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-ß-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).

Fatty acid composition and chemotaxonomic evaluation of species of Stachys.

The fatty acid composition of the seed oil of 23 Stachys taxa was analysed by GC/MS. The main compounds were found to be linoleic (27.1-64.3%), oleic (20.25-48.1%), palmitic (4.3-9.1%), stearic (trace to 5.2%) and 6-octadecynoic (2.2-34.1%) acids. The latter compound could be used as a chemotaxonomic marker of the genus Stachys. A cluster analysis was performed for comparison and characterisation of the seed oil from Stachys species.

Comparison of antioxidant activity in enzyme-independent system of six Stachys species.

The antioxidant activity of six Stachys species native to Hungary in an enzyme-independent lipid-peroxidation system was examined. The methanolic extracts were found to be more effective than the controls alpha-tocopherol succinate and ascorbic acid. The following components were determined by spectrophotometric analysis: hydroxycinnamic acid derivatives, phenols content and flavonoids.

Glycosides of tricetin methyl ethers as chemosystematic markers in Stachys subgenus Betonica.

Nine species from the genus Stachys L. representing subgenera Stachys and Betonica were surveyed for flavonoid glycosides by means of HPLC coupled to diode-array detection and LC-APCI-MS. Those species belonging to subgenus Betonica were characterised by the presence of glycosides of tricetin methyl ethers, including a new derivative, which was isolated from S. scardica Griseb. and identified as tricetin 3',4',5' -trimethyl ether 7-O-beta-glucopyranoside by spectroscopic methods. This type of flavonoid was absent from species belonging to subgenus Stachys and can be considered as a chemosystematic marker for subgenus Betonica.

Essential oil analysis and antimicrobial activity of eight Stachys species from Greece.

The volatile composition of eight Stachys species has been studied. The investigated taxa were St. alopecuros (L.) Bentham., St. scardica (Griseb.) Hayek, St. cretica L. ssp. cretica, St. germanica L. ssp. heldreichii (Boiss.) Hayek, St. recta L., St. spinulosa L., St. euboica Rech. and St. menthifolia Vis., growing wild in Greece. The essential oils were obtained by hydrodistillation in a modified Clevenger-type apparatus, and their analyses were performed by GC and GC-MS. Identification of the substances was made by comparison of mass spectra and retention indices with literature records. Sesquiterpene hydrocarbons were shown to be the main group of constituents of all taxa. Furthermore, the obtained essential oils were tested against the following six bacteria: Pseudomonas aeruginosa (ATCC 27853), Escherichia coli (ATCC 35210), Bacillus subtilis (ATCC 10907), Bacillus cereus (clinical isolates), Micrococcus flavus (ATCC 10240), Staphylococcus epidermidis (ATCC 2228), as well as against the following five fungi: Aspergillus niger (ATCC 6275), Penicillium ochrochloron (ATCC 9112), Epidermophyton floccosum (clinical isolates), Candida albicans (clinical isolates) and Trichophyton mentagrophytes (clinical isolates). The tested essential oils showed better activity against bacterial species than against fungi. Pseudomonas aeruginosa was the most resistant strain, as none of the essential oils was active against this strain. The essential oil of St. scardica has been proven most active against both bacteria and fungi.