Characterization of products formed by the reaction of ¹⁴C-sulphamethazinediazonium tetrafluoroborate with natural products

Abstract

1. When bovine serum albumin (BSA) was incubated with 4-[N-(4,6-dimethyl-2-pyrimidinyl)sulphonamido][U-¹⁴C]benzenediazonium tetrafluoroborate (¹⁴C-SDTFB) in vitro approx. half of the ¹⁴C-activity was bound (¹⁴C-BSA). Cysteine, N-ethylmaleimide, p-chloromercuribenzoate and iodoacetamide inhibited the formation of ¹⁴C-BSA.

2. When SDTFB was reacted with cysteine four major products were formed. These were identified as 3-{4-[N-(4,6-dimethyl-2-pyrimidinyl) benezenesulphonamido]thio}-2-aminopropionic acid (cys-SDAS), 3-{4-[4,6-dimethyl-2-pyrimidinyl) benzenesulphonamido]thio}-2-aminopropionic acid (cys-Sulmet), 4-hydroxy-N-(4,6-dimethyl-2-pyrimidinyl)benzenesulphonamide (hydroxy-Sulmet) and N-(4,6-dimethyl-2-pyrimidinyl)benzenesulphonamide (desamino-Sulmet). Diazosulphides were also formed when SDTFB was incubated with thiophenol and glutathione.

3. The diazosulphides reacted with N,N-dimethylaniline (DMA) and 2-naphthol to yield diazo compounds in 22-29% yield; when ¹⁴C-BSA was reacted with DMA under the same conditions, a diazo compound was formed—but only in 2% yield.

4. Cys-SDAS when incubated overnight (approx. 16 h) in aqueous solutions (pH 3, 5 and 8) decomposed to yield desamino-Sulmet (30-39%), hydroxy-Sulmet (13-21%), and other unidentified soluble products (24-36%); when ¹⁴C-BSA was incubated under the same conditions only 3-4% of the ¹⁴C became dissociated from BSA and only a trace amount of desamino-Sulmet was formed.

5. When ¹⁴C-SDTFB was incubated with calf thymus DNA at pH 3, some of the ¹⁴C became associated with the DNA (¹⁴C-DNA). However, most of the ¹⁴C became dissociated from ¹⁴C-DNA when the latter was incubated overnight in aqueous solutions: a minor dissociation product was identified as ¹⁴C-desamino-Sulmet.