Eva G. Magalhães

Twenty-three flavonoids from Lonchocarpus subglaucescens

Abstract Chemical investigation of Lonchocarpus subglaucescens roots resulted in the isolation of 23 flavonoids, whose structures were elucidated by spectroscopic methods. Ponganone III, ovalichromene B, purpurenone, 12α-hydroxyrotenone, (2,3- trans -3,4- trans )-3,4,5,8-tetramethoxy-[2″,3″:7,6]-furanoflavan, 6″,6″-dimethylchromeno- [2″,3″:7,8]-flavone and 3′,4′-methylenedioxy-6″,6″-dimethylchromeno-[2″, 3″:7,8]-flavone had been previously isolated from other sources. The 16 new flavonoids are 6-methoxy-6″,6″-dimethylchromeno-[2″,3″:7,8]-flavanone, (2 S )-5,6-dimethoxy-[2″,3″:7,8]-furanoflavanone, (2 R ,3 R )-3,5,6-trimethoxy-[2″,3″,7,8]-furanoflavanonol, 3,4-methylenedioxy-2′-methoxy-6″,6″-dimethylchromeno-[2″,3″:4′,3′]-β-hydroxychalcone, ( Z / E )-3,4-methylenedioxy-2′-methoxy-6″,6″-dimethylchromeno-[2″,3″:4′,3′]-9-methoxychalcone, ( E )-2′-methoxy-6″,6″-dimethylchromeno-[2″,3″:4′,3′]-9-methoxychalcone, (2,4- cis )-3′,4′-methylenedioxy-4,5,8-trimethoxy-[2″,3″:7,6]-furanoflavan, (2,4- cis )-4,5,6-trimethoxy-[2″,3″:7,8]furanoflavan, 3,4-dimethoxy-2′-hydroxy-6″,6″-dimethylchromeno-[2″,3″:4′,3′]-chalcone, 3,4-methylenedioxy-2′-hydroxy-3′,6′-dimethoxy-[2″,3″:4′,5′]-furanochalcone, (2,3- trans -3,4- cis -3,4,5,6-tetramethoxy-[2″,3″:7,8]-furanoflavan, (2,3- trans -3,4- trans )-3′,4′-methylenedioxy-3,4,5,8-tetramethoxy-[2″,3″:7,6]-furanoflavan, (2,3- trans -3,4- cis )-3′,4′-methylenedioxy-3,4,5,6-tetramethoxy-[2″,3″:7,8]-furanoflavan, 3,4-methylenedioxy-2′-methoxy-[2″,3″:4′,3′]-dihydrochalcone and 3′,4′-methylenedioxy-8-methoxy-5-hydroxy-6″,6″-dimethylchromeno- [2″,3″:7,6]-isoflavone.

Dihydroisocoumarins and phthalide from wood samples infested by fungi

Abstract Wood samples, infested by fungi during storage, were shown to contain, besides the known 5-methyl-mellein, additional (3 R )-8-hydroxy-3-methyl-3,4-dihydroisocoumarins substituted by 7-methyl, 5-formyl, 5-carboxy, 5-hydroxy, 5-methoxy, 6-methoxy-5-methyl and 6,7-dimethoxy-5-methyl groups, as well as 6-formyl-7-hydroxy-5-methoxy-4-methylphthalide. Several 2-methylchromanones were synthesized in order to show that this class of compounds can be distinguished from 3-methyl-3,4-dihydroisocoumarins by MS.

Coumarins from Pterocaulon balansae and P. lanatum

Abstract Analysis of the petrol-diethyl ether extracts of Pterocaulon balansae and P. lanatum aerial parts afforded, besides puberulin, scopoletin-[2′

