Analysis of the toxic potential of Palicourea corymbifera (Müll. Arg.) Standl. in laboratory animals

Toxicological profile and acetylcholinesterase inhibitory potential of Palicourea deflexa, a source of β-carboline alkaloids

Palicourea genus is chemically and taxonomically close to Psychotria genus, a well-known source of neuroactive alkaloids. It has been previously reported the pharmacological potential of these alkaloids in some targets related to the neurodegenerative process. In this context, this study was carried out in order to evaluate the toxic effects and acetylcholinesterase (AChE) inhibitory potential of Palicourea deflexa fraction of total alkaloids (FTA). P. deflexa FTA was analyzed by means of HPLC-DAD and HRMS-ESI. We performed toxicological screening through Fish Embryo Toxicity (FET) test using zebrafish embryo and abnormal developmental phenotypes were recorded daily. For AChE inhibition, zebrafish brains were used as enzymatic source and formation of thiolate dianion of 5,5'-Dithiobis(2-nitrobenzoic acid) (DTNB) was used to monitor acetylthiocholine hydrolysis. Lineaweaver-Burk double reciprocal plots were used to indicate mode of inhibition. Chemical analysis of the P. deflexa FTA allowed the identification of the main compound as harman-3-carboxylic acid. This fraction was evaluated in vivo for its toxicological effect. The zebrafish embryo test indicated that the FTA has a lethal concentration of 50% (LC₅₀)=72.18μg/mL. Further, the FTA was evaluated for its AChE inhibitory profile, demonstrating an inhibitory concentration of 50% (IC₅₀) of 50.65μg/mL. Lineaweaver-Burk double reciprocal plots indicated a mixed mode of inhibition. It is reported for the first time the toxicological and pharmacological profile of the alkaloid fraction of Palicourea deflexa in zebrafish models.

Safety assessment and behavioral effects of Solanum guaraniticum leaf extract in rats

ABSTRACT Solanum guaraniticum is a medicinal plant traditionally used to treat gastric and liver diseases. However, there is no documented evidence corroborating its safety. The present study evaluated the potential toxicity of S. guaraniticum leaf extract after acute administration in rats. Single doses of the extract (1.250, 2.500, and 5.000 mg/kg) were administered by gavage, and the rats were then monitored for 48 h and/or 14 days. Mortality, acute signs of toxicity, and general activity in the open field test were assessed as well as hematological and biochemical parameters, enzymatic activity (δ-aminolevulinate dehydratase and acetylcholinesterase), and oxidative stress parameters (lipid peroxidation level, non-protein thiol content, tissue catalase activity, and serum ferrous reducing power). Phytochemical analysis was also performed by HPLC. The results showed that extract administration produced no deaths (LD50 > 5,000 mg/kg), and no significant adverse effects regarding food consumption, body weight gain, gross pathology, or other parameters. However, the open field tests showed a decrease in spontaneous activity (crossing and rearing) mainly at 48 h after treatment. The results suggest that S. guaraniticum extract is not acutely toxic, but causes alterations in central nervous system activity.

Acaricidal activity of Palicourea marcgravii, a species from the Amazon forest, on cattle tick Rhipicephalus (Boophilus) microplus

Leaves of Palicourea marcgravii were extracted successively with hexane, ethyl acetate and ethanol in order to evaluate their acaricidal activity on larvae and adult stages of the cattle tick Rhipicephalus (Boophilus) microplus. The ethyl acetate extract showed the highest bioactivity of the tested extracts, which contained 0.12% monofluoroacetic acid. On engorged female, the ethyl acetate extract showed a lethal concentration 50% - LC(50)=30.08 mg ml(-1), inhibitory concentration 50% - IC(50)=5.79 mg ml(-1) and lethal time 50% - LT(50)=4.72 days; 100% reproduction was controlled at concentrations of 50 mg ml(-1) and on larvae the ethyl acetate extract showed a LC(50)=2.46 mg ml(-1). No alkaloids were detected in any of the extracts. This is the first report on the acaricidal activity of P. marcgravii extracts against R. microplus as well as the acaricidal properties of a plant species containing monofluoroacetic acid.