Computer-aided Structure Elucidation of Neolignans

This paper describes a new module of the expert system SISTEMAT used for the prediction of the skeletons of neolignans by (13)C NMR, (1)H NMR and botanical data obtained from the literature. SISTEMAT is composed of MACRONO, SISCONST, C13MACH, H1MACH and SISOCBOT programs, each analyzing data of the neolignan in question to predict the carbon skeleton of the compound. From these results, the global probability is computed and the most probable skeleton predicted. SISTEMAT predicted the skeletons of 75% of the 20 neolignans tested, in a rapid and simple procedure demonstrating its advantage for the structural elucidation of new compounds.

Neolignans, styrylpyrones and flavonoids from an Aniba species

The trunk wood and barks from an Aniba species contain four esters of benzoic acid with cinnamyl alcohol, five benzofuran neolignans, licarin-A, burchellin, cis-burchellin, burchellin-rearranged and cis-burchellin-rearranged, one tetrahydrofuran neolignan, aristolignin, three bicyclooctane guianin-type neolignans, (7S, 8S, 1'R, 5'R)-4-hydroxy-3,3'-dimethoxy-4',6'-dioxo-8.1', 7.5'-neolignan-Delta: 1,3,5,2',8' and the new (7S, 8S, 1'R, 4'R, 5'S)-4'-hydroxy-3,4,3'-trimethoxy-6'-oxo-8.1', 7.5'-neolignan-Delta: 1,3,5,2',8' and (7S, 8S, 1'R, 4'R, 5'S)-4,4'-dihydroxy-3,3'-dimethoxy-6'-oxo-8.1', 7.5'-neolignan-Delta: 1,3,5,2',8', one new bicyclooctane canellin-type neolignan (7S, 8S, 1'S, 4'R, 5'R, 6'S)-4',6'-dihydroxy-3,4-dimethoxy-3'-oxo-8.1', 7.5'-neolignan-Delta: 1,3,5,8', two styrylpyrones, 4-methoxy-6-(11,12-dimethoxy-trans-styryl)-2-pyrone and 6-(11,12-methylenedioxy-trans-styryl)-4-methoxy-2-pyrone, two styrylpyrone dimers: 4'-methoxy-8-(11,12-dimethoxyphenyl)-7-[6-(4-methoxy-2-pyronyl)-6-(E)-styryl-1'-oxabicyclo[4,2,0]octa-4'-en-2'-one and the new 11,12-dimethoxyphenyl-7,7'-di-[6-(4-methoxy-2-pyronyl)]-cyclobutane and six flavonoids, 3,5-dihydroxy-7,4'-dimethoxyflavone, 5-hydroxy-3,7,4'-trimethoxyflavone, 3,5,4'-trihydroxy-7-methoxyflavone, 2,3-dihydro-5-hydroxy-7,4'-dimethoxyflavone, 2,3-dihydro-3,5-dihydroxy-7-methoxyflavone, 2,3-dihydro-3,5-dihydroxy-7,4'-dimethoxyflavone and a new flavan, 6,7,3',4',5'-pentamethoxyflavan. (C) 1997 Elsevier B.V. Ltd.

2,3-Dihydrobenzofuran neolignans from Aristolochia pubescens

From a hexane extract of stems and roots of Aristolochia pubescens, the new neolignans (2S,3S,1'R,2'R)- and (2S,3S, 1'S,2'R)-2,3-dihydro-5-(1',2'-dihydroxypropyl)-2-(4-hydroxy-3-methylbenzofuran) and (2S,3S,1'R,2'R)- and (2S,3S,1'S,2'R)-2,3-dihydro-5-(1',2'-dihydroxypropyl)-2-(3,4-dimethoxyphenyl)-7-methoxy-3-methyl-benzofuran were isolated, together with the known neolignan licarin A, and its bisnor-neolignan aldehyde and acid derivatives. In addition, sitosterol, 8R,9R-oxide-beta-caryophyllene, kobusone, ent-kauran-16 alpha, 17-diol, vanillin, vanillic acid, (+)-sesamin, (+)eudesmin, and (-)-cubebin were isolated. The structures of the new compounds have been elucidated by spectroscopic methods and by chemical transformation using Mosher's acid chloride. (C) 1999 Elsevier B.V. Ltd. All rights reserved.

Neolignans from leaves of Ocotea catharinensis

A hexane extract of Ocotea catharinensis leaves afforded, by chromatographic fractionation, 11 neolignans, eight of the benzofuran- type (including three new compounds) and three of the bicyclo[3.2.1] octane-type (including two new compounds).

Neolignans from fruits of Virola elongata

Fruits of Virola elongata contain, besides the furofuranoid lignans eudesmin, epieudesmin and fargesin, the aryl-benzyl-methyl tetrahydrofuran neolignans magnostellins A and C. The absolute configuration of the magnostellins was detennined.

Neolignans from Aniba citrifolia

The trunk wood of Aniba citrifolia contains hydrobenzofuranoid and bicyclo[3.2.1]octanoid neolignans. © 1984.

