Novel procedures for olive leaves extracts processing: Selective isolation of oleuropein and elenolic acid.

Several processes have been developed in the past to selectively extract oleuropein and its aglycones from olive derived materials. In the present manuscript, we outline a novel approach for processing olive leaves aqueous extracts. This allowed first to select microwave irradiation as the methodology able to provide a large enrichment in oleuropein. Subsequently, the use of lamellar solids led to the selective and high yield concentration of the same. Adsorption on solids also largely contributed to the long term chemical stability of oleuropein. Finally, an eco-friendly, readily available, and reusable catalyst like H2SO4 supported on silica was applied for the hydrolysis of oleuropein into hydroxytyrosol and elenolic acid. This latter was in turn selectively isolated by an acid-base work-up providing its monoaldehydic dihydropyran form (7.8 % extractive yield), that was unequivocally characterized by GC-MS. The isolation of elenolic acid in pure form is described herein for the first time.

A novel and efficient concentration of pomegranate juice with enhanced antioxidant activity.

In the present study we investigated the performance of a panel of 13 solid sorbents comprising layered double hydroxides, zirconium phosphate-based materials, and phyllosilicates as heterogeneous supports for the concentration of pomegranate (Punica granatum L.) juice. Mg-containing clays exhibited an almost complete bleaching capacityof pomegranate juice and more interestingly provided blends with an increased antioxidant capacity (around 1.5-fold) respect to the parent juice when assayed for the Trolox equivalent antioxidant capacity (TEAC) coupled to ABTS decolorization test. Such an activity remained practically unaltered after 4 days during which the pomegranate concentrated preparations remained supported on clays. The approach investigated herein and used for the concentration of pomegranate juice and the discovery of the preservation for long periods of the antioxidant activities of pomegranate extracts when supported on solid sorbents have been reported herein for the first time in the literature to the best of our knowledge.

Pre-concentration of active principles from different varieties of Camellia sinensis extracts by solid sorbents.

In this article we studied the phytochemical composition of leaves extracts of different varieties of Camellia sinensis(L.) Kuntze after treatment with 16 selected solid sorbents (namely hydrotalcites, magnesium oxide and hydroxide, zirconium phosphates, and phyllosilicates). The pre-concentration and selective adsorption of the main active principles of this food and medicinal plant [e.g. gallic acid, (-)-epicatechin, (-)-epicatechin gallate, and caffeine] were investigated. The quantities of phytochemicals adsorbed by solids were measured by HPLC analysis, coupled to photodiode array detection and calculated as the difference between the quantities in the parent untreated extracts and those recorded in the filtrates. Caffeine was selectively adsorbed by bentonite to a large extent, while for the remaining phytochemicals different patterns were recorded depending on the type of leaves extract. A comparison with pure chemicals revealed a strong effect of the phytocomplex composition on the adsorption yields. The methodology outlined herein may be useful to obtain tea extracts enriched in selective active principles also for industrial scopes.

Solid phase adsorption of anthraquinones from plant extracts by lamellar solids.

Solid phase extraction is nowadays a well validated and powerful technique applicable to complex matrices like plant extracts and phytocomplexes. This process provides concentration and/or purification of selected secondary metabolites from these matrices for subsequent analysis and isolation. In this research article sixteen lamellar solids, comprising layered structures (hydrotalcites, zirconium phosphates, magnesium hydroxide), magnesium oxide, and the phyllosilicates talc and bentonite were investigated for their capacity and performance to selectively adsorb five naturally occurring and widespread anthraquinones (aloe, aloe-emodin, rhein, chrysophanol, and physcion) contained in three ethanolic extracts of well known plants with purgative effects (frangula, senna, and rhubarb). Ethanolic solutions of extracts from these species were vigorously magnetically stirred with fixed quantities of each solid support at room temperature for 1 h. Subsequent HPLC analysis, coupled to photodiode array detection, revealed that, among the solids tested, the hydrotalcite zinc aluminum oleate and magnesium aluminum azelate and magnesium oxide were largely the most effective to this concern allowing to recover anthraquinones (all or some) in good to excellent percentages. Another interesting result was the selective and total removal of rhein by some sorbents from senna and rhubarb extracts. Sorbents were also recyclable and could be re-used to accomplish additional steps without appreciable loss of adsorption capacity. The application of the title solid inorganic and mixed inorganic/organic supports for the selective adsorption and concentration in the solid phase of anthraquinones from commonly used laxative plant species is reported herein for the first time.

Solid phase adsorption of emodin on hydrotalcites and inorganic oxides: A preliminary study.

Solid phase extraction applied to plant matrices is nowadays a well validated technique allowing the concentration and purification of selected secondary metabolites for subsequent analysis. In this short communication we screened the efficiency of 16 selected solid supports including layered structures (hydrotalcites and zirconium phosphate), magnesium oxide and hydroxide, and finally the phyllosilicates talc and bentonite for the selective concentration of the anthraquinone emodin from raw solid extracts of Polygonum cuspidatum Siebold & Zucc. (sin. Reynoutria japonica Houtt.) (Polygonaceae), commonly known as "Japanese knotweed". An ethanolic solution of sample extract from this plant was vigorously mixed with fixed quantities of each solid support. Subsequent HPLC analysis, coupled to photodiode array detection, revealed that, among the solid supports assayed, the hydrotalcite zinc aluminum oleate and magnesium oxide were largely the most effective to this concern. Both were able to extract emodin from the raw extract in percentages of 81.5 % and 92.4 %, respectively. The application of the title supports for the extraction and concentration in the solid phase of anthraquinones from raw plant extracts have been reported herein for the first time.