Cecilia Veronica Nunez

Secondary Metabolites from Rubiaceae Species

This study describes some characteristics of the Rubiaceae family pertaining to the occurrence and distribution of secondary metabolites in the main genera of this family. It reports the review of phytochemical studies addressing all species of Rubiaceae, published between 1990 and 2014. Iridoids, anthraquinones, triterpenes, indole alkaloids as well as other varying alkaloid subclasses, have shown to be the most common. These compounds have been mostly isolated from the genera Uncaria, Psychotria, Hedyotis, Ophiorrhiza and Morinda. The occurrence and distribution of iridoids, alkaloids and anthraquinones point out their chemotaxonomic correlation among tribes and subfamilies. From an evolutionary point of view, Rubioideae is the most ancient subfamily, followed by Ixoroideae and finally Cinchonoideae. The chemical biosynthetic pathway, which is not so specific in Rubioideae, can explain this and large amounts of both iridoids and indole alkaloids are produced. In Ixoroideae, the most active biosysthetic pathway is the one that produces iridoids; while in Cinchonoideae, it produces indole alkaloids together with other alkaloids. The chemical biosynthetic pathway now supports this botanical conclusion.

Identificação de componentes de óleos voláteis: Análise espectroscópica de misturas de sesquiterpenos

This paper describes a chromatographic method to fractionate volatile oils and to identify their sesquiterpenic constituents. The fractionation process includes flash chromatography over silica gel and chromatography over silica gel/AgNO3, utilising pentane, CH2Cl2 and/or acetone as eluents. GC chromatograms were obtained in order to get the relative percentage of each constituent in the volatile oils, to get the retention time value of them as well as to analyse and combine the fractions eluted from the columns. Such procedure afford mixtures of sesquiterpenes which are analysed by GC/MS, 13C and 1H NMR.

Sesquiterpenes from the Stem Bark of Guarea guidonia (L.) Sleumer (Meliaceae)

Abstract The chemical composition of the essential oil, isolated by steam distillation from the stem bark of Guarea guidonia, was analyzed for the first time. The major components were identified as β-caryophyllene (25%) and germacrene D (24%) using a combination of GC, GC/MS, 13C- and 1H-NMR.

Chemical profile and biological activities of Deguelia duckeana A.M.G. Azevedo (Fabaceae)

Deguelia duckeana is popularly known as timbó and used by indigenous people as ictiotoxic. On account of there being no literature pertaining to the chemical profile or biological activity of this plant, the hexane, methanol and aqueous crude extracts from leaves, stems and roots were assayed that presented very high cytotoxic potential against Artemia salina, achieving 100% mortality in up to 5.0 µg mL−1 concentration, but lower antioxidant potential on 2,2-diphenyl-1-picryl-hydrazyl and Fe3+/Phenanthroline assays. The phytochemical analysis of crude extracts showed the presence of flavonoids and related compounds as major constituents as well as steroids in all of them, and tannins in polar extracts. All the extracts were assayed for antibacterial activity but only the hexane extract of stems showed moderate activity on Staphylococcus aureus, which was fractionated and yielded a mixture of 3,5,4′-trimethoxy-4-prenylstilbene, lonchocarpine, 4-hydroxylonchocarpine and derricidine, reported for the first time in D. duckeana and other fraction with β-sitosterol and stigmasterol mixture.

Salicilatos isolados de folhas e talos de Salix martiana Leyb. (Salicaceae)

Salix martiana Leyb. is an endemic species from the Amazon river floodplain areas (varzeas), of the State of Amazonas. Stems and leaves were extracted with dichloromethane, methanol and hydro-alcohol and these extracts were fractionated by using conventional chromatographic techniques. The major substances isolated, salicin and trichocarposide (6-0-p-coumaroyl salicin), were determined through analyses of NMR 1D (1H and 13C) and NMR 2D (gHSQC and gHMBC). These compounds were isolated for the first time in Salix martiana Leyb. (Salicaceae). The percentage of these compounds in S. martiana is very high. The extracts were analyzed for their DPPH antioxidant capacity and the methanolic from the leaves and the hydro-alcoholic from the stems were the more active.

Diterpene acids from Mikania sp. nov (Asteraceae)

1. Subject and sourceIn continuation with our studies on Mikania species (Nun˜ez and Roque, 1999;Nun˜ez et al., 2002), leaves of Mikania sp. nov. (Asteraceae) were collected in “Morrodo Pai Ina´cio”, Chapada Diamantina, Bahia, Brazil (S 12°27 341 and W41°28 502 ), in July, 1997. The collection was identified by Prof. Nicholas Hind(Kew Gardens, UK) (Hind, personal communication); a voucher specimen (Nun˜ez003) is deposited in the Herbarium of the Instituto de Biocieˆncias at Universidadede Sa˜o Paulo (SPF), Sa˜o Paulo, SP, Brazil.2. Previous workThe genus Mikania has more than 450 species, 150 of which occur in Brazil (Hind,1993). Almost 40 species of Mikania have been investigated previously, sesquiter-pene lactones and diterpene acids being the main metabolites (Herz, 1998).

