Anti-African trypanocidal and antimalarial activity of natural flavonoids, dibenzoylmethanes and synthetic analogues.

OBJECTIVES: The known anti-protozoal activity of flavonoids has stimulated the testing of other derivatives from natural and synthetic sources. METHODS: As part of our efforts to find potential lead compounds, a number of flavonoids isolated from Neoraputia paraensis, N. magnifica, Murraya paniculata, (Rutaceae), Lonchocarpus montanus, L. latifolius, L. subglaucescens, L. atropurpureus, L. campestris, Deguelia hatschbachii (Leguminosae), dibenzoylmethanes from L. subglaucescens and synthetic analogues were tested for in-vitro activity against chloroquine-sensitive Plasmodium falciparum and Trypanosoma brucei rhodesiense bloodstream form trypomastigotes. An assay with KB cells has been developed in order to compare in-vitro cytotoxicity of flavonoids with a selective action on the parasites. KEY FINDINGS: Thirteen of the compounds tested had IC50 values ranging from 4.6 to 9.9 microm against T. brucei rhodesiense. In contrast, a small number of compounds showed significant activity against P. falciparum; seven of those tested had IC50 values ranging from 2.7 to 9.5 microm. Among the flavones only one had IC50 < 10 microm (7.6 microm), whereas against T. brucei rhodesiense seven had IC50 < 10 microm. Synthetic dibenzoylmethanes were the most active in terms of number (five) of compounds and the IC50 values (2.7-9.5 microm) against P. falciparum. CONCLUSIONS: Dibenzoylmethanes represent a novel class of compounds tested for the first time as antimalarial and trypanocidal agents.

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

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-(alpha,alpha-dimethylallyl)-2", 2"-dimethylpyrano-(5",6":3',4')-dibenzoylmethane (1), 2'-methoxy-8-(alpha,alpha-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%) and lanceolatine B (8.0%), respectively. In the bioautography assay, the extracts, pongamol (9), lanceolatine B (10), isolonchocarpin (14), derriobtusone A (17) and medicarpine (18) were active against Staphylococcus aureus whereas 9 also against Bacillus subtilis and Cladosporium cladosporioides. Compound 1, 2",2"-dimethylpyrano-(5",6":8,7)-flavone (11) and furano-(1200,1300:7,8)- 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.

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

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-(a,a-dimethylallyl)-2", 2"-dimethylpyrano-(5",6":3',4')-dibenzoylmethane (1), 2'-methoxy-8-(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-(1200,1300:7,8)- 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.

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-(a, a-dimetilalil)-2", 2"-dimetilpirano-(5", 6":3',4')-dibenzoilmetano (1), 2'-metoxi-8-(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.

New prenylated metabolites of Deguelia longeracemosa and evaluation of their antimicrobial potential.

The analysis of root extracts from Deguelia longeracemosa (Benth.) A.M.G. Azevedo yielded fifteen prenylated metabolites. Nine of them are novel, and their molecular structures were determined through spectral analyses (UV, IR, MS and NMR) as being five derivatives of 4-hydroxy-3-phenylcoumarin: 4-hydroxy-3-(4'-hydroxyphenyl)-5-methoxy-6-(8',9'-epoxy-9'-methylbutyl)-2'',2''-dimethylpyrano-(5'',6'':8,7)-coumarin; 4-hydroxy-3-(3',4'-methylenedioxyphenyl)-5-methoxy-6-(3,3-dimethylallyl)-2'',2''-dimethypyrano-(5'',6'':8,7)-coumarin; 4-hydroxy-3-(3'-hydroxy-4'-methoxyphenyl)-5-methoxy-6-(3,3-dimethylallyl)-2'',2''-dimethylpyrano-(5'',6'':8,7)-coumarin; 4-hydroxy-3-(3'-hydroxy-4'-methoxyphenyl)-5-methoxy-2'',2''-dimethylpyrano-(5'',6'':6,7)-coumarin and 4-hydroxy-3-[4'-O-(3,3-dimethylallyl)phenyl]-5-methoxy-2'',2''-dimethylpyrano-(5'',6'':6,7)-coumarin, three derivatives of 1,2-diphenyl-1,2-ethanodione (alpha-oxodeoxybenzoin derivatives): 1-[6-hydroxy-2-methoxy-3-(3,3-dimethylallyl)-2'',2''-dimethylpyrano-(5'',6'':5,4)- ]-2-(4'-hydroxyphenyl)-1,2-ethanedione; 1-[6-hydroxy-2-methoxy-2'',2''-dimethylpyrano-(5'',6'':3,4)]-2-(4'-methoxyphenyl)-1,2-ethanedione; 1-[6-hydroxy-2-methoxy-2'',2''-dimethylpyrano-(5'',6'':3,4)]-2-(3',4'-methylenedioxyphenyl)-1,2-ethanedione and one derivative of deoxybenzoin: 2,4'-dimethoxy-6-hydroxy-2'',2''-dimethylpyrano-(5'',6'':3,4)-deoxybenzoin. The antimicrobial activity of roots extracts and some isolated compounds was screened through bioautography against bacteria and fungi.

