1.   Introduction

There are more than 1000 recognized species of Salvia L. (Lamiaceae) according to World Flora Online [1] and many of these have been examined in terms of essential oil composition and biological activities [2–5]. Several Salvia essential oils are important for aromatic therapy, including Salvia desoleana Atzei & V. Picci (Sardinian sage), Salvia fruticosa Mill. (Greek oregano), Salvia lavandulifolia Vahl (syn. Salvia officinalis subsp. lavandulifolia (Vahl) Gams, Spanish sage), Salvia officinalis L. (Dalmatian sage), Salvia sclarea L. (clary sage), Salvia somalensis Vatke (Somalian sage), Salvia stenophylla Burch. ex Benth. (blue mountain sage), and Salvia triloba L.f. (syn. Salvia fruticosa Mill., Greek sage) [6].

Salvia dorrii (Kellogg) Abrams (purple sage, Lamiaceae) is found throughout the western United States from Washington to northern Baja California, Mexico, and east to western Idaho, western Utah, and northern Arizona [7]. There are several infraspecific taxa, namely Salvia dorrii subsp. dorrii (found from southern Oregon, southwestern Idaho, eastern California, Nevada, western Utah, and northern Arizona), Salvia dorrii subsp. mearnsii (Britton) E.M. McClint. (found only in central Arizona, Salvia dorrii var. clokeyi Strachan (found only in southern Nevada), Salvia dorrii var. incana (Benth.) Strachan (syn. Salvia dorrii var. carnosa (Douglas ex Greene) Abrams) (found in Washington, Oregon, and southwestern Idaho), and Salvia dorrii var. pilosa (A. Gray) Strachan & Reveal (found in southern California, southern Nevada, and northwestern Arizona) (Fig. 1).

Figure 1. Range map of Salvia dorrii subspecies based on Strachan, 1982 [7].

The plant is a woody perennial shrub that grows up to 80 cm tall and 150 cm wide. The leaves are opposite oval, 1.5-4 cm long, 0.5-1.5 cm wide, widest at the tip and tapering to the stem. The inflorescence is made up of clusters of several purple flowers. Each cluster is 10-24 mm wide with purple, blue, or rose bracts (Fig. 2) [8]. The Paiute people used a poultice of crushed leaves for chest congestion or coughs from colds, the Shoshoni took an infusion or decoction of the leaves to treat colds [9].

Figure 2. Salvia dorrii. A: Photograph of the plant at the time of collection by  K. Swor. B: Scan of the pressed plant material.

Abietane diterpenoids have been isolated and characterized from S. dorrii [10]. To our knowledge, however, there have been no previous publications on the essential oil of this plant species. As part of our program investigating the essential oils of aromatic and medicinal plants of the intermountain western United States, we present the essential oil obtained from aerial parts of S. dorrii collected from southeastern Oregon. Based on the descriptions and the geographical range [7,11], this is most likely Salvia dorrii var. incana (Benth.) Strachan (syn. Salvia dorrii var. carnosa (Douglas ex Greene) Abrams).

2.   Materials and methods

2.1. Plant material

Aerial parts of S. dorrii var. incana were collected on 8 May 2024 from four individual plants growing in Lake Owyhee State Park (Table 1). The plant was identified in the field by W.N. Setzer using a field guide [12] and verified by comparison with samples from the C.V. Starr Virtual Herbarium [13]. A voucher specimen (WNS-Sdi-0115) was deposited in the University of Alabama in Huntsville Herbarium. The fresh plant material was stored frozen at –20 °C until processed. The fresh-frozen plant material was hydrodistilled using a Likens-Nickerson apparatus with continuous extraction of the distillate with dichloromethane (Table 1).

Table 1. Plant collection and hydrodistillation yields of Salvia dorrii var. incana from southeastern Oregon

2.2. Essential oils extraction

The fresh-frozen plant material was hydrodistilled for four hours using a Likens-Nickerson apparatus with continuous extraction of the distillate with dichloromethane (Table 1).

2.3. Gas chromatographic analysis

The four S. dorrii var. incana essential oils were analyzed by gas chromatography (GC-MS, GC-FID, and chiral GC-MS) as reported previously [14]. Retention indices were calculated using the method of van den Dool and Kratz [15]. Essential oil components were identified by comparison of mass spectral fragmentation patterns and retention indices found in the Adams [16], FFNSC3 [17], NIST20 [18], and Satyal [19] databases.

3.   Results and discussion

3.1. Essential oil composition

Four samples of S. dorrii were collected from Lake Owyhee State Park, eastern Oregon. Hydrodistillation gave yellow essential oils in 1.85-2.33% yield. The essential oils were analyzed by gas chromatographic methods (GC-MS, GC-FID). A total of 119 compounds were identified, which accounted for 99.9-100.0% of the compositions (Table 2). Although the S. dorrii samples are qualitatively similar to one another, there are notable differences in concentrations. It is not clear what is responsible for the differences in compositions. The plants were collected on the same day from similar locations, so edaphic, climate, or phenology are not factors. The major components were 1,8-cineole (20.4-37.0%), bornyl acetate (5.2-19.2%), (E)-β-caryophyllene (3.3-12.4%), α-bisabolol (3.0-8.8%), β-phellandrene (0.1-9.8%), α-pinene (3.1-5.5%), and camphor (0.5-7.5%).

