Abstract
To improve phytochemical stability, polyphenolic extracts prepared from Salvia officinalis L., which is a valuable source of phytocompounds with health benefits, were embedded into mesopores of silica, titania, or titania-ceria materials. Ethanolic and hydroalcoholic extracts were prepared by conventional, microwave- or ultrasound-assisted extraction. The influence of the extraction conditions on chemical profile, radical scavenger activity (RSA), and antimicrobial potential of the extracts was assessed. The extracts were characterized by spectrophotometric determination of total polyphenols, flavonoids, chlorophyll pigment contents, as well as RSA. A reverse phase HPLC- PDA analysis was performed for the identification and quantification of extract polyphenols. The extract-loaded materials exhibited an enhanced RSA compared to the free extract after several months of storage, resulting in better polyphenol stability over time following embedding into a mesoporous matrix. Selected extracts free and embedded into mesoporous support were tested against Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922, and Staphylococcus aureus ATCC 25923; the best antimicrobial activity was obtained for S. aureus. A slight improvement in antimicrobial activity was observed for the ethanolic extract prepared by ultrasound-assisted extraction following embedding into the TiO2 matrix compared to MCM-41 silica due to the support contribution.
Highlights
Polyphenols are an important class of micronutrients found in plants, like vegetables, herbs, fruits, and cereals; they are not synthesized in animal organisms [1,2]
Extraction assisted by high voltage electrical discharge causes the electroporation of the plant membrane, which increases the release of polyphenolic compounds; a 2.1 times higher total polyphenols content in sage extract was obtained compared to conventional extraction [9]
It was observed that the application of low intensity ultrasound during the extraction process, that usually do not alter the state of the vegetal material but decrease the time of the extraction, correlated with higher yield (13.0% for So(US)-1) in natural compounds compared to the conventional method (8.2% for So(Conv)-6)
Summary
Polyphenols are an important class of micronutrients found in plants, like vegetables, herbs, fruits, and cereals; they are not synthesized in animal organisms [1,2]. To obtain polyphenolic extracts from dried common sage leaves, Dent et al used 30%, 50% and 70% aqueous solution of ethanol or acetone and temperatures of either 60 ◦C or 90 ◦C They reported the best efficiency for 30% aqueous solution of ethanol at 60 ◦C [19]. Extraction assisted by high voltage electrical discharge causes the electroporation of the plant membrane, which increases the release of polyphenolic compounds; a 2.1 times higher total polyphenols content in sage extract was obtained compared to conventional extraction [9]. Microwaves-assisted extraction has led to a more efficient recovery of phenolic compounds from common sage than conventional methods due to the higher radical scavenger activity (RSA) of the MW extract compared to the conventional one obtained in the same conditions [7]. High temperature and time enhanced phenolic, flavonoid and proanthocyanidin content and reduced anthocyanin amount in the extracts; this was attributed to the lower resistance to thermal degradation of the latter compared to other phytocompounds [20]
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