Estudo fitoquímico e atividades biológicas das folhas de Pereskia aculeata Miller (Cactaceae)

Abstract

Pereskia aculeata Miller, known as ora-pro-nobis, is a climbing shrub which leaves are used in tradicional cuisine in Brazil. The leaves are used in folk medicine in skin wound healing and to treat inflammation. To contribute to the studies on P. aculeata, the phytochemical characterization of its crude methanol extract and partitions, the quantification of phenols and flavonoids and the search for indoles compounds were carried out. In vitro, we tested the cytotoxic activity to normal macrophages, HL60 and MCF-7 cells and parasites of the genus Leishmania by MTT method and also antimicrobial activity by microdilution method. Furthermore, we evaluated the in vivo anti-inflammatory activity of the crude extract by the model of ear edema induced by croton oil and antinociceptive activity of crude extract and partitions by acetic acidinduced writhing test. Since hydromethanolic partition showed the greatest antinociceptive potential, it was also studied by acetic acid-induced writhing test in animals pretreated with p-chlorophenylalanine (PCPA), formalin and tail-flick tests. The chromatographic profile of the hydromethanolic partition was determined by HPLC. All classes of chemical constituents investigated were found, with the exception of triterpenes and saponins. Alkaloids, flavonoids and indoles were found in all samples. Dichloromethane partition showed higher phenols and flavonoids contents. Crude extract and some partitions showed cytotoxicity against HL60 and MCF-7 cells. None of the samples showed cytoxicity against normal macrophages, Leishmania parasites or bacteria strains. Crude extract showed edematogenic activity in croton oil test when administered orally, but the histological analysis of the ears suggested that the edema should not have been caused by an increase in inflammatory process. The study further revealed that the antinociceptive mechanism of hydromethanolic partition was peripheral and central, but not related to opioid receptors or serotonin synthesis and release. HPLC analysis revealed the presence of indoles in this partition. The leaves of P. aculeata are rich in tryptophan, a serotonin precursor. Serotonin is a vasodilator and a neurotransmitter which inhibits central nociception. In plants, tryptophan leads to indole alkaloids, structurally similar to serotonin. Thus, we hypothesize that indole alkaloids are involved in the in vivo activities observed for crude extract and hydrometanolic partition.