Plantas medicinais do Nordeste do Brasil - Ximenia americana Linn: investigação química dos grãos e seu uso como biocatalisador

Abstract

This work consisted in the study of hexane and ethanol extracts of Ximenia americana grains, abundant plant species in the Northeast of Brazil, especially in Ceará, where it is known as the plum of the woods. Parts of the plant, especially the husks, are popularly used to treat various diseases. The chemical investigation was divided into two parts, the first being directed to the identification of the chemical components of the grain X. americana by gas chromatography coupled to mass spectrometry (GC/MS) and the second one related to the possibility of using these grains as biocatalyst. Identification of chemical components by GC/MS without the knowledge of the possible types of compounds, required as a preliminary step, obtaining volatile derivatives. Thus, in a first step, the hexane extract of the grains after silylation reaction allowed the identification of 18 constituents highlighting, as the major, the octadec-9-enoic acid (38.14%), (9Z, 12Z)-octadec-9,12-dienoic acid (18.83%), ethanedioic (8.21%) and (Z, Z, Z) -9,12,15-octadecatrienoic (7.22%). Meanwhile, the ethanolic extract after silylation possible to identify components having 18 to D-Sucrose (29.36%), L-Sorbose (9.19%), inositol (8.34%) and D-Glucose (7.45%) as major. The constituents were identified as trimethylsilyl (TMS) ethers by using chromatographic and spectrometric techniques mainly GC/MS. In addition to fatty acids and carbohydrates as highlights, it detected the presence of steroids (β-sitosterol) in hexane and triterpene extract (Betulinic and Ursolic acid) in ethanol extract. In a second step, the hexane extract of the beans after saponification reactions/methylation allowed the identification ten fatty acids having main, oleic acid (55%) ximeninic (17%) and cis-19-octacosenoico (10%). The acids were identified as their methyl esters using GC/MS. The fragmentation pattern of the components outlined in the mass spectra, was considered in the review process. They were also carried out some tests of biological activities from hexane and ethanol extracts of the grains. The second part of the study investigated the use of grain as X. americana biocatalyst in the form of integral material biotransformation reactions in the reduction of aldehydes and ketones, alcohols esterification and ester hydrolysis. In the reduction reactions the used substrates were: acetophenone, 3-methoxyacetophenone, 4-fluoroacetophenone, 4-chloroacetophenone, 2,4-dichloroacetophenone, cyclohexanone, octan-2-one, undecan-2-one, benzaldehyde, 3-methoxybenzaldehyde, 4-methoxybenzaldehyde, 3-hydroxy-4-methoxybenzaldehyde (vanillin) and 1-naphthaldehyde. The conditions that allowed the reduced product to be obtained in the best yield were: 50.0 mg of the substrate, 5.0 g of the grains, pH 5 (ketones) and 7 (aldehydes), 175 rpm on the shaker table, 72 hours at 30 °C. The bioconversion in the reduction occurred from low to excellent yield and, as expected, aldehydes were more reactive than ketones. In the hydrolysis reactions the used substrates were: methyl benzoate, ethyl benzoate, benzyl acetate, p-chloro-phenylethyl acetate and phenylethyl acetate. The conditions that allowed the hydrolyzed product to be obtained with the best yield were: 50.0 mg of the substrate, 2.0 g of the grains, 30 mL of distilled water (pH 5), 175 rpm on the shaker table, 72 hours at 30 °C. The bioconversion in the hydrolysis occurred from medium to excellent yield. In the esterification reactions of the alcohols the used substrates were: benzyl alcohol, 3-methoxy benzyl, 4-methoxy benzyl, 1-phenylethanol, cyclohexanol and n-octanol. The conditions that allowed the esterified product to be obtained in the best yield were: 52 mg of the substrate, 2.0 g of the grains, 10 ml of hexane, 100 μL of vinyl acetate, 225 rpm on the shaker table, 24 hours at 30 °C. Bioconversion in esterification occurred from low to excellent yield. The products in the reaction mixtures were analyzed by TLC, GC/MS, GC/FID and 1H and 13C NMR.