Eco-friendly hybrid materials made from Tunisian clay and natural flowers

Abstract Clay minerals are used widely in health products both as cosmetic and pharmaceutical ingredients. To optimize use, natural compounds are mixed with clay powder. The aim of the present study was to synthesize new, coloured hybrids based on purified Tunisian clay and powders of natural flowers: Malva sylvestris, Chrysanthemum coronarium, Silene dioica, Anagallis monellin and Pelargonium × hortorum. The floral pigments in Tunisian flowers were studied. The chlorophylls (a and b), total flavonoids (TF), total phenolic compounds (TPC), and carotenoids were analyzed using UV-Vis spectrophotometry and high-performance liquid chromatography (HPLC-DAD). In addition, the antioxidant capacity was determined using the oxygenated radical absorption capacity assay (ORAC) and the antioxidant capacity to reduce ferric ion assay (FRAP). The properties of the studied clay were evaluated by means of pharmaceutical and microbiological tests. The coloured hybrids were prepared by solid–solid reaction and analyzed using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Chlorophyll a is present in large quantities in the Malva flower which presents the smallest antioxidant capacity. Chlorophyll b and the TPC are more abundant in the Pelargonium × hortorum. The TF appears in large quantities in the Anagallis flower. The carotenoids are present in the largest amounts in the Chrysanthemum. The results of the clay characterization justify its use as a pharmaceutical and cosmetic agent. The mixture of dried flowers and purified clay is used in the synthesis of new and biocoloured hybrids; these can be used as biocosmetic products without negative side effects on human health or the environment.