The aim of this study was to investigate the effects of different cooking methods on the hepatoprotective effects of purple sweet potatoes against alcohol-induced damage in HepG2 cells. Purple sweet potatoes (Ipomeoea batatas L. Danjami) were subjected to different cooking methods, including steaming, roasting, and microwaving. Steaming resulted in a higher cytoprotective effect against alcohol damage than the other cooking methods. Additionally, the highest inhibition of glutathione depletion and production of reactive oxygen species against alcohol-induced stress were observed in raw and/or steamed purple sweet potatoes. Compared to roasted and/or microwaved samples, steamed samples significantly increased the expression of NADPH quinone oxidoreductase 1, heme oxygenase 1, and gamma glutamate-cysteine ligase in alcohol-stimulated HepG2 cells via the activation of nuclear factor erythroid 2-related factor 2. Moreover, ten anthocyanins were detected in the raw samples, whereas five, two, and two anthocyanins were found in the steamed, roasted, and microwaved samples, respectively. Taken together, steaming purple sweet potatoes could be an effective cooking method to protect hepatocytes against alcohol consumption. These results provide useful information for improving the bioactive properties of purple sweet potatoes using different cooking methods.

Yoonjeong Kim, Jihwan Kim, Sungup Kim, Min Young Kim, and Younghwa Kim. Prev Nutr Food Sci 2024;29:563-71. https://doi.org/10.3746/pnf.2024.29.4.563

In this study, we evaluated the antioxidant activities of esculetin and four synthesized derivatives (E1, 2-oxo-2H-1-benzopyran-6,7-diyl diacetate; E2, 7-hydroxy-2-oxo-2H-1-benzopyran-6-yl acetate; E3, 7-(methoxymethoxy)-2-oxo-2H-1-benzopyran-6-yl acetate; E4, 7-hydroxy-2-oxo-2H-1-benzopyran-6-yl 2,4-dinitrobenzene-1-sulfonate) against oxidative stress in hepatocytes. In HepG2 cells, treatment with 1 mM tert-butyl hydroperoxide (TBHP) reduced cell viability to 40%, while co-treatment with esculetin restored cell viability. Among the esculetin derivatives, E2 exhibited the most significant cytoprotective effect, while E4 showed the lowest. Furthermore, E2 at 25 µM concentration showed the similar effects to esculetin in reducing ROS generation and preventing glutathione depletion. The treatment of E2 also enhanced the expression of HO-1 and GCLC proteins against oxidative stress. On the other hand, TBHP-induced oxidative stress decreased antioxidant activities including glutathione reductase, glutathione peroxidase, and catalase; however, E2 significantly increased these antioxidant activities. These findings suggest that the esculetin derivative, particularly E2, possesses potential as an antioxidant aimed at enhancing physiological functions.

Jina Lee, Yoonjeong Kim, Heon-Woong Kim, Dongyup Hahn, and Younghwa Kim. Journal of the Korean Society of Food Science and Nutrition 2024;53:1166-77. https://doi.org/10.3746/jkfn.2024.53.11.1166

Yoonjeong Kim, Jung-Min Choi, and Younghwa Kim. Journal of the Korean Society of Food Science and Nutrition 2022;51:107-14. https://doi.org/10.3746/jkfn.2022.51.2.107

The levels of lignans and the antioxidant capacity of perilla oils (15 types, PO) consumed in Korea were determined. Mass spectrometry coupled with liquid chromatography was used for measuring the lignan content in the perilla oil, while the antioxidant activity was analyzed using the contents of polyphenols and flavonoids along with radical scavenging activity. The range of the total lignan content was 15.281 to 1,336.688 μg/100 g, with PO3 demonstrating the highest amount. The antioxidant activity showed that PO5 had the highest polyphenol content and radical scavenging capacity, while PO2 showed the highest flavonoid content. Radical scavenging activity showed a strong correlation with polyphenol content. These results indicate that perilla oil could function as a functional food, particularly with respect to antioxidant activity.