Extraction of bio-active compounds from Ethiopian plant material Rumex abyssinicus (mekmeko) root A study on kinetics, optimization, antioxidant and antibacterial activity

Bioactive compounds are extracted from mekmeko and characterized for antioxidant, phytochemical, and antibacterial activities. The phytochemical studies of the extracts revealed the presence of condensed tannins, flavonoid, and phenolic compounds. Radical scavenging activity of the extract demonstrates that the ethanol extract has more significant antioxidant activity than the aqueous extract. Ethanolic extract of mekmeko is more effective against gram-positive bacteria compared to gram-negative. A Box-Behnken-design was used to study the response pattern and to determine the optimum combination of variables for maximization of extraction yield. Experiments were carried out to evaluate the four independent variable effects (particle size, temperature, time, and solid-solvent-ratio) on the maximum extraction yield of bioactive compounds. Second order polynomial mathematical model was developed with a high coefficient of determination (R-2=0.99) from the experimental data. A maximum of 18.85% total extraction yield was achieved at the optimal conditions of particle size of 350 mesh, extraction temperature at 41 degrees C, solid-solvent-ratio of 0.07, and extraction time of 24 h. The extracted constituents are predominantly phenolics (39%) and condensed tannins (21%). Under theses optimal conditions, the experimental values agreed well with the predicted values and indicated the suitability of the developed models. (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.