Ioannis Mourtzinos

Bicyclo[3.1.0]hexanes from sugar-derived diazo compounds and iodonium ylides. Diastereocontrol and synthetic applications

Abstract The CuI and Rh 2 (OAc) 4 catalyzed decomposition of ethyl 2-diazo-4,5-isopropylidenedioxy-3-oxo-6-heptenoate results in intramolecular cyclopropanation products with opposite diastereoselectivity. In contrast, decomposition of the respective iodonium ylide can proceed without catalysts to give the cyclopropanation products with diastereoselectivity unchangeable by the presence of CuI and Rh 2 (OAc) 4 , revealing thus, that in this particular case the reaction is an electrophilic addition of the iodonium center to the double bond. The synthetic importance of these reactions has been demonstrated by preparing a number of precursors of cyclopentyl, cyclopropyl and bicyclo[3.1.0]hexyl antiviral carbocyclic nucleosides.

Green extraction of polyphenols from whole pomegranate fruit using cyclodextrins.

Pomegranate is a source of bioactive phytochemicals. The objective of this study was the derivation of a sustainable method to exploit the whole fruit, both edible and non-edible parts, as a source of polyphenols. Pomegranate peel contains a 10-fold higher phenolic content than the pulp. The fruit was freeze-dried and the resulting dry matter was extracted with solid-liquid percolation equipment using non-toxic and eco-friendly extraction solvents: either deionized water or aqueous solutions of cyclodextrins. Cyclodextrins (CDs) are known molecular encapsulators and our results prove enhancement of the extraction of pomegranate polyphenols by 20%. In order to examine the formation of inclusion complexes between CDs and polyphenols of the extract, polyphenols were isolated using solid-phase extraction. NMR studies with the purified extracts and the individual CDs confirmed inclusion complex formation in water. Pomegranate liquid extracts may be used as raw materials for several end-users in the food, cosmetic and pharmaceutical industries.

Optimization of polyphenol extraction from red grape pomace using aqueous glycerol/tartaric acid mixtures and response surface methodology.

ABSTRACT Grape pomace is a food industry waste containing a high burden of antioxidant polyphenols and several methodologies have been developed for their efficient extraction. However, a sustainable and environmentally friendly process should involve recovery means composed of benign, non-toxic solvents, such as tartaric acid and glycerol, which are natural food constituents. In this line, this study examined the extraction of polyphenols using aqueous tartaric acid/glycerol solutions. The aim was to assess the role of acid and glycerol concentration in the extraction yield, employing a Box-Behnken experimental design and response surface methodology. The results showed that solutions containing only glycerol (20%, w/v) are more suitable for retrieving polyphenols, flavonoids, and pigments from grape pomace, while tartaric acid exerted a negative effect in this regard, when tested at concentrations up to 2% (w/v).

Natural food colorants derived from onion wastes: Application in a yoghurt product

The valorization of onion (Allium cepa) solid wastes, a 450 000 tonnes/year waste in Europe, by a green extraction method is presented. Polyphenols of onion solid wastes were extracted using eco‐friendly solvents, such as water and glycerol. The 2‐hydroxypropyl‐β‐cyclodextrin was also used as a co‐solvent for the augmentation of the extraction yield. The process has been optimized by implementing a central composite face centered design of experiments, with two replicates in the central point, taking into consideration the following independent variables: glycerol concentration, cyclodextrin concentration and temperature. The assessment of the extraction model was based on two responses: the total pigment yield and the antiradical capacity. LC‐MS analysis was also employed in order to identify polyphenols and colorants of the obtained extracts. The main polyphenols found were quercetin and quercetin derivatives and the main colorant was cyanidin 3‐O‐glucoside. The extract was also tested as a food colorant in a yoghurt matrix. The onion leaf extract was found to be a stable natural colorant and could be utilized as an alternative ingredient to synthetic coloring agents.