The reactions that tetracyclines undergo are generally of a sophisticated nature, dictated by the complex functionality and the sensitivity of the molecules to mild reaction conditions (acid, base, heat) .
When exposed to dilute acid conditions, tetracycline undergoes dehydration to yield anhydrotetracycline. Anhydroterramycin suffers further cleavage and lactonization to apoterramycin:
Diluted acid promotes epimerization at C-4 as well.
Mild alkali attacks 11a carbon of tetracycline, which is transformed to isotetracycline:
Formation of complexes
Tetracycline possesses a great tendency to form complexes with a number of chemical species, due to its B- and C-ring oxygen atoms:
It complexes most readily with Fe3+, Fe2+, Cu2+, Ni2+, Co2+, Zn2+, Mn2+, Mg2+, Ca2+, Be2+, Al3+ among metal ions, phosphates, citrates, salicylates, p-hydroxybenzoates, saccharin anion, caffiene, urea, thiourea, polivinylpyrrolidone, serum albumin, lipoproteins, globulins, and RNA .