Isolation of Arginase Inhibitors from the Bioactivity-Guided Fractionation of <i>Byrsonima coccolobifolia</i> Leaves and Stems

<i>Byrsonima coccolobifolia</i> leaf and stem extracts were studied in the search for possible leishmanicidal compounds using arginase (ARG) from <i>Leishmania amazonensis</i> as a molecular target. Flavonoids <b>1b</b>, <b>1e</b>–<b>1g</b>, <b>2a</b>, <b>2b</b>, and <b>2d</b>–<b>2f</b> 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 <b>1e</b>, <b>1f</b>, <b>2a</b>, <b>2b</b>, and <b>2e</b> were characterized as noncompetitive inhibitors of ARG with dissociation constants (<i>K</i>_i) 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