Oxalic acid is among the most abundant organic acids found in different biospheres, including plants, as an end product of metabolism. It forms either soluble or insoluble salts with monovalent or divalent cations, respectively. Then, consumption of oxalic acid-rich foods in human diets, particularly leafy vegetables (e.g., spinach, tea, and rhubarb), affects minerals absorption such as calcium. Meanwhile, its high level in blood is associated with many diseases such as hyperoxaluria systemic oxalosis and is thus classified among potential anti-nutrients. Various factors have affected oxalic acid levels in foods, including agricultural traits and consumption practices. Hence, the current review aimed at rediscovering oxalic acid dietary sources, metabolism, and the various processes employed to reduce its content in foods, and consequently, health harmful effects. Among them are physical/cooking, chemical, fermentation, and biotechnological processing. Recent biotechnological approaches have been attempted to produce transgenic crops remodeling oxalate metabolism, particularly its degradation. The soluble form of oxalate seems to be better absorbed and more harmful than insoluble salts in foods aiding in kidney stones formation. Cooking (e.g., boiling, microwaving, and steaming) appears as a useful management strategy to reduce soluble oxalate and, therefore, lowering oxaluria. The present review provides new perspectives on different processing methods to lower oxalate in essential vegetables highlighting their advantages or any limitations to aid improve these foods nutritional value and consumption.

Antinutrients, also known as anti-nutritional factors (ANFs), are compounds found in many plant-based foods that can limit the bioavailability of nutrients or can act as precursors to toxic substances. ANFs have controversial effects on human health, depending mainly on their concentration. While the positive effects of these compounds are well documented, the dangers they pose and the approaches to avoid them have not been discussed to the same extent. There is no dispute that many ANFs negatively alter the absorption of vitamins, minerals, and proteins in addition to inhibiting some enzyme activities, thus negatively affecting the bioavailability of nutrients in the human body. This review discusses the chemical properties, plant bioavailability, and deleterious effects of anti-minerals (phytates and oxalates), glycosides (cyanogenic glycosides and saponins), polyphenols (tannins), and proteinaceous ANFs (enzyme inhibitors and lectins). The focus of this study is on the possibility of controlling the amount of ANF in food through fermentation. An overview of the most common biochemical pathways for their microbial reduction is provided, showing the genetic basis of these phenomena, including the active enzymes, the optimal conditions of action, and some data on the regulation of their synthesis.

Oxalate is a divalent organic anion that affects many biological and commercial processes. It is derived from plant sources, such as spinach, rhubarb, tea, cacao, nuts, and beans, and therefore is commonly found in raw or processed food products. Oxalate can also be made endogenously by humans and other mammals as a byproduct of hepatic enzymatic reactions. It is theorized that plants use oxalate to store calcium and protect against herbivory. Clinically, oxalate is best known to be a major component of kidney stones, which commonly contain calcium oxalate crystals. Oxalate can induce an inflammatory response that decreases the immune system's ability to remove renal crystals. When formulated with platinum as oxaliplatin (an anticancer drug), oxalate has been proposed to cause neurotoxicity and nerve pain. There are many sectors of industry that are hampered by oxalate, and others that depend on it. For example, calcium oxalate is troublesome in the pulp industry and the alumina industry as it deposits on machinery. On the other hand, oxalate is a common active component of rust removal and cleaning products. Due to its ubiquity, there is interest in developing efficient methods to quantify oxalate. Over the past four decades, many diverse methods have been reported. These approaches include electrochemical detection, liquid chromatography or gas chromatography coupled with mass spectrometry, enzymatic degradation of oxalate with oxalate oxidase and detection of hydrogen peroxide produced, and indicator displacement-based methods employing fluorescent or UV light-absorbing compounds. Enhancements in sensitivity have been reported for both electrochemical and mass-spectrometry-based methods as recently as this year. Indicator-based methods have realized a surge in interest that continues to date. The diversity of these approaches, in terms of instrumentation, sample preparation, and sensitivity, has made it clear that no single method will work best for every purpose. This review describes the strengths and limitations of each method, and may serve as a reference for investigators to decide which approach is most suitable for their work.

Clinical and pathological findings in fatal plant oxalosis. A review. Poisoning by ingestion of oxalate-containing plants, such as raw rhubarb, is infrequent, and such deaths are rare. We present a review of the most important clinical and pathological aspects of oxalate poisoning and recommend that the public be educated about the dangers of eating unknown plants with potentially adverse effects. Published in The American journal of forensic medicine and pathology (1992)

Poisoning by ingestion of oxalate-containing plants, such as raw rhubarb, is infrequent, and such deaths are rare. We present a review of the most important clinical and pathological aspects of oxalate poisoning and recommend that the public be educated about the dangers of eating unknown plants with potentially adverse effects.

Rhubarb is the fleshy, edible stalks (petioles) of species and hybrids (culinary rhubarb) of Rheum in the family Polygonaceae, which are cooked and used Rhubarb is the fleshy, edible stalks (petioles) of species and hybrids (culinary rhubarb) of Rheum in the family Polygonaceae, which are cooked and used for food. The plant is a herbaceous perennial that grows from short, thick rhizomes. Historically, different plants have been called "rhubarb" in English. The large, triangular leaves contain high levels of oxalic acid and anthrone glycosides, mak R…