Singlet Oxygen Produced by Aspalathin and Ascorbic Acid Leads to Fragmentation of Dihydrochalcones and Adduct Formation.

Singlet oxygen-mediated fragmentation of various dihydrochalcones and chalcones was reported. (Dihydro)cinnamic acids formed in the fragmentation showed a B-ring substitution pattern of the precursor (dihydro)chalcone. For the first time, the intrinsic generation of singlet oxygen by aspalathin and ascorbic acid under mild aqueous conditions (37 °C, pH 7.

Benzothiazines as Major Intermediates in Enzymatic Browning Reactions of Catechin and Cysteine.

The course of melanin formation is yet not thoroughly resolved on a mechanistic level. With the present study, incubations of catechin (CA)- and cysteine-derived dihydro-1,4-benzothiazine carboxylic acid derivatives were investigated for colored products during enzymatic browning. Analyses by high-performance liquid chromatography (HPLC)-mass spectrometry revealed the formation of two novel decarboxylated dihydro-1,4-benzothiazine derivatives [8-(3,5,7-trihydroxy-3,4-dihydro-2-chromen-2-yl)-5-hydroxy-3,4-dihydro-2-benzothiazine and 7-(3,5,7-trihydroxy-3,4-dihydro-2-chromen-2-yl)-5-hydroxy-3,4-dihydro-2-benzothiazine] preferentially under acidic conditions.

Abiotic transformation products of tetracycline and chlortetracycline in salt solutions and manure.

Tetracyclines belong to the group of the most applied antibiotics in veterinary medicine worldwide. Due to their incomplete absorption and/or metabolism in the animal gut, tetracyclines are frequently detected in manure samples. Within the matrix, an elimination of these compounds has been reported in several studies.