Sesquiterpene lactone from Wunderlichia crulsiana inhibits the respiratory burst of leukocytes triggered by distinct biochemical pathways.

The sesquiterpene lactone tubiferin was chemically purified from the brazilian native plant Wunderlichia crulsiana and identified by NMR and GC/MS data. Its ability to inhibit the respiratory burst of peritoneal inflammatory polymorphonuclear leukocytes (PMN) stimulated upon addition of phorbol miristate acetate (PMA), opsonized zymosan (OZ), and N-formyl-methionyl-leucyl-phenylalanine (fMLP) was evaluated. The tubiferin inhibition was more pronounced when PMN were stimulated through the protein kinase C pathway (PMA) compared to the alternative complement pathway (OZ). The inhibition when PMN were triggered by a chemoattractant stimulus (fMLP) was similar to that achieved with OZ-stimulated phagocytes. Tubiferin showed dose-dependent effects on the PMN respiratory burst triggered by the three different substances, and also decreased substantially the carrageenan-induced mice paw edema.

Triterpenes from Minquartia guianensis (Olacaceae) and in vitro antimalarial activity

Minquartia guianensis, popularly known as acariquara, was phytochemically investigated. The following triterpenes were isolated from the dichloromethane extract of leaves: lupen-3-one (1), taraxer-3-one (2) and oleanolic acid (3). The dichloromethane extract of branches yielded the triterpene 3β-methoxy-lup-20(29)-ene (4). The chemical structures were characterized by NMR data. Plant extracts, substance 3, squalene (5) and taraxerol (6), (5 and 6 previously isolated), were evaluated by in vitro assay against chloroquine resistant Plasmodium falciparum. The dichloromethane extract of leaves and the three triterpenes assayed have shown partial activity. Thus, these results demonstrated that new potential antimalarial natural products can be found even in partially active extracts.

Triterpenos das folhas de Minquartia guianensis Aubl. (Olacaceae)

This article describes the isolation of the triterpenes lupeol, taraxerol, lupen-3-one and squalene from the dichloromethane extract of the leaves of Minquartia guianensis Aubl. belonging to the Olacaceae family. These terpenoids were isolated through chromatographic techniques and identified using 1H and 13C Nuclear Magnetic Resonance (NMR). At the best of our knowledge, this is the first report of these triterpenes in M. guianensis.

Isolation of Flavonoids from Deguelia duckeana and Their Effect on Cellular Viability, AMPK, eEF2, eIF2 and eIF4E

Preparations of Deguelia duckeana, known in Brazil as timbó, are used by indigenous people to kill fish. Reinvestigation of its extracts resulted in the isolation and identification of 11 known flavonoids identified as 3,5,4’-trimethoxy-4-prenylstilbene (1), 4-methoxyderricidine (2), lonchocarpine (3), 4-hydroxylonchocarpine (4), 4-methoxylonchocarpine (5), 5-hydroxy-4’,7-dimethoxy-6-prenylflavanone (6), 4’-hydroxyisolonchocarpine (7), 4’-methoxyisolonchocarpine (8), 3’,4’,7-trimethoxyflavone (9), 3’,4’-methylenedioxy-7-methoxyflavone (10), and 2,2-dimethyl-chromone-5,4’-hydroxy-5’-methoxyflavone (11). Except for 1, 3, and 4 all of these flavonoids have been described for the first time in D. duckeana and the flavanone 6 for the first time in nature. Compounds 2, 3, 4, 7, 9, and 10 were studied for their potential to induce cell death in neuronal SK-N-SH cells. Only the chalcone 4 and the flavanone 7 significantly induced lactate dehydrogenase (LDH) release, which was accompanied by activation of caspase-3 and impairment of energy homeostasis in the MTT assay and may explain the killing effect on fish. Interestingly, the flavone 10 reduced cell metabolism in the MTT assay without inducing cytotoxicity in the LDH assay. Furthermore, the flavonoids 2, 3, 4, 7, and 10 induced phosphorylation of the AMP-activated protein kinase (AMPK) and the eukaryotic elongation factor 2 (eEF2). The initiation factor eIF4E was dephosphorylated in the presence of these compounds. The initiation factor eIF2alpha was not affected. Further studies are needed to elucidate the importance of the observed effects on protein synthesis and potential therapeutic perspectives.