Conversion of aristolochic acid I into aristolic acid by reaction with cysteine and glutathione: biological implications

Photochemical synthesis of 3-hydroxyphenanthro[9,10-c]furan-1(3H)-ones from α-keto acids and alkynes

A novel and efficient method for the synthesis of 3-hydroxyphenanthro[9,10-c]furan-1(3H)-ones has been achieved from α-keto acids and alkynes through photo-initiated transformation, providing a range of products in good to excellent yields.

Aristolochic Acids: Newly Identified Exposure Pathways of this Class of Environmental and Food-Borne Contaminants and its Potential Link to Chronic Kidney Diseases

Aristolochic acids (AAs) are nitrophenanthrene carboxylic acids naturally produced by Aristolochia plants. These plants were widely used to prepare herbal remedies until AAs were observed to be highly nephrotoxic and carcinogenic to humans. Although the use of AA-containing Aristolochia plants in herbal medicine is prohibited in countries worldwide, emerging evidence nevertheless has indicated that AAs are the causative agents of Balkan endemic nephropathy (BEN), an environmentally derived disease threatening numerous residents of rural farming villages along the Danube River in countries of the Balkan Peninsula. This perspective updates recent findings on the identification of AAs in food as a result of the root uptake of free AAs released from the decayed seeds of Aristolochia clematitis L., in combination with their presence and fate in the environment. The potential link between AAs and the high prevalence of chronic kidney diseases in China is also discussed.

Cooking methods employing natural anti-oxidant food additives effectively reduced concentration of nephrotoxic and carcinogenic aristolochic acids in contaminated food grains

Emerging evidence suggests that aristolochic acids (AA) produced naturally by a common weed Aristolochia clematitis in the cultivation fields is contaminating the food products in Balkan Peninsula and acting as the etiological agent in the development of Balkan endemic nephropathy. In this study, we investigated the combined use of natural anti-oxidative "food additives" and different cooking methods to find a solution for the widespread contamination of AA in food products. The results indicated that the addition of healthy dietary supplements (such as cysteine, glutathione, ascorbic acid, citric acid and magnesium) during cooking, is a highly efficient method in lowering the concentration of AA in the final food products. Because previous observation indicated one of the toxicological mechanisms by which AA exert its toxicity is to induce oxidative stress in internal organs, it is anticipated that these added anti-oxidants will also help to attenuate the nephrotoxicity of AA.

Quantitation of Aristolochic Acids in Corn, Wheat Grain, and Soil Samples Collected in Serbia: Identifying a Novel Exposure Pathway in the Etiology of Balkan Endemic Nephropathy

While to date investigations provided convincing evidence on the role of aristolochic acids (AAs) in the etiology of Balkan endemic nephropathy (BEN) and upper urothelial cancer (UUC), the exposure pathways by which AAs enter human bodies to cause BEN and UUC remain obscure. The goal of this study is to test the hypothesis that environmental pollution by AAs and root uptake of AAs in the polluted soil may be one of the pathways by which AAs enter the human food chain. The hypothesis driving this study was that the decay of Aristolochia clematitis L., a AA-containing herbaceous plant that is found growing widespread in the endemic regions, could release free AAs to the soil, which could be taken up by food crops growing nearby, thereby transferring this potent human nephrotoxin and carcinogen into their edible parts. Using the highly sensitive and selective high-performance liquid chromatography coupled with fluorescence detection method, we identified and quantitated in this study for the first time AAs in corn, wheat grain, and soil samples collected from the endemic village Kutles in Serbia. Our results provide the first direct evidence that food crops and soil in the Balkans are contaminated with AAs. It is possible that the presence of AAs in edible parts of crops originating from the AA-contaminated soil could be one of the major pathways by which humans become exposed to AAs.

Determination of aristolochic acids by high-performance liquid chromatography with fluorescence detection

Nephrotoxic and carcinogenic aristolochic acids (AAs) are naturally occurring nitrophenanthrene carboxylic acids in the herbal genus Aristolochia. The misuse of AA-containing herbs in preparing slimming drugs has caused hundred of cases of kidney disease in Belgium women in a slimming regime in the early 1990s. Accumulating evidence also suggested that prolong dietary intake of AA-contaminated food is one of the major causes to the Balkan endemic nephropathy that was first observed in the late 1950s. Therefore, analytical methods of high sensitivity are extremely important for safeguarding human exposure to AA-containing herbal medicines, herbal remedies, and food composites. In this paper, we describe the development of a new high-performance liquid chromatography coupled fluorescence detector (HPLC-FLD) method for the sensitive determination of AAs. The method makes use of a novel cysteine-induced denitration reaction that "turns on" the fluorescence of AAs for fluorometric detections. Our results showed that the combination of cysteine-induced denitration and HPLC-FLD analysis allows for sensitive quantification of AA-I and AA-II at detection limits of 27.1 and 25.4 ng/g, respectively. The method was validated and has been successfully applied in quantifying AAs in Chinese herbal medicines.