Sutherlandia frutescens (Fabaceae) extracts used for treating tuberculosis do not have high activity against Mycobacterium smegmatis

Itumeleng H. Mabusa, Rachmond Howard, Peter Masoko

Abstract


Sutherlandia frutescens (L) R. Br. contains several essential, bioactive compounds with clinically proven pharmacological activities. Sutherlandia is prescribed for people with
tuberculosis but it is still not known what compounds in this plant act against Mycobacterium tuberculosis and its mode of action. This study is aimed at determining if S. frutescens extracts contain antimycobacterial
compounds. Aerial parts of S. frutescens were dried, ground and extracted with ethanol, dichloromethane: methanol 1:1 (v/v) and water. The chemical profiling was done using high-performance liquid chromatography-mass
spectroscopy (HPLC-MS) and thin layer chromatography (TLC). TLC plates were developed in butanol:acetic acid:water (BAW) to the ratio of 21:6:3; chloroform:methanol:water:formic acid (CMWF1) [60:15:2:1] and (CMWF2) [21:9:1:0.3]. Qualitative
antioxidant activity was done, using 2.2-diphenylpacryl-1-hydrazyl (DPPH). Antimycobacterial activity of the plant extracts was evaluated, using micro-dilution and bioautographic methods against Mycobacterium smegmatis.
Low antimycobacterial activity against M. smegmatis was observed on the bioautograms. The ethanol extracts contained more compounds compared to water extracts on HPLC-MS chromatographic profiles. The average Minimum
Inhibitory Concentration (MIC) values for all the extracts were 0.61 mg/mL units and the DCM:MeOH (1:1) extract had the lowest MIC value of 0.28 mg/mL. The results showed that the plant could be further explored for possible antimycobacterial
agents. Low activity was observed, possibly due to low replication of bacilli and non-replicating organisms. The study provides preliminary scientific validation of the traditional medicinal use of this plant. Further studies are required to
identify the bioactive compounds in the DCM:MeOH 1:1 extract which showed significant antimycobacterial activities.

 

Research correlation: This article is the original
version, of which an Afrikaans translation was made available to provide access to a larger readership, available here: https://doi.org/10.4102/satnt.v36i1.1494


Keywords


Sutherlandia frutescens; Mycobacterium tuberculosis; shikimate kinase; High Performance Liquid Chromatography- Mass Spectroscopy; Mycobacterium smegmatis

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