Diterpenes from marine brown alga Dictyota guineensis (Dictyotaceae, Phaeophyceae)

 

 

Joel Campos De-Paula^I; Diana Negrão Cavalcanti^II; Yocie Yoneshigue-Valentin^III; Valéria Laneuville Teixeira^*,II

^IPrograma de Pós-graduação em Biodiversidade Neotropical, Instituto de Biociências, Universidade Federal do Estado do Rio de Janeiro, Brazil
^IIDepartamento de Biologia Marinha, Instituto de Biologia, Universidade Federal Fluminense, Brazil
^IIIDepartamento de Botânica, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil

 

 

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ABSTRACT

The crude extract of the marine brown alga Dictyota guineensis was analyzed by high-resolution gas chromatography-mass spectrometry (HRGC-MS). Five diterpenes were identified: dictyol E (the most abundant diterpene), dictyotadiol, dictyoxide, isopachydictyol A and pachydictyol A, all diterpenes from the chemical group I, i.e., mainly prenylated derivatives of known sesquiterpene skeletons that result from a first cyclization of geranyl-geraniol between positions 1 and 10. These diterpenes are known for their activity against bacteria, fungi and other activities. The results characterize D. guineensis as a species that yields exclusively diterpenes from group I, with low oxidation and low structural complexity. On Brazilian coasts, only D. mertensii provides exclusively prenylated guaiane diterpenes. Although D. guineensis presents alternate branches and fixing by rhizoidal branches, it is easily distinguishable from D. mertensii by the much narrower stem, short stature and flabelliform habit of the former species. On the other hand, both species have been characterized as producers of diterpenes of group I, in particular, prenylated guaiane. However, D. guineensis has a majority dictyol E in the lipophilic extract, while D. mertensii produces more complex prenylated guaianes, like dictyol H.

Keywords: Dictyota guineensis, Dictyotaceae,  Phaeophyceae,  diterpenes.

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Introduction

The algae of the genus Dictyota Lamouroux present difficulties in the establishment of clear limits of separation between species. In previous studies, our group has indicated that the diterpenes from Dictyota species may play an important role as taxonomic markers (e.g., De-Paula et al., 2001, 2007a, 2008; Freitas et al., 2007; Teixeira et al., 1990, 2001). On the other hand, the algae of the family Dictyotaceae are very important sources of antiviral natural products (e.g., Pereira et al., 2004, 2005; Barbosa et al., 2004; Cirne-Santos et al., 2006, 2008; Vallim et al., 2010).

Based on a revised biogenetic scheme proposed by Teixeira & Kelecom (1988), the diterpenes have been distributed into three groups (I-III), depending on the structure of the products resulting from the first formal cyclization of the geranyl-geraniol precursor. Thus, group I compounds result from a first cyclization of geranyl-geraniol between positions 1 and 10; group II compounds derive from a first cyclization of the precursor between positions 1 and 11, and group III compounds from either a first formal cyclization between positions 2 and 10 or by ring contraction of the prenylated germacrane (Scheme 1).

Many species of algae of the genus Dicytota have been studied on the Brazilian coast and their chemical composition examined. In many cases, variability is observed between populations along the coast (Teixeira, 2010) and the species were classified into taxonomic groups A, B and C. Taxonomic group A comprises the species of Dictyota that produce diterpenes of chemical groups I e III. In this group are included the Brazilian populations of Dictyota crenulata J. Agardh (= Dictyota jamaicensis W.R.Taylor) (De-Paula et al., 2008), D. ciliolata Sonder ex Kützing, and D. menstrualis (Hoyt) Schnetter, Hörning & Weber-Peukert (Cavalcanti et al., 2006). Dictyota mertensii (Martius) Kützing (Freitas et al., 2007) can be included as a subgroup because, so far, Brazilian and Caribbean populations (like D. dentata J.V. Lamouroux) produce only diterpenes of group I, in particular prenylated guaianes (Alvarado & Gerwick, 1985; Freitas et al., 2007). The taxonomic group B includes Brazilian populations of Dictyota pfaffii Schnetter (Barbosa et al. 2004) and Dictyota dolabellana De Paula, Yoneshigue-Valentin & Teixeira (De-Paula et al. 2007b), a new species, both characterized as producing exclusive type dolabellane diterpenes and derivatives. The taxonomic group C comprises the species Canistrocarpus cervicornis (Kützing) De-Paula & De Clerck (e.g. Kelecom & Teixeira, 1988, as Dictyota cervicornis Kützing) and C. crispatus (De-Paula et al., 2007a, as Dictyota crispata J.V.Lamouroux), producing exclusively dolastane and secodolastane diterpenes.

