Preliminary studies on the volatile constitution of Mikania species

Estudos preliminares dos constituintes voláteis de espécies de Mikania

ARTIGO

Preliminary studies on the volatile constitution of Mikania species

Estudos preliminares dos constituintes voláteis de espécies de Mikania

Anair A. Reis^I; Tatiana L. Ferraz^I; Dirceu Martins^I; Frederico G. Cruz^I; Maria Lenise da S. Guedes^II; Nidia F. Roque^{I, *}

^IDepartamento de Química Orgânica, Instituto de Química, Universidade Federal da Bahia, Campus Universitário de Ondina, 40170-290 Salvador-BA, Brazil

^IIInstituto de Biologia, Universidade Federal da Bahia, Campus Universitário de Ondina, 40170-290 Salvador-BA, Brazil

ABSTRACT

Volatile oils obtained from the aerial parts of three Mikania species plants were analyzed by GC-MS and NMR. Forty-six terpenes among monoterpenes, sesquiterpenes and diterpenes were identified by this methodology. The analysis classified Mikania hookriana as diterpene producer as the majority Mikania species occurring in Brazil.

Keywords: Mikania hookeriana, Mikania hagei, Mikania jeffrey, Asteraceae, volatile diterpenes, kaurane diterpenoids.

RESUMO

Óleos voláteis obtidos das partes aéreas de plantas de três espécies de Mikania foram analisados por CG-EM e RMN. Quarenta e seis terpenos, entre monoterpenos, sesquiterpenos e diterpenos, foram identificados. A análise classificou Mikania hookeriana como produtora de diterpenos, de acordo com a maioria das espécies de Mikania que ocorrem no Brasil.

Unitermos: Mikania hookeriana, Mikania hagei, Mikania jeffrey, Asteraceae, terpenos voláteis, diterpenos kaurano.

INTRODUCTION

We have been studding Mikania plants, from Asteraceae family, for twenty years (Knudsen et al., 1986; Nunez et al., 2004). This genus is the largest of the Eupatorieae tribe, with more than 450 species. Brazil is the country where the genus is best represented with more than 150 species occurring all over the country. Many new endemic Mikania species were discovered in Chapada Diamantina, Bahia, Brazil (Hind, 1993).

As terpenes are de major constituents isolated from plants of this genus and essential oils compounds have large applications in pharmaceutics and cosmetics industries (Silva-Santos, et al., 2004; ), the analysis of the essential oils of same Mikania species was accomplished. In this paper we describe for the first time the composition of the volatile oil from the aerial part plants of three Mikania species, M. jeffreyi, M. hagei and M. hookeriana collected in Chapada Diamantina, Bahia. 15-oxy-kaurenoic acid derivatives were found in the resin of M. hookeriana (Reis et al., 2003). These compounds have anti-bacterial properties (Davino et al., 1989) and are also present in the active fractions of M. glomerata, used in Brazil, for treatment of respiratory diseases (Moura et al., 2002). M. hagei and M. jeffreyi have not been studied from the chemical point of view.

MATERIAL AND METHODS

The aerial parts of M. hookeriana DC and M. hagei R. King/H. Robinson were collected in Chapada Diamantina in November 1999 and M. jeffreyi J. D. Hind in October 2000 in the same region. Voucher specimens were deposited at the herbarium Alexandre Leal Costa (HALC) of the Instituto de Biologia, UFBA, under the numbers 045688, 045687 and 048657, respectively.

