SPATIAL VARIATION OF OXALATE, PHENOLIC CONTENT, AND CALCIUM OXALATE CRYSTAL COVERAGE IN SELECTED ROOT VEGETABLES

Abstract

Oxalates are naturally occurring antinutritional compounds in root vegetables, existing in both soluble and insoluble forms, often deposited as calcium oxalate crystals. The present study evaluated the tissue-specific distribution of total oxalate, total phenolic content, and calcium oxalate crystal morphology in selected root vegetables—Manihot esculenta, Ipomoea batatas, Raphanus sativus, Beta vulgaris, and Daucus carota. Total oxalate content was quantified using permanganometric titration and spectrophotometric methods, while total phenolic content was estimated using standard colorimetric assays. Crystal morphology and the area occupied by calcium oxalate crystals in the outer skin, middle cortex, and inner pith were analyzed using ZEN 4 and ImageJ software. Crystal sand was the predominant crystal type observed, with druse crystals restricted to Ipomoea batatas. The study highlights differential oxalate partitioning and crystal deposition patterns within root tissues, providing insights into oxalate bioavailability, plant physiological regulation, and dietary implications for human consumption.