Spectrophotometric determination of acidity constants of 4- dedimethylamino sancycline (Col-3), a new antitumor drug

Sirirat Pinsuwan, Fernando A. Alvarez-Núñez, S. Esmail Tabibi, S. H. Yalkowsky

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A spectrophotometric technique was used to determine the acidity constants of 4-dedimethylamino sancycline (Col-3), a new antitumor drug. The apparent pK(a) values of Col-3 in 0.5% methanol aqueous media at approximately 25 °C with a constant ionic strength of 0.2 were calculated manually and graphically to be 5.64 ± 0.17 (pK(a1)) and 8.35 ± 0.07 (pK(a2)). In addition, the computer program SQUAD was used to confirm Col-3 pK(a) values. The pK(a) values obtained by SQUAD were pK(a1) 5.63 ± 0.14 and pK(a2) 8.39 ± 0.04. These results are in agreement with the tetracycline- like structure of Col-3.

Original languageEnglish (US)
Pages (from-to)535-537
Number of pages3
JournalJournal of pharmaceutical sciences
Issue number5
StatePublished - May 1999


ASJC Scopus subject areas

  • Pharmaceutical Science

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