Two new bis-iridoids isolated from Scabiosa stellata and their antibacterial, antioxidant, anti-tyrosinase and cytotoxic activities

Abstract

This study presents the chemical profile investigation of a 70% ethanol extract obtained from Scabiosa stellata, a medicinal herbaceous traditionally used to treat heel cracks. A C NMR-based dereplication methodology was firstly applied on centrifugal partition chromatography-generated fractions in order to quickly identify the major compounds of the extract. The dereplication process was then completed by semi-preparative high-performance liquid chromatography in order to identify unknown or minor compounds. Two new bis-iridoids, namely 7-O-caffeoyl-sylvestroside I (1) and 7-O-(p-coumaroyl)-sylvestroside I (2), together with ten known compounds (3-12) were isolated. Their structures were elucidated by spectroscopic methods including NMR and HR-ESI-MS. The antibacterial, anti-tyrosinase and DPPH radical scavenging activities of the crude extract, fractions, and isolated compounds were evaluated. A significant antibacterial activity was observed for nine isolated compounds, particularly 1 and 2 which yielded MIC values of 31.2μg/mL against Enterococcus faecalis and 62.5μg/mL against Staphylococcus epidermidis. The cytotoxic activity of these new bis-iridoids was evaluated on a fibrosarcoma cell line (HT1080) and only compound 1 exhibited a moderate cytotoxic activity (IC 35.9μg/mL).

Scabiosa stellata L. Phenolic Content Clarifies Its Antioxidant Activity

“…Regarding Scabiosa stellata L., and as far as we are aware of, only three studies involving its chemical composition were recently reported [ 9 , 10 , 11 ], its medicinal use in traditional medicine was also reported [ 12 ] but has not yet been validated. These previous phytochemical studies revealed the presence of important secondary metabolites, such as fatty acids and triterpenoids [ 9 , 11 ], among which several are new triterpenoid saponins [ 11 ].…”

“…These previous phytochemical studies revealed the presence of important secondary metabolites, such as fatty acids and triterpenoids [ 9 , 11 ], among which several are new triterpenoid saponins [ 11 ]. Furthermore, new bis-iridoids and three known flavonoids were also described [ 10 ]. Important biological activities were recently reported [ 10 ], among which the antioxidant activity of a 70% EtOH extract (In the table of the original manuscript, is indicated that the extract evaluated is a 70% MeOH.…”

An overview of the two-phase solvent systems used in the countercurrent separation of phenylethanoid glycosides and iridoids and their biological relevance

“…As compared to PhGs, when very few compounds were separated with CPC, this technique was more often employed for isolating iridoids (8 papers out of 11 found for the CPC part of the review). In three applications, CPC was practically used for the production of iridoids from large quantities of extracts isolating seven C-9 iridoids from the aerial part extract (Lemus et al 2015), five secoiridoids from another aerial part extract (Mandova et al2017) and four bissecoiridoids and two secoiridoids from a whole plant extract (Lehbili et al 2018) with an average loading of 1.3 g per every 100 mL of column volume in normal phase elution mode.…”

“…Two new bis-secoiridoids (7-O-(E-p-coumaroyl)sylvestroside I, 7-O-(E-caffeoyl)-sylvestroside I) together with two other known bis-secoiridoids and three secoiridoids (sylvestroside I, septemfidoside, sweroside, eustomoside and eustomoruside) were isolated from Scabiosa stellata Cav. with less polar solvents of tert-butyl methyl ether-acetonitrile-water (3:3:4) (Lehbili et al 2018). This type of solvent systems seems working well for less polar iridoids.…”

“…In the anti-tyrosinase assay, none of the compounds was active at the concentration of 665 lg/mL. The cytotoxic activity of the previously unknown iridoids was tested in vitro against HT1080 fibrosarcoma cell line and only 7-O-(E-caffeoyl)sylvestroside I was active, with an IC 50 value of 35.9 ± 0.06 lg/mL (Lehbili et al 2018). Zhang et al (2014) developed a bioassay-guided isolation of pure constituents from Olea europea L. using an on-line HSCCC method coupled with a postcolumn a-amylase anti-diabetic assay.…”