Artigo Safrole and the Versatility of a Natural Biophore Lima, L. M.* Rev. Virtual Quim., 2015, 7 (2), 495-538. Data de publicação na Web: 31 de dezembro de 2014 http://www.uff.br/rvq Safrol e a Versatilidade de um Biofóro Natural Resumo: Safrol (1) obtido de óleos essenciais de diferentes espécies vegetais tem ampla aplicação na indústria química como precursor sintético do butóxido de piperonila, piperonal e de fármacos como a tadalafila, cinoxacina e levodopa. Do ponto vista toxicológico, é considerado uma hepatotoxina por mecanismo de bioativação metabólica conduzindo a formação de intermediários eletrofílicos, e tem sido descrito como inibidor de diferentes isoenzimas da família CYP450. A versatilidade de sua estrutura, permitindo várias transformações químicas, e a natureza biofórica de sua unidade benzodioxola ou metilenodioxifenila conferem-lhe características singulares, que o tornam atrativo material de partida para a síntese de compostos com distintas atividades farmacológicas. Exemplos selecionados de compostos bioativos, naturais e sintéticos, contendo o sistema benzodioxola serão comentados, incluindo aqueles provenientes de contribuição específica do LASSBio®. Palavras-chave: Safrol; benzodioxola; metilenodioxi; CYP450; bióforo; compostos bioativos. Abstract Safrole (1), obtained from essential oils from different plant species, has wide application in the chemical industry as a synthetic precursor of piperonyl butoxide, piperonal and drugs such as tadalafil, cinoxacin and levodopa. From the toxicological point of view, it is considered a hepatotoxin through metabolic bioactivation, leading to the formation of electrophilic metabolites, and has been described as an inhibitor of different CYP450 isoenzymes. The versatility of its structure, allowing various chemical transformations, and the biophoric nature of its benzodioxole or methylenedioxy subunit, give it unique features and make it an attractive starting material for the synthesis of compounds with different pharmacological activities. Selected examples of natural and synthetic bioactive compounds containing the benzodioxole system will be discussed, including those from specific contribution of LASSBio®. Keywords: Safrole; benzodioxole; methylenedioxy; CYP450; biophore; bioactive compounds. * Universidade Federal do Rio de Janeiro, LASSBio (http://www.farmacia.ufrj.br/lassbio/) - Laboratório de Avaliação e Síntese de Substâncias Bioativas, Programa de Pesquisa em Desenvolvimento de Fármacos, Instituto de Ciências Biomédicas, PO Box 68024, CEP 21944-971, Rio de Janeiro-RJ, Brasil. [email protected] DOI: 10.5935/1984-6835.20150023 Rev. Virtual Quim. |Vol 7| |No. 2| |495-538| 495 Volume 7, Número 2 Março-Abril 2015 Revista Virtual de Química ISSN 1984-6835 Safrol e a Versatilidade de um Biofóro natural Lídia M. Lima* Universidade Federal do Rio de Janeiro, LASSBio (http://www.farmacia.ufrj.br/lassbio/) - Laboratório de Avaliação e Síntese de Substâncias Bioativas, Programa de Pesquisa em Desenvolvimento de Fármacos, Instituto de Ciências Biomédicas, PO Box 68024, CEP 21944- 971, Rio de Janeiro-RJ, Brasil. * [email protected] Recebido em 3 de dezembro de 2014. Aceito para publicação em 3 de dezembro de 2014 1. Physicochemical properties, natural sources and industrial applications 2. Toxicity and metabolism 3. Role of cytochrome P450 4. 1,3-Benzodioxole in nature 5. Synthetic bioactive compounds 6. LASSBio’s ontriution 7. Final remarks 1. Physicochemical properties, Cinamomum mollissimum and Sassafras 1 natural sources and industrial albidum Nutt. applications Util ’s Brazil as the ajor eporter of sassafras oil in the world, nowadays China and Vietnam are the great producers. The Ocotea pretiosa, a native tree in Mata Safrole (1, C H O ), also known as safrol, 10 10 2 Atlantica, typical from tropical rainforests, 1,3-benzodioxole-5-(2-propenyl); 3,4- was the main store of the Brazilian sassafras methylenedioxy-allylbenzene; 3-(3,4- oil until the depletion of this natural methylenedioxyphenyl)-prop-1-ene; 5- resource, placing it on the endangered list. allylbenzo[d][1,3]dioxole, is a colorless or Several others Lauraceae trees, which wood slightly yellow liquid with boiling point 233.1 distillation was performed to yield a rich ± 30.0 °C, density 1.118 ± 0.06 g/cm3 (at 20 source of sassafras oil containing high °C, 760 Torr), molar volume 145.0 ± 3.0 amount of safrole, are also at risk of cm3/mol (at 20 °C, 760 Torr) and molecular extinction.2-4 weight 162.19 g/mol. It is obtained by distillation of sassafras oil, currently derived Many attempts to identify alternative from endangered plants of the Lauraceae natural sources from safrole have been family such as Ocotea pretiosa, Ocotea made. Among then, the Piperaceae emerge odorifera, Cinamomum petrophilum, as a promising alternative. First described by 496 Rev. Virtual Quim. |Vol 7| |No. 2| |495-538| Lima, L. M. Yunker in 1972,1 Piper hispidinervium (known crucial component in the natural pyrethroid as long pepper) is a safrole-rich plant well insecticides, due its synergist activity, and for distributed throughout South America and