Evaluation of anti-leishmanial and antibacterial activity of Waldheimia tomentosa (Asteraceae), and chemical profiling of the most bioactive fraction
Purpose: To evaluate the anti-leishmanial and antibacterial activities of a relatively unexplored whole plant of Waldheimia tomentosa (Asteraceae) and the chemical profiling of its most bioactive fraction.
Methods: The whole plant material was extracted with methanol - water (9 : 1) and fractionated into nhexane (C6H14 or n-Hex), dichloromethane (CH2Cl2 or DCM), ethyl acetate (C4H8O2 or EtOAc) fractions and aqueous residue. The fractions were screened for leishmanicidal activity against promastigotes and intracellular amastigotes of L. donovani, while antibacterial activity was evaluated against four multidrug resistant (MDR) clinical isolates by bioassay guided fractionation. Scanning Electron Microscopy (SEM) performed on S. aureus at the minimum inhibitory concentration (MIC). Chemical profiling of the most bioactive fraction was performed using gas chromatography-mass spectrometry (GC-MS).
Results: The most significant leishmanicidal activity was exhibited by n-Hex fraction against promastigotes (DD8 strain) with half maximal inhibitory concentration (IC50 of 89.85 ± 0.84 μg/mL) and intracellular amastigotes (IC50 of 48.3 ± 0.40 μg/mL). The same fraction also exhibited maximum potency against S. aureus and E.coli at MIC of between 62.5 and 125 μg/mL. The fraction comprised mainly fatty acids and alkyl ketones. SEM examination performed on S. aureus at MIC revealed swelling and multiple blisters on cell surface compared to untreated control.
Conclusion: The profound antibacterial activity of Waldheimia tomentosa justifies the use of the plant in traditional medicine for stomach ache and food preservation.
Keywords: Waldheimia tomentosa, Antibacterial activity, Leishmanicidal activity, Stomach ache, Food preservation