Artemisia annuaandArtemisia afraextracts exhibit strong bactericidal activity againstMycobacterium tuberculosis

Abstract

ABSTRACTEthnopharmacological relevanceEmergence of drug-resistant and multidrug-resistantMycobacterium tuberculosis(Mtb) strains is a major barrier to tuberculosis (TB) eradication, as it leads to longer treatment regimens and in many cases treatment failure. Thus, there is an urgent need to explore new TB drugs and combinations, in order to shorten TB treatment and improve outcomes. Here, we evaluate the potential of two medicinal plants,Artemisia annua, a natural source of artemisinin (AN), andArtemisia afra, as sources of novel antitubercular agents.Aim of the studyOur goal was to measure the activity ofA. annuaandA. afraextracts against Mtb as potential natural and inexpensive therapies for TB treatment, or as sources of compounds that could be further developed into effective treatments.Materials and MethodsThe minimum inhibitory concentrations (MICs) ofA. annuaandA. afradichloromethane extracts were determined, and concentrations above the MICs were used to evaluate their ability to kill Mtb andMycobacterium abscessus in vitro.ResultsPrevious studies showed thatA. annuaandA. afrainhibit Mtb growth. Here, we show for the first time thatArtemisiaextracts have a strong bactericidal activity against Mtb. The killing effect ofA. annuawas much stronger than equivalent concentrations of pure AN, suggesting thatA. annuaextracts kill Mtb through a combination of AN and additional compounds.A. afra, which produces very little AN, displayed bactericidal activity against Mtb that was substantial but weaker than that ofA. annua. In addition, we measured the activity ofArtemisiaextracts againstMycobacterium abscessus. Interestingly, we observed that whileA. annuais not bactericidal, it inhibits growth ofM. abscessus, highlighting the potential of this plant in combinatory therapies to treatM. abscessusinfections.ConclusionOur results indicate thatArtemisiaextracts have an enormous potential for treatment of TB andM. abscessusinfections, and that these plants contain bactericidal compounds in addition to AN. Combination of extracts with existing antibiotics may not only improve treatment outcomes but also reduce the emergence of resistance to other drugs.