Aristolochic Acids as Persistent Soil Pollutants: Determination of Risk for Human Exposure and Nephropathy from Plant Uptake

Abstract

Exposure to aristolochic acids (AAs) from Aristolochia plants is one of the major global causes of nephropathy, renal failure and urothelial cancer, including Balkan endemic nephropathy (BEN). The high incidence of BEN on the Balkan Peninsula is assumed to result from consumption of Aristolochia clematitis L. seeds co-harvested with crops. Here we show that AAs are long-lived soil contaminants that enter wheat and maize plants by root uptake, with strong pH-dependence. Soil and crops from Serbian farms in areas endemic for A. clematitis were found to be extensively contaminated with AAs, with contamination strongly correlated with local incidence of BEN. The persistence of AAs as soil contaminants suggests that weed control for A. clematitis plants is needed to reduce the incidence of BEN and aristolochic acid nephropathy, and that systematic surveys of soil and crop AA levels would identify high-risk regions and it is imperative to research soil remediation methods.

Liquid chromatography–tandem mass spectrometry analysis of aristolochic acids in soil samples collected from Serbia: Link to Balkan endemic nephropathy

“…The mixture was then subjected to ultrasonication at 50°C for 1 h to extract AAs from the soil. Following centrifugation at 6000 g for 10 min, 1 mL of the sample extract was reacted with 20 mg of pre‐activated zinc dust at 60°C for 15 min to reduce AAs to their respective aristolactams (ALs; Figure ) . After cooling to room temperature, 50 μL of internal standard, benz[ cd ]indol‐2(1 H )‐one (200 ng/mL), was spiked to the samples, which were vortex‐mixed and centrifuged at 13 800 g for 5 min prior to analysis using the LC/MS/MS method described below.…”

“…Soil pH analyses were performed according to the international standard procedure ISO 10390:2005 . In brief, soil samples were mixed with distilled water at a ratio of 1:5 (w/v) and agitated continuously for 1 h. After standing for 30 min, the pH of the soil/water mixture was measured with a calibrated pH meter (model 420A, Orion Research Inc., Boston, MA, USA).…”

“…Since the 1990s, the use of AA‐containing herbs has been prohibited for preparing herbal medicines in many countries, including the USA . Despite the worldwide ban on the use of AA‐containing Aristolochia plants as traditional herbal medicine and in herbal remedies, it was estimated that over a hundred million people are potential victims of AA poisoning, due to the traditional practice of Chinese herbal medicine, the misuse of AA‐containing herbs and environmental exposure …”

“…It was not until 2007 that AAs were identified to be the disease‐causing agent of BEN . It is suspected that BEN is an environmentally induced disease caused by the dietary intake of AA‐tainted food . Such food contamination was speculated to have been caused by the commingling of AA‐containing seeds of Aristolochia clematitis L. (commonly known as birthwort) with wheat grains during the harvesting process.…”

“…There is some emerging evidence suggesting that AAs are environmental pollutants released into cultivation soil as the dead mass of A. clematitis decomposes . Free AAs in the contaminated soil are then taken up by food crops via root absorption and translocated into their edible parts .…”