Essential Oils from Salvia sp. (Lamiaceae). III. Composition and Antimicrobial Activity of the Essential Oil of Salvia palaestina Benth. Growing Wild in Lebanon

Journal of Essential Oil Research: JEOR, Jul/Aug 2005 by Senatore, Felice, Formisano, Carmen, Arnold, Nelly Apostolides, Piozzi, Franco

Abstract

The essential oil of Salvia palaestina Benth. (Lamiaceae), grown in Lebanon, obtained by hydrodistillation of aerial parts was analyzed by GC and GC/MS. Thirty-four compounds were identified constituting 96.4% of the oil, the major components being sclareol (20.2%), β-caryophyllene (16.6%) and linalool (8.6%). The oil shows activity against Gram-positive bacteria.

Key Word Index

Salvia palaestina, Lamiaceae, essential oil composition, sclareol, β-caryophyllene, antimicrobial activity.

Introduction

The genus Salvia (sage), one of the most important genera of the Lamiaceae family, subfamily Nepetoideae, comprises nearly 900 species spread widely throughout the world. Marked morphological and genetic variation was observed in the plants of this genus according to their geographical origin. Several species of Salvia are cultivated because of their aromatic nature (1) and are used as a flavor and food condiments, in cosmetics, perfumes (2) and in folk medicine (3-6). Salvia palaestina Benth. is a perennial herb with stems characterized by dense glandular hairs. In the framework of our investigations on the oils of Salvia species (5,6), we report in this paper die chemical constituents and the antimicrobial activity of the essential oil of S, palaestina Benth. growing wild in Lebanon. To the best of our knowledge, there are only some reports on several flavonoids (7), terpenoids (8) and diterpenoids (9,10) detected in this plant from different origin (Turkey and Egypt).

Experimental

Aerial parts of S. palaestina were collected at the full flowering stage from Kozhaye (northern Lebanon, 1100 m s. 1.) near the Convent of St. Antoine, in June 2002. A voucher specimen (leg. and det. N. Arnold s. n., confirm. Th. Raus) was deposited in the Herbarium of the Botanischer Garten, Berlin University. The air-dried samples were crushed, then hydrodistilled for 3 h according to the standard procedure described in the European Pharmacopoeia (11) usingaClevenger-type apparatus to produce oil in a 0.39% yield. The oil was analyzed by GC and GC/MS. GC analyses were performed on a Perkin-Elmer Sigma 115 gas chromatograph equipped with an HP-I fused-silica column (30 m x 0.25 mm, coating thickness 0.25 pm) and with a data handling system and FID. Analytical conditions were: injector and detector temperatures 250°C and 285°C, respectively; oven temperature program, 5 min isothermal at 40°C, subsequently at 2°C/min up to 260°C and then held isothermally at 260°C for 20 min; carrier gas He. Injection mode splitless (1 pL of a 1:1000 pentane solution). GC/MS analysis was performed using a Hewlett Packard 5890 A apparatus, equipped with a DB-5 fused-silica column (30 m x 0.25 mm, film thickness 0.33 pm), linked on line with an HP Mass Selective Detector (MSD 5970 HP); ionization voltage 70 eV; electron multiplier energy 2000 V. Gas chromatographic conditions were as given; transfer line temperature, 295°C. The identification of constituents was established by comparison of the retention indices and MS spectra with those reported in literature (12-14), and by computer matching with the NIST 98 and Wiley 5 libraries, as well as, whenever possible, co-injections with authentic compounds available in our laboratories. The retention indices were determined in relation to homologous series of n-alkanes (C^sub 8^-C^sub 22^) under the same operating conditions. Component relative concentrations were calculated based on GC peak areas without using correction factors.

Antimicrobial assay: The antimicrobial activity was evaluated by determining the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) using the broth dilution method (15). Eight bacteria species, selected as representative of the class of Gram-positive and Gram-negative, were tested: Bacillus cereus (ATCC 11778), Bacillus subtilis (ATCC 6633), Staphylococcus aureus (ATlC 25923), Streptococcusfaecalis (ATCC 29212),Escherichiacoll (ATCC 25922), Proteus vulgaris (ATCC 13315), Pseudomonas aeruginosa (ATCC 27853), Salmonella typhi Ty2 (ATCC 19430). The strains were maintained on tryptone soya agar; for the antimicrobial tests, tryptone soya broth was used. In order to facilitate the dispersion of the oils in the aqueous nutrient medium they were diluted with Tween 20 at a ratio of 10%. Each strain was tested with samples that were serially diluted in broth to obtain concentrations ranging from 100 µg/mL to 0.8 µg/mL. The samples were previously sterilized with Millipore filter of 0.45 mm in of 0.20 µm. The samples have been stirred, inoculated with 50 µg/mL of physiologic solution containing 5 x10^sup 6^ microbial cells, and incubated for 24 h at 37°C. The MIC value was determined as the lowest concentration of the sample that does not permit any visible growth of the tested microorganism after incubation. Solution containing only Tween 20 instead of the oil was not toxic to the microorganism. Cultures containing only sterile physiologic solution Tris buffer were used as positive control. MBC was determined by subculture of the tubes with inhibition in 5 mL of sterile nutrient broth. After incubation at 37°C the tubes were observed. When the germs did not grow, the sample denoted a bactericidal action. oil samples were tested in triplicate. Gentamycine was used as standard antibacterial agent. Sterile distillated water and medium served as a positive growth control.