ARTICLE IN PRESS JID: JTICE [m5G;March 22, 2017;9:44] Journal of the Taiwan Institute of Chemical Engineers 000 (2017) 1–12 Contents lists available at ScienceDirect Journal of the Taiwan Institute of Chemical Engineers journal homepage: www.elsevier.com/locate/jtice Extraction of bio-active compounds from Ethiopian plant material Rumex abyssinicus (mekmeko) root—A study on kinetics, optimization, antioxidant and antibacterial activity Shegaw Ahmed Mohammed a,b , Rames C. Panda b,∗ , Balaraman Madhan b , Berhanu Assefa Demessie a a School of Chemical and Bio Engineering, Addis Ababa Institute of Technology, Addis Ababa University, P.O. Box 385, Addis Ababa, Ethiopia b CSIR - Central Leather Research Institute, Adyar, Chennai 600 020, India a r t i c l e i n f o Article history: Received 5 August 2016 Revised 12 January 2017 Accepted 1 March 2017 Available online xxx Keywords: Rumex abyssinicus Box–Behnken-design Antioxidant activity Antibacterial activity Extraction optimization Mathematical modeling a b s t r a c t 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 tan- nins, 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 vari- able 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 co- efficient 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 °C, solid–solvent-ratio of 0.07, and extraction time of 24 h. The extracted constituents are predomi- nantly 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. © 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. 1. Introduction Mekmeko is a family of Polygonaceae, and most of the species of Polygonaceae genus contain phytoconstituents viz., flavonoids, an- thraquinones, and triterpenoids. Mekmeko is widespread in tropi- cal Africa, particularly in central and eastern Africa, and Madagas- car. The plant is generally considered as a native of Africa, espe- cially Ethiopia (Abyssinicus means from Abyssinia, Ethiopia) and the plant in the Amharic language referred as mekmeko [1-3]. Mek- meko plant grows on any type of soil and it can grow in any soil pH viz., acid, neutral and alkaline soils. The propagation of the plant is carried out through seeds [3]. Traditionally, the root part of mekmeko is used in butter as a condiment for protection against rancidness. Mekmeko has been investigated by various researchers for treating skin problems and other medicinal applications [4 3]. Thus, the root parts of mekmeko plant were selected and used for ∗ Corresponding author. E-mail addresses: panda@clri.res.in, rames.panda@gmail.com (R.C. Panda), madhan@clri.res.in (B. Madhan). the current studies. It is reported that the root of mekmeko plant material has antibacterial activity [5]. About 60–70% w/w of moisture and nearly 25–30% w/w protein are the main constituents of hides/skins, which makes the material susceptible to bacterial attack [6]. Raw skins/hides as a raw mate- rial for leather manufacture contains a wide range of microorgan- isms viz., Bacillus subtilis, Staphylococcus aureus, Micrococcus roseus, Staphylococcus epidermidis, and Pseudomonas aeruginosa. These mi- croorganisms produce proteolytic and collagenolytic enzymes re- sulting in the disintegration of skin by attacking the protein fibers after the death of the animal [7-10]. Therefore, it is essential to preserve proteins in skin from the bacterial attack at their source. Currently, there is a growing interest for the use of plant extracts for the treatment of diseases and food preservation owning to their antioxidant as well as antibacterial activity. In recent times, major research activity in the leather process industry is focused on the use of natural materials for preservation of hides/skins and leather processing [11]. In such an attempt, we have recently established the use of mekmeko material for preservation of goat skins [12]. In leather making process, natural vegetable tannins are one of http://dx.doi.org/10.1016/j.jtice.2017.03.004 1876-1070/© 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Please cite this article as: S.A. Mohammed et al., Extraction of bio-active compounds from Ethiopian plant material Rumex abyssinicus (mekmeko) root—A study on kinetics, optimization, antioxidant and antibacterial activity, Journal of the Taiwan Institute of Chemical Engineers (2017), http://dx.doi.org/10.1016/j.jtice.2017.03.004