Isolation of bioactive compounds from medicinal plants used in traditional medicine: Rautandiol B, a potential lead compound against Plasmodium falciparum.

Background: Neorautanenia mitis, Hydnora abyssinica, and Senna surattensis are medicinal plants with a variety of traditional uses. In this study, we sought to isolate the bioactive compounds responsible for some of these activities, and to uncover their other potential medicinal properties.

Methods: The DCM and ethanol extracts of the roots of N. mitis and H. abyssinica, and the leaves of S. surattensis were prepared and their phytochemical components were isolated and purified using chromatographic methods. These extracts and their pure phytochemical components were evaluated in in-vitro models for their inhibitory activities against Plasmodium falciparum, Trypanosoma brucei rhodesiense, Mycobacterium tuberculosis, α-amylase (AA), and α-glucosidase (AG).

Results: Rautandiol B had significant inhibitory activities against two strains of Plasmodium falciparum showing a high safety ratio (SR) and IC values of 0.40 ± 0.07 μM (SR - 108) and 0.74 ± 0.29 μM (SR - 133) against TM4/8.2 and K1CB1, respectively. While (-)-2-isopentenyl-3-hydroxy-8-9-methylenedioxypterocarpan showed the highest inhibitory activity against T. brucei rhodesiense with an IC value of 4.87 ± 0.49 μM (SR > 5.83). All crude extracts showed inhibitory activities against AA and AG, with three of the most active phytochemical components; rautandiol A, catechin, and dolineon, having only modest activities against AG with IC values of 0.28 mM, 0.36 mM and 0.66 mM, respectively.

Conclusion: These studies have led to the identification of lead compounds with potential for future drug development, including Rautandiol B, as a potential lead compound against Plasmodium falciparum. The relatively higher inhibitory activities of the crude extracts against AG and AA over their isolated components could be due to the synergistic effects between their phytochemical components. These crude extracts could potentially serve as alternative inhibitors of AG and AA and as therapeutics for diabetes.