Background: One of the most important causative agents of visceral leishmaniasis (VL) is Leishmania infantum, which is mainly spread by Phlebotomus and Lutzomyia sandflies in the Old and New World, respectively. Novel and effective drugs to manage this neglected vector-borne disease are urgently required. In this study, we evaluated the toxicity of carvacrol, thymol and linalool, three common essential oil constituents, on amastigotes and promastigotes of L. infantum. Methods: in vitro experiments were performed by 24 h MTT assay. Carvacrol, thymol and linalool at concentrations ranging from 1.3 to 10 μg/mL were tested on promastigotes of L. infantum. For in vivo test, two groups of hamsters (Mesocricetus auratus) received 100 mg/kg of body weight/day of carvacrol and thymol as intraperitoneal injection on day 7 post-infection, followed by a 48 h later injection. The third group was treated with the glucantime as standard drug (500 mg/kg) and the last group (control) just received normal saline. On the 16th day, the number of parasites and histopathological changes in liver and spleen were investigated. Results: 24 h MTT assay showed promising antileishmanial activity of thymol and carvacrol, with IC₅₀ values of 7.2 (48 μM) and 9.8 μg/mL (65 μM), respectively. Linalool at all concentrations did not affect L. infantum promastigote viability. In vivo toxicity data of carvacrol and thymol showed that the former at 100 mg/kg was the safest and most effective treatment with little side effects on the liver. Conclusions: Overall, thymol and carvacrol are highly promising candidates for the development of effective and safe drugs in the fight against VL.

The present study investigated the protective efficacy of dietary supplementation with clove essential oil (CEO), its main constituent eugenol (EUG), and their nanoformulated emulsions (Nano-CEO and Nano-EUG) against experimental coccidiosis in broiler chickens. To this aim, various parameters (oocyst number per gram of excreta (OPG), daily weight gain (DWG), daily feed intake (DFI), feed conversion ratio (FCR), serum concentrations of total proteins (TP), albumin (ALB), globulins (GLB), triglycerides (TG), cholesterol (CHO) and glucose (GLU), serum activity of superoxide dismutase (SOD), glutathione s-transferase (GST), and glutathione peroxidase (GPx)] were compared among groups receiving CEO supplemented feed (CEO), Nano-CEO supplemented feed (Nano-CEO), EUG supplemented feed (EUG), Nano-EUG supplemented feed (Nano-EUG), diclazuril supplemented feed (standard treatment, ST), or basal diet [diseased control (d-CON) and healthy control (h-CON)), from days 1–42. Chickens of all groups, except h-CON, were challenged with mixed Eimeria spp. at 14 days of age. Coccidiosis development in d-CON was associated with impaired productivity (lower DWG and higher DFI and FCR relative to h-CON; p < 0.05) and altered serum biochemistry (decreased TP, ALB, and GLB concentrations and SOD, GST, and GPx activities relative to h-CON; p < 0.05). ST effectively controlled coccidiosis infection by significantly decreasing OPG values compared with d-CON (p < 0.05) and maintaining zootechnical and serum biochemical parameters at levels close to (DWG, FCR; p < 0.05) or not different from (DFI, TP, ALB, GLB, SOD, GST, and GPx) those of h-CON. Among the phytogenic supplemented (PS) groups, all showed decreased OPG values compared with d-CON (p < 0.05), with the lowest value being measured in Nano-EUG. All PS groups showed better values of DFI and FCR than d-CON (p < 0.05), but only in Nano-EUG were these parameters, along with DWG, not different from those of ST. Furthermore, Nano-EUG was the only PS group having all serum biochemical values not different (or even slightly improved) relative to ST and h-CON. In conclusion, the tested PS diets, especially Nano-EUG, can limit the deleterious effects of coccidiosis in broiler chickens, due to anticoccidial activity and possibly their reported antioxidant and anti-inflammatory properties, thereby representing a potential green alternative to synthetic anticoccidials.

Pain and inflammation are the severe problems of the world. Essential oils (EOs) have been considered for treating pain and inflammation. As EOs are unstable and insoluble in water, nanoemulsions can improve bioavailability and efficacy. This study formulated Pelargonium graveolens essential oil nanoemulsion (PGEO-NE) using Tween 80 as a carrier. The activity of PGEO-NE (50 and 100 mg/kg) and the involvement of the opioid pathway were investigated in different models of nociception and inflammation in mice. The droplets in PGEO-NE are spherical, with a particle size of around 553 nm and a polydispersity index of 0.113. GC/MS analysis of PGEO revealed citronellol (34.9%), geraniol (16.1%), citronellyl formate (12.3%), and linalool (6.8%) as the main constituents. PGEO-NE significantly reduced the duration of formalin-induced paw licking/biting in both phases and the number of acetic acid-induced writhings, and increased the hot plate latency, compared to vehicle and PGEO (10 mg/kg), equivalent to the PGEO-NE dose of 100 mg/kg. The anti-nociceptive potential of PGEO-NE (100 mg/kg) in the hot plate and acetic acid tests was reversed by the opioid antagonist. After formalin and carrageenan injections, PGEO-NE significantly inhibited paw edema, but PGEO (10 mg/kg) had no effect. These results confirm that PGEO-NE inhibits pain and inflammation via the opioid pathway.