Chemotaxonomic significance of the volatiles in the genus Stachys (Lamiaceae): Essential oil composition of four Balkan Stachys species

Antimicrobial activity of Stachys rupestris Montbret et Aucher ex Benth. and inactivation of the pathogens inoculated on lab-made skin by the essential oil

The aim of this study was to investigate the antimicrobial activity of Stachys rupestris essential oil and inactivation of the pathogens on lab-made skin the oil in the fight against Escherichia coli, Acinetobacter baumannii, Staphylococcus aureus, Enterococcus faecalis, Candida albicans and Candida tropicalis. S. rupestris EO was extracted by hydrodistillation, and its contents were analyzed by GCMS. Logarithmic reduction of the pathogens inoculated on the artificial skin surface by S. rupestris EO was studied for the first time. The highest inhibition zone was 22.1 mm on C. tropicalis, while the lowest IZ was 0.1 mm on E. coli. The other zones were 20.01 mm for Acinetobacter baumannii, 20.02 mm for Enterococcus faecalis, 20.01 mm for Staphylococcus aureus, 22.03 for Candida albicans (p < 0.05). As a result, S. rupestris essential oil was effective on most of the microorganisms and might be increased to use in the treatment of skin infections in the future.

Chemical Composition and Future Perspectives of Essential Oil Obtained from a Wild Population of Stachys germanica L. Distributed in the Balkan Mountains in Bulgaria

Stachys germanica L. (Lamiaceae) is a plant associated with a rich history in the traditional medicine of Iran, Turkey, and Serbia. However, researchers have not fully investigated the pharmacological potential of the herb, and scientific data on this plant species are limited. The aim of the current study was to evaluate the chemical composition of the essential oil (EO) obtained from the aerial parts of S. germanica L. growing wild in Bulgaria and to perform a comparative analysis of the chemical composition of EOs obtained from the same plant species from other geographical regions. For the evaluation of the chemical profile of the isolated EO, gas chromatographic analysis with mass spectrometry was performed. The most abundant terpene class was oxygenated monoterpenes, which accounted for 59.30% of the total EO composition. The bicyclic monoterpene camphor, as a compound of this class, was identified as the major constituent in the EO, accounting for 52.96% of the total oil composition. The chemical profile of Bulgarian EO is quite different compared to that of EOs from other regions. It is the only one to contain more than 50% camphor. In addition, EO contains significant amounts of the diterpene geranyl p-cymene (10.49%). This is the first study describing the chemical composition of EO from Bulgarian Stachys germanica L., and our results reveal some future perspectives for the evaluation of the biological activity of EO from the studied plant species as a new therapeutic agent or natural remedy targeting different medical conditions. The EO has a promising potential to be used as a biopesticide and repellent as well, an environmentally friendly and safer alternative to standard pesticides.

Development and Evaluation of Phytosomes Containing Callistemon citrinus Leaf Extract: A Preclinical Approach for the Treatment of Obesity in a Rodent Model

Callistemon citrinus has several biological effects; it is anti-inflammatory, anti-obesogenic, antioxidant, hepatoprotection, and chemoprotective. Its bioactive compounds include terpenoids, phenolic acids, and flavonoids which have low oral bioavailability and absorption. This study aimed at developing phytosomes of C. citrinus to improve oral bioavailability and absorption. Phytosomes were formulated with soybean phosphatidylcholine and C. citrinus leaf extract using the thin layer sonication method. Phytosomes were evaluated by scanning electron microscopy (SEM), entrapment efficiency, solubility, and particle size determination. Antioxidant capacity and total phenolic, flavonoid, and terpenoid contents were also measured. The in vivo anti-obesogenic activity was evaluated. Phytosomes loaded with C. citrinus (P C.c) extract had small spherical shapes. The average particle size was 129.98 ± 18.30 nm, encapsulation efficiency 80.49 ± 0.07%, and solubility 90.00%; the stability study presented no significant changes in the average particle size at 20 °C. P C.c presented high antioxidant capacity. For the first time, ellagic acid is reported in this plant. The in vivo obesity study showed a strong anti-obesogenic activity of phytosomes with C. citrinus to reduce 40% body weight as well as morphometric and biochemical parameters.

