Determination of Oxalate Content in Herbal Remedies and Dietary Supplements Based on Plant Extracts

Lifestyle, especially diet, is a prominent risk factor that affects the formation of calcium oxalate stones. Urinary oxalate excretion is directly related to the amount of oral intake and intestinal absorption rate of oxalate. This work evaluated the possibility of increasing oxalate ingestion, which could lead to secondary hyperoxaluria, associated with the intake of herbal remedies and dietary supplements containing plant extracts. A wide variety of 17 commercially available drugs and dietary supplements were analyzed using ion chromatography. The results showed remarkable differences in oxalate contents of the extracts. Total oxalate concentrations ranged from 0.03 to 2.2 mg/g in solid samples and from 0.005 to 0.073 mg/mL in liquid samples. The selected herbal remedies and dietary supplements containing plant extracts represent only a low risk for calcium oxalate stone formers, if the recommended daily dose is not exceeded.