Swartziarboreol diterpenes from Swartzia langsdorffii Raddi.

Two new swartziarboreol diterpenes (1 and 2) and swartziarboreol C were isolated from the petroleum ether extract of the roots of Swartzia langsdorffii. Their structures were elucidated by spectroscopic evidence. The biological activity of the root extracts and 2 was evaluated through bioautography and brine shrimp lethality assays.

Flavonoids from Lonchocarpus muehlbergianus

O extrato éter de petróleo das raízes de Lonchocarpus muehlbergianus foi submetido a sucessivas análises cromatográficas (CC, CCD e CDC preparativa) levando ao isolamento de nove flavonóides (1-9) dos quais seis são inéditos na literatura (1-6) destacando-se as quatro flavanas 2,4-dioxigenadas (1-4) que representam uma nova classe de flavonóides. As estruturas moleculares foram determinadas através da análise dos respectivos espectros de RMN 1H, RMN 13C e DEPT, RMN-2D (COSY, HETCOR e COLOC), NOE, IV, UV e EM. A análise quantitativa por CLAE, mostrou que a nova flavana 1 é o flavonóide que ocorre em maior abundância no extrato.

Flavonoids from Lonchocarpus muehlbergianus.

The light petroleum extract from the roots of Lonchocarpus muehlbergianus Hassl contained nine flavonoids, including six new ones. These are 2,4-cis-2,4,5,8-tetramethoxy-(2'',3'':6,7)-furanoflavan; 2,4-cis-4-hydroxy-2,5,8-trimethoxy-(2'',3'':6,7)-furanoflavan; 2,4-cis-2-prenyloxy-4,5,8-trimethoxy-(2'',3'':6,7)-furanoflavan; 2,4-cis-2-prenyloxy-4-hydroxy-5,8-dimethoxy-(2'',3'':6,7)-furanoflavan; 2',5',6'-trimethoxy-9-(1,1-dimethylallyoxy)-[2'',3'':3',4']-furanochalcone; 5,6-dimethoxy-(2'',3'':7,8)-furanoflavone, identified by analysis of their spectral data (UV, IR, 1H and 13C NMR, 2D-NMR, NOE and MS). The natural occurrence of 2,4-dioxygenated flavan derivatives is being reported for the first time. Quantitative analysis of the petrol extract, by using reversed-phase HPLC, showed that the most abundant flavonoid in the extract is 2,4-cis-2,4,5,8- tetramethoxy-(2'',3'':6,7)-furanoflavan.

Steroids and triterpenes from Eleocharis acutangula and E. sellowiana (Cyperaceae).

From the hexane extract of the underground parts of Eleocharis acutangula (Roxb.) Schult., lup-20(29)-ene-3beta,16beta-diol and a mixture of campesterol, stigmasterol and sitosterol were isolated. The hexane extracts of aerial and underground parts of E. sellowiana Kunth furnished two new substances, namely neohop-13(18)-en-3alpha-ol and stigmast-22-en-3beta,6beta,9alpha-triol, together with a mixture of steroids, betulinic acid, stigmast-4-en-6beta-ol-3-one and fern-9(11)-en-3alpha-ol. The molecular structures were determined by spectral analysis (1D- and 2D-NMR experiments and MS) and comparison with literature data.

A novel sunscreen agent having antimelanoma activity.

A novel series of eight dibenzoylmethane derivatives having both sunscreen and cytotoxic activity has been obtained by derivatizing commercial dibenzoyl methanes. Four human cancer cell lines (MCF 7 (breast), NCI ADR (breast expressing the multidrug resistance phenotype), NCI 460 (lung) and UACC 62 (melanoma)) were used for the cytotoxic assay. Eight among the 19 dibenzoylmethane derivatives showed cytotoxicity against these four cell lines. Absorption spectroscopies revealed that these compounds can be used as sunscreens against UV radiation.

Detection of polyhydroxyalkaloids in Lonchocarpus extracts by GC-MS of acetylated derivatives.

The methanol extracts of the roots of Lonchocarpus cultratus, L. latifolius and L. subglaucescens, species native to Brazil, were all active in the brine shrimp lethality test. Fractions rich in polyhydroxylated alkaloids were obtained from these extracts and, following acetylation, were analysed by GC-MS leading to the identification of acetylated derivatives of 2,5-trans-dihydroxymethyl-3,4-trans-dihydroxypyrrolidine (1), 1-deoxymannojirimycin, 1-deoxynojirimycin, fagomine and homonojirimycin. Only from L. subglaucescens could a compound with the constitution and relative configuration expected for the penta-acetate of 1 be isolated, and its molecular structure was determined for the first time through extensive spectral data analysis.