The plant world represents an enormous reservoir of biologically active molecules. Essential oils, the odorous principles of plants, are widely employed because of their commercial uses and medicinal properties. Extensive application of essential oils for their antimicrobial activity in food preservations, pharmaceuticals, alternative medicine, and natural therapies has resulted in a large number of studies concerning this effect of essential oils.

Salvia L., with a cosmopolitan distribution and about 900 species, is the largest genus of Lamiaceae family and is a rich source of volatile constituents and biologically active molecules. In Iran, this genus is represented by 58 species of which 17 are endemic [1]. The antimicrobial activity of the essential oils of Salvia species is the subject of more than 70 articles, according to the ISI Web of KnowledgeSM. In this work, the essential oils of six Iranian Salvia species, including S. eremophila, S. santolinifolia, S. reuterana, S. virgata, S. multicaulis, and S. hydrangea, are tested for antimicrobial activity. Among these species, only the S. santolinifolia and S. hydrangea essential oils were the subjects of a previous work [2]. Also the compositions of the oil of these six species have been studied.

Data on the constituents of the six Salvia oils are shown in Table 1. According to this table, the first major compounds of S. eremophila and S. santolinifolia were α-pinene. The major constituents of S. eremophila were α-pinene (21.5%), borneol (20.8%), and geranyl linalool (10.7%). In a previous work, α-pinene was also the first major compound of this species with 24.3% of the total oil, and bornyl acetate (18.9%) and camphene (16.0%) were the second and third compounds [8]. In S. santolinifolia oil, α-pinene (35.7%), camphor (15.9%), and α-eudesmol (4.9%) were the major compounds. In two previous works, α-pinene was also the first major compound with more than 50% of the total oils in both reports [2–4]. β-Pinene and limonene were the second and third major compounds in both previous works. Hedge, in Flora Iranica, have placed Salvia species in several groups and subgroups according to the morphological characters [5]. Salvia eremophila and S. santolinifolia, which are dwarf desert subshrubs, have been placed together in the subgroup IIa. Relatively similar essential oil compositions of these species are in agreement with their morphological similarities. Caryophyllene oxide (61.5%), β-caryophyllene (8.3%), and borneol (5.6%) were the major compounds of S. hydrangea. The essential oils of this species were the subjects of several previous articles, and in all reports, compounds with the caryophyllene skeleton were the major constituents [2, 6–8]. The constituents with this skeleton were also the major compounds in S. virgata oil in our work and two previous works [9, 10]. Caryophyllene oxide (26.0%), tetradecanoic acid (11.2%), and hexadecanoic acid (10.5%) were the major compounds in the oil of our work. It seems that caryophyllene backbone compounds are a dominant group in the oil of these two species. Borneol (11.6%), β-caryophyllene (8.5%), and α-pinene (8.3%) were the major compounds of S. multicaulis. Previous reports on the oil composition of this species completely differed from each other and also from ours [11–14]. The different localities of the collected plant materials may explain the considerable different chemical compositions of these oils. Benzyl benzoate comprised 75.9% of S. reuterana total oil, which was completely different from previous work. E-β-Ocimene (32.3%), α-gurjunene (14.1%), and germacrene D (11.2%) were the main components of the oil of previous work [15].

Table 1 The Chemical Constituents of Six Salvia Essential Oils, %
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Antimicrobial assay results are presented in Table 2. As can be seen, all the oils show considerable effect against all the microorganisms. The greatest effect of S. santolinifolia was against gram negative bacteria; in two cases, K. pneumonia and S. typhi, its effect was better than gentamycin. It was also very effective against two tested yeasts. S. eremophila oil was also very effective against K. pneumonia. It had a good effect against S. aureus. The best effect of S. multicaulis, S. hydrangea, and S. virgata was against S. epidermidis. In light of the fact that caryophyllene-skeleton compounds constituted the majority of S. virgata and S. hydrangea oil compositions and β-caryophyllene is one of the major compounds of S. multicaulis oil, this effect can be attributed to these structures. S. virgata’s effect against C. albicans was also considerable and S. hydrangea oil was also effective against S. typhi and E. coli. S. reuterana oil was most effective against S. typhi and E. coli which can be related to benzyl benzoate, which comprises more than three-fourths of the total oil of this species. None of the six examined species was active against Bacillus subtilis.

Table 2 Antimicrobial Activities of the Essential Oils of Six Salvia Species
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