Estudo químico e avaliação do potencial farmacológico e herbicida de Maytenus imbricata Mart. ex. Reissek

Abstract

In this work, it was studied leaves, branches and seeds of Maytenus imbricata, whose chemical constitution and activities pharmacological until this moment had not been reported in literature. From Maytenus imbricata leaves and branches hexane extracts were isolated and identified 3-oxo-lup-20(29)-en-30-al, 30-hydroxy-lup-20(29)-en-3-one, 11 -hydroxy-lup-20(29)-en-3-one, 3ß,30-dihydroxy-lup-20(29)-ene, lupenone, 3 -esteariloxy-lupan-20(29)-ene, friedelin, 3,4-seco-friedelan-3-oic acid and 1-hydroxy-3,6-dimethoxy-8-methyl-9-xantone. Also it was identified mixtures of friedelin and friedelinol, fat acid esters mixtures and mixtures of the above cited lupanes. The leave chloroform extract was analyzed by GC-MS, being detected the presence of palmitic and stearic acids like as major compounds. From the leave and branche ethyl acetate extracts were isolated epicatechin and a mixture of proanthocyanidines. In these extracts, palmitic and adipic acids, the sugar D-sorbitol and the long chain hydrocarbons n-octadecane and eicosane, also were identified by GC-MS. During the branches ethanolic extract preparation precipitation, of dulcitol was observed. This poliol is commonly encountered in various species of the Celastraceae family. Through GC-MS analysis in this extract was possible to identify the sugars ß-D-glucopyranose and D-sorbitol, and adipic and eicosanoic acids. The essential oil isolated from leaves showed as constituents: 1 -pinene, 2 -pinene, 2-phenyltridecane, 3-phenyltridecane and dioctyl hexanedioate. In the seeds and elaiosome were identified mainly fat acid esters, among which predominated palmitic, stearic and oleic acids. The constituents of M. imbricata were obtained and characterized by chromatographic techniques (TLC, CC, GC-MS and HPLC) and spectrometric methods (IR, 1H and 13C NMR, including DEPT-135 and 2D experiments). The crystallographic analysis by X-ray diphratometry was used to confirm the molecular and conformational structure of the lupanes 30-hydroxy-lup-20(29)-en-3-one, 11 -hydroxy-lup-20(29)-en-3-one and 3 ,30-dihydroxy-lup-20(29)-en. By Maytenus imbricata foliar anatomy study was possible to verify the presence of characters commonly observed in other species of Celastraceae family, like as sclereids and thick cuticle, idioblasts with phenolic compounds, calcium oxalate crystals and absence of trichomes. The Bayer-Villiger reaction showed efficient for the friedelin oxidation and to obtain the 3,4-seco-friedelan-3-oic acid. This seco-friedelan shows important pharmacological activities. Extracts and substances isolated from Maytenus imbricata were submitted to antioxidant activity assays to evaluate its potentiality as phytotherapic. The leaves ethyl acetate extract, and ethanol, chloroform and hydroalchoolic extracts from roots, the branche ethyl acetate extract and epicatechin showed very promising results showing potential antioxidant activity, high total phenolic content and reductor power effect. In relation to ATP synthesis inhibition, the 3,4-seco-friedelan-3-oic acid was highly efficient.