Table 2. Essential oil composition of four Salvia dorrii var. incana samples from southeastern Oregon

RIcalc = Retention index determined with respect to a homologous series of n-alkanes on a ZB-5ms column. RIdb = Reference retention index obtained from the databases [16–19]. tr = trace (< 0.05%).

This is the first report on the essential oil composition of S. dorrii, so there are no previous reports to compare. However, the composition obtained is similar to those reported for other Salvia species. In fact, there are at least five chemotypes of S. officinalis; one of these chemotypes is a 1,8-cineole/camphor chemotype that shows 1,8-cineole (39.9 ± 16.3%), camphor (12.9 ± 5.6%), α-pinene (4.1 ± 1.7%), (E)-β-caryophyllene (3.1 ± 1.7%), and bornyl acetate (0.8 ± 0.7%) [20]. Similarly, three chemotypes of S. lavandulifolia have been described, including a 1,8-cineole/pinene chemotype with 1,8-cineole (16.5 ± 7.8%), α-pinene (12.2 ± 6.1%), camphor (9.2 ± 6.8%), (E)-β-caryophyllene (4.3 ± 2.2%), and bornyl acetate (0.8 ± 0.9%) [21].

The major components of S. dorrii essential oils, 1,8-cineole, bornyl acetate, and (E)-β-caryophyllene, have shown anti-inflammatory activities generally by decreasing pro-inflammatory factors [22]. 1,8-Cineole has also demonstrated protective effects on the respiratory system in animal models by inhibiting inflammatory factors (TNF-α, IL-6, IL-1β, NF-κB) and modulating neutrophils and macrophages [23]. Furthermore, human clinical trials have indicated that 1,8-cineole shows beneficial effects in treating respiratory disorders such as chronic obstructive pulmonary disease (COPD), asthma, bronchitis, and rhinosinusitis [24, 25]. Additionally, 1,8-cineole lowered the severity and shortened the duration of the common cold [26] and camphor showed antitussive effects in animal models [27, 28]. Thus, the composition of S. dorrii essential oil is consistent with the traditional Paiute and Shoshoni use of this plant to treat chest congestion, coughs, and colds.

3.2. Enantiomeric distribution of chiral monoterpenoids

Enantioselective GC-MS was carried out on the S. dorrii essential oils (Table 3) in order to more fully characterize the essential oil composition. The predominant enantiomers were (+)-α-thujene (70.7 ± 11.9%), (+)-α-pinene (60.6 ± 9.2%), (–)-camphene (72.2 ± 17.9%), (–)-β-pinene 58.6 ± 4.6%), (+)-α-phellandrene (100%), (+)-β-phellandrene (99.3 ± 0.7%), (–)-linalool (86.5 ± 2.9%), (+)-camphor (99.2 ± 0.9%), and (+)-α-terpineol (95.1 ± 9.9%). Limonene, terpinen-4-ol, and borneol showed inconsistent enantiomeric distributions. That is, the major enantiomers for limonene, terpinen-4-ol, and borneol are not consistent over the four samples.

Table 3. Enantiomeric distribution of chiral monoterpenoid components in Salvia dorrii var. incana essential oil from southeastern Oregon

RIdb = Retention index from our in-house database based on commercially available compounds available from Sigma-Aldrich and augmented with our own data. RIcalc = Calculated retention index based on a series of n-alkanes on a Restek B-Dex 325 capillary column. n.d. = not detected.

This is the first report describing the enantiomeric distributions of terpenoid components of S. dorrii. However, there have been several investigations on enantiomeric distribution in other Salvia species for comparison (Table 4). The enantiomeric distributions for α-pinene, limonene, and camphor are inconsistent throughout the genus. The (–)-enantiomers are largely the major for β-pinene and for linalool, however. There are too few data to draw conclusions regarding the other chiral monoterpenoid components.

Table 4. Enantiomeric distribution of chiral monoterpenoid components in Salvia species.

4.   Conclusions

This is the first report on the essential oil composition of Salvia dorrii var. incana. However, this preliminary report is based on only four individuals collected from the same habitat in southeastern Oregon. The essential oil showed variation not only in quantitative composition, but also in enantiomeric distribution. In addition, there is wide variation in the enantiomeric distribution of chiral terpenoid components within the Salvia genus. It is apparent that additional research is needed on S. dorrii essential oils from other geographical locations within its natural range, particularly on other infraspecific taxa, in order to further define the volatile phytochemical characteristics of this species.

Authors’ contributions

Conceptualization, W.N.S.; Methodology, A.P., P.S., W.N.S.; Software, P.S.; Validation, W.N.S., Formal analysis, A.P., W.N.S.; Investigation, K.S. A.P., P.S., W.N.S.; Resources, P.S., W.N.S.; Data curation, W.N.S.; Writing – original draft preparation, W.N.S.; Writing – review & editing, K.S., A.P., P.S., W.N.S.; Project administration, W.N.S.

Acknowledgements

This work was carried out as part of the activities of the Aromatic Plant Research Center (APRC, https://aromaticplant.org/).

Funding

This research received no specific grant from any funding agency.

Availability of data and materials

All data will be made available on request according to the journal policy.

Conflicts of interest

The authors declare no conflict of interest.

References