Dried Spinach Leaves and Stems

Micronization is an emerging technology used in food production, in which the size of particles is reduced to microns in the processing of plant raw materials and by-products, thus making it an interesting research topic. Spinach stems are by-products of spinach leaf processing, but there is little information regarding their processing and possible reuse. In this study, wet and dry ball mill micronization, in combination with freeze drying, was used to process spinach stems and leaves to obtain functional powders. The color and particle size of the micronized spinach leaf and stem powders were evaluated. The antioxidant activity (AA) of the powders and phenolic compounds present in them were determined using GC-MS analysis. The results obtained showed that the dry micronization of leaves and stems resulted in smoother and brighter powders than wet micronization. Significantly smaller particle sizes were achieved using the dry micronization of the leaves and stems (Dv50 = 19.5 and 10.1 µm, respectively) rather than wet micronization (Dv50 = 84.6 and 112.5 µm, respectively). More phenolic compounds, such as o-coumaric acid and gallic acid, were extracted from the dry-micronized powders. The dry micronization of the stems significantly increased the total phenolic content, and the AA of these powders was also increased. These findings demonstrate that spinach leaves and stems subjected to dry micronization can be valuable functional components of food.