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Artemisia afra and Artemisia annua Extracts Have Bactericidal Activity against Mycobacterium tuberculosis

Bushra Hafeez Kiani

Bushra Hafeez Kiani †

Lead Researcher

With: Maria Natalia Alonso †, Pamela J. Weathers, and Scarlet S. Shell

Published in Pathogens, February 2023

Key Findings

  • Both Artemisia afra and Artemisia annua extracts show significant bactericidal activity against Mycobacterium tuberculosis (Mtb)
  • Efficacy is maintained across different carbon sources (glycerol, glucose, cholesterol)
  • Activity is preserved under hypoxic conditions similar to those in TB granulomas
  • Effectiveness is independent of artemisinin content

Abstract

Mycobacterium tuberculosis (Mtb) is a deadly pathogen and causative agent of human tuberculosis, causing ~1.5 million deaths every year. The increasing drug resistance of this pathogen necessitates novel and improved treatment strategies.

In this study, Artemisia annua and Artemisia afra dichloromethane extracts were tested for bactericidal activity against Mtb strain mc26230 under hypoxia and various infection-associated carbon sources (glycerol, glucose, and cholesterol). Both extracts showed significant bactericidal activity against Mtb, regardless of carbon source.

Based on killing curves, A. afra showed the most consistent bactericidal activity against Mtb for all tested carbon sources, whereas A. annua showed the highest bactericidal activity in 7H9 minimal media with glycerol. Both extracts retained their bactericidal activity against Mtb under hypoxic conditions.

Research Highlights

In Vitro Results

  • Both extracts showed bactericidal activity across all tested carbon sources
  • A. afra demonstrated more consistent activity across different conditions
  • Activity was maintained under hypoxic conditions similar to those in TB granulomas

Methodology

  • Dichloromethane (DCM) extracts of A. annua and A. afra leaves
  • Tested against Mtb strain mc26230
  • Hypoxic conditions achieved using the Wayne model
  • Multiple carbon sources tested: glycerol, glucose, cholesterol

Significance

This study is particularly significant because:

  1. It demonstrates activity under conditions that mimic the in vivo environment of TB infection
  2. The extracts remain effective against non-replicating Mtb, a major challenge in TB treatment
  3. The bactericidal activity is independent of artemisinin content, suggesting other active compounds are involved
  4. It provides a foundation for further research into plant-based TB treatments

Full Publication

This research was published in the journal Pathogens in February 2023. You can access the full paper through the link below:

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Citation

Kiani, B.H.; Alonso, M.N.; Weathers, P.J.; Shell, S.S. Artemisia afra and Artemisia annua Extracts Have Bactericidal Activity against Mycobacterium tuberculosis in Physiologically Relevant Carbon Sources and Hypoxia. Pathogens 2023, 12, 227. https://doi.org/10.3390/pathogens12020227

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