What carcinogenic acid is found in birthworts of the genus Aristolochia?

The carcinogenic acid found in birthworts of the genus Aristolochia is aristolochic acid.

Aristolochic acid is actually a family of related plant chemicals, commonly abbreviated AAs. Aristolochia species, known as birthworts or pipevines, are important natural sources, and aristolochic acid I is generally described as the most abundant member. These compounds are carcinogenic, mutagenic, and strongly nephrotoxic.

After exposure, aristolochic acids can form persistent DNA adducts and characteristic mutations. They are associated with aristolochic acid nephropathy, a progressive kidney disease that may lead to kidney failure and cancers of the urinary tract. The danger became widely recognized after cases linked to contaminated or incorrectly identified herbal weight-loss products in Belgium in the early 1990s.

A common mix-up is treating “aristolochic acid” as the name of one harmless botanical acid, like salicylic acid. Here it refers to a toxic chemical family associated with Aristolochia and some related plants, including Asarum.