Chemometric Analysis Based on GC-MS Chemical Profiles of Three Stachys Species from Uzbekistan and Their Biological Activity

The chemical composition of the essential oils (EOs) of Stachys byzantina, S. hissarica and S. betoniciflora growing in Uzbekistan were determined, and their antioxidant and enzyme inhibitory activity were assessed. A gas chromatography-mass spectrometry (GC-MS) analysis revealed the presence of 143 metabolites accounting for 70.34, 76.78 and 88.63% of the total identified components of S. byzantina, S. hissarica and S. betoniciflora, respectively. Octadecanal (9.37%) was the most predominant in S. betoniciflora. However, n-butyl octadecenoate (4.92%) was the major volatile in S. byzantina. Benzaldehyde (5.01%) was present at a higher percentage in S. hissarica. A chemometric analysis revealed the ability of volatile profiling to discriminate between the studied Stachys species. The principal component analysis plot displayed a clear diversity of Stachys species where the octadecanal and benzaldehyde were the main discriminating markers. The antioxidant activity was evaluated in vitro using 2,2-diphenyl-1-picryl-hydrazyl (DPPH), 2,2-azino bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), cupric reducing antioxidant capacity (CUPRAC), ferric reducing power (FRAP), chelating and phosphomolybdenum (PBD). Moreover, the ability of the essential oils to inhibit both acetyl/butyrylcholinesterases (AChE and BChE), α-amylase, α-glucosidase and tyrosinase was assessed. The volatiles from S. hissarica exhibited the highest activity in both the ABTS (226.48 ± 1.75 mg Trolox equivalent (TE)/g oil) and FRAP (109.55 ± 3.24 mg TE/g oil) assays. However, S. betoniciflora displayed the strongest activity in the other assays (174.94 ± 0.20 mg TE/g oil for CUPRAC, 60.11 ± 0.36 mg EDTA equivalent (EDTAE)/g oil for chelating and 28.24 ± 1.00 (mmol TE/g oil) for PBD. Regarding the enzyme inhibitory activity, S. byzantina demonstrated the strongest AChE (5.64 ± 0.04 mg galantamine equivalent (GALAE)/g oil) and tyrosinase inhibitory (101.07 ± 0.60 mg kojic acid equivalent (KAE)/g) activity. The highest activity for BChE (11.18 ± 0.19 mg GALAE/g oil), amylase inhibition (0.76 ± 0.02 mmol acarbose equivalent (ACAE)/g oil) and glucosidase inhibition (24.11 ± 0.06 mmol ACAE/g oil) was observed in S. betoniciflora. These results showed that EOs of Stachys species could be used as antioxidant, hypoglycemic and skincare agents.

The chemical composition of the aerial parts essential oil of S. spreitzenhoferi Heldr. (Lamiaceae) growing in Kythira island (Greece)

Stachys is a large genus of economically important plants belonging to Lamiaceae family that includes about 300 species as annual or perennial herbs. Several species of this genus are extensively used in various traditional medicines. In the present study the chemical composition of the essential oil from aerial parts of Stachys spreitzenhoferi Heldr., a very rare plant, belonging to Section Candidae, endemic of South Greece and collected in the island of Kythira, was analysed by GC-MS. No one reports have been previously published on this species. The result showed the presence of large quantity of diterpenoids with manoyl oxide (22.1%), as the most abundant component. Other metabolites present in high quantity were trans-nerolidol (18.5%), β-caryophyllene (11.0%) and germacrene D (8.1%). Chemotaxonomic considerations with respect all the other oils of Stachys taxa, belonging to the same section studied so far, were carried out.

