Abstract:
Background: Tuberculosis (TB) is implausibly still considered as one of the leading causes
of death, in the 21st century. Despite the curative treatments and measures of control in the
communities, TB plays a significant role in human infectious disease. Studies have shown that
there is an emergence of major drug-resistant TB.
Aim: This study was aimed at evaluating the biological activities of silver and gold
nanoparticles capped with selected medicinal plant extracts against Mycobacterium
tuberculosis.
Methodology: P. africanum and Z. mucronata barks and leaves were collected in the
Vhembe district of Limpopo. Plant phytochemical constituents were extracted using distilled
water and absolute methanol. The silver nanoparticles (AgNP) and gold nanoparticles (AuNP)
were capped using crude extracts through the process of green synthesis; and were
characterized by Ultraviolet-Visible spectrophotometry (UV-VIS), and transmission electron
microscopy (TEM). Metabolites present in the plant extracts were profiled using liquid
chromatography mass spectrometry (LC-MS). Cytotoxicity activity of plant extracts and
nanoparticles were determined by MTS assay on HEK293 cells. The anti-inflammatory activity
was determined through the nitric acid synthase (NOS) inhibitory test. The antimycobacterial
activity was determined using microbroth dilution.
Results: Following extraction by maceration, methanol was able to yield more extracts
compared to distilled water due to their differences in polarity. The selected plants were found
to contain numerous antioxidant significant for anti-inflammatory and cytotoxic activity. The
metabolites play a role in the formation of the nanoparticles. Plant extracts and gold
nanoparticles had little impact on the cell lines, thus were concluded to be non-toxic. Whilst
silver nanoparticles exhibited toxic activity on the cell line at both concentrations, hence were
considered toxic to human. Silver nanoparticles of ZML and ZHL, and gold nanoparticles and
plant extracts of PML exhibited anti-inflammatory activity at 100 μg/mL, whereas PML was
able to decrease nitrite concentration at both concentrations.
Conclusion: Adoption of TB strategies recommended by World Health Organization (WHO)
to reduce TB deaths and incidence rate by 90% and 80%, respectively, (less than 20 TB cases
per 100 000 population).
