Antituberculosis activity of alkylated mulinane diterpenoids

Area of Science:

• Natural product chemistry
• Medicinal chemistry
• Microbiology

Background:

• Azorellane and mulinane diterpenoids possess inherent antituberculosis properties.
• Methylation of the carboxyl group in these diterpenoids has been shown to increase their efficacy.

Purpose of the Study:

• To systematically investigate the impact of alkylation on the bioactivity of azorellane and mulinane diterpenoids.
• To identify specific semisynthetic derivatives with enhanced antituberculosis activity.

Main Methods:

• Systematic alkylation of natural diterpenoids.
• Evaluation of antituberculosis activity using minimum inhibitory concentration (MIC) assays.
• Testing against a drug-resistant strain of Mycobacterium tuberculosis.

Main Results:

• The introduction of short alkyl groups (linear and branched) had a minimal effect on the bioactivity profile.
• Three semisynthetic diterpenoids, including 13-hydroxy-mulin-11-en-20-oic acid n-propyl ester and the n-propyl and n-butyl esters of isomulinic acid, demonstrated significant antituberculosis activity.
• An MIC of 6.25 microg/mL was recorded for these potent derivatives against a drug-resistant Mycobacterium tuberculosis strain.

Conclusions:

• Alkylation, particularly esterification, can yield potent antituberculosis agents from natural diterpenoids.
• Specific semisynthetic diterpenoid esters show promise for combating drug-resistant tuberculosis.