Assessment of calcium oxalate in nopal (Opuntia mesacantha) powder by SEM/EDX

Cactus cladode powder derived from the plant Opuntia megacantha (also known as nopal powder) is a dietary supplement that is highly appreciated for its culinary and medicinal benefits, mostly due to its significant amount of antioxidants. However, an assessment of its bioactive chemical compounds revealed the existence of high levels of calcium oxalates. This could pose a risk of toxicity in vulnerable individuals, such as those with kidney failure or diabetes. Scanning electron microscopy (SEM) combined with an energy-dispersive X-ray spectroscopy (Energy Dispersive X-ray), EDX probe showed the presence of calcium oxalate that resembles sugar cubes. Additionally, the EDX spectrum indicated the existence of calcium, carbon, and oxygen, along with some trace elements such as sodium, magnesium, and chlorine. The powder of cladodes from the spiny variety of cactus consists mainly of epidermal cells, parenchyma, and chlorenchyma, similar to cladodes from the spiny variety of cactus according to Boutakiout (Int J Technol Enhanc Emerg Eng Res 3(1):1–8, 2015) and Malainine (Z Naturforsch 58:812–816, 2003).