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The present study investigated the phenolic profile, antioxidant activity, and neuroprotective properties of ‘Tadanishiki’ yuzu (Citrus junos, a seedless variety of yuzu) according to harvesting period and extraction condition. High-performance liquid chromatography (HPLC) was used to identify the functional components. To evaluate the neuroprotective properties, scopolamine was used to induce cholinergic dysfunction in human neuroblastoma SH-SY5Y cells pretreated with yuzu extracts. Among the harvesting periods, September provided the optimum fruit weight of yuzu and relatively high amounts of total phenolics (3.67 mg/g DW), flavonoids (10.13 mg/g DW), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity (29.10 μg Vit. C eq.). Of the functional compounds, hesperidin (13.57 mg/100 g DW) and naringin (5.84 mg/100 g DW) were the highest in 5% (w/v) yuzu extracted with 80% ethanol and this extract showed the highest DPPH (289.2 μg Vit. C eq.) scavenging activity. This same extract showed the highest cell viability and lowest cortisol or acetylcholinesterase content in scopolamine-treated SH-SY5Y cells. These results indicate that ‘Tadanishiki’ yuzu harvested in September should be extracted at 5% (w/v) yuzu with 80% EtOH, and this extract might be useful for application as a natural functional additive.

This study was performed to compare the physiochemical properties and nutritional components including sugars, amino acids, and minerals of 10 common pear cultivars cultivated in Korea (four Pyrus spp.). Furthermore, the pear cultivars were characterized for functional properties with respect to phenolic compounds by HPLC/DAD analysis and antioxidant activities using DPPH and ABTS assays. Among the 10 pear cultivars that were tested, Niitaka and Hanareum pears show the best physiochemical properties such as higher sugar/acid ratio and proper firmness. They also showed relatively enriched soluble sugar (12.6 ~ 13.0 g/100g FW), amino acid (4.5 ~ 7.3 g/100 g DW) or mineral contents with high K/Na ratio. For functional properties, Niitaka and Hanareum pears have significantly higher contents of total phenolics (240 mg/100 g DW), arbutin (103 ~ 124 mg/100 g DW), and chlorogenic acid (11 mg/100 g DW) as well as strong antioxidant activities (49 % or 86 %) among cultivars. These results indicate that Niitaka, and Hanareum cultivars, could be best for consumption or favorable processing due to excellent product quality and high concentrations of nutritional and functional compounds.

The present study was the first evaluation of the arbutin content, antioxidant activity, and whitening function of the unripe pears of five major Korean pear cultivars. Unripe pears were investigated 30 days after florescence for possible utilization as a whitening ingredient, instead of being thrown away for thinning out. Among the five cultivars tested, Gamcheonbae and Manpungbae had significantly higher total phenolics and arbutin contents, while Niitaka had lower values of both total phenolics and arbutin. For whitening activity related to tyrosinase and cellular melanin formation, Manpungbae also showed the strongest tyrosinase inhibition (4.9 %), and achieved 74% reduction of the cellular melanin compared to non-treated cells. These results indicate that unripe pears, especially the Manpungbae cultivar, could be useful for application as a possible natural whitening additive with high arbutin content and excellent whitening activity.