Metabolomics-Driven Discovery of an Introduced Species and Two Malaysian Piper betle L. Variants

The differences in pungency of “sirih” imply the probable occurrence of several variants of Piper betle L. in Malaysia. However, the metabolite profiles underlying the pungency of the different variants remain a subject of further research. The differences in metabolite profiles of selected Malaysian P. betle variants were thus investigated; specifically, the leaf aqueous methanolic extracts and essential oils were analyzed via ¹H-NMR and GC-MS metabolomics, respectively. Principal component analysis (PCA) of the ¹H-NMR spectral data showed quantitative differences in the metabolite profiles of “sirih melayu” and “sirih india” and revealed an ambiguous group of samples with low acetic acid content, which was identified as Piper rubro-venosum hort. ex Rodigas based on DNA sequences of the internal transcribed spacer 2 (ITS2) region. The finding was supported by PCA of two GC-MS datasets of P. betle samples obtained from several states in Peninsular Malaysia, which displayed clustering of the samples into “sirih melayu” and “sirih india” groups. Higher abundance of chavicol acetate was consistently found to be characteristic of “sirih melayu”. The present research has provided preliminary evidence supporting the notion of occurrence of two P. betle variants in Malaysia based on chemical profiles, which may be related to the different genders of P. betle.

Chemical composition of the essential oil and n-hexane extract of Stachys tmolea subsp. Tmolea Boiss., an endemic species of Turkey, and their mosquitocidal activity against dengue vector Aesdes aegypti

Stachys tmolea subsp. tmolea Boiss. is endemic to Turkey and is a species of the genus Stachys L. which is one of the largest genera of the family Lamiaceae with about 300 species. The aims of this study were to examine the chemical composition of the essential oil and n-hexane extract of S. tmolea subsp. tmolea as natural sources of insecticidal activity against the dengue vector, Aedes aegypti. Analysis of the essential oil by GC-FID and gas chromatography-mass spectrometry (GC-MS) systems identified hexahydrofarnesyl acetone (15%), viridiflorol (10%), hexadecanoic acid (7%) and 9-geranyl-p-cymene (6%) as major components. The volatile components of the n-hexane extract were extracted using headspace solid-phase microextraction (HS-SPME) and were analyzed using GC-MS. The principal constituents were 3,4-dimethyl decane (16%), 3-methyl-3-pentanol (15%), 2-methyl-2-pentanol (12%), 1,4-bis (1,1-dimethylethyl) benzene (12%), heptanal (10%), acetic acid (6%) and decane (4%). Bioassay of the n-hexane extract, at 5 µg/mosquito, produced 90% mortality against adult Ae. aegypti while the S. tmolea essential oil demonstrated 13% mortality. No larvicidal activity was observed both in essential oil and n-hexane extract. Further studies are needed to assess the adulticidal activity of the responsible compounds in the crude extract.

Variations in Essential Oil Composition and Antioxidant Activity in Perovskia abrotanoides Kar. Collected from Different Regions in Iran

Essential oil (EO) composition, phenolic content, and antioxidant activity were investigated in 17 P. abrotanoides populations collected from different geographical regions in Iran. The highest (3.61%) and lowest (1.25%) essential oil yields were measured in populations from Semnan Province (PSESM₂ ) and PISKS from Isfahan Province, respectively. GC/MS analysis identified camphor (4.05 - 35.94%), 1,8-cineole (7.15 - 24.34%), borneol (0 - 21.75%), and α-pinene (2.05 - 10.33%) as the main constituents of Perovskia essential oil. Cluster analysis classified the studied populations into four different groups: (I) high camphene, (II) high camphor/1,8-cineole, (III) high borneol/δ-3-carene, and (IV) high α-cadinol/trans-caryophyllene. The highest flavonoid and phenolic contents were detected in PISAK from Isfahan Province (4.09 ± 0.05 mgQE/gDW, 58.51 ± 1.63 mgGAE/gDW) and PKRGS from Khorasan Province (3.80 ± 0.002 mgQE/gDW, 66.86 ± 0.002 mgGAE/gDW). DPPH and reducing power activity model systems identified PMASA and PKRKL as the populations with the highest antioxidant activity. Finally, the data obtained represented valuable information for introducing elite populations with EO components favorable to pharmaceutical and industrial applications.

