Comparison of the estimates of the oxalate content of taro leaves and corms and a selection of Indian vegetables following hot water, hot acid and in vitro extraction methods

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.

A comparative review on the anti-nutritional factors of herbal tea concoctions and their reduction strategies

Tea is an important beverage consumed worldwide. Of the different types of tea available, herbal tea is an important beverage consumed owing to its popularity as a drink and stress relieving factors, several different herbal concoctions made from seeds, leaves, or roots are currently consumed and sold as herbal teas. The herbal teas are not the usual tea but "tisanes." They are caffeine free and popular for their medicinal property or immune boosters. Herbal tea formulations are popularly sold and consumed by millions owing to their health benefits as they are rich in antioxidants and minerals. However, plants are also known to contain toxic and anti-nutritional factors. Anti-nutritional factors are known to interfere with the metabolic process and hamper the absorption of important nutrients in the body. These anti-nutritional factors include saponins, tannins, alkaloids, oxalates, lectins, goitrogens, cyanogens, and lethogens. These chemicals are known to have deleterious effects on human health. Therefore, it is important to understand and assess the merits and demerits before consumption. Also, several techniques are currently used to process and reduce the anti-nutrients in foods. This review is focused on comparing the contents of various anti-nutritional factors in some underutilized plants of North-East India used as herbal tea along with processing methods that can be used to reduce the level of these anti-nutrients.

Nutritional, phytochemical composition and potential health benefits of taro (Colocasia esculenta L.) leaves: A review

Colocasia esculenta(L) or taro is a tropical crop largely produced for its tubers (corms) while leaves and stems remain underutilized and untapped by-products with promising potential applications.Colocasialeaves are low in calories, rich in proteins, dietary fiber, and micronutrients. However, its utilization as food remains limited owing to the lack of awareness vis-à-vis its nutritional profile and the presence of antinutrients such as tannins, phytates and oxalates. The antinutritional factors can be overcome by cooking and varied processing techniques thereby unveiling the nutritional benefits. The high content of bioactive compounds and antioxidative potential of colocasia leaves renders several health benefits such as anticancer, antidiabetic, anti-inflammatory activity. The paper reviews the available literature on the nutritional, antinutritional, phytochemical profile of taro leaves and the advanced analytical techniques for their identification and quantification. Further, its health benefits and food applications have been discussed.

Plant food anti-nutritional factors and their reduction strategies: an overview

Abstract

Legumes and cereals contain high amounts of macronutrients and micronutrients but also anti-nutritional factors. Major anti-nutritional factors, which are found in edible crops include saponins, tannins, phytic acid, gossypol, lectins, protease inhibitors, amylase inhibitor, and goitrogens. Anti-nutritional factors combine with nutrients and act as the major concern because of reduced nutrient bioavailability. Various other factors like trypsin inhibitors and phytates, which are present mainly in legumes and cereals, reduce the digestibility of proteins and mineral absorption. Anti-nutrients are one of the key factors, which reduce the bioavailability of various components of the cereals and legumes. These factors can cause micronutrient malnutrition and mineral deficiencies. There are various traditional methods and technologies, which can be used to reduce the levels of these anti-nutrient factors. Several processing techniques and methods such as fermentation, germination, debranning, autoclaving, soaking etc. are used to reduce the anti-nutrient contents in foods. By using various methods alone or in combinations, it is possible to reduce the level of anti-nutrients in foods. This review is focused on different types of anti-nutrients, and possible processing methods that can be used to reduce the level of these factors in food products.

Graphical abstract

A brief overview of beneficial effects of anti-nutrients and reduction strategy.

Effect of Room Temperature Ionic Liquid on the Formation of the Complex Oxalate-Sodium Morin-5-Sulfonate-Aluminium(III): Application to the Fluorescence Determination of Oxalate Ion

The effect of room temperature ionic liquid (RTIL) on the formation of the fluorescence ternary complex oxalate-sodium morin-5-sulfonate (NaMSA)-Aluminium(III) has been studied. In weakly acidic medium and in the presence of RTIL, 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6), total complex formation is achieved as compared with the formation of the binary complex of NaMSA-Aluminium(III). The fluorescence characteristics of the system allowed the establishment of a very sensitive method for the spectrofluorimetric determination of oxalate ion. The ternary complex formed its highest fluorescence signal at 513 nm and excitation at 420 nm. In these conditions, the method produces a detection limit of 0.57 ng mL(-1). The procedure has been satisfactorily applied to the determination of oxalate ion in a vegetal tissue (spinach leaves).

Total and soluble oxalate content of some Indian spices

Spices, such as cinnamon, cloves, cardamom, garlic, ginger, cumin, coriander and turmeric are used all over the world as flavouring and colouring ingredients in Indian foods. Previous studies have shown that spices contain variable amounts of total oxalates but there are few reports of soluble oxalate contents. In this study, the total, soluble and insoluble oxalate contents of ten different spices commonly used in Indian cuisine were measured. Total oxalate content ranged from 194 (nutmeg) to 4,014 (green cardamom) mg/100 g DM, while the soluble oxalate contents ranged from 41 (nutmeg) to 3,977 (green cardamom) mg/100 g DM. Overall, the percentage of soluble oxalate content of the spices ranged from 4.7 to 99.1% of the total oxalate content which suggests that some spices present no risk to people liable to kidney stone formation, while other spices can supply significant amounts of soluble oxalates and therefore should be used in moderation.