Recebido em 28/3/11; aceito em 1/7/11; publicado na web em 19/8/11SESQUITERPENES FROM THE SEEDS OF Guarea guidonia (MELIACEAE). Two new sesquiterpenes 6α-ethoxyeudesm-4(15)-en-1β-ol (1) and (7R*)-5-epi-opposit-4(15)-ene-1β,7-diol (7) were isolated from the seeds of a specimen of Guarea guidonia (Meliaceae). Five other known sesquiterpenes, eudesm-4(15)-ene-1β,6α-diol (2), 5-epi-eudesm-4(15)-ene-1β,6β-diol (3), eudesm-4(15)-ene-1β,5α-diol (4), eudesm-4(15),7-dien-1β-ol (5) and (7R*)-opposit-4(15)-ene-1β,7-diol (6), were also isolated in this work. Their structures were determined on the basis of spectral data (MS, IR, and NMR-1D and 2D) and subsequent comparisons with the literature. The substances 3, 4 and 6 are reported for the first time in Meliaceae and 5 for the first time in the genus Guarea.Keywords: Guarea guidonia; Meliaceae; eudesmane. INTRODUÇÃOGuarea guidonia L. Sleumer (sin. Guarea trichilioides L.), pertencente à família Meliaceae e popularmente conhecida como carrapeta-verdadeira, é uma árvore ocorrente no Brasil desde a região Amazônica até o estado do Rio Grande do Sul, 1 podendo atingir 20 m de altura. Na medicina popular é utilizada no tratamento de reumatismo, hidropsia e tumores artríticos, tendo, ainda, propriedades adstringentes, purgativas, febrífugas, abortivas, eméticas e anti-inflamatórias. 1 Estudos fitoquímicos prévios dos extratos hexânico e etanólico da casca do tronco desta espécie, além do óleo volátil de suas folhas, resultaram no isolamento de limonoides, 2-3 esteroides, 4 seco-esteroides, 5 cumarinas, 2 di-, 4,6,7 tri-4 e sesquiterpenos. 2,4,8 O presente trabalho trata do estudo fitoquímico de sementes de um espécime de G. guidonia, que levou ao isolamento de sete sesquiterpenos, sendo dois deles inéditos: 6α-etoxieudesm-4(15)-eno-1β-ol (1), eudesm-4(15)-eno-1β,6α-diol (2), 5-epi-eudesm-4(15)-eno-1β,6β-diol (3), eudesm-4(15)-eno-1β,5α-diol (4), eudesm-4(15),7-dien-1β-ol (5), (7R*)-oposit-4(15)-eno-1β,7-diol (6) e (7R*)-5-epioposit-4(15)-eno-1β,7-diol (7) (Figura 1). As substâncias 1 e 7 são inéditas na literatura, enquanto 3, 4 e 6 estão sendo descritas pela primeira vez em Meliaceae e 5 pela primeira vez no gênero Guarea. PARTE EXPERIMENTAL Instrumentação e procedimentos geraisPara cromatografia em camada fina utilizaram-se placas de gel de sílica (Whatman), com indicador de fluorescência UV 254 , em camadas de 0,25 mm de espessura, empregando-se como revelador solução saturada de sulfato de cério IV em ácido sulfúrico 36%. A separação cromatográfica em coluna foi realizada utilizando-se gel de sílica 230-400 mesh (Acros Organics). Os experimentos de RMN 1 H e 13 C (uni-e bidimensionais) foram obtidos em espectrômetro Bruker DPX-300 (300/75 MHz), utilizando-se CDCl 3 como solvente e o sinal do CHCl 3 residual como referência. Os espectros de IV foram registrados em espectrômetro Bomem-Hartmann & Braun FT, tendo sido as amostras preparadas sob a forma de filme. As medidas de rotação óptica foram determinadas em polarímetro Perkin-Elmer 341 e os espectros de massas obtidos no es...

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The chemical investigation of the roots and stems of Combretum laxum yielded a new dihydrostilbene derivative, 4′-hydroxy-3,3′,4-trimethoxy-5-(3,4,5-trimethoxyphenoxy)-bibenzyl (1), two phenanthrenes (2–3), and three dihydrophenanthrenes (4–6), along with one lignan, three triterpenoids, one aurone, one flavone, one naphthoquinone, and two benzoic acid derivatives. Their structures were determined by 1D and 2D nuclear magnetic resonance (NMR) spectroscopic techniques and/or mass spectrometry data. The occurrence of dihydrostilbenoid, phenanthrene and dihydrophenanthrene derivatives is unprecedented in a Combretum species native to the American continent. 2,7-Dihydroxy-4,6-dimethoxyphenanthrene, 2,6-dihydroxy-4,7-dimethoxy-9,10-dihydrophenanthrene and 5-O-methyl apigenin are novel findings in the Combretaceae, as is the isolation of compounds belonging to the chemical classes of aurones and naphthoquinones, while (+)-syringaresinol is reported for the first time in the genus Combretum. Compounds 1–6 were also evaluated for their in vitro cytotoxicity against five human cancer cell lines, and radical-scavenging ability against 1,1-diphenyl-2-picryl-hydrazyl (DPPH). 6-Methoxycoelonin (4) was the most cytotoxic against melanoma cells (IC50 2.59 ± 0.11 µM), with a high selectivity index compared with its toxicity against nontumor mammalian cells (SI 25.1). Callosin (6), despite exhibiting the strongest DPPH-scavenging activity (IC50 17.7 ± 0.3 µM), proved marginally inhibitory to the five cancer cell lines tested, indicating that, at least for these cells, antioxidant potential is unrelated to antiproliferative activity.

The chemical composition and the phytotoxicity potential of the essential oil from leaves of Unonopsis guatterioides (A.DC.) R.E.Fr. (Annonaceae) was investigated. Gas chromatography/mass spectrometry analyses revealed 16 constituents representing 99.50% of the total essential oil, composed mainly of sesquiterpenes. α-copaene, bicyclogermacrene and trans-caryophyllene were the major components (15.7% each), followed by α-humullene, allo-aromadendrene and (+)-spathulenol (9.0, 8.4 and 7.3%, respectively). The essential oil inhibited seed germination and growth in both monocotyledon (Allium cepa) and dicotyledon (Lactuca sativa) models, pointing to a promising application of this oil obtained from the leaves of U. guatterioides as a new bioherbicide.

Two new tetrahydrofuran lignans 1-2, along with 2,3-seco-lup-20(29)-en-2,3-dioic acid(3), (-)-larreatricin (4), and 15 additional compounds were isolated from Combretum mellifluum (Combretaceae). Their structures were determined by 1D and 2D NMR spectroscopic data and HRESIMS. Another 15 compounds were identified after HPLC-DAD-MS/MS analysis. Tested against HT-29 (colon) neoplastic cells, lignan 1 showed marked cytotoxicity (GI50 = 3.9 µM) and high selectivity (SI > 227), compared with non-neoplastic NIH/3T3 cells, while 2 proved less cytotoxic, despite exhibiting SI > 75. Seco-triterpene 3 was strongly cytotoxic to 786-0 (kidney) and HT-29 cells (GI50 = 0.5 and 2.9 µM, respectively), proving roughly 107 and 18 times more selective for these cell lines, respectively, than for NIH/3T3 cells. After 48 h of incubation, 1-3 exhibited potent cytostatic activity against HT-29 cells at all concentrations tested, while 3 had a cytocidal effect on 786-0 cells at 25 µg.mL -1 .

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