Optimization of rutin isolation from Amaranthus paniculatus leaves by high pressure extraction and fractionation techniques

• 70/30 (v/v) water/ethanol ratio, at 188 °C and 20 min were optimal parameters for rutin recovery.
• PLE recovered 4 times more of rutin than conventional extraction.
• Application of SAF increased rutin concentration up to 1.5 times.
• A PLE-SAF integrated process was successfully optimized and applied.

A procedure based on the application of pressurized liquid extraction (PLE) was employed to recover the major Amaranthus spp. flavonoid glycoside rutin from dried ground plant leaves. A central composite design (CCD) was used to optimize rutin extraction; three factors were considered: extraction solvent (water/ethanol ratio, from 0/100 to 100/0), extraction time (from 5 to 20 min) and extraction temperature (from 50 to 200 °C). Optimization of the three extraction parameters revealed that water/ethanol ratio in the solvent mixture was the most-significant factor influencing rutin yield, followed by extraction temperature. The total rutin recovery varied from 6.95 to 14.03 g/kg dry matter (DM) depending on the experimental conditions tested. The optimum extraction conditions for the highest rutin content were 70/30 (v/v) water/ethanol ratio, at 188 °C and 20 min as static extraction time. In this case rutin recovery from the leaves (14.30 g/kg DM) was 4-times higher compared to that attainable using conventional ultrasound assisted extraction (3.62 g/kg DM) with methanol:ethanol mixture (90:10) as solvent. Rutin recovery from defatted and non-defatted seeds of amaranth under optimum PLE conditions was 35.3 and 41.1 mg/kg DM, respectively, whereas using ultrasound assisted extraction 19.7 and 34.6 mg/kg DM were obtained, respectively.Extracts obtained under optimum conditions were further fractionated by using supercritical antisolvent fractionation (SAF). Extracts of amaranth leaves containing 70% water were mixed with supercritical CO2 and separated into two fractions according to the molecular mass and solubility of the contained compounds. A central composite experimental design was applied for the determination of the best fractionation conditions to maximize rutin enrichment. Maximum rutin concentration in raffinate (22.57 g/kg) was recovered at 15 MPa using a feed mixture flow rate of 0.3 mL/min.

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