Sonoran propolis and some of its chemical constituents inhibit in vitro growth of Giardia lamblia trophozoites.

Propolis is a cereus resin with a complex chemical composition that possesses a wide range of biological activities. The aim of this study was to evaluate the in vitro anti- Giardia lamblia activity of Sonoran propolis collected from three different areas of Sonoran Desert in northwestern Mexico (Caborca, Pueblo de Alamos, and Ures) and some of its chemical constituents. Additionally, we also analyzed the seasonal effect on the anti- G. lamblia activity of propolis. G. lamblia trophozoite cultures were treated with different concentrations of Sonoran propolis or chemical compounds during 48 h cell proliferation and cell viability were determined. Ures propolis showed the highest inhibitory activity against G. lamblia (IC 50 63.8 ± 7.1 µg/mL) in a dose-dependent manner (Ures > Pueblo de Alamos > Caborca). Season had a significant effect on the in vitro anti- G. lamblia activity of Ures propolis. Summer propolis showed the highest inhibitory effect on the G. lamblia trophozoite growth (IC 50 23.8 ± 2.3 µg/mL), followed by propolis collected during winter (IC 50 59.2 ± 34.7 µg/mL), spring (IC 50 102.5 ± 15.3 µg/mL), and autumn (IC 50 125.0 ± 3.1 µg/mL). Caffeic acid phenethyl ester, an Ures propolis exclusive constituent, had the highest growth-inhibitory activity towards G. lamblia [IC 50 63.1 ± 0.9 µg/mL (222.1 ± 3.2 µM)]. To our knowledge, this is the first study showing that caffeic acid phenethyl ester possesses antiparasitic activity against G. lamblia . Naringenin [IC 50 125.7 ± 20.7 µg/mL (461.8 ± 76.3 µM)], hesperetin [IC 50 149.6 ± 24.8 µg/mL (494.9 ± 82.2 µM)], and pinocembrin [IC 50 174.4 ± 26.0 µg/mL (680.6 ± 101.7 µM)] showed weak anti- G. lamblia activity. On the other hand, chrysin and rutin did not show significant antiparasitic activity. In conclusion, our results suggest that Sonoran propolis and some of its chemical constituents had inhibitory effects on the in vitro growth of G. lamblia trophozoites.