Extratos bioativos e óleos essenciais de plantas endêmicas da República Dominicana no controle de nematoides gastrointestinais de pequenos ruminantes

Abstract

Small ruminant production faces significant economic losses due to diseases caused by gastrointestinal nematodes (GIN), which are capable of rapidly developing anthelmintic resistance. Phytotherapy emerges as a promising alternative for controlling these diseases. This study aimed to evaluate extracts, fractions, and essential oils from endemic plants of Hispaniola, including Pimenta racemosa var. ozua (Po), Pimenta haitiensis (Ph), Croton coronatus, Croton poitaie, Simarouba berteroana (Sb), and Lippia dominguensis (Ld), considering their in vitro and in vivo effects on GIN control in small ruminants. Spectrophotometric and chromatographic chemical analyses were conducted to determine the chemical profiles of the plant derivatives, along with an in vivo acute toxicity assessment of the most promising derivatives. In the egg hatching test, essential oils were found to be more active than extracts and fractions, with 50% inhibitory concentrations (IC50) of 0,294 mg/mL (Ph essential oil: OEPh). However, the hexane fraction from the second collection of the Po extract (IC50 = 0,65 mg/mL) and the hydroalcoholic fraction from the first collection of S. berteroana (IC50 = 0,925 mg/mL) also demonstrated potent egg hatching inhibition. In the larval artificial exsheathment assay, most of the extracts and fractions inhibited the exsheathment process of H. contortus larvae at 300 µg/mL, with the exception of the hexane fractions. In the adult nematode motility test, after 3h of exposure, the essential oils of L. dominguensis 1 st collection (OELd1) and P. racemosa var. ozua 1st collection (OEPo1), at 1 mg/mL, inhibited motility by > 95%. These oils caused changes in the cuticle of adult nematodes, as observed using scanning electron microscopy. Gas chromatography coupled with mass spectrometry indicated that the majority compounds of OELd1 were: linalool (33,85%) and 1,8-cineole (30,88%), of OEPo1: 1,8-cineole (93,7%), and of OEPh: estragole (66,32%) and menthatriene <1,3,8-ρ-> (17,66%). S. berteroana's isobutanol and ethyl acetate fractions showed the highest levels of phenols, flavonoids and total tannins by spectrophotometry. Liquid chromatography coupled with mass spectrometry showed that the crude extracts and fractions of S. berteroana have quassinoids, terpenoid quinones, phytosterol lipids, alkaloids and the naphthoquinone javanicin D, also present in other species of the family. In the acute oral toxicity test on mice, it was observed that OELd1 and the essential oil of P. racemosa var. ozua (2nd collection) and the crude extract of Po 2 nd collection (Po2) showed low toxicity (LD50 > 2.000 mg/kg), and the LD50 of OELd2, OEPh and the crude extract of S. berteroana 2nd collection (Sb2) was between 1.100 – 2.000 mg/kg. In the experiments with goats, it was observed that 350mg/kg of Sb2 decreased the parasite burden by 71% on day 14, showing a concentration-dependent efficacy. Therefore, the crude extract Sb2, containing quassinoids and a significant phenolic content, was the most promising plant derivative from S. berteroana. Similarly, the essential oils from Ld (containing linalool and piperitenone) and Ph (containing estragole) could be considered for the development of anthelmintic agents for small ruminants.