Dictyota guineensis (as Dilophus guineensis (Kützing) J. Agardh) was cited for the Brazilian coast by Taylor (1930). However, in his review in 1960, Taylor put in doubt the occurrence of this species in Brazil. Only recently, the occurrence of this species in Brazil is cited in the literature (Villaça et al., 2010; Széchy & De Paula, 2010). In the present study, we present the terpenoid composition of the dichloromethane extract from the brown alga Dictyota guineensis collected on the Bahia coast. These data may be important for future projects to obtain new prototypes with potential antiviral activity.

 

Materials and Methods

Algal material

Specimens of Dictyota guineensis were collected at Penha Beach, Itamaracá Island, Santa Cruz City, State of Bahia, located in the northeastern part of the country on the Atlantic coast, Brazil, during April, 2004, and January, 2005. The algae were collected at depths ranging from 1 to 2 m. The seaweeds were washed with local sea water and separated from sediments, epiphytes and other associated organisms. The algae were collected and identified by Dr. Joel Campos De Paula and voucher specimens were deposited in the Herbarium of the Universidade do Estado do Rio de Janeiro and the Museu Nacional, Universidade Federal do Rio de Janeiro (HRJ10.846, HRJ10.312, HRJ10.932, R207.449).

Experimental

All solvents were HPLC grade. Analytical thin-layer chromatographic (TLC) separations were carried out on Merck silica gel 60 F-254 (0.2 mm) precoated aluminum plates. Once developed, plates were visualized by spraying with 2% ceric sulphate in sulfuric acid, followed by gentle heating. Silica gel 60 (Merck, 70-230 and 230-400 mesh) was used for column chromatography. Nuclear magnetic resonance spectra (NMR) were recorded in CDCl₃ (100% Aldrich) on a Varian Unity Plus 300 spectrometer using TMS as internal standard.

Chemical analysis

Air-dried D. guineensis was extracted with dichloromethane (100%) at room temperature. The solvent was evaporated under reduced pressure, yielding brownish residues. An aliquot of the dichloromethane extract was diluted in an appropriate volume of ethyl acetate and analysed by HRGC-MS on a HP 6890 series GC system, coupled to a HP 5973 mass selective detector in the electron impact mode (70 eV), equipped with an HP-1 MS capillary column (30 m x 0.25 mm; film thickness 0.25 μm). Injector and detector temperatures were set at 270 ^oC and 290 ºC, respectively. The temperature was kept at 160 ºC, then programmed to 260 ºC at a rate of 4 ºC/min and finally raised at a rate of 15 ºC/min to 290 ºC for 15 min. Hydrogen was the carrier gas at a flow rate of 1 mL/min. Diluted samples were injected manually in the split mode (1/10). The chemical components were identified based on comparisons of their mass spectral data with those of standards and/or literature data, by co-injection of these samples in the HRGC, and from Wiley 275 library data of the HRGC-MS system.

An aliquot (10 mg) of crude extract was dissolved in CDCl₃ and the ¹H NMR (300 MHz) spectrum was obtained in a Varian-Unity Plus 300 (TMS as internal reference).

 

Results and Discussion

The diterpenes from Dictyota guineensis were analyzed by the HRGC-MS technique. This analysis revealed the presence of peaks in the mass spectra compatible with the fragmentation patterns of five diterpenes: dictyol E (the most abundant diterpene), dictyotadiol, dictyoxide, isopachydictyol A and pachydictyol A (1-5). This is the first chemical record for Dictyota guineensis from Brazil. The only other study was carried out with algae collected from the coast of Puerto Rico by Schlenk & Gerwick (1987). In this study, two natural products were isolated: dictyol E, a prenylated guaiane diterpene (1) and the major product, and dilophic acid (6), a xeniane diterpene (Table 1).

