We extracted and hydrolyzed bioactive flavonoids from C. unshiu peel using subcritical water (SW) in a semi-continuous mode. The individual flavonoid yields, antioxidant and enzyme inhibitory activities of the SW extracts were analyzed. The extraction yields of hesperidin and narirutin increased with increasing temperature from 145 °C to 165 °C. Hydrothermal hydrolysis products (HHP), such as monoglucosides (hesperetin-7-O-glucoside and prunin) and aglycones (hesperetin and naringenin) were obtained in the SW extracts at temperatures above 160 °C. The sum of hesperidin and its HHP in the SW extracts was strongly correlated with antioxidant activities, whereas the contents of hesperetin and naringenin were strongly correlated with enzyme inhibitory activities. Hesperetin exhibited the highest antioxidant activities (2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, ferric-reducing antioxidant power, and oxygen radical absorbance capacity), whereas hesperetin-7-O-glucoside exhibited the highest enzyme inhibitory activities (angiotensin-I converting enzyme (ACE) and pancreatic lipase (PL)). Naringenin exhibited the highest enzyme inhibitory activities (xanthine oxidase and α-glucosidase). PMFs (sinensetin, nobiletin, and tangeretin) also exhibited relatively high inhibitory activities against ACE and PL. This study confirms the potential of SW for extracting and hydrolyzing bioactive flavonoids from C. unshiu peel using an environmentally friendly solvent (water) and a shorter extraction time.

Many studies on broccoli have analyzed the functional components and their functionality in terms of antioxidant and anticancer activities; however, these studies have focused on the florets of different varieties. Investigation of the functionality of broccoli by-products such as leaves, stems, and leaf stems from different cultivars and harvest dates might be valuable for utilizing waste materials as useful food components. Total phenolics and sulforaphane contents, and antioxidant and anticancer activities were measured in the leaves, leaf stems, and stems of early-maturing (Kyoyoshi), middle-maturing (Myeongil 96), and late-maturing broccoli (SK3-085) at different harvest dates. Total phenolics in the leaves of Kyoyoshi were about 1.8-fold to 12.1-fold higher than those in all of the other cultivars and parts. The sulforaphane content of Kyoyoshi was 2.8-fold higher in the stems than in the florets. Antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity and oxygen radical absorbance capacity were highest in Kyoyoshi, followed by Myeongil 96 and SK3-085, most notably in the leaves harvested at the immature stage. Inhibition activity of cell growth against the NCI-H1299 cell lines was highest in the leaves of all cultivars in decreasing order of florets, leaf stems, and stems. The leaves harvested in October (nonflowering stage) had the highest inhibition activity, while those harvested in January (mature broccoli) showed the lowest. The results of this study demonstrate that broccoli leaves and stems contain high levels of total phenolics, and high antioxidant and anticancer activities and can provide opportunities for early-maturing broccoli as functional fresh raw vegetables.

Broccoli (Brassica oleracea var. italia) florets were extracted with 80% methanol and the extract was sequentially fractionated with n-hexane, ethyl acetate, n-butanol, and distilled water. The extract and the fractions were evaluated for total phenolic content, sulforaphane content, antioxidant activity, and anti-inflammatory activity in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. The total phenolic content and sulforaphane content of the ethyl acetate fraction (EF) were 35.5 mg gallic acid equivalents/g and 620.2 μg/g, respectively. These values were higher than those of the 80% methanol extract and organic solvent fractions. The oxygen radical absorbance capacity of the EF [1,588.7 μM Trolox equivalents (TE)/mg] was 11-fold higher than that of the distilled water fraction (143.7 μM TE/mg). The EF inhibited nitric oxide release from LPS-stimulated RAW 264.7 cells in a dose-dependent manner and inhibited IκB-α degradation and nuclear factor-κB activation in LPS-stimulated RAW 264.7 cells. In conclusion, the EF of broccoli florets exerted potent antioxidant and anti-inflammatory effects.

Dietary guidelines recommend the consumption of flavonoid-rich extracts for several health benefits. Although immature Citrus unshiu pomace (ICUP) contains high levels of flavanone glycosides, many studies have concentrated on the optimization of flavonoid extraction from mature citrus peels. Therefore, we developed an optimized extraction method for hesperidin and narirutin from ICUP, and evaluated their antioxidant activities using ten different assay methods. The extraction conditions for the highest flavonoid yields based on a response surface methodology were 80.3 °C, 58.4% (ethanol concentration), 40 mL/g (solvent/feed), and 30 min, where the hesperidin and narirutin yields were 66.6% and 82.3%, respectively. The number of extractions was also optimized as two extraction steps, where the hesperidin and narirutin yields were 92.1% and 97.2%, respectively. Ethanol was more effective than methanol and acetone. The ethanol extract showed high scavenging activities against reactive oxygen species but relatively low scavenging activities for nitrogen radicals and reactive nitrogen species. The antioxidant activities showed a higher correlation with hesperidin content than narirutin content in the extracts. This study confirms the potential of an optimized method for producing antioxidant-rich extracts for the functional food and nutraceutical industries.

Nutraceutical use of algae requires understanding of the diversity and significance of their active compositions for intended activities. Ishige okamurae (I. okamurae) extract is well-known to possess α-glucosidase inhibitory activity; however, studies are needed to investigate its active composition in order to standardize its α-glucosidase inhibitory activity. In this study, we observed the intensity of the dominant compounds of each I. okamurae extract harvested between 2016 and 2017, and the different potency of each I. okamurae extract against α-glucosidase. By comparing the anti-α-glucosidase ability of the dominant compounds, a novel Ishophloroglucin A with highest α-glucosidase inhibitory activity was identified and suggested for standardization of anti-α-glucosidase activity in I. okamurae extract. Additionally, a validated analytical method for measurement of Ishophloroglucin A for future standardization of I. okamurae extract was established in this study. We suggest using Ishophloroglucin A to standardize anti-α-glucosidase potency of I. okamurae and propose the significance of standardization based on their composition for effective use of algae as marine-derived nutraceuticals.