Seasonal Variation of the Essential Oil of Cabralea canjerana

Abstract

The leaves of C. canjerana were collected in the town of Chapeco, Brazil, in July and November (2008) and January and April (2009), and a voucher specimen (SMDB 12.356) has been deposited in the Herbarium of the UFSM. The fresh leaves were submitted to hydrodistillation (4 h) to yield ca. 0.5% of oil. The oil was submitted to GC analysis in a Shimadzu (GCMS-QP2010 Plus) chromatograph equipped with a capillary fused silica column (30 m 0.25 m) coated with RTx-5MS. The injector and detector temperatures were 240 and 260C, respectively. He was used as carrier gas at a flow rate of 1 mL min –1 , injection was in the split mode (1:10), and the injection volume was 1 mg mL –1 of a solution containing oil in hexane. MS spectra were obtained using electron impact at 70 eV with a scan interval of 2.94 scan s –1 . The compound identification was based on a comparison of retention index with the same columns and mass spectra described [5, 6]. Retention indices (RI) have been obtained according to the method of Van den Dool relative to C7–C30 saturated n-alkane standards. Quantitative analyses of the chemical constituents was performed using a flame ionization detector (FID) and a Shimadzu (GC-2010) instrument under the same conditions and with the same column as reported for the GC-MS. The antimicrobial activity of the essential oil of C. canjerana was evaluated in vitro using the method of filter paper disc diffusion [7–9]. Fifty-seven compounds were identified in the essential oil of C. canjerana, showing only sesquiterpenes, especially oxygenated sesquiterpenes. The main component that showed a variation in concentration in different seasons was spathulenol (1); in spring time a lower concentration (10.8%) of this compound was found (Fig. 1). Spring, which is the season of fullest blossoming of C. canjerana, also showed the major compounds to be caryophyllene oxide (2) and -cadinol (3). These two compounds were found in oils from other seasons in lower concentrations. The oil collected in the autumn showed cubebol (6, 9.3%) and globulol (5, 9.8%). Cubebol was not found in the essential oil during the summer and winter seasons. The highest concentration of dihydroeudesmol (4) was found in summer but not found at all in autumn. The oil of C. canjerana was active against all bacteria tested. However, S. flexneri bacteria were less sensitive to the oil, only showing sensitivity to the oil collected in the spring. The bacteria most sensitive to the oil of C. canjerana were