Industrial Crops and Products 70 (2015) 34–40 Contents lists available at ScienceDirect Industrial Crops and Products jo u r n al homep age: www.elsevier.com/locate/indcrop Mixture approach for optimizing the recovery of colored phenolics from red pepper (Capsicum annum L.) by-products as potential source of natural dye and assessment of its antimicrobial activity Imen El Ksibi a,∗ , Rihab Ben Slama b , Khaled Faidi a , Manel Ben Ticha a , Med Farouk M’henni a a Research Unit of Applied Chemistry and Environment, Faculty of Sciences of Monastir, 5000 Monastir, Tunisia b Laboratory of Analyze, Treatment and Valorization of Environmental Polluants and Products, Faculty of Pharmacy, Monastir University, Tunisia a r t i c l e i n f o Article history: Received 7 October 2014 Received in revised form 4 March 2015 Accepted 6 March 2015 Keywords: Red pepper Extraction Mixture design Antibacterial activity a b s t r a c t The aim of this study was to investigate whether complexly constituted phenolics extracts from pepper waste may be utilized for the recovery of natural colored preparations. At first, different solvents mixture were compared to determine the best solvent for extraction of phenolic compounds from pepper by-product. The three solvents ethanol, acetone and water were used. The total phenolic content (TPC), the total flavonoid content (TFC) and the relative color strength (K/S) were studied using a simplex-centroid design. Acetone–water (68–32%) with 224 mg/L for total phenolic content and acetone–water (61–38%) with 0.446 mg/L for total flavonoid content were the best solvent mixtures for the extraction. The colored extract of pepper by-products was applied on woolen fabrics to investigate the dyeing char- acteristics and antimicrobial efficacy against common human pathogens such as Pseudomonas aeruginosa and Staphylococcus aureus. The results indicate that extract can be applied on woolen fabrics to produce colored clothing and textiles with acceptable antimicrobial properties. © 2015 Elsevier B.V. All rights reserved. 1. Introduction During the last few decades, there has been a growing inter- est in the improvement of bioactive textile materials and garments with antimicrobial properties. This fact necessitates the develop- ment of methods to convey microbial resistance to textiles with all usual desirable characteristics of textiles (Sathianarayanan et al., 2010). Although the synthetic antimicrobial agents are very effec- tive against a range of microbes and give durable effect onto textile materials, they act on non-target microorganisms and may cause a harmful effect on human body (Gupta et al., 2004). Those facts led to think of natural colorants usable in coloration of textile materi- als, cosmetic and in food coloration, which are believed to be safe because of their non-toxic, non-allergic and biodegradable nature (Ali et al., 2009; Sivakumar et al., 2011). With ever increasing environmental concern on the use of syn- thetic dyes and adjuvants, researches were conducted to discover new sources especially from by-products of agri-food industry in ∗ Corresponding author. Tel.: +216 73500280; fax: +216 73500278. E-mail address: imenksibi@yahoo.fr (I.E. Ksibi). order to extract from them their coloring substances (Prusty et al., 2010; Haddar et al., 2014). Almost all of the organic solid waste (50% in weight of the orig- inal raw material source) are colored and contains compounds of interest for their potential use as nutritional or functional ingre- dients (proteins, vitamins, pigments, antioxidants, antimicrobials and fragrances etc.). Therefore, obtaining these ingredients is one of the most interesting alternatives for their reuse (Louli et al., 2004). The red pepper variety (Capsicum annum L.) is highly demanded by the global food industry. After processing, a by-product is pro- duced, which amounts to approximately 65% in weight of raw material. It is currently disposed of as municipal solid waste (Romo- Hualde et al., 2012). Peppers are a good source of several health-promoting com- pounds such as phenolic compounds particularly flavonoids, quercetin and luteolin, carotenoids and capsaicinoids. Among the compounds, flavonoids are the most abundant compounds pre- sented in green, sweet and hot peppers (Bae et al., 2012; Kim et al., 2010; Hervert-Hernandez et al., 2010). The present investigation, aimed to identify the most appropri- ate leaching solvents mixture for pepper pigments to produce the best concentrated extract by examining the efficiency of different http://dx.doi.org/10.1016/j.indcrop.2015.03.017 0926-6690/© 2015 Elsevier B.V. All rights reserved.