Original article Sacha inchi (Plukenetia volubilis L.) shell: an alternative source of phenolic compounds and antioxidants Rosana Chirinos, 1 Ornella Necochea, 1 Romina Pedreschi 2 & David Campos 1 * 1 Instituto de Biotecnolog  ıa (IBT), Universidad Nacional Agraria La Molina – UNALM, Av. La Molina s/n, Lima, Peru 2 School of Agronomy, Pontificia Universidad Cat olica de Valpara  ıso, Calle San Francisco s/n, La Palma, Casilla 4-D, Quillota, Chile (Received 18 August 2015; Accepted in revised form 10 December 2015) Summary Sacha inchi seed (SI) is known as a rich source of oil with high content of polyunsaturared fatty acids of the x-3 and x-6 type (~85% of total fatty acids). However, few studies have focused on the use of by- products from the seed. The aim of this study was to characterise the main phenolic families present in SI shell and to evaluate the best extraction solvent for the extraction of phenolic compounds (PC) and antioxidant capacity (AOXC). The PC content corresponded to 74.5  5.1 mg g 1 of which 93.1% were condensed tannins and the remaining compounds corresponded to free and bound phenolic acids, hydrolyzable tannins, flavonoids and flavanoids. Protocatechic and p-coumaric acids but also hydroxyci- nammic acid derivatives of ferulic and o-coumaric type and lignan derivatives were identified. Acetone containing solvents favoured the extraction of higher amounts of total PC and AOXC. This study high- lights the potential use of SI shell as a novel and alternative source of PC antioxidants for the nutraceuti- cal and/or functional food industries. Keywords Antioxidant capacity, phenolic compounds, Plukenetia volubilis, shell. Introduction Sacha inchi (Plukenetia volubilis L.) is an oleaginous plant that belongs to the Euphorbiaceae family. It grows in the lowlands of the Peruvian Amazon having been cultivated for centuries by the indigenous population (Hamaker et al., 1992; Guti errez et al., 2011). Sacha inchi (SI) seeds are composed of~33–35% of shell and ~65–67% of kernel. Kernel contains approximately 54% oil and 33% proteins (Hamaker et al., 1992). SI seeds are mainly industrialised into oil due to its unique fatty acid composition, comprising approximately 34% linoleic acid (x-6) and 51% linolenic acid (x-3), respec- tively (Hamaker et al., 1992; Guti errez et al., 2011; Chirinos et al., 2015). However, SI seed industrialisa- tion generates by-products such as the shell and cake and both are discarded without any further use. Several investigations state that the by-products gen- erated from different plant sources after processing could become important sources of antioxidant bioactive com- pounds of the phenolic type. For instance, antioxidant bioactive compounds have been reported in almond shell (Garrido et al., 2007), hazelnut shell (Shahidi et al., 2007; Contini et al., 2008), sunflower shell (Weisz et al., 2009), triticale bran and straw (Hosseinian & Mazza, 2009), chesnut fruit pericarp and integument (de Vascon- celos et al., 2010), pecan nut shell (do Prado et al., 2014), rice brand and rice husk (Wanyo et al., 2014) to cite a few plant sources. Previous studies carried out in our lab- oratory showed that the phenolic compounds (PC) con- tent of the shell is eight fold higher that the PC content of the cake (D. Campos, R. Chirinos and R. Pedreschi, un- published results). Up to date, to our knowledge, there are no investigations reported related to the PC content and antioxidant properties of the SI shell as an alterna- tive by-product source of antioxidant compounds. Thus, the main aims of this study were: to characterise the main phenolic families present in SI shell (by-product) and to evaluate the best extraction solvent for the extraction of total phenolic compounds (TPC) and antioxidant capac- ity (AOXC). Results from this study will allow to add- value to this by product as a source of natural antioxi- dant bioactive compounds. Materials and methods Sample material Seeds of Plukenetia volubilis, ecotype Pinto Redondo were obtained from Tarapoto city, province of San *Correspondent: E-mail: dcampos@lamolina.edu.pe International Journal of Food Science and Technology 2016, 51, 986–993 doi:10.1111/ijfs.13049 © 2016 Institute of Food Science and Technology 986