Activation of Leishmania (Leishmania) amazonensis arginase at low temperature by binuclear Mn2+ center formation of the immobilized enzyme on a Ni2+ resin

Isolation of arginase inhibitors from the bioactivity-guided fractionation of Byrsonima coccolobifolia leaves and stems

Byrsonima coccolobifolia leaf and stem extracts were studied in the search for possible leishmanicidal compounds using arginase (ARG) from Leishmania amazonensis as a molecular target. Flavonoids 1b, 1e-1g, 2a, 2b, and 2d-2f showed significant inhibitory activity, with IC50 values ranging from 0.9 to 4.8 μM. The kinetics of the most active compounds were determined. Flavonoids 1e, 1f, 2a, 2b, and 2e were characterized as noncompetitive inhibitors of ARG with dissociation constants (Ki) ranging from 0.24 to 3.8 μM, demonstrating strong affinity. Structure-activity relationship studies revealed some similarities in the structural features of flavonoids related to ARG activity.

Leishmanicidal activity of Cecropia pachystachya flavonoids: arginase inhibition and altered mitochondrial DNA arrangement

The plant Cecropia pachystachya Trécul is widely used in Brazilian ethnomedicine to treat hypertension, asthma, and diabetes. Arginase is an enzyme with levels that are elevated in these disorders, and it is central to Leishmania polyamine biosynthesis. The aims of this study were to evaluate antileishmanial activity and inhibition of the arginase enzyme by C. pachystachya extracts, and to study changes in cellular organization using electron microscopy. The ethanol extract of C. pachystachya was tested on Leishmania (Leishmania) amazonensis promastigote survival/proliferation and arginase activity in vitro. Qualitative ultrastructural analysis was also used to observe changes in cell organization. The major bioactive molecules of the ethanol extract were characterized using liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS). The ethyl acetate fraction of the ethanol extract diminished promastigote axenic growth/survival, inhibited arginase activity, and altered a mitochondrial kinetoplast DNA (K-DNA) array. The bioactive compounds of C. pachystachya were characterized as glucoside flavonoids. Orientin (9) (luteolin-8-C-glucoside) was the main component of the methanol-soluble ethyl acetate fraction obtained from the ethanol extract and is an arginase inhibitor (IC50 15.9 μM). The ethyl acetate fraction was not cytotoxic to splenocytes at a concentration of 200 μg/mL. In conclusion, C. pachystachya contains bioactive compounds that reduce the growth of L. (L.) amazonensis promastigotes, altering mitochondrial K-DNA arrangement and inhibiting arginase.