Constituintes químicos das folhas de Senna spectabilis (DC) Irwin & Barneby var. excelsa (Schrad.) Irwin & Barneby

Abstract

Recebido em 31/12/09; aceito em 15/6/10; publicado na web em 22/9/10 Chemical COMPOUNDS OF LEAVES FROM SENNA SPECTABILIS (DC) IRWIN & BARNEBY var. excelsa (SCHRAD.) IRWIN & BARNEBY. From leaves of Senna spectabilis var. excelsa were isolated caffeine, the triterpenes lupeol, α-amyrin, β-amyrin, cycloeucalenol, friedelin and ursolic, oleanolic and betulinic acids, besides the steroids sitosterol and stigmasterol and their respective glucosides. The structures of these compounds were established by spectroscopic analysis including two-dimensional NMR methods and comparison with published spectral data. This paper deals with the first report of these compounds in S. spectabilis var. excelsa.Keywords: Senna spectabilis var. excelsa; triterpene; caffeine. INTRODUÇÃONo Brasil ocorrem 200 gêneros e 1.500 espécies da família Fabaceae. Presente na maioria dos ecossistemas brasileiros, é relatada como a família botânica mais bem representada na caatinga, com 293 espécies em 77 gêneros, constituindo aproximadamente um terço de todos os vegetais deste bioma. 3 Atividade laxativa comparável ao padrão bisacodil (princípio ativo da Lacto-purga ® ) e anti-inflamatória similar ao diclofenaco de sódio foi observada para o extrato das folhas de Senna macranthera. 4 Outras diversas atividades relevantes como antimicrobiana, analgésica, antiparasitária, inseticida, antitumoral e hepatoprotetora são comprovadas para várias espécies de Senna. O estudo químico das folhas de S. spectabilis var. excelsa (Schrad) levou ao isolamento e identificação de oito triterpenos pentacíclicos: quatro na forma pura (ácido betulínico, lupeol, cicloeucalenol, friedelina) e quatro como misturas (α-amirina, β-amirina, ácido ursólico e oleanólico). Apesar de serem substâncias conhecidas, este é o primeiro relato dessa classe química na espécie Senna spectabilis var excelsa. Também foram identificadas duas misturas de esteroides (estigmasterol e β-sitosterol) na forma livre e glicosilada, além de um alcaloide (cafeína) ainda inédito no gênero Senna. RESULTADOS E DISCUSSÃOO extrato etanólico das folhas de S. spectabilis var. excelsa (Schrad) através de técnicas cromatográficas levou ao isolamento dos triterpenos pentacíclicos ácido betulínico (1), lupeol (2), α-amirina e β-amirina (3 e 4), da fração não alcaloídica (FNA) (m = 13,5 g). A identificação foi possível após a análise dos dados espectrais de RMN 1 H, RMN 13 C e DEPT 135 e comparação com dados da literatura. A comparação dos dados obtidos com a literatura permitiu identificar o composto 1 como um triterpeno pentacíclico de esqueleto lupano denominado ácido betulínico. O tratamento cromatográfico da fração diclorometânica levou ao isolamento e identificação de (5), (6) (7)

Update: Biological and Chemical Aspects of Senna spectabilis

“…6 This cyclic nitrogen compounds show high pharmacological interest, exhibiting strong antitumor, leishmanicidal, analgesic, antimicrobial, purgative and anticonvulsant effects, as well as modulating the treatment of neurodegenerative diseases by the inhibition of superoxide, lipid peroxidation and against ciclooxigenase (COX) 1 and 2. [10][11][12][13][14][15][16] Piperidine alkaloids were extensively studied through the years, being (−)-cassine (1) the first alkaloid discovered on leaves of S. spectabilis.…”

“…[29][30][31] These secondary metabolites, isolated from leaves, flowers and green fruits of S. spectabilis, were found in both mixture (α-amyrin (22), β-amyrin (23), ursolic acid (24) and oleanolic acid (25)) and pure forms (betulinic acid (26), lupeol (27), cycloeucalenol (28), friedelin (29)), showing biological activity in animal and human models ( Figure 2). 31 Lupeol (27), also called lup-20-(29)-en-3β-ol, is widely found in fruits and vegetables as well as in a variety of medicinal plants such as Tamarindus indica, Emblica officinalis and Celastrus paniculatus. 32,33 This triterpene shows several pharmacological activities, acting against inflammation, several cancer cell lines, such as human lung carcinoma and human colorectal adenocarcinoma, arthritis, heart diseases, diabetes and renal/liver toxicity.…”

“…31,61,62 Betulinic acid, isolated from leaves, fruits and flowers of Senna, is a highly bioactive triterpene, displaying anti-HIV, antibacterial, antimalarial and anti-inflammatory effects. 5,31,[63][64][65] Commonly known as 3β-hydroxy-lup-20-(29)-en-28-oic acid, this triterpene promises to be a potential drug for cancer treatment due to its cytotoxicity against various cancer cell lines (lung, ovarian, neuroand glioblastoma and head/neck carcinomas), selective inhibition of human melanoma, apoptosis induction in human neurobastoma and low toxicity to healthy cells. 66 Ursolic acid, found either free or bounded to saponins, is a common constituent of fruits from human diet such as apple, guava and blueberry.…”

“…66 Ursolic acid, found either free or bounded to saponins, is a common constituent of fruits from human diet such as apple, guava and blueberry. 31,67 Known as 3β-hydroxy-urs-12-en-28-oic-acid, this metabolite has protective properties against fatty liver induced by high-lipid diet and liver injury as well as anti-bacterial, anti-inflammatory and antioxidative properties. [67][68][69][70][71] Oleanolic acid, an ursolic acid isomer, is found in over 1620 plant species.…”

“…Found as a mixture, this phytosterols are presented in both free and glycosylated form on the leaves, flowers and green fruits of S. spectabilis, possessing similar spectroscopic properties to other steroids ( Figure 3). 31 Stigmasterol (3β-hydroxy-24-ethyl-5,22-cholestadiene) (30) is found in numerous roots from trees and grass plants, as well as algae and fungi. 22,77,78 This steroid was firstly reported in 1907 by Windhaus and Hauth, 79 isolated from Calabar beans (Physostigma venenosum) and its absolute configuration was determined in 1963 by Fitches.…”