Quercetin (Que) and its derivatives are naturally occurring phytochemicals with promising bioactive effects. The antidiabetic, anti-inflammatory, antioxidant, antimicrobial, anti-Alzheimer’s, antiarthritic, cardiovascular, and wound-healing effects of Que have been extensively investigated, as well as its anticancer activity against different cancer cell lines has been recently reported. Que and its derivatives are found predominantly in the Western diet, and people might benefit from their protective effect just by taking them via diets or as a food supplement. Bioavailability-related drug-delivery systems of Que have also been markedly exploited, and Que nanoparticles appear as a promising platform to enhance their bioavailability. The present review aims to provide a brief overview of the therapeutic effects, new insights, and upcoming perspectives of Que.

Background: Leishmaniasis is a zoonotic disease caused by protozoan parasites from Leishmania genus. Currently, there are no effective vaccines available and the available therapies are far from ideal. In particular, the development of new therapeutic strategies to reduce the infection caused by Leishmania amazonensis could be considered desirable. Different plant-derived products have demonstrated antileishmanial activity, including the essential oil (EO) from Artemisia absinthium L. (EO-Aa), Asteraceae. Methods: In the present study, the EO-Aa formulated in nanocochleates (EO-Aa-NC) was investigated in vitro against intracellular amastigotes of L. amazonensis and non-infected macrophages from BALB/c mice. In addition, the EO-Aa-NC was also evaluated in vivo against on experimental cutaneous leishmaniasis, which body weight, lesion progression, and parasite load were determined. Results: EO-Aa-NC displayed IC50 values of 21.5 ± 2.5 μg/mL and 27.7 ± 5.6 μg/mL against intracellular amastigotes of L. amazonensis and non-infected peritoneal macrophage, respectively. In the animal model, the EO-Aa-NC (30 mg/kg/intralesional route/every 4 days 4 times) showed no deaths or weight loss greater than 10%. In parallel, the EO-Aa-NC suppressed the infection in the murine model by approximately 50%, which was statistically superior (p < 0.05) than controls and mice treated with EO-Aa. In comparison with Glucantime®, EO-Aa-NC inhibited the progression of infection as efficiently (p > 0.05) as administration of the reference drug. Conclusions: Encochleation of EO-Aa resulted in a stable, tolerable, and efficacious antileishmanial formulation, facilitating systemic delivery of EO, with increased activity compared to administration of the free EO-Aa. This new formulation shows promising potential to future studies aimed at a new therapeutic strategy to treat leishmaniasis.

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Current antileishmanial drugs are toxic, expensive, and resistance to them has emerged. Several studies have focused on natural products as alternatives. In the present work, the chemical composition, in vitro antileishmanial activity, cytotoxicity effects, and the influence on mitochondrial function of the essential oil from Tagetes lucida Cav. was determined, as well its main compound estragole. Forty-nine compounds were detected in the oil by gas chromatography-mass spectrometry (GC-MS), of which estragole was the main constituent (97%). The oil showed inhibition of the promastigotes of L. tarentolae and L. amazonensis (IC50 = 61.4 and 118.8 µg/mL, respectively), decreased oxygen consumption of L. tarentolae, disrupted mitochondrial membrane potential in L. amazonensis, inhibitory activity on the intracellular amastigote of L. amazonensis (IC50 = 14.2 ± 1.6 µg/mL), and cytotoxicity values ranging from 80.8 to 156 µg/mL against murine macrophages and J774 cells. Estragole displayed higher activity on promastigotes (IC50 = 28.5 and 25.5 µg/mL, respectively), amastigotes (IC50 = 1.4 ± 0.1 µg/mL), and cytotoxicity values ranging from 20.6 to 14.5 µg/mL, respectively, while on mitochondria, it caused a decrease of the membrane potential but did not inhibit oxygen consumption. The potential antileishmanial activity of the essential oil from T. lucida and estragole makes these compounds favorable candidates for exploration in further studies.

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