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UPLC-MS/MS characterization of phenolic constituents in fennel seed extracts (Foeniculum vulgare Mill.)
- Zoran Zorić, Maja Repajić, Valentina Kruk, Branka Levaj, Danijela Bursać Kovačević, Irena Landeka Jurčević, Verica Dragović-Uzelac
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- Journal:
- Proceedings of the Nutrition Society / Volume 79 / Issue OCE2 / 2020
- Published online by Cambridge University Press:
- 10 June 2020, E395
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Reports in the recent literature indicate that consumption of phytochemicals (e.g. plant polyphenols) has been associated with a wide range of health benefits. Fennel (Foeniculum vulgare Mill.) is common Mediterranean plant that has been widely used as medicinal and aromatic herb. Numerous studies reported the use of fennel extracts (plant or seed) due to its diversity of phenolic compounds to whom inhibitory effects against several diseases are prescribed. Hence, phenolic compounds isolated from fennel are of the great interest for the use in food, chemical and pharmaceutical industries.
In order to obtain the highest quality of the fennel extracts, the selection of an effective extraction procedure is required. Nowadays, innovative extraction techniques have been introduced for isolation of bioactive compounds from plant material, among which pressurized liquid extraction (PLE) was reported as automated extraction procedure that combines effects of elevated temperature and pressure to increase the efficiency of the extraction process. Improved efficiency is also achieved by selecting the right solvent and by optimizing processing conditions (temperature, static time, cycle number).
Thus, PLE was applied for the extraction of phenolic compounds from fennel seeds. The effects of exhaustive extraction (acetone followed by methanol) as well as extraction temperatures (75 and 100 °C), static time (5 and 10 min) and cycle number (1,2,3) on the phenolic compounds concentrations were evaluated. A total of 27 phenolic compounds were identified and characterized by UPLC-ESI-MS/MS whereas 6 different categories are distinguished: (1) simple phenolic acid derivatives, (2) hydroxycinnamoylquinic acid derivatives, (3) flavonoid diglycosides, (4) flavonoid O-rhamnoglucosides, (5) flavonoid glucuronides and (6) flavonoid glycosides. Phenolic compounds were identified by comparing retention time and m/z values obtained by MS and MS/MS with the mass spectra from corresponding standards whereas the quantification was made on the basis of their peak areas and comparison with calibration curve obtained with the corresponding standards. Obtained results indicated that hydroxycinnamoylquinic acid derivatives (10 compounds) and flavonoid glucuronides (3 compounds) were found as the most abundant phenolics in acetone and methanol extracts, respectively. Statistical analysis showed that optimized PLE conditions for the most effective extraction of phenolic compounds were as follows: 100 °C/10 min/3 cycles for acetone and 100 °C/5 min/3 cycles for methanol extracts. In conclusion, PLE might be considered as a rapid and effective extraction procedure that could be useful in production of fennel seeds extracts.
Bioactive compounds and antioxidant capacity in fennel seeds influenced by pressurized liquid extraction
- Maja Repajić, Petra Tonković, Valentina Kruk, Zoran Zorić, Ivona Elez Garofulić, Igor Palčić, Verica Dragović-Uzelac
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- Journal:
- Proceedings of the Nutrition Society / Volume 79 / Issue OCE2 / 2020
- Published online by Cambridge University Press:
- 10 June 2020, E547
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- Article
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- You have access Access
- Export citation
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Fennel (Foeniculum vulgare Mill.) is a well-known aromatic plant, widely used as spice and remedy herb. It provides many beneficial effects and is used as diuretic and expectorant, as well as for various dyspeptic disorders. Beside essential oils, fennel seeds are abundant with various phenols, which are known as strong antioxidants and thereby contribute to human health. Among different extraction methods for phenols isolation, pressurized liquid extraction (PLE) represents a novel technique with numerous advantages over conventional extraction approaches. Its efficiency manifests through combination of high temperature and pressure, enabling extraction time shortening, as well as decreased solvent consumption, thus being environment-friendly technique. In order to achieve maximum extraction yield, it is of great importance to select optimal PLE conditions, e.g., extraction temperature and time. Additionally, solvent selection also affects on content of targeted compounds, where phenols amount depends on polarity of solvent. Hence, the aim of this study was to examine the effect of temperature (75 and 100 °C), static time (5 and 10 min) and cycle number (1, 2 and 3) on total phenols (TP) and total flavonoids (TF) content, as well as the antioxidant capacity (AC) in fennel seeds using three-step exhaustive PLE. Firstly, grinded dry fennel seeds were subjected to PLE using non-polar solvent (hexane) under the mentioned conditions in order to remove seeds' lipid fraction. Afterwards, defatted samples were extracted with polar solvents by the increasing polarity: aqueous acetone solution (30 %, v/v) followed by aqueous methanol solution (30 %, v/v). Obtained acetone (AE) and methanol (ME) extracts (n = 24) were analyzed for TP (Folin-Ciocalteu method), TF (aluminium chloride colorimetric assay) and AC [ferric reducing antioxidant power (FRAP) method]. Multivariate analysis of variance (MANOVA) and Tukey's HSD test (p ≤ 0.05) were applied for statistical analysis of collected data. Expectedly, AE were described with higher values of analyzed parameters (grand means: TP = 416.18 mg/100 g, TF = 41.87 mg/100 g, AC = 359.57 mg AAE/100 g) in comparison with ME (grand means: TP = 80.25 mg/100 g, TF = 16.41 mg/100 g, AC = 96.13 mg AAE/100 g. Furthermore, all examined influences significantly affected TP, TF and AC in all samples, except temperature on TP in ME. Thus, conditions of 100 °C/10 min/3 cycles showed the greatest yield of tested parameters in AE, while 100 °C/5 min/1 cycle were sufficient for maximum TP and AC levels in ME. Regarding TF in ME, slightly longer extraction time was required to achieve the highest efficiency (100 °C/10 min/1 cycle).