Extraction of biologically active compounds from Sideritis ssp. L.

In this study extraction of polyphenols and flavonoids from cultivated hybrid Sideritis scardica × Sideritis syriaca, known for its rich content of phenolics and flavonoids with antioxidant activity, was investigated. Extractions have been done by ethanol and water–ethanol, respectively. High equilibrium values of the extracted species were obtained—17.55 mg/(g solid) total phenolics and 5.7 mg/(g solid) total flavonoids with ethanol as solvent. The influence of the solvent on the total yield and the content of biologically active compounds were studied. Maximum polyphenolics and flavonoids extraction was observed for water–ethanol solvent ratio 20/80. Increase of the content of ethanol in the solvents led to lower total yield of extracts but higher percentage of polyphenolics. The extraction kinetics showed that 90% of the phenolic compounds were extracted during the first 2.5 h. The experimental kinetics was described by a constant effective diffusion coefficient De = 1.5 × 10−12 m2/s in the solid, accounting for the actual particle size distribution.

Research highlights▶ Ethanol and water–ethanol extraction of polyphenols and flavonoids from Sideritis L. ▶ Extraction kinetics shows that 90% of the phenolic compounds were extracted during the first 2.5 h. ▶ A maximum in the extracted polyphenols and flavonoids (mg/g of dry solid) was observed with 20/80 water–ethanol solvent. ▶ Experimental kinetics was described by solid diffusion model with constant effective diffusion coefficient.