Leaf blade structure of Verbesina macrophylla (Cass.) F. S. Blake (Asteraceae): ontogeny, duct secretion mechanism and essential oil composition

Secretory structures are common in Asteraceae, where they exhibit a high degree of morphological diversity. The species Verbesina macrophylla, popularly known as assa-peixe, is native to Brazil where it is widely used for medicinal purposes. Despite its potential medical importance, there have been no studies of the anatomy of this species, especially its secretory structures and secreted compounds. This study examined leaves of V. macrophylla with emphasis on secretory structures and secreted secondary metabolites. Development of secretory ducts and the mechanism of secretion production are described for V. macrophylla using ultrastructure, yield and chemical composition of its essential oils. Verbesina macrophylla has a hypostomatic leaf blade with dorsiventral mesophyll and secretory ducts associated with vascular bundles of schizogenous origin. Histochemistry identified the presence of lipids, terpenes, alkaloids and mucopolysaccharides. Ultrastructure suggests that the secretion released into the duct lumen is produced in plastids of transfer cells, parenchymal sheath cells and stored in vacuoles in these cells and duct epithelial cells. The essential oil content was 0.8%, and its major components were germacrene D, germacrene D-4-ol, β-caryophyllene, bicyclogermacrene and α-cadinol. Secretory ducts of V. macrophylla are squizogenous. Substances identified in tissues suggest that both secretions stored in the ducts and in adjacent parenchyma cells are involved in chemical defence. The essential oil is rich in sesquiterpenes, with germacrene D and its derivatives being notable components.

Phytoecdysteroids-containing extract from Stachys hissarica plant and its wound-healing activity

A number of phytoecdysteroid compounds, such as ecdysterone, polipodin V, 2-deoxy-20-hydroxyecdysone, integristeron A and 2-deoxydizon were isolated from Stachys hissarica plant and their structures were confirmed by NMR, mass and IR spectroscopy. In addition, the biological activity of the S. hissarica plant's extract was tested on rats for wound healing activity. It was shown that the extract at repeated oral (per os) administration at a dose of 10 mg/kg speeds up the healing process of linear skin wounds in rats. The wound-healing activity of S. hissarica extract is confirmed to be effective and exceeds known drug methyluracil (2,4-dioxo-6-methyl-1,2,3,4-tetrahydropyrimidine), especially in case of alloxan induced diabetic animals.

Phytochemical composition of the essential oil of different populations of Stachys lavandulifolia Vahl

OBJECTIVE

To examine the chemical variability in inflorescences of wild populations of Stachys lavandulifolia Vahl (S. lavandulifolia) collected throughout two provinces (Isfahan and Chaharmahal va Bakhtiary), Southwest Iran.

METHODS

The essential oils of S. lavandulifolia Vahl from seven locations were obtained by hydro-distillation and analysed by gas chromatography and gas chromatography-mass spectrometry.

RESULTS

The results revealed that distinct differences in the content of compounds depending on region of sample collection. The main constituents of the essential oils were α-thujone (0.3%-32.3%), α-pinene (trace to 37.3%), myrcene (0.5%-15.9%), β-phellandrene (1.1%-37.9%), germacrene D (0.4%-11.3%), Δ-cadinene (trace to 11.6%) and 1, 4-methano-1 H-indene (trace to 10.1%).

CONCLUSIONS

The results of the present study indicated that essential oil components of S. lavandulifolia Vahl can be varied with genetic (ecotype), environmental conditions and geographic origin. In general, the essential oils of various populations of S. lavandulifolia Vahl were rich in monoterpenoids and sesquiterpenoids.

Phytochemical and biological studies of Stachys species in relation to chemotaxonomy: a review

The genus Stachys is comprised of about 300 species spread throughout the world, hence representing one of the largest genera of the Lamiaceae. Several Stachys species have been exploited in traditional medicine as astringent, wound-healing, anti-diarrhoeal, anti-nephritic and anti-inflammatory agents. Moreover, antimicrobial, antioxidant and cytotoxic activities of some Stachys species are documented. Iridoids, flavonoids, phenolic acids and diterpenoids are reported as secondary metabolites of different species of this genus. The aim of the present review is to summarize and to highlight the recent advances in current knowledge on Stachys species and to compile reports of chemical constituents isolated from the genus Stachys over the past decades, together with their structural features, biological activities, and structure-activity relationships. Diversity of chemical constituents is discussed in relationship with current Stachys infrageneric taxonomy, classification and relationships with systematically close genera.

