Validation of smoke inhalation therapy to treat microbial infections

In traditional healing, the burning of selected indigenous medicinal plants and the inhalation of the liberated smoke are widely accepted and a practiced route of administration. This study elucidated the rationale behind this commonly practiced treatment by examining the antimicrobial activity for five indigenous South African medicinal plants commonly administered through inhalation (Artemisia afra, Heteropyxis natalensis, Myrothamnus flabellifolius, Pellaea calomelanos and Tarchonanthus camphoratus).

An apparatus was designed to simulate the burning process that occurs in a traditional setting and the smoke fraction was captured for analysis and bioassay. Methanol and acetone extracts as well as the essential oil (for the aromatic species) were prepared and assayed in parallel with the smoke fraction.

Antimicrobial data revealed that in most cases, the 'smoke-extract' obtained after burning had lower minimum inhibitory concentration (MIC) values than the corresponding solvent extracts and essential oils. The combustion, acetone and methanol extracts produced different chromatographic profiles as demonstrated for Pellaea calomelanos where several compounds noted in the smoke fraction were not present in the other extracts.

These results suggest that the combustion process produces an 'extract' with superior antimicrobial activity and provides in vitro evidence for inhalation of medicinal smoke as an efficient mode of administration in traditional healing.