Phenolic Characterization and Bioactivity of Fennel Seed (Foeniculum vulgare Mill.) Extracts Isolated by Microwave-Assisted and Conventional Extraction

Abstract

The aim of this study was to evaluate the effectiveness of microwave-assisted extraction (MAE) as an environmentally friendly approach compared to conventional heat-reflux extraction (CE) for the isolation of fennel (Foeniculum vulgare Mill.) seed polyphenols and to assess the bioactivity of the obtained extracts. Water, ethanol (30%, v/v) and acetone (30%, v/v) were used as extraction solvents, and the extraction was carried out varying the temperature (40, 60 and 80 °C), irradiation time (5 and 10 min) and microwave power (300 and 600 W). According to the total phenolic content (TPC), 30% acetone at 80 °C after 5 min of irradiation at 300 W proved to be the optimal MAE conditions for obtaining the highest yield of polyphenols. The phenolic profile of both extracts comprised 21 compounds, with cinnamic acids and flavonols being the most abundant. When compared to CE, the MAE extract showed a lower amount of TPC as well as the sum of all identified individual phenols, although both extracts showed similar antioxidant capacity. The antimicrobial activity of the extract with the highest phenolic content was weak, showing inhibitory activity only against Pseudomonas fragi, Shewanella putrefaciens and Campylobacter jejuni strains, while Gram-positive bacteria and yeasts were not sensitive to the extract.

Maximizing the Recovery of Phenolic Antioxidants from Wild Strawberry (Fragaria vesca) Leaves Using Microwave-Assisted Extraction and Accelerated Solvent Extraction

“…To the best of our knowledge, our study is the first to identify derivatives of myricetin in the leaves of wild strawberry. Compounds 16 and 18 were identified as quercetin-3-glucuronide and kaempferol-3-glucuronide, respectively, according to previous work [37]. Compounds 6, 7, 11, 21, and 27 were identified as isorhamnetin-3-rhamnoside, isorhamnetin-3-hexoside, kaempferol-3-O-hexoside, kaempferol-3-O-deoxyhexoside, and kaempferol-3-O-pentoside, respectively, following previous work [35].…”

“…UPLC/MS-MS analysis was performed to investigate the phenolic profile of wild strawberry leaf extracts obtained using the defined optimal MAE and ASE parameters. A total of 54 phenolics, consisting of phenolic acids, proanthocyanidins, flavonols, flavan-3ols, and flavones, were identified through a comparison with their authentic standards or on the basis of their molecular formulas, exact mass measurements, and MS/MS fragmentations, as presented in previous works [34][35][36][37] by our experts (specified below). Among the phenolic acids, compounds 1, 3, 5, 12, 13, and 39 were identified as ferulic, rosmarinic, chlorogenic, syringic, caffeic, and gallic acids, respectively, through a comparison with authentic standards.…”

Effect of Instant Controlled Pressure Drop (DIC) on Polyphenols, Flavonoids and Antioxidant Capacity of Green Lentils (Lens culinaris)

“…In particular, raw GL has been reported to have a total chlorophyll content of approximately 90 μg/g [ 15 ]. Therefore, chlorophyll can interfere with the Folin–Ciocalteu reagent, increasing the absorbance value and therefore the estimated content of total phenols in raw GL [ 16 , 17 , 18 ].…”

Nutraceutical Aspects of Selected Wild Edible Plants of the Italian Central Apennines

“…This low antimicrobial activity also seems to be related to strain susceptibility and the essential oil's composition, which is poor in components such as carvacrol and thymol, which are usually associated with higher antimicrobial activity [294]. Other authors specifically describe controversial antimicrobial properties obtained using different extraction methods [295].…”