Separation and Purification Technology 55 (2007) 381–387 Optimization of extraction of phenolics from Inga edulis leaves using response surface methodology E.M. Silva a,b , H. Rogez b,∗ , Y. Larondelle a a Unit´ e de biochimie de la nutrition, Universit´ e catholique de Louvain & Institut des sciences de la vie, Croix du Sud, 2/8, B-1348 Louvain-la-Neuve, Belgium b Faculdade de Engenharia de Alimentos, Universidade Federal do Par´ a, av. Perimetral s/n, 66.095-780 Bel´ em-PA, Brazil Received 4 August 2006; received in revised form 9 January 2007; accepted 10 January 2007 Abstract The extraction of phenolic compounds from Inga edulis leaves was optimized by the simultaneous maximization of the yield in total phenolics (TP), total flavanoids (TFA), and total flavonols (TFO), using the response surface methodology (RSM). A first set of experiments allowed identifying the temperature, the time of contact and the ethanol proportion in the extraction solution, as the main variables affecting the extraction efficiency. A rotatable central composite design consisting of 18 experimental runs with three replicates at the centre point was then applied and a second-order polynomial model was used to describe the experimental data regarding TP, TFA and TFO. The experimental results fitted well to the model and more than 85% of the variability was explained. TP, TFA and TFO showed different patterns of extractability, with significant variation in the linear, quadratic, and interaction effects of the independent variables. The optimized conditions were 86.8% ethanol, 58.2 ◦ C and a time of contact of 46.8 min. The corresponding predicted values were 134.6 mg gallic acid equiv./g dry matter (DM), 26.0 mg catechin equiv./g DM and 13.8mg rutin equiv./g DM, for TP, TFA and TFO, respectively. The experimental values agreed with those predicted within a 95% confidence interval, thus indicating the suitability of RSM in optimizing the extraction of phenolics from I. edulis. © 2007 Elsevier B.V. All rights reserved. Keywords: Solid–liquid extraction; Response surface methodology; Optimization of extraction; Polyphenol; Flavonoid; Inga edulis 1. Introduction The search for a natural and healthy lifestyle has increased the interest for natural bioactive compounds that could be introduced in our diet or be used as natural drugs. In this context, phenolic antioxidants are the most promising group of molecules due to their high antioxidant activity [1]. There is subsequently an increasing number of investigations on polyphenols because of their positive effects on anti-inflammatory, cardiovascular and neurodegenerative diseases, as well as cancers [2]. The most generally accepted mechanism of action of these compounds is the scavenging of free radicals, contributing to reduce the oxidative stress. Due to its great biodiversity, Amazonia is an inestimable source of antioxidant-rich plants and several of them may be included in a sustainable exploitation of non-timber products. Inga edulis Mart. (Leguminosae-Mimosoideae), a fruit tree ∗ Corresponding author. Tel.: +55 91 3201 74 56; fax: +55 91 3201 74 56. E-mail address: frutas@ufpa.br (H. Rogez). growing in the tropical secondary forest, is widespread in Central and South America. It has been used by native people to these areas in folk medicine as anti-inflammatory [3]. This property may be linked to the fact that the leaves are very rich in polyphenols [3], especially in flavan-3-ols ((+)-catechin and (-)-epicatechin) and flavonols (myricetin-3-O--l- rhamnopyranoside and quercetin-3-O--l-rhamnopyranoside) [4]. Considering the diversity in composition of the natural sources of polyphenols, as well as the structure and physico- chemical properties of these compounds, a universal extraction protocol is not conceivable, and specific processes must be designed and optimized for each phenolic source [5,6]. More- over, co-extraction of undesirable compounds such as sugars, fats, terpenes or pigments, must be avoided and has to be taken into account during the optimization of the process. Many fac- tors contribute to the efficacy of solvent extraction, such as the type of solvent, the pH, the temperature, the number of steps, the liquid-to-solid ratio, and the particle size and shape of the plant matrix [7]. Solvent extraction from a milled plant material includes first a swelling step consisting in the sorption of the 1383-5866/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.seppur.2007.01.008