The stems and leaves of M. hookeriana were separated and the fresh and ground material submitted to hydrodistillation in a Clevenger-type apparatus for 2 hours. The stem oil yield was 0.20 v/w % and the leave oil yield was 0.15 v/w %. The aerial parts of M. hagei and M. jeffreyi were submitted to the same procedure without separation of the aerial plant parts. The yields of the extractions were 0.10% v/w for M. hagei and 0.70% v/w for M. jeffreyi. The crude oils obtained were analyzed by a methodology that combines ¹³C NMR spectra, CG-MS and Kovats Index. NMR spectra were recorded at 300 MHz for ¹H and 75 for ¹³C on a Varian Gemini 300 using CDCl₃ as solvent and internal standard. GC-MS analyses were performed using a gas chromatograph HP 6890 interfaced with a HP 5873 Mass Selective Detector (ionization voltage 70 eV) equipped with capillary HP-5MS column (30 m x 0.25 mm, film thickness 0.25 µm), using He as the carrier gas (1.0 mL min^-1). The oven temperature was programmed from 60º to 240 ºC at 3^º/ min and isothermal at 240 ºC for 10 min. The injector and detector temperatures were 240º and 300 ºC, respectively. The RIs were calculated by the Kovats algorithm (Kovats, 1958) with C₉-C₂₅ hydrocarbons as standard. The library used for MS comparison was NIST 1998.

RESULTS AND DISCUSSION

Forty-six terpenes were identified in the three oils analyzed. The percentages of mono-, sesqui- and diterpenes identified in each oil are showed in Table 1. As in other Mikania, the chemical composition of the oils showed from one to three major compounds. Therefore, after obtaining the oils, ¹³C NMR spectra (BBD and DEPT) were run, in order to confirm the identification made by CG-MS analysis and Kovats index (KI) of the principal oil constituents.

The methodology adopted allowed a more precise identification of the main compound (45.78%) from the stems and leaves of M. hagei, as β-selinene. The comparison of the mass spectra with those of NIST 98 library suggested that the compound could be eremophilene or β-selinene with the same confidence (97%). The KI for both compounds is the same 1486 (Joulain & König, 1998) so, as the major signals present in the ¹³C NMR spectra equal those of β-selinene, the identity of the compound could be established. The ¹³C NMR spectrum also confirmed the presence of α-selinene in the oil.

The major compound (23.34 %) of the volatile oil from the stems of M. hookeriana was identified as α-pinene followed by germacrene D (11.14 %) and kaurenal (6.32 %). The oil from the leaves has the same two major constituents.

The three major compounds of M jeffreyi are limonene, α and β-pinene. Sesquiterpenes are less representative in this species.

In all oils, the presence of the monoterpenes α and β-pinene, limonene, β-thujene and the sesquiterpenes cariophyllene and germacrene D was observed. Diterpenes, detected by the retention time and mass fragmentation pattern, are present as traces in all species. Only in M. hookeriana we could identify kaurane diterpenes and they are even representatives (9.52%). The low percentage of identified compounds in the oils from M. hookeriana is due to the presence of diterpenes. That compounds are not identified by the CG-MS analysis.

The study of the CHCl₃/MEOH extract from aerial parts of M. hookeriana was made and 15-oxy-kauranoic acid derivatives were present as major compounds (Reis et al., 2003). This suggests that volatile oil analysis could be used to indicate the presence of fixed kaurane or other diterpenes in plants. Thus volatile chemical composition of Mikania species could direct the search for plants rich in the bioactive kaurenoic acids derivatives, as shown by this analysis in Mikania hookeriana.

Herz (1998) described the occurrence of a dichotomy between diterpenes and sesquiterpenes lactones in the constitution of Mikania species. Furthermore, reports on Mikania chemical constitution suggested that when kaurane diterpenes are present in the plant, the other kind of diterpenoids, whether they are present, is found in very small amounts (Nunez et al., 2004). As showed in this report, the volatile compounds analysis could detect the presence of diterpenes in the oil. In that way M. hookeriana could be classified as diterpene producer as the majority Mikania species occurring in Brazil.

ACKNOWLEDGEMENTS

This work was supported by CNPq and FINEP.

Received 20 March 2008

Accepted 7 August 2008

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Publication Dates

• Publication in this collection
  09 Mar 2009
• Date of issue
  Dec 2008

History

• Received
  20 Mar 2008
• Accepted
  07 Aug 2008