versión impresa ISSN 0366-1644
Bol. Soc. Chil. Quím. v.46 n.1 Concepción mar. 2001
EXTRACTABLE COMPOUNDS OF NATIVE TREES
CHEMICAL AND BIOLOGICAL STUDY I: Bark of Prumnopytis
andina (Podocarpaceae) and Austrocedrus chilensis
C. Flores, J. Alarcón +, J. Becerra, M. Bittner, M. Hoeneisen
y M. Silva
Laboratorio Química de Productos Naturales, Dpto. de Botánica,
Facultad de Ciencias Naturales y Oceanográficas,
Universidad de Concepción, Concepción, Chile.
+ Departamento de Ciencias Básicas, Facultad de Ciencias,
Universidad del Bío Bío, Chillán, Chile. E-mail firstname.lastname@example.org
(Received: March 15, 2000 - Accepted: October 30, 2000)
Four diterpenes (abietatriene, ferruginol, acetyl ferruginol and isopimarol) were isolated from the bark of Prumnopytis andina (Poepp. ex Endl.) de Laub. and two diterpenes (sugiol and an unidentified diterpene) from the bark of Austrocedrus chilensis (D. Don) Pic. Serm. et Bizzarri. The structures were established by spectroscopic methods (1D and 2D NMR techniques including DEPT, COSY and HETCOR). Abietatriene, ferruginol, the unidentified diterpene and the extracts were tested for antimicrobial activity against standard bacterial strains (Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas sp.)KEYWORDS: Gymnosperms Prumnopytis andina Austrocedrus chilensis, diterpenes, antimicrobial activity.
Cuatro diterpenos (abietatrieno, ferruginol, acetil ferruginol e isopimarol) fueron aislados desde la corteza de Prumnopytis andina (Poepp. ex Endl.) de Laub. y dos diterpenos (sugiol y un diterpeno no identificado) desde la corteza de Austrocedrus chilensis (D. Don) Pic.- Serm et Bizz. Las estructuras fueron determinadas mediante métodos espectroscópicos (RMN uni- y bidimensional incluyendo DEPT, COSY y HETCOR). Se evaluó la actividad antimicrobiana de abietatrieno, ferruginol, el diterpeno no identificado y de los extractos frente a las cepas bacterianas: Staphylococcus aureus, Bacillus subtilis, Escherichia coli y Pseudomonas sp.
PALABRAS CLAVES: Gimnospermas, Prumnopytis andina, Austrocedrus chilensis, diterpenos, actividad antimicrobiana.
At present many synthetic compounds are used intensively to protect wood. In general these compounds should be replaced urgently by products of natural origin, because in many cases they cause severe damage to the environment 1). The ideal wood resistant to all biotic and abiotic agents does not exist, but there are some with remarkable resistance against different agents due to the composition of the extractives, in addition to other factors such as density and silica content.
Woods and tree barks contain compounds with different structures with interesting biological activities. These metabolites are responsible for the woods smell, colour, flavour and fragrance. Also, these compounds give the wood the capacity of resisting fungal, bacterial and insect attack 2-4). Although a great number of chemical studies exist on the extractives of woods and tree barks, very little has been investigated on the feasibility of using these types of compounds in industrial form to protect wood from the attack of larvae of herbivorous insects 5). Many of the mentioned structures, which are normally present in small amounts in the plant, have been synthesised to be able to determine their biological activities in the control of different pathogenic organisms6).
Previous works on species of the Cupressaceae and Podocarpaceae families have shown the presence of terpenoids, diterpenoids, phenolic diterpenoids, diterpene lactones, sesquiterpenoids and lignans as compounds in wood, bark and leaves 7-10). Podophyllotoxin has been isolated from Austrocedrus chilensis wood, a lignan with interesting cytotoxic activity, while flavones and terpenes have been identified from the aerial part 11- 14). From stems and leaves of Prumnopytis andina, diterpenes, podocarpusflavone, crustecdysone, linear hydrocarbons, alcohols and ketones have been isolated 15,16).
This work reports the chemical and biological results obtained from a study of the extractives of bark of two native Chilean gymnosperms: Austrocedrus chilensis (D. Don.) Pic. Serm. et Bizzarri (Cupressaceae) and Prumnopytis andina (Poepp. ex Endl.) de Laub. (Podocarpaceae), also known by their older names Libocedrus chilensis and Podocarpus andina respectively, by which they are cited in the chemical literature.
The plant material of Austrocedrus chilensis and Prumnopytis andina was collected between March and September, 1999 in the VIII and X Region of Chile. Voucher specimens are deposited in the herbarium of the Faculty of Natural Science and Oceanography, University of Concepción.
Wood and bark were separated mechanically. The bark (800 g) from Prumnopytis andina was finely chopped and then extracted with methanol. The extract was concentrated in vacuo to give 98 g of residue. The residue was extracted with different solvents to afford four fractions [n-hexane (24.6 g), CH2Cl2 (1 g), AcOEt (10.3 g) and n-BuOH (25.2 g)]. The n-hexane extract was fractionated by CC on silica gel, eluting with n-hexane, followed by a gradient of AcOEt. The compounds obtained from the column were further separated and/or purified on preparative TLC plates. The following compounds were obtained from the n-hexane fraction:
Abietatriene (1, 15mg). Mp 175º C . The 13C NMR spectrum was similar to previously reported data17. Ferruginol (2, 20 mg). Mp: 175ºC. The 13C NMR spectrum was similar to previously reported data18. Acetyl ferruginol (3, 18 mg), amorphous compound. The 13C NMR was similar to previously reported data19. Isopimarol (4, 25 mg), amorphous compound. The13C NMR was similar to previously reported data20.
The bark from A. chilensis (300 g) was finely chopped and then extracted with methanol. The extract was concentrated in vacuo to give 17.9 g of residue. The residue was extracted with different solvents as with P. andina [n-hexane (5 .0 g), CH2Cl2 (6.1 g), AcOEt (4.0 g) and BuOH (2.8 g)].The CH2Cl2 extract was fractionated by CC on silica gel, eluting with n-hexane, followed by gradients of AcOEt. The compounds obtained from the column were further separated and/or purified on preparative TLC plates. The following compounds were obtained from the CH2Cl2 fraction:
Sugiol (5, 35 mg), was crystallized from MeOH, Mp 273-275ºC. The13C NMR was similar to previously reported data21. Compound 6 (unidentified diterpene; 26 mg). Amorphous compound.
The structures of the compounds were determined by spectroscopic methods. NMR spectra were recorded on a Bruker 250 MHz spectrometer; GC-MS were performed on a HP 5972 instrument; UV spectra were obtained on a Shimadzu UV-160 spectrometer.
The disc-diffusion method was used to determine the inhibition zone of the extracts and some of the pure compounds isolated from plant the material studied. Standard bacterial strains were used for the test. Streptomycin was used as a standard and the results are shown in table 1.
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