Hexahydrobenzofuranoid neolignans from an Aniba species

The trunk wood of an Amazonian Aniba species contains three novel neolignans: (2R, 3R, 3aS, 5R)-3a-allyl-5-methoxy-2-(3,4,5-trimethoxyphenyl)-3-methyl-2,3,3a,4,5,6-hexahydro-6-oxobenzofuran (canellin-D), (2R,3R,3aS,5R)-3a-allyl-5,7-dimethoxy-2-(3-methoxy-4,5-methylenedioxyphenyl)-3-methyl-2,3,3a,4,5,6-hexahydro-6-oxobenzofuran (canellin-E) and (2S,3S,3aS,5R)-3a-allyl-5-methoxy-2-(3-methoxy-4,5-methylenedioxyphenyl)-3-methyl-2,3,3a,4,5,6-hexahydro-6-oxobenzofuran (armenin-C). The absolute stereochemistries of these and of all other known hexahydro-6-oxobenzofurans were determined by CD comparisons with model compounds. © 1984.

Cyclooxygenase inhibitory properties of nor-neolignans from Styrax pohlii

Chemical investigation of the n-hexane and EtOAc fractions of the ethanolic extract from Styrax pohlii (Styracaceae) aerial parts resulted in the isolation of the benzofuran nor-neolignan derivatives egonol (1), homoegonol (2), homoegonol gentiobioside (3), homoegonol glucoside (4) and egonol gentiobioside (5). This is the first report of compounds 1-5 in S. pohlii. Compounds 1-5, the acetyl derivatives 1a and 2a, the ethanolic extract (EE), the n-hexane fraction (HF) and EtOAc fraction (EF) were tested for their inhibitory activities against COX-1 and COX-2. The results showed that EE, HF, EF and compounds 1-5 and 1 a-2 a shown weak to moderate inhibition of COX-1 and COX-2. Among the assayed nor-neolignans, 4 gave a COX-1 inhibition of 35.7% at 30 mu M. Compound 5 displayed a COX-2 inhibition of 19.7% at 30 mu M.

Constituents of the Leaves of Magnolia ovata

Two new lignans, magnovatins A (1) and B (2), along with nine known compounds, were isolated from the leaves of Magnolia ovata. The known compounds were identified as acuminatin (3), licarin A (4), kadsurenin M, 4-O-demethylkadsurenin M, oleiferin A, oleiferin C, spathulenol, parthenolide, and 11,13-dehydrocompressanolide. In addition, compounds I and 2 yielded four new derivatives (1a, 1b, 2a, and 2b). The structures of the new compounds were established on the basis of spectrometric data evaluation. Free-radical scavenging and antimicrobial activities of the major compounds 1, 3, and 4 were investigated.

Disruption of Chrysomya megacephala Growth Caused by Lignan Grandisin

The toxicity of tetrahydrofuran lignan grandisin was evaluated against larvae of Chrysomya megacephala F. (Diptera: Calliphoridae). The bioassay involved topical treatment on larvae, topical treatment oil egg masses, and incorporation in the larval diet. Grandisin showed inhibition of postembryonic development by ovicidal (30%) and larvicidal (38%) effects and reduced larval weight (4 mg), when topically applied oil egg masses and starving larvae (L1) at a concentration of 100 mu g/mu l. These findings elucidated the effect of grandisin on the C. megacephala life cycle and its potential to control C. megacephala populations.

LARVICIDAL ACTIVITY OF GRANDISIN AGAINST AEDES AEGYPTI

Dengue is a tropical disease caused by an arbovirus transmitted by the mosquito Aedes aegypti. Because no effective vaccine is available for the disease, the strategy for its prevention has focused on vector control by the use of natural insecticides. The aim of this study was to evaluate the larvicidal activity of the lignan grandisin, a leaf extract from Piper solmsianum, against Ae. aegypti.

Metabolism of (-)-grandisin from Piper solmsianum in Coleoptera and Lepidoptera species

The biotransformation of the major Piper solmsianum leaf phenylpropanoids, such as the tetrahydrofuran lignan grandisin and derivatives was investigated in the beetle Naupactus bipes as well as in the caterpillars Heraclides hectorides and Quadrus u-lucida. Analysis of fecal material indicated that metabolism occurred mainly through mono- and di-O-demethylation at para positions of 3,4,5-trimethoxyphenyl rings of tetrahydrofuran lignans during digestion by these insects. Additionally, 3-hydroxy-4,5-dimethoxycinnamyl and 3,4,5-trimethoxycinnamyl alcohols were identified in fecal extracts of N. bipes. (C) 2008 Elsevier Ltd. All rights reserved.

Trypanocidal tetrahydrofuran lignans from Peperomia blanda

Five tetrahydrofuran lignans and two known flavones were isolated from the aerial parts of Peperomia blanda. The structures of the isolated lignans were elucidated by interpretation of their spectroscopic data, including by gHMQC and gHMBC. The relative and absolute configurations of the isolates were determined from NOESY interactions and optical properties, respectively. Four of the lignans were diastercomeric whilst one was of mixed biosynthetic origin. All but one of the lignans exhibited high in vitro trypanocidal activity when assayed against epimastigotes of Trypanosoma cruzi strain Y. (C) 2007 Elsevier Ltd. All rights reserved.

Computer-Assisted Approach to Structural Elucidation of Lignans

This paper reports an expert system (SISTEMAT) developed for structural determination of diverse chemical classes of natural products, including lignans, based mainly on 13C NMR and 1H NMR data of these compounds. The system is composed of five programs that analyze specific data of a lignan and shows a skeleton probability for the compound. At the end of analyses, the results are grouped, the global probability is computed, and the most probable skeleton is exhibited to the user. SISTEMAT was able to properly predict the skeletons of 80% of the 30 lignans tested, demonstrating its advantage during the structural elucidation course in a short period of time.