Zapoteca formosa: sulfur chemistry and phytotoxicity.

Chemical analysis of Zapoteca formosa extracts show that a variety of volatile sulfur-containing components, including cyclic polysulfides, are responsible for the distinctive odor of its germinating seeds and young plants. The major sulfur-containing compounds include acetyl djenkolic acid, djenkolic acid, taurine, cystine, benzothiazole, dimethyl disulfide, 2,4-dithiapentane, 2-hydroxyethylmethylsulfide, trithiane, 1,2,4-trithiolane, and 1,2,4,6-tetrathiepane. Decreased amounts of djenkolic acid in seedlings and young plants, as compared to the seed, indicate that this is likely the metabolic precursor of the volatile sulfur components. Germination and radicle elongation assays show that germinating seeds of Zapoteca and mixtures of volatile sulfur-containing compounds are highly phytotoxic to Cucumis sativa, Lactuca sativa, Lycopersicon esculentum, and Acacria farnesiana.