Giselle Maria Skelding Pinheiro Guilhon

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.

Alkaloids and coumarins from Esenbeckia species

Abstract Investigation of two species of Esenbeckia, E. almawillia and E. grandiflora , has led to the isolation and identification of kokusaginine, maculine, maculosidine, flindersiamine, xanthotoxin, pimpinellin, 4-methoxy-1-methylquinolin-2-one, two new 2-arylquinolin-4-one alkaloids and two 3-(1′,1′-dimethylallyl)dihydrofurocoumarins derivatives. Structures of all compounds were elucidated by spectroscopic methods.

Antibacterial activity of alkaloids produced by endophytic fungus Aspergillus sp. EJC08 isolated from medical plant Bauhinia guianensis

Bauhinia guianensis is a typical plant in the Amazon region belonging to the family Leguminosea, used by local populations for the treatment of infectious and renal diseases. Previous work on the plant B. guianensis led to the isolation of substances with anti-inflammatory and analgesic activities. Thus, compounds isolated from B. guianensis with antimicrobial activities had not been identified. Given that there is a possibility of biological activity reported for a given plant being found in the endophytic fungi, we decided to isolate endophytic fungi from B. guianensis and test their antimicrobial activities. The alkaloids known as fumigaclavine C and pseurotin A were isolated by column chromatography and identified by 1D and 2D NMR techniques and mass spectrometry. The alkaloids are first reported as broad-spectrum antibacterial agents with good activity.

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.

2-Alkyl-4-quinolone alkaloids and cinnamic acid derivatives from Esenbeckia almawillia

Abstract Chemical investigation of Esenbeckia almawillia afforded, in addition to a known furocoumarin and a cinnamaldehyde derivative, three new quinolone alkaloids, 8-methoxy-1-methyl-2-pentyl-, 8-methoxy-1-methyl-2-hexyl- and 8-methoxy-1-methyl-2-heptyl-4-quinolone, and a cinnamic acid derivative, 3-methoxy-4,5-methylenedioxycinnamic acid methyl ester. All compounds were elucidated through analysis of spectroscopic data.

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).

Atividade potencialmente alelopática do óleo essencial de Ocimum americanum

C de temperatura constante e fotoperiodo de 24 horas) das plantas daninhas malicia (Mimosa pudica) e mata-pasto (Senna obtusifolia). Fatores relacionados a concentracao, especificidade das plantas receptoras e parâmetros analisados foram decisivos para os efeitos obtidos. A tendencia geral foi de relacao positiva entre concentracao e efeito inibitorio. Malicia foi mais sensivel aos efeitos do que matapasto. Comparativamente, a germinacao, seguida do desenvolvimento da radicula, foi afetada pelo oleo essencial em maior magnitude, ficando o desenvolvimento do hipocotilo como o de menor sensibilidade. Os efeitos observados podem ser atribuidos a presenca, no oleo essencial, de monoterpenos, monoterpenos oxigenados, sesquiterpenos, alifaticos e fenilpropanoides, com destaque para os constituintes com atividade alelopatica ja comprovada, como o limoneno, a cânfora e o linalol.

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.

Constituents and Pharmacological Activities of Myrcia (Myrtaceae): A Review of an Aromatic and Medicinal Group of Plants

Myrcia is one of the largest genera of the economically important family Myrtaceae. Some of the species are used in folk medicine, such as a group known as “pedra-hume-caá” or “pedra-ume-caá” or “insulina vegetal” (insulin plant) that it is used for the treatment of diabetes. The species are an important source of essential oils, and most of the chemical studies on Myrcia describe the chemical composition of the essential oils, in which mono- and sesquiterpenes are predominant. The non-volatile compounds isolated from Myrcia are usually flavonoids, tannins, acetophenone derivatives and triterpenes. Anti-inflammatory, antinociceptive, antioxidant, antimicrobial activities have been described to Myrcia essential oils, while hypoglycemic, anti-hemorrhagic and antioxidant activities were attributed to the extracts. Flavonoid glucosides and acetophenone derivatives showed aldose reductase and α-glucosidase inhibition, and could explain the traditional use of Myrcia species to treat diabetes. Antimicrobial and anti-inflammatory are some of the activities observed for other isolated compounds from Myrcia.

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.