## 2 Materials and Methods  
**Plant material description:** The vegetal raw material (_Stokesia laevis L.-Ierba et flores_) was acquired from a specialized plant distributor in Romania, and its taxonomic identity was confirmed by the botanist's team of National Institute of Chemical-Pharmaceutical R&D, Bucharest, Romania. The fresh flowering plant was cut (the aerial part), shade dried, and ground to a medium-size powder product. Voucher specimens, the dried plant, and the powder product (Slaae), are deposited in the ICCF Plant Material Storing Room. **Chemicals, reagents and references:** Chemicals (e.g., sodium carbonate), reagents (e.g., _Folin-Ciocalteau_, _Natural Product_-NP/PEG), solvents (e.g., ethanol, ethyl acetate, formic acid, and glacial acetic acid), the reference compounds for quantitative and qualitative studies namely ruitin (min. 95%), quercetin-3-O-rhammoside (>90%), luteolin (>98%), luteolin-7-O-glucose(>98%), luteolin-8-C-glucose (>97%), caffeic acid (99%), chlorogenic acid (>95%), gallic acid (95%), gentisic acid (>99%), and PABA (>99%) and the cell culture reagents used, Dulbecco's Modified Essential Media (DMEM) and Foetal Bovine Serum (FBS), were purchased from Sigma-Aldrich Distributor in Romania. **Plant extracts preparation:** Fifty (50) grams of stokes aster plant powder were extracted on the water bath (in a glass device of 2 L) with 1000 mL of 70% (_v/v_) ethanol, for one hour at the boiling temperature. The filtered ethanolic extract (Slaae) in a volume of 745 mL was analyzed for qualitative (polyphenols profile) and quantitative (total phenols content) aspects. An aliquot of 250 mL of ethanol extract with the content of 0.61 mg GAE per 1 mL sample was further concentrated at sicc product (residue), and the sicc product was solved into 30.5 mL ethanol 40% (_v/v_) to achieve the content of exactly 5 mg GAE per 1 mL sample. The new (40%) ethanolic extract was sonicated 15 min at room temperature, then was filtered on the glass fiber filter. The resulting brown, homogeneous solution (Slaae26) was used in pharmacological studies. **Polyphenol's assessment in extracts:** Total phenols content was estimated using Folin-Ciocalteau reagent, by standard Romanian Pharmacopoeia (F.R.X) method [35]; results were expressed as mg gallic acid equivalents [GAE] per 1 mL sample (R\({}^{2}\) = 0.9912). Polyphenols profile in 70% stokes aster ethanolic extract was assessed by [PERSON] and [PERSON] [36] and [PERSON] [37] thin layer chromatography recommendation (solvent system: ethyl acetate-glacial acetic acid-bormic acid-water/100:12:12:26), as described in the previous work [33]. **Pharmacological studies in vitro:** In vitro cell pharmacological studies were done on the human cancer colon cells Caco-2 (ATCC-HTB-37), using MTS test [38]. Studies were designed to evaluate both, cytotoxic activity and antiproliferative potency of singular vegetal extract Slae26, of singular polyphenol compounds (reference substances, ref. ), and of Slae26 combinations with each reference substance selected for the study. The combination of the test vegetal extract (Slaae26) with the five reference substances was made to provide a 1:1 mass ratio (_w/w_) between the total phenols in the plant extract (expressed as \(\mu\)g GAE/mL sample) and the amount of the reference compound tested, the punctual concentrations in test series of 10, 25, 50 and 100 \(\mu\)g total active compounds per 1 mL sample, respectively. Punctually, three-test series and corresponding control samples were prepared: (1) Slae26 test series and Slae26 solvent sample (40% ethanol) control series;(2) polyphenol compounds test series (ref.) and their solvent sample (70% ethanol) control series; and (3) Slae26 plus reference compound test series, 1:1 mass rate (_w/w_), and their solvent sample (40% ethanol plus 70% ethanol, 1:1, _w/w_) control series.