Adolfo H. Müller

Potencial alelopático de Myrcia guianensis

The use of fire and mowing as weed methods have proved inefficient. Although more efficient, synthetic chemical herbicides are usually related to environmental problems. Thus, the search for natural herbicides has become a priority matter. Based on these facts, research was conducted on Myrcia guianensis (pedra-ume-caa) including the isolation and identification of chemical substances with allelophatic activity. The allelophatic effects of extracts, fractions, essential oils, and isolated chemical substances (gallic acid and protocatechuic acid) on germination and radicle and hypocotyl growth of weed species Mimosa pudica (malicia) and Senna obtusifolia (mata-pasto) were analyzed. Extracts and fractions were analyzed at a concentration of 1%, essential oils at 15, 30, 45, 60 ppm and the isolated chemical substances at 15, 30, 45, 60 ppm. Malicia showed more sensitivity to the allelophatic effects of extracts and fractions. The essential oil inhibited the germination of M. pudica but stimulated that of S. obtusifolia. The allelophatic effects of the chemical substances were concentration dependent and the strongest activity was observed at 60 ppm.

A dimeric ArC2 compound from Peperomia pellucida.

Pellucidin A, a novel dimeric ArC2 compound, together with dill-apiol have been isolated from the aerial parts of Peperomia pellucida. The structure of pellucidin A was established by 1D and 2D NMR spectroscopy (1H-1H COSY; 1H-13C COSY; DEPT; NOESY and double irradiation) and other spectroscopic techniques. The biogenesis of pellucidin A is also briefly discussed.

Potencial alelopático de catequinas de Tachigali myrmecophyla (leguminosae)

13 C NMR spectral data and comparison with literature data. The compounds (+)-catechin and epicatechin were submitted to germination inhibition and radicle and hypocotyl growth assays. Results showed some significant activities confirming the initial hypothesis about allelopathic properties of that plant.

Eudesmane sesquiterpenoids from Pluchea quitoc

Two new sesquiterpenoids with an eudesmane carbon skeleton, 3β-angeloyloxy-4β-hydroxy-7α-H-eudesman-8-one and 3β-angeloyloxy-4β-acetoxy-7α-hydroxy-eudesm-11-en-8-one, were isolated from the hexane extract of the aerial parts of Pluchea quitoc and characterized mainly by 1D and 2D NMR spectroscopy. 7β-H-eudesman-4α,11-diol was also obtained from the same extract and ilicic acid was isolated from the chloroform-soluble fraction of the ethanolic extract.

Chemical constituents and allelopathic and antioxidant activities of Alchorneopsis floribunda Müll. Arg. (Euphorbiaceae)

Chemical investigation of extracts from the stems and leaves of Alchorneopsis floribunda Müll. Arg., collected in the Amazon region, was performed. The main isolated compounds were triterpenes (α-amyrin, β-amyrin, lupeol, betulin, betulinic acid, uvaol, erythrodiol and oleanolic acid) and phenolic acid derivatives from 4-hydroxybenzoic acid (gallic and protocatechuic acids and isocorilagin). In the germination assays, high inhibitory allelopathic effects of the extracts and isocorilagin were observed and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity of isocorilagin was higher than those of the standards used (Trolox and butylated hydroxyanisole). This is the first chemical study of the genus Alchorneopsis (Euphorbiaceae).

Estudo fitoquímico biomonitorado pelos ensaios de toxicidade frente à Artemia salina e de atividade antiplasmódica do caule de aninga (Montrichardia linifera)

Montrichardia linifera is an aquatic plant widely use in Amazon folkmedicine. However, very little is known about the chemical composition and biological activity. In search of biologically active (s) substance (s) phytochemical bioassay-guided study was conducted evaluating hexane extract and ethanol extract obtained from stems of this species. Since only the ethanol extract presented toxicity against Artemia salina and activity against Plasmodium falciparum, this extract was selected for chromatographic fractionation. The biological activities were concentred in dichloromethane fraction which showed high toxicity against A. saline (LD50< μg mL-1) and high antiplasmodial activity (IC50 <10 μg mL-1), showing promising antimalarial activity. Of this fraction, the aromatic compound p-hydroxybenzaldehyde was isolated for the first time in this plant.

Eudesmanolides and epoxycuauthemones from Pluchea quitoc

Abstract Three new eudesman-8,12-olides named 3 β -angeloyloxy-4 β -acetoxy-eudesm-7(11)-en-8 α ,12-olide; 3 β -angeloyloxy-4 β -acetoxy-8 β -hydroxy-eudesm-7(11)-en-8 α ,12-olide and 3 β -angeloyloxy-4 α ,8 β -dihydroxy-eudesm-7(11)-en-8 α ,12-olide and three new epoxycuauthemones, 3 β -angeloyloxy-7 β ,11-epoxy-4 α -hydroxyeudesman-8-one; 4 β -acetoxy-3 β -angeloyloxy-7 α ,11-epoxyeudesman-8-one and 3 β -angeloyloxy-7 α ,11-epoxy-4 α -hydroxy-5,6-dehydroeudesman-8-one, together with the furofuran lignan pinoresinol were obtained from the hexane extract and from the chloroform-soluble portion of the ethanolic extract of the aerial parts of Pluchea quitoc . Their structures were deduced by spectroscopic studies, including 2D-shift correlation experiments.

Dihydrochalcones, coumarins and alkaloids from Metrodorea nigra

Abstract Two novel dihydrochalcones, 2′,3,4′,6′-tetrahydroxy-4-methoxy-3′,5-di-(3,3-dimethylallyl)-dihydrochalcone and 2′,.3,6′-trihydroxy-4-methoxy-5-(3,3-dimethylallyl)-3′,4′-(2″,2″-dimethyldihydropyran)-dihydrochalcone, have been isolated from fresh fruits of Metrodorea nigra . Stems and leaves showed a similar composition and we have isolated common steroids, simple coumarins, several furocoumarins, furoquinoline alkaloids and a furofuran lignan. From stems, we have also isolated the pentacyclic 6- C -monoterpenyl-5,7-dioxycoumarin, deoxybruceol. Structures of the isolated compounds were elucidated on the basis of spectral data.

Two flavans from Brosimum acutifolium

Abstract Two new flavans were isolated from a dichloromethane extract of the bark of Brosimum acutifolium and identified as 4′-hydroxy-7,8-(2″,2″-dimethylpyran)flavan and 4′-hydroxy-7,8-(3″-hydroxy-2″,2″-dimethylpyran)flavan. Structures were elucidated by spectral data.

Methoxyflavones from Ficus maxima

Abstract Four methoxyflavones were obtained from the leaves of Ficus maxima , one of which is the novel 5,6,7,3′,5′-pentamethoxy-4′-prenyloxyflavone. Their structures were determined on the basis of spectral data.