Phytochemical analysis, biological evaluation and micromorphological study of Stachys alopecuros (L.) Benth. subsp. divulsa (Ten.) Grande endemic to central Apennines, Italy

Stachys alopecuros subsp. divulsa (Lamiaceae), a perennial herb endemic to central Italy growing on mountain pastures, was investigated for the first time for the content of secondary metabolites, for the micromorphology and histochemistry of glandular trichomes, and for the biological activity of the volatile oil, namely cytotoxic, antioxidant and antimicrobial. The plant showed the molecular pattern of iridoids, among which a new iridoid diglycoside (4'-O-β-D-galactopyranosyl-teuhircoside) was detected, together with a sterol glucoside and a phenylethanoid glycoside. The essential oil from the flowering aerial parts was characterized by a high proportion of sesquiterpene hydrocarbons (65.1%), with (E)-caryophyllene (33.2%) as the most abundant, while other main components were germacrene D (7.6%), α-humulene (6.4%) and the oxygenated cis-sesquisabinene hydrate (10.2%). Taken together, polar and apolar chemical profiles support the classification of the species within the section Betonica of the genus Stachys. Micromorphological study revealed three types of glandular hairs secreting different classes of compounds, with type A peltate hairs producing the bulk of the essential oil. MTT assay revealed the potential of the volatile oil in inhibiting A375, HCT116 and MDA-MB 231 tumor cells (IC₅₀ values below 20 μg/ml).

Chemical Composition and Antibacterial Activity of Essential Oils from Myrcia alagoensis (Myrtaceae)

The chemical composition and antibacterial activity of essential oils obtained from fresh and dried leaves of Myrcia alagoensis O. Berg, collected in a secondary forest remnant in north-eastern Brazil, was compared. The essential oils were obtained by hydrodistillation from fresh and dried leaves, and analysed by GC/FID and GC/MS. The antimicrobial properties of the oils were investigated against five bacteria by determination of the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC). The essential oils were rich in cyclic sesquiterpenes, such as germacrene B, with antibiotic action against Gram-positive and Gram-negative bacteria. The drying process after collection interfered with the chemical composition and antibacterial activity of the assessed samples.

Composition of the Essential Oils and Antibacterial Activities of Hymenocrater yazdianus, Stachys obtusicrena and Nepeta asterotricha Three Labiatae Herbs Growing Wild in Iran

Water-distilled essential oils from leaves of Hymenocrater yazdianus Rech.f., flowers of Stachys obtusicrena Boiss., and stems and flowers of Nepeta asterotricha Rech.f, which are endemic to Iran, were analyzed by GC and GC/MS. Fifty-five components of the leaf oil of H. yazdianus were characterized, representing 95.1% of the total components detected. The major constituents were identified as 1,8-cineole (17.6%), β-caryophyllene (13.9%), α-pinene (10.6%) and caryophyllene oxide (10.4%). Germacrene-D (37.5%) and α-bisabolol (23.5%) were the main components among the twenty constituents characterized in the flower oil of S. obtusicrena, representing 90.8% of the total components detected. Thirty-five compounds representing 93.0% of the stem oil of N. asterotrica were identified among which terpinen-4-ol (22.8%) and γ-terpinene (14.1%) were the major ones. The flower oil of the species was characterized by higher amounts of terpinen-4-ol (24.8%), 4aα, 7aβ-nepetalactone (18.2%) and 1,8-cineole (11.6%) among the thirty-three components comprising 98.5% of the total oil detected.

The antibacterial activity of the stem, leaf and flower oils of Hymenocrater yazdianus, Stachys obtusicrena and Nepeta asterotricha against seven Gram-positive and Gram-negative bacteria were determined using the MIC method. The growth inhibitory zone (mm) was also measured.

Essential Oil Composition, Antimicrobial and Cytotoxic Activities of Two Endemic Stachys Cretica Subspecies (Lamiaceae) from Turkey

The chemical compositions of the water-distilled essential oil of Stachys cretica ssp. lesbiaca Rech. fil. and S. cretica ssp. trapezuntica Rech. fil. were determined by GC and GC–MS. Altogether 63 compounds were identified. The sesquiterpene hydrocarbon, germacrene D (20.3% and 12.9% respectively) was the main component identified in both oils. Furthermore, ethanol, light petroleum, dichloromethane, ethyl acetate and n-butanol extracts prepared from the aerial parts of the plants were tested for their antimicrobial activities against six bacterial strains and the yeast Candida albicans. The extracts exhibited no antibacterial activity, but the light petroleum and n-butanolic fractions showed low antifungal activities. Crude ethanolic extracts of the two subspecies were tested for their ability to inhibit the growth of HL-60 and Ishikawa human tumor cell lines. The IC50 values were 100 μg/mL for the HL-60 cell line and 200 μg/mL for the Ishikawa cell line.

