Flavonoids of Lonchocarpus montanus A.M.G. Azevedo and biological activity

ABSTRACT

The analysis of root extracts from Lonchocarpus montanus A.M.G. Azevedo resulted in the isolation of twenty three compounds chiefly flavonoids of which five (four flavonoids and one benzophenone) are described for the first time. The molecular structures of the new compounds (1-5) were determined through spectral analysis (UV, IR, MS and NMR) as being 2'-hydroxy-8-(FACE="Symbol">a,a-dimethylallyl)-2", 2"-dimethylpyrano-(5",6"3',4')-dibenzoylmethane (1), 2'-methoxy-8-(FACE="Symbol">a, a-dimethylallyl)-2", 2"-dimethylpyrano-(5",6"3',4')-dibenzoylmethane (2), 4'-methoxy-2",2"-dimethylpyrano-(5",6"8,7)-flavone (3), 2"-(1-hydroxy-1-methylethyl)-furano-(4",5"8,7)-flavone (4) and [2'-methoxy-furano-(4",5"3',4')-phenyl]-phenylmethanone (5). Additionally, fifteen fatty acids were detected through GC-MS analysis of the corresponding methyl esters [(CH3)2CH(CH2)8COOH and CH3(CH2)nCOOH (n = 6, 12-24)]. Quantitative RP-HPLC showed that the most abundant flavonoids in the petroleum ether and dichloromethane extracts were pongamol (19 percent) and lanceolatine B (8.0 percent), respectively. In the bioautography assay, the extracts, pongamol (9), lanceolatine B (10), isolonchocarpin (14), derriobtusone A (17) and medicarpine (18) were active against Staphilococus aureus whereas 9 also against Bacillus subtilis and Cladosporium cladosporioides. Compound 1, 2",2"-dimethylpyrano-(5",6"8,7)-flavone (11) and furano-(1200,13007,8)- 4'-methoxy flavone (12) were active against Fusarium oxysporium whereas 11 also against Rhizopus orizae. The extracts, compounds 9, 10, 17 and (E)-7-O-methoxypongamol (23) displayed high toxicity in the brine shrimp lethality assay.

RESUMO

A análise dos extratos das raízes de L. montanus A.M.G. Azevedo resultou no isolamento de vinte e três compostos principalmente flavonóides dos quais cinco são descritos pela primeira vez. As estruturas moleculares dos novos compostos (1-5) foram propostas através da análise dos espectros de UV, IV, EM e RMN como sendo 2'-hidroxi-8-(FACE="Symbol">a, a-dimetilalil)-2", 2"-dimetilpirano-(5", 6"3',4')-dibenzoilmetano (1), 2'-metoxi-8-(FACE="Symbol">a,a-dimetilalil)-2", 2"-dimetilpirano-(5", 6"3',4')-dibenzoilmetano (2), 4'-metoxi-2", 2"-dimetilpirano-(5", 6"8,7)-flavona (3), 2"-(1-hidroxi-1-metiletil)-furano-(4", 5"8,7)-flavona (4) e [2'-metoxi-furano(4", 5"3',4')-fenil]-fenilmetanona (5). Adicionalmente quinze ácidos graxos foram detectados através da análise de CG-EM dos ésteres metílicos correspondentes [(CH3)2CH(CH2)8COOH e CH3(CH2)nCOOH (n = 6, 12-24)]. A análise quantitativa por CLAE mostrou que os flavonóides mais abundantes nos extratos éter de petróleo e diclorometânico foram pongamol (19 por cento) e lanceolatina B (8.0 por cento), respectivamente. Nos ensaios de bioautografia, os extratos, pongamol (9), laceolatina B (10), isolonchocarpina (14), derriobtusona A (17) e medicarpina (18) foram ativos contra Staphilococcus aureus enquanto 9, também contra Bacillus subtilis e Cladosporium cladosporióides. O composto 1, 2", 2"-dimetilpirano-(5", 6"8,7)-flavona (11) e furano-(2", 3"7,8)-4'-metoxiflavona (12) foram ativos contra Fusarium oxysporium, enquanto 11, também contra Rhizopus oryzae. Os extratos assim como os compostos 9, 10, 17 e (E)-7-O-metoxipongamol (23) apresentaram alta toxicidade no ensaio de letalidade com Artemia salina.