Peel of Traditional Apple Varieties as a Great Source of Bioactive Compounds: Extraction by Micro-Matrix Solid-Phase Dispersion

Abstract

Micro matrix solid phase dispersion (micro-MSPD) was optimized by response surface methodology for the extraction of polyphenols from the peel of twelve traditional and eight commercial apple varieties grown in Croatia. The optimized micro-MSPD procedure includes the use of 0.2 g of sample, 0.8 g of dispersant, a 57% solution of methanol in water as the solvent and 5 mL of extract volume. The total polyphenolic index (TPI) and antioxidant activity (AA) were measured by spectrophotometric assays. Eighteen polyphenolic compounds were identified in all investigated apples by HPLC-DAD and LC-(ESI)-MS. The peel of traditional apple varieties had higher contents of all investigated polyphenols. Calculated relative contribution of polyphenol groups indicated non-flavonoids (28.6%) and flavanols (46.2%) as the major contributors to the total polyphenolic content in traditional and commercial apple varieties, respectively. The most abundant polyphenol in traditional apple peel was chlorogenic acid, procyanidin B2 and epicatechin (1143 ± 755 µg/g dw, 954 ± 343 µg/g dw and 560 ± 362 µg/g dw, respectively). The peel of varieties ‘Apistar’, ‘Bobovac’ and ‘Božićnica’ could be highlighted as an important source of polyphenols.

Valorization of Apple Peels through the Study of the Effects on the Amyloid Aggregation Process of κ-Casein

“…The polyphenolic profile of Fuji apple peel extract was studied using ultra-highperformance liquid chromatography with heated electrospray ionization coupled to mass spectrometry (UHPLC-HESI-MS) techniques, and seven phenolic compounds were identified (Supplementary Materials, Figure S1). In good agreement with the literature data [5], the qualitative profile showed vanillin, gentisic acid, sinapinic acid, ferulic acid, epicatechin, quercetin, and procyanidin A2.…”

“…Research has shown that apples are a great source of bioactive compounds [5] with marked antioxidant activity and antiproliferative activity [5][6][7], and we demonstrated that the peels from the Fuji apples under study presented higher phenolic contents and more marked antioxidant activity with respect to the flesh and whole fruit (Table 1). The polyphenolic profile of Fuji apple peel extracts was studied using UHPLC-HESI-MS techniques, and seven phenolic compounds were identified (Supplementary Materials, Figure S1).…”

“…The two spectra, at the beginning (t start ) and after 24 h (t end ) of incubation, almost overlap. At the APP concentrations' intermediate range (5,10, and 20 µg/mL), the higher the polyphenol content (Supplementary Materials, Figure S3), the more evident the changes in the spectra between that recorded at initial time t start and after 24 h (t end ) of incubation. To better visualize these results, we reported, in Figure 4c, the difference squared between the κ-casein spectra recorded at t start and t end in the wavelength region around 222 nm.…”

“…In this regard, an important opportunity is provided by the valorization and recycling of peels from apples, which are a rich source of bioactive compounds, like polyphenols [ 3 ]. In fact, similar to the whole fruit, the apple peel polyphenol content includes abundant amounts of flavan-3-ols/procyanidines, phenolic acids, flavonols, dihydrochalcones, and anthocyanins [ 4 ], known for their beneficial effects in human health [ 5 ]. There is evidence that apple polyphenols are strong antioxidants [ 6 ] and have, among other benefits, anti-tumor [ 7 ], anti-allergy [ 8 ], and life-extending properties [ 9 ].…”

The Qualitative and Quantitative Compositions of Phenolic Compounds in Fruits of Lithuanian Heirloom Apple Cultivars

“…Currently, consumers are looking for high-quality products with a known composition and health benefits [ 25 ]. Research into the qualitative and quantitative composition of biologically active compounds is important in assessing the quality and nutritional properties of apples.…”