Several studies with kaempferol (KP) and linearolactone (LL) have shown antiparasitic activities. However, the toxicity of treat-ments with both active principles is unknown. Therefore, this study aimed to evaluate the toxicological effects of treatments with KP and LL on the amoebic liver abscess (ALA) model in M. auratus administered intraperitoneally (i.p.). For this, ALA in-duction was carried out in male hamsters with 1.5 x105 E. histolytica trophozoites inoculated in the left hepatic lobe. The lesion evolved for four days and the i.p. of the treatments with KP (5 mg/kg body weight/day) and LL (10 mg/kg body weight/day) was carried out for four consecutive days. For histopathological evaluation, NMR studies, paraclinical analysis, and necropsy were performed. The results revealed that the inhibition of ALA by KP and LL were similar to that metronidazole (MTZ). Biochemical parameters revealed hepatic and renal alterations in all treatment groups, mainly for KP (AST and BUN). The lesions found in the organs were those that are directly linked to the pathology. In conclusion, KP and LL decrease ALA development but have few toxicological effects. Both compounds combined with MTZ could be therapeutic alternatives for amoebiasis caused by E. histolytica.

Abstract: Chemical investigation of the leaves from Ageratina glabrata yielded four new thymol derivatives, namely: 10-Benzoyloxy-8,9-dehydro-6-hydroxythymol isobutyrate (4), 10-benzoyloxy-8,9-dehydro thymol (5), 10-benzoyloxythymol (6) and 10-benzoyloxy-6,8-dihydroxy-9-isobutyryloxythymol (7). In addition, (8S)-10-benzoyloxy-8,9-epoxy-6-hydroxythymol isobutyrate (1), together with other two already known thymol derivatives identified as: 10-benzoyloxy-8,9-epoxy-6-methoxythymol isobutyrate (2) and 10-benzoyloxy-8,9-epoxythymol isobutyrate (3). In this paper, we wish to publish the structures and complete assignments of ¹H and ¹³C NMR data of compounds 1 – 7, and the absolute configuration for compound 1, unambiguously established by single crystal X-ray diffraction, and evaluation of the Flack parameter. The in vitro antiprotozoal assay showed that compound 1 and its derivative 1a were the most potent antiamoebic and antigiardial compounds. Both compounds showed selectivity and good antiamoebic activity like emetine and metronidazole, respectively, two antiprotozoal drugs used as positive controls. In relation of anti-propulsive effect, compound 1 and 1a showed moderate inhibitory activity, their activities were comparable to quercetin and compound 9, respectively, two natural antipropulsive compounds used as positive controls. These data suggest that compound 1 may play an important role in antidiarrheal properties of Ageratina glabrata.