In the Brazilian seaweed extract, no compounds of diterpene group III were detected. In the ¹H NMR spectrum, there were no signals that would indicate the presence of aldehydes (present in most of the group III diterpenes) or carboxylic acids (present in dilophic acid). Nevertheless, D. guineensis should be considered to belong to the taxonomic group A. Despite the difference in the presence of xeniane diterpenes, the two populations (Puerto Rico and Brazil) presented dictyol E (2) as the major natural product.

The xeniane diterpenes and their derivatives have shown excellent results against HSV-1 (herpes simplex type 1) and HIV-1(Human immunodeficiency virus type 1) (Ninomya et al., 1995; Pereira et al., 2004, 2005), while prenylated guaianes have not shown promise as candidates for antiviral agents.

For these reasons, studies on the biotechnological potential of the diterpenes of D. guineensis as a source of antiviral agents should be discouraged. Moreover, the algae are not abundant and frequent on the Brazilian coast, their populations have a small biomass and the diterpenes can be obtained from more abundant sources or by synthesis for assessment in vitro and in vivo.

Nevertheless, the analysis of the chemical composition of D. guineensis can be an important tool for taxonomic, phylogenetic and biogeographic studies.

 

Acknowledgment

We are grateful to the Conselho Nacional de Pesquisa e Desenvolvimento Tecnológico for financial support, productivity fellowships to YYV and VLT, and a PostDoctor al fellowship to DNC.

 

References

Alvarado AB, Gerwick WH 1985. Dictyol H, a new tricyclic diterpenoid from the brown seaweed Dictyota dentata Lamouroux. J Nat Prod 48: 132-134.         [ Links ]

Barbosa JP, Teixeira VL, Pereira RC 2004. A dolabellane diterpene from the brown alga Dictyota pfaffii as chemical defense against herbivores. Bot Mar 47: 147-151.         [ Links ]

Cavalcanti DN, Rezende CM, Pinto AC, Teixeira VL 2006. Diterpenoid constituents from the brown alga Dictyota menstrualis (Dictyotaceae, Phaeophyta). Nat Prod Comm 1: 609-611.         [ Links ]

Cirne-Santos CC, Souza TML, Teixeira VL, Fontes CFL, Rebello MA, Castello-Branco LR, Abreu CM, Tanuri A, Frugulhetti ICPP, Bou-Habib DC 2008. The dolabellane diterpene Dolabelladienetriol is a typical non competitive inhibitor of HIV-1 reverse transcriptase enzyme. Antiviral Res 77: 64-71.         [ Links ]

Cirne-Santos CC, Teixeira VL, Castello-Branco LR, Frugulhetti ICPP, Bou-Habib DC 2006. Inhibition of HIV-1 replication in human primary cells by a dolabellane diterpene isolated from marine brown algae Dictyota pfaffii. Planta Med 72: 295-299.         [ Links ]

De-Paula JC, Bueno LB, Cavalcanti DN, Yoneshigue-Valentin Y, Teixeira VL 2008. Diterpenes from the Brown Alga Dictyota crenulata, potential source of antiviral products. Molecules 13: 1238-1245        [ Links ]

De-Paula JC, Bueno LB, Frugulhetti ICPP, Yoneshigue-Valentin Y, Teixeira VL 2007b. Dictyota dolabellana sp. nov. (Dictyotaceae, Phaeophyceae) based on morphological and chemical data. Bot Mar 50: 288-293.         [ Links ]

De-Paula JC, Cassano V, Yoneshigue-Valentin Y, Teixeira VL 2007a. Diterpenes from the Brazilian brown alga Dictyota crispata (Dictyotaceae, Phaeophyta). Nat Prod Comm 2: 135-137.         [ Links ]

