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

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.

Solid-phase adsorption methodologies of naturally occurring anthraquinones: A review

INTRODUCTION

Solid-phase extraction applied to plant matrices is nowadays a well-validated technique allowing to concentrate and purify different secondary metabolites. Several classes of phytochemicals have been selectively extracted by this methodology. During the last decade attention has been focused on biologically active anthraquinones from numerous sources like edible, healthy, and medicinal plants.

OBJECTIVES

The aim of this review is to provide a detailed literature survey of the solid-phase adsorption methodologies for the extraction of natural anthraquinones reported so far and to discuss and propose future directions in this field of research.

MATERIALS AND METHODS

Substructure search was performed in the SciFinder Scholar, PubMed, Medline, and Scopus databases.

RESULTS

The first report about application of solid-phase adsorption for the purification of anthraquinones appeared in the literature in 2002. From this date, and in particular during recent years, the most notable examples included the use of chitin- and chitosan-based polymers, of molecularly imprinted polymers, of coated magnetic nanoparticles, of miniaturized matrix solid-phase dispersion, of functionalized resins, of differently structured lamellar solids, and finally of vortex-synchronized matrix solid-phase dispersion.

CONCLUSIONS

The herein detailed solid-phase adsorption methodologies are powerful tools to selectively extract natural anthraquinones and/or provide anthraquinone-enriched phytopreparations. Nevertheless, many other important methods have been applied to synthetic anthraquinones (e.g., azo dyes). These could be conveniently employed also for natural anthranoids. Studies in this field are discussed in this review article.

An easy way for the hydrolysis, pre-concentration, and chemical stabilization of crocetin from saffron powder

To date there are no methods in the literature leading to crocetin selective concentration from saffron powder aqueous solutions. To this aim, we decided to test the performance of its heterogeneous extraction by means of a panel of 21 synthetic clays, 4 of which demonstrated to selectively retain crocetin in the solid phase after hydrolysis of its digentiobyosil ester (crocin) (and its isomers) and to its chemical stabilization (e.g., oxidation) over time. The best adsorption yield was obtained with zinc hydroxy chloride (66.18 ± 0.06 μg/g dry powder). This phenomenon was assessed by HPLC-DAD analyses after desorption of crocetin from the respective support and assessing its degradation along a period of 30 days. The method we established could represent a good mean to provide pure crocetin from saffron powder, preserving in the meantime its chemical properties for a concrete future exploitation for food pharmaceutical, and cosmetic purposes.

A Novel Auraptene-Enriched Citrus Peels-Based Blend with Enhanced Antioxidant Activity

The aim of this study was to establish a convenient process to get auraptene-enriched blends from Citrus limon L. Osbeck (Rutaceae) peels powder with functional food and nutraceutical potential and antioxidant properties. The process consisted in the selective adsorption of auraptene by bentonite followed by desorption and evaporation of solvents to get the final product. HPLC analyses revealed an adsorption > 99% from lemon fruit peel powder and a 13.7-fold enrichment of the obtained composition respect to the parent food-derived sample. The antioxidant and radical scavenger activities of the Citrus peels based preparation were assayed by the DPPH and ABTS tests and reveal deffects higher than ascorbic acid and Trolox® used as the references. To the best of our knowledge, the findings described herein is the first example reported in the literature of solid phase adsorption experiments carried out on auraptene as a component of edible fruits.

An improved method for the isolation of amarogentin, the bitter principle of yellow gentian roots

Amarogentin is well known to be among the most bitter naturally occurring compound. Either as an individual one or extracts, amarogentin is used as a food additive and as a dietary supplement. The aim of the present investigation is to set-up a convenient process to selectively isolate amarogentin from the ethanolic roots extract of Gentiana lutea. The process consisted in the treatment of an aqueous suspension of such an extract with a panel of 21 solid inorganic / organic sorbents followed by filtration, desorption, and high performance liquid chromatography (HPLC) analyses. Among the solid materials tested, those containing Mg⁺² in the frame of a lamellar structure provided very good adsorption yields in the range 86.4% - 99.9% (p < 0.05 at Student's t-test). The method we set up could be in principle useful to obtain a pure nature-derived food additive to provide bitter taste to foods and beverages.