Investigation of oxalate levels in sorrel plant parts and sorrel-based products

Abstract

The oxalate content of the leaves and stems of green and variegated cultivars of sorrel (Rumex acetosa) were extracted and measured using HPLC chromatography. The larger, more mature leaves of both cultivars contained higher levels of total, soluble and insoluble oxalates. The stems also contained appreciable levels of oxalates. The mean soluble oxalate content of the variegated leaves was 14.7%, which was significantly higher than found in the leaves of the green-leaved cultivar (11.9%). The proportion of soluble oxalate to total oxalate in the stems ranged from 12.7% to 24.4% for both cultivars. Sorrel sprouts contained a much higher proportion of soluble oxalates than the green sorrel leaves but were similar in oxalate content to the variegated leaves. Pesto and soup made from sorrel leaves retained their characteristic sour taste despite containing much lower levels of oxalates. The levels of oxalates in sorrel leaves were high and it was recommended that the leaves should be consumed occasionally as a delicacy because of their unique taste rather than as a significant part of the diet. However, the products made from sorrel leaves were less of a problem as they contained lower levels of oxalates.