Saponins from Swartzia langsdorffii: Biological Activities

The presence of saponins and the molluscicidal activity of the roots, leaves, seeds and fruits of Swartzia langsdorffii Raddi (Leguminosae) against Biomphalaria glabrata adults and eggs were investigated. The roots, seeds and fruits were macerated in 95% ethanol. These extracts exerted a significant molluscicidal activity against B. glabrata, up to a dilution of 100 mg/l. Four mixtures (A2, B2, C and D) of triterpenoid oleanane type saponins were chromatographically isolated from the seed and fruit extracts. Two known saponins (1 and 2) were identified as beta-D-glucopyranosyl-[alpha-L-rhamnopyranosyl-(1->3)- beta-D-glucuronopyranosyl-(1->3)]-3beta-hydroxyolean-12-ene-28 -oate, and beta-D-glucopyranosyl-(1->3)-beta-D-glucuronopyranosyl-(1 ->3)]-3beta-hydroxyolean-12-ene-28-oate, respectively. These two saponins were present in all the mixtures, together with other triterpenoid oleane type saponins, which were shown to be less polar, by reversed-phase HPLC. The saponin identifications were based on spectral evidence, including H- H two-dimensional correlation spectroscopy, nuclear Overhauser and exchange spectroscopy, heteronuclear multiple quantum coherence, and heteronuclear multiple-bond connectivity experiments. The toxicity of S. langsdorffii saponins to non-target organisms was prescreened by the brine shrimp lethality test.

Avaliação da atividade tóxica em Artemia salina e Biomphalaria glabrata de extratos de quatro espécies do gênero Eleocharis (Cyperaceae)

The genus Eleocharis R. Br. comprises about 200 species, occurring in wet environments like swamps, lakes and river margins. In the search for new molluscicides, extracts from Eleocharis acutangula (Roxb.) Schult., Eleocharis interstincta (Vahl) Roem. & Schult., Eleocharis maculosa (Vahl) Roem. & Schult. and Eleocharis sellowiana Kunth were tested for molluscicidal activity (spawns and adult snails) and toxicity (Brine Shrimp Lethality - BSL - bioassay). The hexane extract of Eleocharis acutangula (fresh subterraneous parts) was active in the BSL bioassay (LC50 = 476 mg/mL), while the other extracts showed LC50 >> 103 mg/mL, suggesting they have low toxicity. The aqueous ethanol extract of Eleocharis sellowiana (fresh subterraneous parts) was active against Biomphalaria glabrata spawns (LC50 = 24.27 mg/mL) but it was not lethal to adult snails. No other plant extract tested in this study showed molluscicidal activity.

Three dibenzoylmethane derivatives from Lonchocarpus species

Abstract Three new dibenzoylmethane derivatives were isolated from petrol extracts of the roots of Lonchocarpus latifolius and L. muehlbergianus . Molecular structures were determined from spectroscopic data, especially NMR techniques. An alkyl group bonded to the central carbon (C-8) of a natural dibenzoylmethane, had not been found before. Spectral data analysis suggested a preponderance of the respective diketotautomers.

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.

Rubranine from Aniba rosaeodora

Abstract Aniba rosaeodora wood was shown to contain (—)-rubranine. An optically inactive form of this citrylidene-chalcone was previously considered to be an artifact of extraction. The constitution of rubranine was confirmed by pyrolysis and syntheses, involving previously reported pyridine-catalysed condensation of pinocembrin and citral, whereby novel intermediates were prepared, and the acid-catalysed condensation of pinocembrin with geraniol followed by oxidation.

QUENCHING OF SINGLET MOLECULAR OXYGEN BY NATURAL FURAN DITERPENES

Abstract Singlet molecular oxygen O 2 ( 1 Δ g ) is a reactive oxygen species capable of damaging biological molecules and triggering oxidative stress. The quenching of this species by naturally occurring furans was measured using O 2 ( 1 Δ g ) from two different sources: (1) the thermal decomposition of 1,4-dimethylnaphthalene endoperoxide (1,4-DMNO 2 ); (2) tetraphenylporphyrin sulphonate photosensitization. Four furan diterpenes were isolated from alcoholic extracts of Sucupira branca (Pterodon sp., Leguminosae) seeds, which are used for the treatment of rheumatic diseases, suggesting anti-inflammatory activity. Using time-resolved near-IR (NIR) emission after photosensitization, the overall (physical + chemical) O 2 ( 1 Δ g ) quenching rate constants by these compounds were found to be of the order of 10 8 M −1 s −1 , with the exception of the conjugated furan diterpenes 3,5,6-trimethoxy-7,8-furano-3′,4′-methylenedioxy-2″,3″-flavane and 3,4,5,6-tetramethoxy-7,8-furano-2″,3″-flavane for which 20-fold lower values were observed. These lower values are attributed to the conjugation of the furan moiety with the aromatic ring, which prevents (2 + 4) cucloaddition of O 2 ( 1 Δ g ) to the furan ring. Although the non-conjugated furans exhibit a low scavenging effect on lipid peroxidation in microsomes, their high O 2 ( 1 Δ g ) quenching constant may minimize the extent of tissue damage associated with the inflammatory process.

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.