Estudo dos metabólitos secundários de Scutia buxifolia e suas atividades biológicas

Abstract

In this work, four new neutral cycle peptide , scutianenes W (210), X (211), Y (212) and Z (213), have been isolated from Scutia buxifolia Reiss (Rhamnaceae) , along with seven know compounds, four cylopeptide alkaloids, scutianine B (99), scutianine C (100), scutianine D (101), and scutianine E (102), two triterpenoids , ursolic acid (215) and betulic acid (216), and two steroids, β-sitosterol (214) and β-sitosterol glycoside (217). The structures of compounds isolated were established by various spectroscopic techniques, including 1H and 13C NMR, COSY, NOESY, DEPT, HMQC and HMBC experiments, and comparison with authentic samples. Scutianenes W, X and Y are three diastereoisomeric compounds, with a 3- hydroxileucine as a β-hydroxiamino acid unit, which is connected to the styryl fragment via an ether bridge, and a β-phenylserine as a common ring-bonded amino acid. Attached to the amino group of the 3-hydroxiamino acid unit is a side chain trans CO-CH=CH-PH. In its turn, scutianene Z (213) has a phenylserine as the β-hydroxiamino acid unit, isoleucine as a common ring-bonded amino acid and the same side chain trans CO-CH=CH-PH. The stereochemistry of the four new compounds was established from coupling constants between H3/H4 and H-7/H-28, and by differences in chemical shifts of CH-3, CH-4, CH-7 and CH-28, on the 1H and 13C NMR spectra. The absolute stereochemistry of the diastereoisomeric scutianenes X (211) and Y (212), were confirmed by X-ray diffraction analysis of its O-acetyl derivatives. In addition, extracts and compounds isolated were evaluated for its antimicrobial activity against Gram-positive and Gram-negative bacteria and yeasts, and for its Acetylcholinesterase inhibitory activity.