ABSTRACT The Genus Casearia is a rich source of cleordane - type diterpenes. To search for practical sources of potential cleordane - type diterpenes, and to study the structure and activity relationship of cleordane - type diterpenes, the twigs and leaves of Casearia membranacea Hance ( Flacourtiaceae ) was collected for phytochemical and anti-tumor investigation. Bioassay-directed fractionation of an ethyl acetate layer of Casearia membranacea has resulted in the isolation of six new clerodane-type diterpenes. The structures of these cleordane-type diterpenes were established and designated as Caseamembrins G¡ãL¡]1¡ã6¡^and their derivatives compounds 7 and 8. The structures of compounds 1¡ã8 were determined by application of NMR techniques included 1H NMR, 13C NMR, DEPT, COSY, HMQC, HMBC, NOESY and another physical methods which include MS, UV, IR and optical rotation, and the published reports about the data of related compounds. The spectral data of 1¡ã8 are in conformity with the basic skeleton of cleordane-type diterpenes previously isolated from Casearia membranacea Hance. The basic structures of 1¡ã8 contain two 6- menbered ring. The structures were identified as rel-(2S,5R,6R,8S,9S,10R, 18S,19R)-2-hydroxy-6-butanoyloxy-18,19-acetyloxy-18,19-epoxy-cleroda-3,13(16),14-triene (Caseamembrin G, 1¡^¡Brel-(2S,5R,6R,8S,9S,10R,18S, 19R)-2-hydroxy-6,18-dibutanoyloxy-19-acetyloxy-18,19-epoxy-cleroda -3,13(16),14-triene (Caseamembrin H, 2¡^¡Brel-(2S,5R,6R,8S,9S,10R,18S ,19R)-2-(2-methylbutanoyloxy)-6-hydroxy-18-methoxy-19-acetyloxy-18,19-epoxy-cleroda-3,13(16),14-triene¡]Caseamembrin I, 3¡^¡Brel-(2R,5R ,6R,8S,9S,10R)-2-(2-methylbutanoyloxy)-6-hydroxy-cleroda-3,13(16),14 -triene-18,19-dicarboxaldehyde ( Caseamembrin J, 4¡^¡Brel-(2S,5R,6R,7R, 8S,9S,10R)-2,7-diacetyloxy-6-hydroxy-cleroda-3,13(16),14-triene-18,19-dicarboxaldehyde¡]Caseamembrin K, 5¡^¡Brel-(2S,5R,6S,7R,8S,9S,10R, 18S,19R)-2-butanoyloxy-6,7-dihydroxy-18-butanoyloxy-19-acetyloxy-18,19-epoxy-cleroda-3,13(16),14-triene¡]Caseamembrin L, 6¡^¡A¤Îrel-(2S,5R ,6R,8S,9S,10R,18S,19R)-2-O-acetyl-6-butanoyloxy-18,19-acetyloxy-18,19-epoxy-cleroda-3,13(16),14-triene ( 7¡^¡Brel-(2S,5R,6R,8S,9S,10R,18S,19 R)-2-O-acetyl-6,18-dibutanoyloxy-19-acetyloxy-18,19-epoxy-cleroda-3,13(16),14-triene¡]8¡^. It is worthy to mention that this is the first report of the isolation of 1¡Ð6 from a natural source and their derivatives compounds 7 and 8. Compound 1 exhibited moderate cytotoxicity against¡]Hepa59T/VGH¡^ ,¡]KB¡^and ¡]Hela¡^cancer cells , but compound 3 and 4¡B5 show no activity against those cancer cell lines.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Sabendo da importÃncia de cÃlulas de mamÃferos em cultura para avaliar a citotoxicidade de novas substÃncias com aÃÃo terapÃutica, o presente trabalho determinou, inicialmente, a atividade citotÃxica por MTT e hemolÃtica de 7 diterpenos clerodanos (Ãcido hardiwickiico, casearinas L, O, U e sua forma degradada, e casearinas X e Y) isolados a partir das folhas de Casearia sylvestris frente a um painel de 9 linhagens de cÃlulas tumorais e a eritrÃcitos de camundongos. Na ausÃncia de hemÃlise de todos os diterpenos, a Casearina U (Cas U) mostrou ser o mais ativo contra cÃlulas tumorais. A atividade citotÃxica da Cas U parece depender do anel formado pelos carbonos C-18 e C-19, uma vez que a hidrÃlise Ãcida e sua abertura levam à diminuiÃÃo ou perda total da bioatividade. Posteriormente, os estudos de mecanismo de aÃÃo com a Cas U (0,4; 0,8 