Chemical composition of the essential oil of Stachys menthifolia Vis

Stachys menthifolia Vis. (Lamiaceae) is an endemic species from the Balkan Peninsula spread throughout Albania, Greece, Montenegro, and Croatia. This article presents the first investigation of the essential oil composition of this species from Croatia. Aerial parts of the plant were collected from three different natural habitats in the region of Biokovo Mountain. The studied populations showed similarity in qualitative, but not in quantitative, composition of their essential oils. Hydrodistilled volatile oil obtained from the plant material of S. menthifolia was subjected to gas chromatographic analysis coupled to mass spectrometry. More than 100 compounds were identified in the three samples, representing 86.8-90.8% of the total oil. The terpene profile of S. menthifolia is characterized by a high content of oxygenated sesquiterpenes (48.4-58.9%) and diterpene hydrocarbons (3.5-25.2%), with 8-alpha-acetoxyelemol (6.9-21.3%), abietatriene (3.5-21.1%), and 4'-methoxyacetophenone (4.5-17.0%) as the main constituents.

Chemical composition and screening of the antimicrobial and anti-oxidative activity of extracts of Stachys species

GC and GC/MS analyses of the diethyl ether and ethyl acetate extracts obtained from the aerial parts of Stachys germanica subsp. heldreichii (Boiss) Hayek, Stachys iva Griseb., Stachys plumosa Griseb. and Stachys scardica Griseb., Balkan peninsula endemics, were performed. One hundred and seventy-nine constituents, accounting for 88.8-98.1% of the total composition of the extracts, were identified. The common feature of the diethyl ether extracts was the high content of terpenoids and fatty acidderived compounds, while the common feature of the ethyl acetate extracts was the prevalence of fatty acid-derived compounds. A disk diffusion method was used for the evaluation of the antimicrobial activities of the extracts against a panel of microorganisms (bacteria: Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Salmonella enteritidis; fungi: Aspergillus niger and Candida albicans). The total antioxidant capacity of the extracts was evaluated by the phosphomolybdenum method. The preliminary bioassay results indicated that the diethyl ether extract of S. plumosa could be a possible source of antioxidant and antimicrobial compounds.

Germacrene D, a common sesquiterpene in the genus Bursera (Burseraceae)

The volatile components of the leaves of five Bursera species, B. copallifera, B. exselsa, B. mirandae, B. ruticola and B. fagaroides var. purpusii were determined by gas chromatography–mass spectrometry (GC–MS). Germacrene D was one of the predominant components (15.1–56.2%) of all of these species. Germacrene D has also been found in other Bursera species and some species of Commiphora, the sister group of Bursera, suggesting that the production of germacrene D might be an ancient trait in the genus Bursera.

Composition of Essential Oils from Leaves and Flowers of Stachys Germanica Subsp. Salviifolia (Ten.) Gams (Labiatae) and Related Secretory Structures

The essential oils from both leaves (L) and flowers (F) of Stachys germanica subsp. salviifolia (Ten.) Gams (Labiatae/Lamiaceae) from Italy were analyzed by GC-MS for the first time. The distribution, morphology and histochemistry of the different types of glandular trichomes present on the epidermal surface were also determined. Twenty-nine constituents, representing 89.4% of the total leaf oil, and forty-one compounds, forming 97.8% of the total flower oil, were identified. Germacrene D (39.4%), phytol (10.2%), β-bourbonene (3.5%) and β-ylangene (3.3%) were recognized as the main constituents of the leaf essential oil, while limonene (24.1%), β-pinene (18.7%), germacrene D (12.8%) and ( E)-nerolidol (6.6%) were the main compounds of the flower essential oil.