Estudo químico de Bowdichia virgilioides (Fabaceae) na busca de inibidores seletivos de cisteíno peptidases
Abstract
This work describes the isolation of bioactive secondary metabolites of the plant
species Bowdichia virgilioides in the search for selective inhibitors of cathepsins K, L
and V. Cathepsins are enzymes that have as primary function the degradation of
proteins in the lysosomes, and are also related to development of diseases such as
osteoporosis, rheumatoid arthritis, atherosclerosis and various cancers. This
dissertation describes the bioactivity-guided study of the ethanol extracts and
fractions obtained from the stems and leaves of B. virgilioides through fluorimetric
inhibition assay of the enzymes studied. The extracts of B. virgilioides were subjected
to successive fractionations using different chromatographic techniques leading to
several pure substances. The isolated substances had their structures elucidated by
NMR uni- and bi-dimensional and mass spectrometry. The hexane and ethyl acetate
fractions of stem afforded eleven substances: 2 triterpenes, lupeol and lupenona; the
mixture of steroids β-sitosterol and stigmasterol; 1 ester derivative of trans pcoumaric acid; 1 furofuran lignan, syringaresinol; 1Benzofuran derivative, bowdenol; 1 coumestrol derivative, 8-methoxycoumestrol, and 3 isoflavones, 7,3'-dihydroxy-4'- methoxyisoflavone, 5,4'-dihydroxy-7'-methoxyisoflavone and 4-hydroxy-7-methoxyisoflavone. All compounds were tested on their ability to inhibit the enzymes at a
concentration of 100μM. 8-Methoxycoumestrol showed inhibition superior to 70% for
cathepsin V. The potency of this inhibitor was determined and the IC50 value was
found to be 17.4 ± 1.0μM for cathepsin V. The ester derivative of trans p-coumaric
acid also showed good inhibition above 70% for cathepsin L and V at a concentration
of 50μg/mL. So, a series of 8 esters derived from p-hydroxybenzoic acid, p-coumaric
acid, cinnamic and ferulic were prepared, and have been evaluated regarding their
inhibitory activities of the cathepsins at a concentration of 100μM. n-Octyl pcoumarate
ester showed the best percentage inhibition for the three enzymes. The constituents of the hexane fraction of leaves of B. virgilioides were analyzed using the techniques 1H NMR and GC-MS.