Oxalic Acid and Calcium Determination in Wild Edible Plants

Abstract

The contents of oxalic acid and calcium in several wild edible plants were analyzed. Oxalic acid was determined by an espectrophotometric method based on the decrease of absorbance at 335 nm due to the dissociation of the zirconium(IV)−chloranilate complex, consecutive to the addition of oxalic acid. Calcium was determined by atomic absorption spectroscopy. The results show the absence of this acid in two of the studied plants: hoary cress (Cardaria draba (L.) Desv.) and vervain (Verbena officinalis L.). Also noticeable is the high content of oxalic acid in goosefoot (Chenopodium album L.), with a range of values from 360 to 2000 mg/100 g of fresh weight, and the high ratio (oxalic acid/calcium) in curly dock (Rumex crispus L.), with a mean value of 32. Keywords: Oxalic acid; calcium; antinutritive substance; wild edible plants

Mediterranean non-cultivated vegetables as dietary sources of compounds with antioxidant and biological activity

“…Scolymus hispanicus and Silybum marianum. This may indicate that vitamin C in plants is often located at higher levels in photosynthetic tissues, as previously reported by Loewus As also found by Guil, Torija, Giménez, Rodríguez-García, & Giménez (1996), oxalic acid was the major organic acid in the basal leaves of all the analyzed non-cultivated species (Table 2), except in Taraxacum obovatum and Cichorium intybus that revealed malic acid as the main organic acid with values around 106.20 and 92.51 mg/100 g, respectively. Other authors previously reported high oxalic acid accumulation in the leafy tissues of some species from the families Asteraceae, Euphorbiaceae, Chenopodiaceae, Portulacaceae or Liliaceae, which has been attributed to the way of incorporation of HCO 3 -and CO 2 in photosynthesis mechanisms, for organic acid biosynthesis pathways.…”

“…For those reasons although oxalic acid has a quite low toxicity (with 5 g as the minimal lethal dose for an adult), the ingestion of high levels of this organic acid is not desirable. Some authors (Guil et al, 1996) recommended an oxalic acid/Ca ratio not higher than 2.5 in the foods to avoid this toxic effect.…”

Wild edible plants: Nutritional and toxicological characteristics, retrieval strategies and importance for today's society

“…For this reason, the ingestion of foods with high levels of this antinutritional compound is not desirable. Some authors (Guil et al, 1996) recommend an oxalic acid/Ca ratio not higher than 2.5 to avoid this negative effect. Among the selected plants, this limit is greatly exceeded by M. fontana (∼11.8) but also by other species, namely B. maritima, C. ambrosioides, S. marianum, R. pulcher, A. nodiflorum, A. acutifolius, S. oleraceus, P. oleracea, N. officinale and R. papillaris ( Fig.…”

“…Wild plants of the genus Oxalis, Rumex, Amaranthus and Chenopodium have been referred as having significant levels of oxalic acid (Guil et al, 1996;Vizgirdas and Rey-Vizgirdas, 2006). Amounts between 137 and 256 mg/100 g were described for R. pulcher, R. papillaris (Morales et al, 2014;Sánchez-Mata et al, 2012) and R. acetosella ; but a small amount of 0.7 mg/100 g was reported in tender leaves of R. induratus (Pinela et al, 2016c).…”

Nutrient composition of selected traditional United States Northern Plains Native American plant foods

“…For example, oxalic acid has been reported in C. album L. (lambsquarters) in some studies, and this antinutrient could reduce the bioavailability of calcium (Guil et al, 1996(Guil et al, , 1997). While it is not possible to discuss all aspects of potential antinutritional factors in a scientific report on nutrient composition of native plant foods, obviously any contraindications with respect to consumption of wild plants and any mitigation of those factors that might occur in different preparations (e.g.…”