Calcium Oxalate Crystals and Oxalate Content in some Vegetables from Nong Khai Province

Abstract

The presence of calcium oxalate crystals in twenty vegetables from Nong Khai Province was studied through transverse sections of fresh leaves followed by observation under light microscope. Calcium oxalate crystals were found in twelve plant species. Of these, five types of calcium oxalate crystals were observed; druses, raphides, prisms, styloid and crystal sands. Crystals density (number/mm²) in leaves from the first to the fifth leaves of three selected species; Amaranthus gracilis Desf., Corchorus olitorius L. and Sarcostemma secamone (L.) Bennet., was evaluated by clearing technique. The result showed that the density of crystals decreased in older leaves. Total oxalate in edible parts of sixteen species was analyzed. Most of plants species contained total oxalate more than 100 mg/100 g, except in peppermint (Mentha cordifolia) which contained total oxalate only 26.40 mg/100g. Moreover, some species without crystals found contained higher total oxalate content than the species in which crystals
observed.