Sesquiterpenes from Essential Oil from Fruits of Guarea macrophylla Vahl ssp. tuberculata (Meliaceae)

Abstract

The hydrodistillated essential oil from fruits of Guarea macrophylla Vahl ssp. tuberculata (Meliaceae) was analyzed by capillary GC and GC/MS. Twenty-four sesquiterpenes were identified, representing 92.9% of volatiles, among which 78.2% were hydrocarbons and 14.7% were oxygenated components. The major components were found to be α-copaene (10.3%), viridiflorene (14.6%) and cadina-1,4-diene (17.5%).

Key Word Index

Guarea macrophylla ssp. tuberculata, Meliaceae, essential oil composition, GC/MS, α-copaene, viridiflorene, cadina-1,4-diene.

Plant Name

Guarea macrophylla VaM ssp. tuberculata Vellozo (Meliaceae)

Source

The fruits of G. macrophylla ssp. tuberculata were collected in "Bosque da Biologia," at Universidade de São Paulo campus, São Paulo, São Paulo State, Brazil on October 10, 2000. A voucher specimen was classified by José Rubens Pirani (Institute de Biociências of Universidade de São Paulo) and was deposited in SPF Herbarium from the same institute.

Previous Work

Chemical studies of Meliaceae species mainly describe the characterization of meliacines (limonoids), which are known to possess a high biological potential (1). However, other compounds have been isolated from Meliaceae such as sesquiterpenes, diterpenes, triterpenes and coumarins (2-5). Different parts of G. macrophylla have been studied and several compounds other than meliacines have been reported. Sesquiterpenes and diterpenes were identified in the oil from the leaves and stem bark (5,6). Diterpenes and one triterpene were isolated from the CH^sub 2^Cl^sub 2^ extract from the leaves (7). Continuing our studies with this species, we have investigated, for the first time, the oil composition from the fruits.

Experimental

Plant material: The fresh fruits of G. macrophylla ssp. tuberculata (220 g) were hydrodistilled for four h in a Clevenger-type apparatus, yielding 67 mg of crude volatile oil (0.03%).

Component identification: The crude oil was subjected to GC and GC/MS analysis. GC analysis was performed in a Shimadzu GC-17A Chromatograph equipped with a Shimadzu GC 10 software, using a fused silica capillary column (30 m × 0.25 mm, coated with 0.25 µm film thickness DB-5) and helium as the carrier gas. The temperature programming was from 60°-280°C at 5°C/min. The FID injector and detector temperatures were 180°C and 260°C, respectively. The percentage compositions were obtained from electronic integration measurements using flame ionization detection without taking into account relative response factors.

Gas chromatography/mass spectrometry: Analysis were carried out in a Shimadzu GC-quadrupole MS system (QP 5000) operating at 70 eV fitted with a similar column operated using the same conditions as describe above. The identification of the compounds was performed by comparison of retention index (determined relatively to the retention times of a series of n-alkanes) and mass spectra with those of authentic sample.

Results and Discussion

A total of 24 components were identified corresponding to 92.9% of the crude oil. In this work, we can observe that the oil was composed exclusively of sesquiterpenes, among which 78.2% were sesquiterpene hydrocarbons, α-copaene, viridiflorene and cadina-l,4-diene as the major components (10.3%, 14.6% and 17.5%, respectively). The oxygenated components were present with 14.7% in the oil.

The oils from leaves, stem bark and fruits of G. macrohylla were composed mainly of sesquiterpenes. However, in the leaves a higher amount of oxygenated sesquiterpenes (35.9%) were detected while in the fruits the hydrocarbons were predominant (5-7).

In a previous paper it was concluded that the oils from Guarea species did not contain any monoterpenes (5,6,8,9). As we also were not able to detect monoterpenes in fruit oil from G. macrophylla, these findings might corroborate this hypothesis.

Acknowledgements

The authors are gratefull to FAPESP and CNPq for the financial support and scholarships.

References

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