Physical and chemical properties and uses of tetracyclines

Tetracyclines (TCs) are a class of broad-spectrum antibiotics produced by actinomycetes.
They are named after the chemical structure of the tetracene nucleus.
They mainly include natural chlortetracycline (CTC) and tetracycline (tetracycline ).
, TC) and oxytetracycline (oxytetracycline, OTC), and semisynthetic doxycycline (doxycycline, DC), methacycline (metacycline, MTC), minocycline (minocyclne, MNC), norepinephrine chlortetracycline (demeclocycline, DMCT), meclocycline (meclocycline, MCC) and Raleigh PGI (rolitetracycline, RTC) and the like
.

TCs mainly inhibit bacterial protein synthesis and are widely used in the prevention and treatment of various bacteria and infectious diseases caused by rickettsiae, chlamydia, and mycoplasma

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1 Physical and chemical properties and uses

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1 Physical and chemical properties

The physical and chemical properties of commonly used TCs are shown in Table 12-1
.

Table 12-1 Physical and chemical properties of commonly used TCs

TCs is soluble in polar solvents such as acids, alkalis, alcohols , and has different solubility in n-butanol , acetone , acetonitrile and ethyl acetate .
It is slightly soluble in water but insoluble in saturated alkanes, ether and chloroform
.

These drugs are all amphoteric compounds, and all contain acidic phenolic hydroxyl group, enol hydroxyl group and basic dimethylamino group in the structure, with pKa values ​​of 2.

TCs are relatively stable under dry conditions, but can change color when exposed to light
.

It is not stable enough under acidic and alkaline conditions and is prone to hydrolysis

In acidic solutions (pH 2～6), TCs can undergo reversible epimerization, the ratio can reach 40%～60%, such as 4-epit-etracycline (4-epiTC), epichloromycin (4-epichlortetracycline, 4-epiCTC), Epioxytetracycline (4-epiOTC) and Epidoxycycline (4-epidoxycycline, 4-epiDC)
.

The pharmacological activity of the epimers of TCs is very low or not, and the toxic and side effects are increased

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2 Purpose

TCs are commonly used antibiotics in veterinary clinics, and their antibacterial effect is not strong.
They are broad-spectrum antibacterial agents
.

Bacteria that are sensitive to TCs include Streptococcus, Brucella, Haemophilus, Escherichia coli, Pasteurella, Salmonella, Bacillus anthracis, etc.

TCs mainly bind to the 30S small subunit, which interferes with the binding of the amino acid tRNA and the 30S small subunit, so that the aminoacyl tRNA cannot enter the receptor site on the mRNA and inhibits peptide chain elongation during protein synthesis
.

In addition, it can also prevent the release of synthesized protein peptide chains

In veterinary clinics, OTC is often used to treat intestinal infections with multiple pathogens
.

Its clinical applications include: ①Treatment of calf pullorum caused by Salmonella, chick pullorum and E.

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