Abstract:
Mycobacterium tuberculosis, the causative agent of tuberculosis (TB) has
infected approximately 1/3 of the world population, with 9.4 million new TB
cases in 2008. In addition to increased cases of drug-resistant strains it is
vital that novel antitubercular compounds are discovered in order to treat
infections and reduce the time of current TB therapy courses. Natural
resources such as plants are now being considered as the focus for
discovering new compounds. Plants have long been investigated as a
source of antibiotics for the treatment of human disease. New Zealand
(NZ) contains a unique and diverse flora; however, to current knowledge
no native plants have been examined for antimycobacterial activity. Using
ethnobotany as a basis for selection, a total of 58 native plant samples
were collected and tested for direct antimycobacterial activity. Samples
were extracted with sterile distilled water (SDW), ethanol (EtOH) or
methanol (MeOH) and screened for inhibition against the surrogate
species, Mycobacterium smegmatis. Active plant samples were then
validated for bacteriostatic activity towards M. bovis BCG and M.
tuberculosis H37Ra as well as other clinically-important species. Nine
extracts from the species Laurelia novae-zelandiae, Lophomyrtus bullata,
Metrosideros excelsa, Myoporum laetum, Pittosporum tenuifolium,
Pseudopanax crassifolius and Pseudowintera colorata were found to be
active against M. smegmatis. Two active extracts were the bark and
cambium extracts of Laurelia novae-zelandiae (Pukatea), which were
reportedly used by indigenous Māori for the treatment of tubercular
lesions. Upon further investigation these extracts also demonstrated bactericidal activity towards M. smegmatis as well as bacteriostatic activity
towards the slow-growing species M. bovis BCG and M. tuberculosis.
Purification techniques were then performed to improve the efficiency of
activity and initial exploration of delivery systems was also examined. The
bioactive extracts determined in this research offer a starting point for
identifying their chemical basis of antimycobacterial activity with the
objective of potentially discovering new anti-tubercular drugs.
