Hybrid materials based on smectite clays and nutraceutical anthocyanins from the Açaí fruit

Abstract

Hybrid materials were prepared by combining clay mineral (montmorillonite SWy-2 and saponite SapCa-1) and dyes extracted from the açaí (Euterpe oleracea Mart.) fruit, which contains mainly anthocyanins from the 3-glucoside class, to increase the stability of the dye and facilitate its handling and storage. Clay minerals are common ingredients in therapeutic and pharmaceutical products and açaí phytochemicals show disease prevention properties. The extract of the açaí fruit was mixed with water suspensions of layered silicates in different proportions. The dye-clay hybrids presented incorporated organic material in amounts up to 24 wt.-%. X ray diffractometry and vibrational (FTIR and Raman) and electronic spectroscopic data showed that flavylium cations were successfully intercalated between the inorganic layers. Mass-coupled thermogravimetric analysis (TGA-MS) data showed a significant gain in the thermostability of the organic species in relation to anthocyanins in the extract. MS curves related to CO2 release (m/z = 44) are ascendant above 200 °C when the dye cations are confined to the inorganic structure. The radical scavenging activity of the hybrid materials was monitored by electron paramagnetic resonance (EPR) toward the stable radical DPPH (1,1-diphenyl-2-picrylhydrazyl) and compared to the activity of the açaí extract. In addition to the fact that interaction with clay minerals improves the stability of the açaí dyes against heat, their properties as radical scavengers are preserved after intercalation. The improvement in the properties of the nutraceutical species by intercalation by using biocompatible inorganic structures can be valuable for human therapy. New materials were prepared by combining clay minerals and natural purple dyes extracted from a native Amazonian palm fruit known as açaí. Intercalation into clay minerals improves the stability of the natural dyes against heat and preserves their properties as radical scavengers. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.