Ergastic Crystals in Lettuce Tree: A Potential Antinutrient

Abstract

Plants are known for enriching human life with nutrition, but many plant parts have ergastic crystals in the form of calcium oxalate crystals. The dietary ergastic crystals are believed to be anti–nutrients as they accumulate in many medical cases and form complexes. Several of the medicinally useful plants contain these crystals and consumption of such plant materials afresh can cause health problems in humans. Present study focuses on the anti-nutrient component in the form of ergastic crystals, which is present in its vegetative parts of Pisonia alba. 
Pisonia alba commonly known as lettuce tree or cabbage tree belonging to Nyctaginaceae family is widely used as a leafy vegetable and medicine in South India. Calcium oxalate crystals are abundant in its leaf, stem and petiole as raphide bundles. On an average size of raphide bundles ranges from 0.009mm-0.012mm in length and 0.008mm-0.011mm in thickness. Individual crystals are pointed on both ends, needle like and transparent with size ranging from 0.006mm-0.011mm in length. L.S of stem and petiole reveal raphide bundles arranged parallel to the long axis, distributed in cortex and stele. In leaves raphide bundles show a transverse arrangement on the lamina interspersed with the photosynthetic tissue. Older leaves exhibit elevated number of raphide bundles than younger leaves. Length, breadth and fresh weight of the individual leaf ranges from 19-26 cm, 11-18 cm and 0.003-0.008 gm respectively. Area of lamina ranges from 150-400 cm2. The crystals are persistent in the material even after cooking and processing like stir-frying in oil, blanching, and pickling in apple cider vinegar. Therefore, careful evaluation of traditional and ethno-botanical knowledge is required before establishing plants and their parts as vegetable, as some of them may have deleterious phyto-constituents that has elevated potential to cause renal defects.