Abstract
The in vitro activity of
L. donovani
(promastigotes, axenic amastigotes and intracellular amastigotes in THP1 cells) and
T. brucei
, from the fractions obtained from the hydroalcoholic extract of the aerial part of
Hypericum afrum
and the isolated compounds, has been evaluated. The chloroform, ethyl acetate and
n
-butanol extracts showed significant antitrypanosomal activity towards
T. brucei
, with IC
50
values of 12.35, 13.53 and 12.93 µg/mL and with IC
90
values of 14.94, 19.31 and 18.67 µg/mL, respectively. The phytochemical investigation of the fractions led to the isolation and identification of quercetin (
1
), myricitrin (
2
), biapigenin (
3
), myricetin (
4
), hyperoside (
5
), myricetin-3-
O
-β-
d
-galactopyranoside (
6
) and myricetin-3’-
O
-β-
d
-glucopyranoside (
7
). Myricetin-3’-
O
-β-
d
-glucopyranoside (
7
) has been isolated for the first time from this genus. The chemical structures were elucidated by using comprehensive one- and two-dimensional nuclear magnetic resonance (1D and 2D NMR) spectroscopic data, as well as high-resolution electrospray ionization mass spectrometry (HR-ESI–MS). These compounds have also been evaluated for their antiprotozoal activity. Quercetin (
1
) and myricetin (
4
) showed noteworthy activity against
T. brucei
, with IC
50
and IC
90
values of 7.52 and 5.71 µM, and 9.76 and 7.97 µM, respectively. The
T. brucei
hexokinase (TbHK1) enzyme was further explored as a potential target of quercetin and myricetin, using molecular modeling studies. This proposed mechanism assists in the exploration of new candidates for novel antitrypanosomal drugs.