Biologically Active Neolignans from Amazonian Trees

Abstract

Typical magnolialean species of the Amazonian forest contain an especially characteristic class of natural products, the neolignans. Many of their isolated representatives are distinguished by important biological properties. The expectations for further successful pharmacological investigations are justified by several striking features of neolignans. With respect to their biosynthesis, one marvels that not less than 40 structural types and close to 700 derivatives can originate by oxidative dimerization of allylphenols and propenylphenols, from only two simple precursors. The second fact concerns a series of rearrangements which, possibly involving cyclic reaction paths, occur spontaneously under natural conditions. Neolignans can be defined as oxidative dimers of propenylphenol/propenylphenol as shown in Figure 1, propenylphenol/allylphenol as presented in Figure 2 and allylphenol/allylphenol. Different coupling modes of these units and further modifying steps increase the number of neolignans (J). Based on more than 400 neolignans isolated from Amazonian species of Myristicaceae and Lauraceae, Gottlieb and Yoshida (2) proposed a model of evolution in a micromolecular system. In this scheme the Cope, retro-Claisen, Claisen rearrangements constitute an example of microscopic reversibility as pictured in Figure 3. Neolignans from MyristicaceaeEthnopharmacological interest in Myristicaceae species first evidenced by Schultes in 1954 (3), inspired Gottlieb and co-workers to develop phytochemical investigations on these arboreal plants dispersed over Amazonia. The occurrence of γ-lactones, flavonoids and neolignans was observed in trunk wood and a 0097-6156/95/0588-O085$12.00/0

Structural Diversity in Lignans and Neolignans

“…Formation of the arylcoumaran arises from radical coupling between the Ο and C-5 atomic centers to give an intermediate quinonemethide and subsequent cyclization leads to the arylcoumaran product. Forty years after Erdtman's paper describing the structure of dehydrodiisoeugenol, the compound was reported as a 8-3'-neolignan in the wood of Licaria aritu (55) and in nutmeg (Myristica fragrans) (56), and since that time it has been isolated from other plant materials also (57)(58)(59)(60)(61).…”

Cytotoxic lignans from the stems ofStyrax camporum(Styracaceae)

“…The present article deals with the isolation from stems of S. camporum, and the identification and cytotoxicity evaluation of two benzofuran lignans, egonol (1) and homoegonol (2), and one furofuran lignan, (AE)syringaresinol ( originally isolated from Styrax obassia [4,5] and Forsythia intermedia [6], respectively. Lignans are known to possess several biological activities [7][8][9][10][11], including antitumor, e.g., some podophyllotoxin derivatives, currently in clinical use, and cytotoxic, e.g., the benzofuran lignan licarin A which is active against KB cells. In order to evaluate the cytotoxicity of compounds 1-3 against C6, Hep-2 and HeLa human carcinoma cells, the MTT spectrophotometric assay was used.…”

Efeitos da grandisina sobre o sistema hematopoético, em camundongos

“…A resina da casca desta árvore é usada no tratamento de erisipelas e o chá de sua folha é usado para cólicas e dispepsia. Os índios da Venezuela usam sua seiva para o tratamento de feridas bucais (YOSHIDA, 1995). (LOPES et al,1999).…”