e 1,6 Âg/mL) revelaram reduÃÃo concentraÃÃo-dependente na viabilidade celular por azul de tripan e na sÃntese de DNA por incorporaÃÃo de BrdU, sendo o mecanismo antiproliferativo da Cas U independente de aÃÃo inibitÃria sobre a topoisomerase I. As anÃlises morfolÃgicas feitas por hematoxilina/eosina e por incorporaÃÃo de brometo de etÃdio/laranja de acridina mostraram alteraÃÃo no padrÃo de morte em favorecimento da necrose proporcional à concentraÃÃo, como desintegraÃÃo membranar e picnose nuclear (1,6 Âg/mL), embora tenha ocorrido tambÃm retraÃÃo celular, condensaÃÃo e fragmentaÃÃo da cromatina nucleares (0,4 e 0,8 Âg/mL), sinais condizentes com apoptose. Nos ensaios de fragmentaÃÃo do DNA por citometria de fluxo e de genotoxicidade por cometa, a atividade da Cas U foi concentraÃÃo-dependente e sem diferenciaÃÃo entre cÃlulas normais (linfÃcitos perifÃricos humanos) e cancerosas (HL-60). A avaliaÃÃo antitumoral (10 e 25 mg/kg/dia, intraperitoneal; 25 mg/kg/dia, oral) em camundongos transplantados com Sarcoma 180 revelou atividade apenas na maior dose via intraperitoneal, causando reduÃÃo de 90 % do crescimento tumoral e alteraÃÃes renais incipientes e reversÃveis, enfatizando a potencialidade da Cas U como molÃcula modelo para a sÃntese de novos compostos com propriedades anti-cÃncer. / Knowing the importance of mammalian cell culture in evaluating the cytotoxicity of new substances with therapeutic action, this work initially examined the cytotoxicity (by MTT assay) and hemolytic activity of 7 clerodane diterpenoids (acid hardiwickiico, casearins L, O and U and its degradation product, and casearins X and Y) isolated from leaves of Casearia sylvestris against a panel of 9 tumor cell lines and on mouse erythrocytes. All diterpenes studied showed no hemolytic effect, while casearin U (Cas U) was found to be the most active against tumor cells. Cytotoxic activity of Cas U seems to depend on the ring structure formed by carbons C-18 and C-19, since acid hydrolysis and ring opening led to a decrease or total loss of bioactivity. Subsequently, studies on the mechanism of action of Cas U (0.4, 0.8 and 1.6 Âg/mL) revealed a concentration-dependent decrease in cell viability as determined by trypan blue dye exclusion and in DNA synthesis assayed by BrdU incorporation, where this antiproliferative mechanism of Cas U was not found to be dependent on an inhibitory action on topoisomerase I. Morphological analysis assessed by hematoxylin/eosin and ethidium bromide/acridine orange staining showed alterations in the pattern of cell death toward necrosis according to concentration, as seen by membrane disintegration and pyknotic nuclei (1.6 Âg/mL). However, there also were cell volume reduction, and condensation and fragmentation of nuclear chromatin, consistent signs with apoptosis. DNA fragmentation was examined by flow cytometry and genotoxicity determined with the comet assay, and Cas U activity was found to be dependent on concentration but did not differ between normal (human peripheral lymphocytes) and malignant (HL-60) cells. Antitumor activity of Cas U was tested in mice transplanted with sarcoma 180 (10 and 25 mg/kg/day, intraperitoneally; 25 mg/kg/day, orally), and only the highest intraperitoneal dose was found to effective, leading to 90 % inhibition of tumor growth, with reversible changes in the kidneys. These findings point to the potential of Cas U as a model molecule to synthesize new compounds with anticancer properties.