Methodologies for determining oxalic acid in plant species consumed by humans: An integrative review

• Published in: Journal of herbal medicine 2023-08, Vol.40, p.100682, Article 100682
• Main Authors: Filho, José Odimar de Caldas Brandão, Magalhães, Cledson dos Santos, de Santana, Danielle Cristine Almeida Silva, Martins Filho, José Pedro Barbosa, Sá, Rafaela Damasceno, Luz da Silva, Rodrigo Vinícius, Randau, Karina Perrelli, de Santana, Fernando José Malagueño
• Format: Article
• Language: English
• Subjects: Oxalic Acid; Plant Bioactive Compound; Quantification; Toxicological Phenomena
• ISSN: 2210-8033
• DOI: 10.1016/j.hermed.2023.100682

Plant species are highly consumed worldwide. Plant matrices are complex, containing bioactive compounds with pharmacological and/or toxicological effects. For example, oxalic acid or oxalate is a metabolite present at high concentrations in different plant species. Its consumption can cause short- and long-term renal complications, especially if plasma concentration is ≥ 0.8–2.5 μmol.L−1 and urinary concentration is ≥ 20–30 mg 0.24 h−1. People predisposed to kidney complications (e.g. those with noncommunicable chronic diseases - NCDs) make use of medicinal plant species as adjuvant therapy. This study consists of an integrative review of the main analytical methods for quantifying oxalic acid in plant species consumed by humans. The authors conducted a search of the databases ScienceDirect, Web of Science, Scopus, Pubmed, and Scielo for publications from 2010 to 2020. A total of 808 studies were initially identified, out of which 21 were included in the review. Oxalic acid was predominantly identified using chromatographic methods in over 140 plant species of food and medicinal interest. The total concentration of oxalic acid/oxalate ranged from undetected to 6.2 g per 100 g of dry plant matter. The presence of oxalic acid in plant species raises concerns because of its role in the development or exacerbation of kidney problems. This concern has driven significant scientific research on the topic. However, most of the studies lack a comprehensive and validated methodological description.