Anti-Leishmania activity of condensed tannins isolated from Mimosa tenuiflora and β-1,3-1,6 glucan isolated from commercial nutraceuticals

This study evaluated the anti-Leishmania activity of condensed tannins from Mimosa tenuiflora and β -glucan (1,3 − 1,6) from commercial nutraceuticals to identify less toxic alternatives against leishmaniasis, a neglected disease affecting millions in tropical and subtropical regions. Current treatments rely on toxic drugs, motivating research on natural compounds with leishmanicidal activity. M. tenuiflora is known for antimicrobial, antioxidant, and anti-inflammatory properties, while β-glucans are immunomodulatory polysaccharides capable of activating macrophages and enhancing pathogen control. Condensed tannins showed activity against promastigotes (IC₅₀ = 24.56 µg/mL) but were ineffective against intracellular amastigotes, suggesting action on extracellular structures, possibly via membrane destabilization, nucleic acid alteration, or enzyme inhibition. β-glucan did not affect promastigotes but significantly reduced internalized amastigotes (IC₅₀ = 17.94 µg/mL). Cytotoxicity was low for both compounds (CC₅₀ >1,000 µg/mL), resulting in high selectivity indices: >40 for tannins (promastigotes) and > 55 for β-glucan (amastigotes).The anti-amastigote activity of β-glucan appears linked to immunomodulation via receptors such as Dectin-1 and TLR2 on macrophages, stimulating reactive oxygen species and proinflammatory cytokines production, which control intracellular parasites.In conclusion, condensed tannins demonstrated limited potential, acting only on promastigotes, while β-glucan was effective against amastigotes, the pathogenic form of leishmaniasis, with excellent cytotoxic safety. β-glucan (1,3–1,6) emerges as a promising candidate for novel therapeutic strategies, warranting further investigation of its immunological mechanisms and in vivo efficacy.