Abstract: The aerial parts of Salvia lanigera (Labiatae) afforded an essential oil on steam distillation, which was analyzed by gas chromatography-mass spectrometry (GC/MS) using direct injection. Out of forty-eight peaks (representing 99.4% of the oil), forty-two components were identified representing 98.8% of the total oil composition. The major components were 1,8-cineole (36.2%), α-pinene (10.7%), terpin-4-ol (7.5%), β-pinene (6.5%), limonene (5.6%) and bornyl acetate (4.5%). Furthermore, the oil exhibited a very interesting antimicrobial profile after it was tested against seven gram-positive and –negative bacteria and two pathogenic fungi.
Introduction
Salvia, the largest genus of the labiatae family, includes about 900 species widespread all over the world. In this genus, section Salvia contains the Salvia species richest in essential oils. Some members of this section, like S. officinalis and S. fruticosa, are of economical importance as flavouring agents in perfumery and cosmetology. Sage has been credited with a long list of medicinal uses: spasmolytic, antiseptic and astringent (Newall et al., 1996). In our continuing research on the essential oils of Greek plants, we have investigated the essential oil of Salvia lanigera and its biological activity. Salvia lanigera belongs to section Salvia. It is a perennial plant growing wild in the Mediterranean area (Hedge et al., 1976). The leaves of S. lanigera are used as an aromatic tea for a variety of abdominal troubles (AL-Hazimi et al., 1984). Previous reports on the plant have shown the presence of four diterpene-quinones of the royleanone type (Saleh et al., 1978). In addition, three diterpenes, namely isocarnosol, 12-hydroxyisocarnosol and methyl carnosoate were isolated from the petrol extract of the plant (Al-Hazimi et al., 1986). As no phytochemical and pharmacological studies on the essential oil of S. lanigera are reported. It was thought worthwhile to explore out its chemical composition as well as its antimicrobial activities to correlate the results with the traditional use of this plant for abdominal troubles.
Materials and Methods
Plant material: The aerial parts of Salvia lanigera were collected in March 2002 from Wadi Sabha near Zabirah, 200 Km north of Buraydah, Najd Province, Saudi Arabia. Dr. Atiqur-Rehman, Taxonmist identified the plant and a voucher specimen has been deposited at the herbarium, College of Pharmacy, King Saud University, for future reference.
Analysis of the essential oil: Fresh aerial parts (450 g) were crushed to coarse powder and steam distilled in a Clevenger apparatus for about 5 h to obtain the yellow coloured oil (2.4 ml, 0.53% v/w) which was subjected to analysis by GC/MS using direct injection in the split mode under the following conditions:
Hewlett-Packard 5973 MSD GC/MS equipped with a quartz capillary column: 30 x 0.32 mm2 x 1.0 μ Rtx- 5 sil MS (Restek); oven temperature: 40°C (hold 3 min) to 200°C at 8°C/ min then to 320°C at 6°C/min (hold 4 min); injector temperature: 320°C; sample size: 0.2 μ L, split 1: 100; mass range: 35- 500 amu, 3.17 scans/sec; carrier gas: He; ionization energy: 70 eV. The qualitative identification of different constituents was performed by comparison of their retention times and mass spectra with those of the library.
Pharmacological screening: The antimicrobial activity was tested according to the National Committee of Clinical Laboratory Standards (NCCLS 2000) using American type of Culture Collection (ATCC) standard (Ferraro et al., 2000) against various microorganisms namely: Bacillus subtilis, Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa, Mycobacterium smegmatis, Candida albicans and Candida vaginalis. The positive antibacterial and antifungal activities were established by the presence of measurable zones of inhibition after 24 h incubation periode.
Results and Discussion
The results of the analysis of the essential oil was qualitative and semi-quantitative. The fresh aerial parts of Salvia lanigera yielded 0.53% v/w of essential oil.
| Table 1: | Identified chemical constituents in the essential oil of Salvia |
| Table 2: | Antimicrobial activity of the essential oil of Salvia lanigera |
| NT: Not tested NA: Not active | |
This means that the plant was relatively rich in oil and fat constituents. The constituents identified by GC/MS analysis, their retention times and area percentage are summarized in Table 1. Out of forty-eight peaks (representing 99.4% of the oil), forty-two components were identified representing 98.8% of the total oil composition. Monoterpenic alcohols were the major constituents in the oil. In addition to 1,8-cineole (36.2%), that was the major monoterpenic alcohol, α-pinene (10.7%), terpin-4-ol (7.5%), β-pinene (6.5%), limonene (5.6%) and bornyl acetate (4.5%) were present in fairly good amount.
On the other hand, guaiol (5.4%) was the major oxygenated sesquiterpene present in the oil. Other sesquiterpene hydrocarbons such as β-caryophyllene (2.5%) and δBcadinene (2.0%) were also detected in appreciable amounts. Moreover, some minor components were also detected of which trans-sabinol (1.3%), thymol (1.2%), carvacrol (1.2%), linalool (1.1%) and α-terpineol (1.0%) were identified.
Table 2 summarises the antimicrobial properties of the S. lanigera essential oil. The oil showed significant antibacterial and antifungal activity with 50 Fl on various microorganisms tested. The minimum inhibitory concentration (MIC) of the oil was 600 Fg ml–1 against Bacillus subtilis. Also, the oil exhibited the same MIC (450 Fg ml–1) against the two species of gram positive bacteria, Staphyllococcus aureus and S. epidermidis as well as the two species of the pathogenic fungi, Candida albicans and C. vaginalis. In addition, the minimum inhibitory concentration against the two gram (-) bacteria, Proteus mirabilis and Mycobacterium smegmatis was 550 Fg ml–1. Other microorganisms that were tested such as Escherichia coli and Pseudomonas aeruginosa were resistant to the oil.
The above results strongly support using this plant traditionally as an aromatic tea for abdominal disorders caused by microorganisms tested. Further toxicological and clinical studies are required to prove the safety of the oil as a medicine.
Acknowledgment
The author is thankful to Mr. Mohammad Mukhair, the technician of the center, for technical assistance. In addition, the author gratefully acknowledge the financial support of the Research Center at College of Pharmacy, King Saud University.