Abstract Echinodorus scaber Rataj and Echinodorus grandiflorus (Cham. & Schltdl.) Micheli, Alismataceae, are popularly used to relieve inflammatory complaints and as diuretic. A study on the antinociceptive effect and selected marker compounds in eleven extracts from different locations was undertaken and their antinociceptive effect was assessed. The fingerprints were compared by HPLC-DAD and the content of vitexin, isovitexin, isoorientin and vitexin-2-O-rhamnoside were determined. All samples presented antinociceptive activity reducing the writhes by 36.4-62.5% and 47.4-79.8% at 10 and 50 mg/kg, respectively; indomethacin (5 mg/kg) reduced writhes by 82.6-90.1%. The content of the flavonoids C-glycosides, however, presented a strong variation. Isovitexin and isoorientin were found in all the samples, with content ranging from traces to 14.70 µg/mg and 2.12-84.27 µg/mg extract, respectively, while vitexin-2-O-rhamnoside occurred in quantifiable amounts only in 3 out of 11 samples ranging from 5.43 to 33.13 µg/mg extract; vitexin was not detected at all or detected in trace amounts. According to the fingerprints, the samples could be arranged in four main groups. All eleven extracts showed antinociceptive activity. Isovitexin was the only flavonoid present in all samples and can be regarded, acting in synergy with the other compounds or not, as the responsible for the antinociceptive activity. Therefore, isovitexin is a good choice as chemical marker when the antinociceptive activity of E. scaber and E. grandiflorus is investigated.

O biflavonóide 2",3"-diidroochnaflavona, isolada de espécies de Luxemburgia (Ochanaceae), foi tratada com diazometano e forneceu o éter trimetílico que, em seguida, foi tratado com anidrido acético/piridina obtendo-se um novo derivado, 5-acetil-7,4'-dimetil-flavona-(3'→O-4'")-5"-acetil-7"-metil-flavanona. Fez-se o completo assinalamento dos dados de RMN ¹H e 13C através da análise dos espectros uni- e bidimensionais do derivado.

The biflavonoid 2",3"-dihydroochnaflavone, isolated from the Luxemburgia species (Ochanaceae), was treated with diazomethane to obtain the trimethyl-ether that was treated with pyridine/acetic anhydride to yield a new derivative, 5-acetil-7,4'-dimethyl-flavone-(3'→O-4'")-5"-acetil-7"-methyl-flavanone. The complete ¹H and 13C NMR data assignments of the new derivative were made by the one- and two-dimensional spectral analysis.

A reação do flavonol 3,7,3',4'-tetra-O-metilquercetina (1) e da isoflavona 7,4'-di-O-metilgenisteina (2) com iodo/KOH em metanol forneceu como produto quatro derivados iodados: 8-iodo-5-hidroxi-3,7,3',4'-tetrametoxiflavona (1a) e 6-iodo-5-hidroxi-3,7,3',4'-tetrametoxiflavona (1b) a partir da iodação de 1; a partir de 2 foi obtida uma mistura racêmica composta de (±)-trans-5-hidroxi-2,3,7,4'-tetrametoxi-8-iodo-isoflavanona (2a) e (±)-trans-5-hidroxi-2,3,7,4'-tetrametoxi-6,8-diiodo-isoflavanona (2b). A formação destes diferentes produtos revela a significante diferença envolvendo a interação química entre o sitio reativo de cetonas α, β-insaturadas de flavonol e de isoflavonas nas condições experimentais testadas (usando I2/KOH/MeOH). Além disso, ressalta-se a estereosseletividade trans na adição de metanol ao sistema α, β-insaturado da isoflavona. As estruturas foram identificadas com análise nos dados espectrométricos de RMN 1D e 2D e massas.

The reaction of the flavonol 3,7,3', 4'-tetra-O-methylquercetin (1) and of the isoflavone 7,4'-di-O-methylgenistein (2) with alkaline iodine in methanol afforded four new iodine derivatives: 8-iodo-5-hydroxy-3,7,3', 4'-tetramethoxy- flavone (1a) and 6-iodo-5-hydroxy-3,7,3', 4'-tetramethoxyflavone (1b) from 1; 2 afforded a mixture of two compounds, identified as a racemic mixture of (±)-trans-5-hydroxy-2,3,7,4'-tetramethoxy-8-iodo-isoflavanone (2a) and (±)-trans-5-hydroxy-2,3,7,4'-tetramethoxy-6,8-diiodo-isoflavanone (2b). The formation of these different products reveals a significant difference involving the chemical interaction between the reactive site of α, β-unsaturated ketones of flavonol and isoflavone under the tested reaction conditions (using I2/KOH/MeOH). Furthermore, the trans stereo selectivity is noteworthy in the nucleophylic addition of methanol at the isoflavone α, β-unsaturated system. The structures were identified on the basis of spectral data, mainly 1D and 2D NMR and mass spectra.