Saponinas triterpênicas da espécie Pentaclethra macroloba Kuntze

Abstract

In the present work it is reported, for the first time, the phytochemical investigation related to the isolation of present saponins in the specie Pentaclethra macroloba Kuntze - mimosoideae, popularly known as " pracaxi " in the Amazon Region . From an ethanolic seed (PES), bark (PEC) and stem (PEL) extracts of a specimen of Pentaclethra macroloba were isolated eight triterpenoid saponins of the acid oleanolic and the hederagenin, constituted of two to seven sugars: 3-0-a-L-rhamnopyranosyl-(1—>2)-a-Larabinopyranosyl oleanolic acid (1); 3-0-a-L-rhamnopyranosyl-(1-*2)-a-L-arabinopyranosyl hederagenin (2); 3-0-{(3-D-glucopyranosyl-(1-*4)-[a-L-rhamnopyranosyl-(1—+2)])-a-Larabinopyranosyl oleanolic acid (3), 3-0-{ j3-D-glucopyranosyl-(1—*4)-[f3-D-glupyranosyl-(1--*3)- a-L-ramnopyranosyl-(1-*2)])-a-L-arabinopyranosyl oleanolic acid (4); 3-0-{0-Dglucopyranosyl-(1—*4)-[(3-D-glupyranosyl-(1--*3)-a-L-ramnopyranosyl-(1—*2)] ) -a-Larabinopyranosyl hederagenin (5); 3-0-{[3-D-glucopyranosyl-(1-*4)-[(3-D-glucopyranosyl(1-*4) - {i-D-glupyranosyl-(1—*3)-a-L-ramnopyranosyl-(1--*2)]}-a-L-arabinopyranosyl oleanolic acid (6); 3-0-{ 3-D-glucopyranosyl-(1--*3) - 0-D-glucopyranosyl-(1-*4)-[0-D-glucopyranosyl-(1—*2) - 13-D-glucopyranosyl(1—*4) - [3-D-glupyranosyl-(1-*3)-a-L-ramnopyranosyl-(1—*2)])-a-Larabinopyranosyl oleanolic acid (7) and 3-0-{(3-D-glucopyranosyl-(1—*3) -13-D-glucopyranosyl- (1—b4)-[(3-D-glucopyranosyl-(1-->2) - (3-D-glucopyranosyl(1- >4) - R-D-glupyranosyl-(1—>3)-aL-ramnopyranosyl-(1—>2)]}-a-L-arabinopyranosyl hederagenin(8). It is noteworthy that, among the aforementioned compounds, the saponins 5, 6, 7 and 8 were novel saponins. Quantitative analyses of saponins by HPLC, in reverse phase, of the ethanolic extract of seeds (mixture saponins), showed the major presence of saponins components (1) [ 23%], (2) [18,5%] and (3) [30%]. The structures were elucidated by spectroscopy methods such as IR, MS (FAB, ESI), 'H NMR and13C NMR including two dimensional techyniques (COSY, NOESY, HMQC and HMBC) and comparation with literature data.