heliotropin (3), used in flagrances and as endemic in the state of Acre in Brazil. Its flavoring agent (Figure 1).4,5 unique conditions for cultivation in areas The finding that heliotropin or piperonal with facilities for harvest, associated with (3), easily synthesized from safrole6-8(Figure high levels of safrole in its leaves, make the 2), was a key intermediate in the synthesis of sustainable management and its economic complex organic molecules expanded its exploration feasible. Others Piper species, value and its industrial application. In fact, 3 including P. divaricatum P. nigrum, P. can be used as starting material from the callosum and P. aduncum are also considered synthesis of several biological active eventual sustainable source of safrole.4,5 compounds, including the drugs cinoxacin Historically, the demand for sassafras oil (5), tadalafil (6) and levodopa (7) (Figure 2). It depends mainly on the international market is also used in the synthesis of illicit drug 3,4- for piperonyl butoxide (PBO, 2), a methylenedioxy-N-methylamphetamine semisynthetic derivative of safrole, that is a (MDMA, ecstasy, 8). SASSAFRAS OIL O O safrole (1) O O O O O O H O O PBO (2) heliotropin or piperonal (3) Chemical industry applicatons: synergist agent of natural pyrethrum insecticide; fragrance; flavoring agent Figure 1. Safrole (1) a raw material for the synthesis of PBO (2) and heliotropin (3) Rev. Virtual Quim. |Vol 7| |No. 2| |495-538| 497 Lima, L. M. O HO OH NH HO 2 O CH3 levodopa (7) O NHCH3 MDMA (8) H O O o O KOH 3N/n-BuOH 1- O2/O3, AcOH, 0 C O O reflux, 6h, 98% O 2- Zn, AcOH, 0oC, 70% O safrole (1) isosafrole (4) heliotropin or piperonal (3) O CH3 H N O O N O O OH N N H O O H N O CH3 tadalafil (6) cinoxacin (5) Figure 2. Heliotropin (3) obtained from safrole (1) and its use as raw material for the synthesis of cinoxacin (5), tadalafil (6), levodopa (7) and MDMA (8) 2. Toxicity and metabolism cytochrome P450 (CYP450) family (Figure 3). In the first hypothesis, the allyl double bond of safrole (1) is oxidized to epoxide The most important dietary sources of metabolite (9), which can alkylate DNA (10). safrole (1) are nutmeg, mace and its essential This hypothesis is considered less likely, since metabolite 9 is fast hydrolyzed by oils, although it is also a natural constituent 14,16 of cinnamon, anise, black pepper and sweet microsomal epoxide hydrolase. The most basil and is present in cola drinks.9,10 Safrole well-established hypothesis is based on the (1) was first recognized to be a reatiit of ethlee C’, oth alllic and benzylic, presented in the alkyl side chain of hepatoarioge i the ’s ad a 14,17 animal studies have been documented safrole (1). This position is easily oxidized concerning this toxicology.11-15 to ’-hydroxy derivative (11), by a classical CYP450 mediated hydroxylation. This Seeral attepts to eplai safrole’s metabolite (11) undergoes phase-2 muta- and genotoxicity have been made. In metabolism by sulfotransferase (SULT), that general, all hypotheses predict its catalyze the transfer of a sulfonate group (- bioactivation to produce electrophilic SO− fro the ofator ′- intermediates that are able to interact with phosphoadenosine-′-phosphosulfate (PAPS) 14-18 DNA. This bioactivation process is to the hydroxyl group of 11, to furnish the dependent of previous oxidative reactions metabolite 12 (Figure 3)18. This reactive catalyzed by different isoenzymes of metabolite can interact with DNA by a 498 Rev. Virtual Quim. |Vol 7| |No. 2| |495-538| Lima, L. M. classical SN2 reaction, eliminating sulfate ion methylenedioxy bridge. As demonstrated by (SO−) and forming a covalent adduct of this Clemens and Barz (1995),28 the microsomal essential macromolecule (13). An alternative preparations from elicited heterotrophic cell mechanism is also possible and provides the cultures of chickpea in the presence of 02 and loss of O-sulphate, resulting in a stabilized NADPH catalyze methylenedioxy bridge carbonium ion that form adducts with DNA formation (21 and 22) from pratensein (19) and may be assumed to play a role in and calycosin (20) (Figure 4). They also tumorigenesis.19-22 The third hypothesis is demonstrated that methylenedioxy bridge based on the bioactivation of safrole (1) by O- formation, in these conditions, was blocked dealkylation step of methylenedioxy by various CYP450 inhibitors, characterizing a subunity. The O-dealkylation process, cytochrome P450-dependent process.28 catalyzed by CYP450 enzymes and which CYP450 enzymes have been shown to play mechanism was elucidated by Fukuto and essential roles in plant secondary coworkers (1991),23 furnish the catechol metabolism,29 and all members of the metabolite (14). This metabolite can CYP719A subfamily, that have been undergoes oxidation of 1 or 2 electrons to characterized so far, catalyze methylenedioxy provide the ortho-semiquinone (15) or ortho- bridge formation in isoquinoline alkaloid quinone (16), respectively, generating biosynthesis.30 As exemplified in Figure 5, (S)- reactive oxygen species that can promote scoulerine (23) are converted at (S)- oxidative DNA damage (Figure 3).