Chloramphenicol has two chiral carbon atoms in the acylamidopropanediol chain.

In chloroamphenical 2 (TWO) CHIRAL carbons

Dear Aspirant,

TWO

Chemically, chloramphenicol is a simple structure (Fig. 45.12) consisting of a nitrobenzene ring bound with non-ionic chlorine. It consists of two rare components— one nitro (-NO2) group and one dichloroacetyl (-COCHCl2) group. The molecule has two asymmetric carbon atoms (marked with an asterisk in the figure). As a consequence, four optical chloramphenicol isomers are possible. Of these isomers, only the D-) (threo isomer is antibioticly active.

Chloramphenicol is bacteriostatic and a broad-spectrum antibiotic active against both gram-positive and gram-negative bacteria, including rickettsia (rock-mountain fever) and chlamydia. It is also found to be effective against Haemophilus influenzae causing meningitis.

Chloramphenicol, as has been described, has a wide range of action, but it is unfortunately very toxic and causes serious side effects. The most common side effect is temporary or permanent bone marrow depression, which results in the cessation of the production of blood cells.

This antibiotic was found to inhibit the introduction of haemoglobin into the blood cells, contributing to aplastic anaemia. It also causes thrombocytopenia and leukopenia (depletion of platelets and leukocytes). Other side effects include allergic reactions or neurotoxic reactions. Therefore, chloramphenicol is generally used only in life-threatening situations where other suitable medications are ineffective.

Chloramphenicol, like many other antibiotics, such as streptomycin, gentamicin, tetracycline, erythromycin, etc., inhibits protein synthesis. This binds to the 23S rRNA of the 50S subunit of bacterial ribosome and inhibits the action of the enzyme peptidyl transferase. Peptidyl transferase transfers the growing polypeptide from the peptidyl tRNA to the amino acid bound to the amino acid tRNA resulting in the formation of a peptide bond and therefore lenthens the polypeptide by one amino acid remaining.

Hope this helps. All the best!