Physical and chemical properties and uses of macrolides and lincosamide drugs

6.
1.
1.
1 Physical and chemical properties

(1) Macrolides

The structural feature of MALs is that it contains a highly substituted fourteen- or sixteen-membered lactone ring glycoside.
The lactone ring is connected to one or two sugar chains (methylamino sugar or neutral sugar) through a glycoside bond
.

Linked glycosides are generally rare in nature, mainly including L-cladinose, D-desosamine, L-mycinose, and L-mycarose , D-mycaminose (D-mycaminose) and other types

MALs are colorless and weakly basic compounds (Sedicamycin is neutral), with high molecular weight (500-900), and mostly negative optical rotation
.

Determined by its overall structure, MALs is easily soluble in organic solvents with fixed polarity, such as methanol , acetonitrile , ethyl acetate , chloroform , ether, etc.

MALs are quite stable in the dry state, but their aqueous solutions have poor stability
.

Under acidic conditions (pH<4), glycoside bonds are prone to hydrolysis, and the structure of aminoglycosides is much more stable than neutral glycosides.

Table 6-1 Physical and chemical properties of MALs

(2) Lincosamides

Lin lincomycin hydrochloride salt as a white crystalline powder, slight odor or special smell, bitter taste, soluble in water or methanol, slightly soluble in ethanol
.

The pH of 20% aqueous solution is 3.

Clindamycin hydrochloride is white or off-white crystal powder, which is easily soluble in water
.

6.
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1.
2 Purpose

(1) Macrolides

MALs are medium-spectrum antibiotics, which have outstanding antibacterial activity against Gram-positive bacteria and Mycoplasma, and are also effective against Spirochetes, Rickettsia and Mycoplasma
.

Among them, ERM has the strongest effect on gram-positive bacteria; TYL has strong effect on mycoplasma.

The antibacterial mechanism of MALs is to interfere with the synthesis of bacterial protein
.

MALs bind to the 50s subunit of the ribosome of sensitive bacteria to inhibit the catalysis of transpeptidase and hinder the generation and extension of peptide chains

Compared with other antibacterial drugs, MALs is very effective against respiratory infections caused by general bacteria.
It has antibacterial activity against penicillin-resistant gram-positive bacteria, and penicillin-resistant Staphylococcus aureus has strong antibacterial activity.
Campylobacter, Helicobacter pylori, and Mycobacterium avium also have strong antibacterial activity
.

Clinically, it is mainly used to treat respiratory tract, digestive tract and urogenital infections caused by sensitive bacteria, such as pneumonia, bacterial enteritis, postpartum infection, mastitis, etc.

(2) Lincosamides

The antibacterial spectrum of Lincosamide drugs is similar to that of macrolides.
It has a strong antibacterial effect on Gram-positive bacteria such as Staphylococcus, Streptococcus hemolyticus and Pneumococcus.
Bacillus and mycoplasma (pigs, chickens) also have inhibitory effects, but they are not effective against Gram-negative bacteria
.

Among them, the combined use of lincomycin and spectinomycin is more effective against mycoplasmosis or colibacillosis than a single drug