Aspectos químicos do estudo interdisciplinar (química-agronomia-farmacologia) de Amburana cearensis A.C. Smith

Abstract

Amburana cearensis A.C. Smith is a typical tree of the northeastern Brazil flora designated “caatinga”. It is popularly known either as “imburana-de-cheiro” or “cumaru” and characterized by its red-gray bark of peculiar and pleasant smell due to coumarin. Despite A. cearensis relevant economical (particularly for carpentry and perfumery) and medicinal importance (therapeutic properties against respiratory affections scientifically proved), it is one of the plant species treated of extinction due to predatory extractivism. Taking in account the necessity of elaborating a sustainable plan of exploitation it was suggested an integrated study covering the chemical, agronomical and pharmacological aspects of A. cearensis. This work reports the phytochemical component of the interdisciplinary study pursuing the isolation, purification and structure characterization of new secondary metabolites of the wild adult plant, as well as the identification and quantification of the already known chemicals, considered the plant biomarkers, from young cultivated specimens at different developmental stages. The chemical investigation of adult wild plants was performed with the ethanol extract from barks of A. cearensis collected at Quixeramobim County, Ceará state, and the hexane extract of seeds purchased from herbal stores at Fortaleza. The ethanol extracts were submitted to liquid-liquid partition, conventional (silica gel adsorption and gel exclusion with dextran) and modern (HPLC) chromatography leading to the isolation and characterization of: A. Coumarins 6-hydroxy-coumarin, 6-coumaryl protocatechuate, acid; B. Phenol Acids- vanillic acid, o-coumaric; C. Flavonoids- quercetin, formononetin, amburanin A and B; Amburosídes- amburoside A, 6”-amburosyl-ferulate, 6”-amburosyl-protocatechuate, 6”-amburosyl-galate, 6”-amburosyl-acetate, 6”-amburosyl-sinapate and 6”-amburosyl-vanillate. The cultivated specimens, separated in aerial part and xylopode, were extracted with ethanol and submitted to the same methodology employed for the wild plant. From the aerial part were isolated coumarin, ayapin, amburanin B, isokaempferide, vanillic acid, (E)-o-coumaric acid glucoside, while from the xylopode were isolated p-hydroxy-benzoic acid, (Z)-o-coumaric acid glucoside and amburoside B. All chemical substances had their structures elucidated through physical (mp and optical rotation) and spectroscopical methods (IR, MS and NMR, including uni and bidimensional techniques) and comparison to the literature wherever the case. The ethanol extracts from either wild or cultivated (aerial part and xylopode) plants were compared by HPLC through a validated chromatographic method (acceptable linearity, precision, accuracy and recovering factor) using as standard the protocatechuic acid, vanillic acid, coumarin and amburoside A, obtained from the previous studies. Amburoside A was the major component of wild plant, while coumarin and vanilic acid take turns as the principal metabolites of cultivated young plants depending on the plant part and plant age.