Alberto C. Arruda

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.

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).

Dihydroflavonols from the leaves of Derris urucu (Leguminosae): structural elucidation and DPPH radical-scavenging activity

Derris urucu e uma planta da Amazonia com propriedades inseticida e ictiotoxica. Estudos com esta especie reportam a presenca de flavonoides, principalmente rotenoides, bem como de estilbenos. A partir do extrato etanolico das folhas de Derris urucu (Leguminosae), tres novos diidroflavonoides, denominados urucuol A (1), B (2) e C (3) e o diidroflavonol isotirumalina (4), foram isolados e identificados. As estruturas destes compostos foram elucidadas por uma extensiva analise espectroscopica de RMN uni e bidimensional, UV, IV e dados de EM, alem de comparacao com dados da literatura. Os compostos isolados (1-4) foram avaliados quanto ao seu potencial sequestrador do radical DPPH• e apresentaram baixo poder antioxidante quando comparados ao antioxidante comercial trans-resveratrol.

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.

Antraquinonas e naftoquinonas do caule de um espécime de reflorestamento de Tectona grandi (Verbenaceae)

O fracionamento do extrato hexânico do caule de um especime de reflorestamento de Tectona grandis (Verbenaceae), atraves de procedimentos fitoquimicos classicos, levou ao isolamento das naftoquinonas lapachol e desidro-a-lapachona e das antraquinonas tectoquinona e obtusifolina. As estruturas das substâncias foram caracterizadas atraves da analise de metodos espectrometricos de RMN. Este e o primeiro estudo fitoquimico de um especime de reflorestamento de Tectona grandis, no Brasil, sendo o objetivo principal deste trabalho a comprovacao da presenca de tectoquinona em especimes cultivados.

Coumarins and Alkaloids from the Stems of Metrodorea Flavida

Uma nova cumarina , a 5,6-metilenodioxi-7,8-dimetoxicumarina, foi isolada a partir dos galhos de Metrodorea flavida, juntamente com outras cumarinas e alcaloides conhecidos. As estruturas das substâncias isoladas foram definidas por analises de seus dados espectrais , bem como por comparacao com dados da literatura.

Alkaloids and coumarins from Ticorea longiflora

Abstract A new dihydropyranocoumarin, (−)-6-methoxy- trans -khellactone, has been isolated from the stems of Ticorea longiflora , in addition to the known coumarins, osthol, O -methylcedrelopsin and braylin, the anthranilate alkaloids, skimmianine, γ-fagarine, dictamnine, evolitrine and 4-methoxy- N -methyl-2-quinolone, and trimethoxyphloroglucinol. From the leaves, we have isolated the coumarin, braylin, the furoquinoline alkaloids, skimmianine, evolitrine and γ-fagarine, and the steroids, stigmasterol and β-sitosterol. The structures of the isolated compounds were elucidated on the basis of spectral data.