De-Paula JC, Pedrini AG, Pinheiro MD, Pereira RC, Teixeira VL 2001. Chemical similarity between the brown algae Dictyota cervicornis and D. pardalis (Dictyotales, Phaeophyta). Biochem Syst Ecol 29: 425-427.         [ Links ]

Freitas OSP, Oliveira AS, De-Paula JC, Pereira RC, Cavalcanti DN, Teixeira VL 2007. Chemical variation in the diterpenes from the Brazilian brown alga Dictyota mertensii (Dictyotaceae, Phaeophyta). Nat Prod Comm 2: 13-15.         [ Links ]

Kelecom A, Teixeira VL 1988. Dolastane diterpenes from the marine brown alga Dictyota cervicornis. Phytochemistry 27: 2907-2909.         [ Links ]

Ninomya M, Matsuka S, Kawakubo A, Bito N 1995. HIV-1 reverse transcriptase inhibitors containing hydroxydictyodial or dictyodial. Jpn Kokai Tokkyo Koho JP 285: 877.         [ Links ]

Pereira HS, Leão-Ferreira LR, Moussatché N Teixeira VL, Cavalcanti DN, Costa LJ, Diaz R Frugulhetti ICPP 2005. Effects of diterpenes isolated from the Brazilian marine alga Dictyota menstrualis on HIV-1 reverse transcriptase. Planta Med 71: 1019-1024.         [ Links ]

Pereira HS, Leão-Ferreira LR, Moussatché N, Teixeira VL, Cavalcanti DN, Costa LJ, Diaz R, Frugulhetti ICPP 2004. Antiviral activity of diterpenes isolated from the Brazilian marinealga Dictyota menstrualis against human immunodeficiency virus type 1 (HIV-1). Antiviral Res 64: 69-76.         [ Links ]

Schlenk D, Gerwick WH 1987. Dilophic acid, a diterpenoid from the tropical brown seaweed Dilophus guineensis. Phytochemistry 26: 1081-1084.         [ Links ]

Széchy MTM, De-Paula JC 2010. Phaeophyceae. In: Forzza RC (ed) Catálogo de plantas e fungos do Brasil, Andrea Jakobsson Estúdio, Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Rio de Janeiro, p. 404-408.         [ Links ]

Taylor WR 1930. A synopsis of the marine algae of Brazil. Revue Algologique 5: 1-35.         [ Links ]

Teixeira VL 2010. Taxonomia química. In: Pedrini AG (org.). Macroalgas: uma introdução à taxonomia, Technical Books Editora, Rio de Janeiro, p. 83-97.         [ Links ]

Teixeira VL, Almeida SAS, Kelecom A 1990. Chemosystematic and biogeographic studies of the diterpenes from the marine brown alga Dictyota dichotoma. Biochem Syst Ecol 18: 87-92.         [ Links ]

Teixeira VL, Cavalcanti DN, Pereira RC 2001. Chemotaxonomic study of the diterpenes from the brown alga Dictyota menstrualis. Biochem Syst Ecol 29: 313-316.         [ Links ]

Teixeira VL, Kelecom AA 1988. Chemotaxonomic study of diterpenes from marine brown algae of the genus Dictyota. Sci Total Environ 75: 271-283.         [ Links ]

Vallim MA, Barbosa, JE, Cavalcanti DN, De-Paula JC, Giongo VA, Teixeira VL, Paixão ICNP 2010. In vitro antiviral activity of diterpenes isolated from the Brazilian brown alga Canistrocarpus cervicornis. J Med Plant Res 4: 2379-2382.         [ Links ]

Villaça R, Fonseca AC, Jensen VK, Knoppers B 2010. Species composition and distribution of macroalgae on Atol das Rocas, Brazil, SW Atlantic. Bot Mar 53: 113-122.         [ Links ]

 

 

*Correspondence
Valéria Laneuville Teixeira
Departamento de Biologia, Instituto de Biologia, Universidade Federal Fluminense
Caixa Postal 100.644 Niterói, 24001-970, RJ, Brazil
valerialaneuville@id.uff.br
Tel: +55 21 26292296

Received 25 Nov 2011
Accepted 20 Dec 2011