Abstract:
AIM: This study aimed to investigate the antimycobacterial activity of total alkaloid and ethanolic aqueous extracts of Rauvolfia vomitoria
and R. caffra. It further aimed to evaluate antioxidant activity and cytotoxicity effect of the extracts which would have shown high
antimycobacterial efficacy.
METHODS: The alkaloids from the roots of two plant species were extracted according to standard procedures. Antimycobacterial activity
of the extracts was evaluated using a two fold microdilution method. The antioxidant activity of the alkaloids and ethanolic extracts was determined
using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and reducing capacity assays. The potential cytotoxicity of the extracts was evaluated
using brine shrimp toxicity assay. Comparison of alkaloidal composition of the two alkaloidal extracts was done using HPLC analysis.
RESULTS: The study revealed that, alkaloid extracts from the roots of Rauvolfia species had higher antimycobacterial activity against
Mycobacterium madagascariense (MM) and M. indicus pranii (MIP). The minimum inhibition concentration (MIC) values of alkaloid
extracts ranged between 0.078 to 1.25 mg/ml, while the ethanolic extracts were generally moderately active against test organism. The
alkaloids and ethanolic aqueous extracts of R. vomitoria exhibited high antioxidant activity. In the cytotoxicity assay, extracts did not exhibit
any toxicity against brine shrimps.
CONCLUSION: The alkaloids from the roots of R. vomitoria have high antimycobacterial and antioxidant activity. The alkaloids ability to
inhibit the growth of two Mycobacterium strains may be associated to its antioxidant activity. The cytotoxicity of the most active extract is
negligible when compared to the standard anticancer drug, this may explain why R. vomitoria is highly used in the treatment of various
infectious and physiological ailments.
