This study evaluated the biological activity and cytoprotective effect of guava (Psidium guajava L.) branch against oxidative stress. The contents of vitamin C, beta-carotene, total carotenoids, quercetin and catechin determined were 26.783, 43.676, 65.083, 58.245, and 8.309 mg/100 g, respectively. To measure antioxidant activity, the guava branch was extracted using various concentrations of ethanol (60, 80, or 100%) and water. The highest content of polyphenols (0.245 mg gallic acid equivalent/mg residue) and flavonoids (0.128 mg cathechin equivalent/mg residue) was found in the 100% ethanol extract of the branch (E100). Moreover, E100 also possessed the highest radical scavenging activities and showed the highest inhibition rate of α-glucosidase (77.692%). E100 was the most effective extract to impart cytoprotectant activity against oxidative stress in HepG2 cells. Taken together, our results determine the promising antioxidant activity of guava branch, and indicate the potential to be applied as a natural antioxidant.

This study examined the bioactive compound content and the antioxidant activities of bitter melon (Momordica charantia Linn.) leaves. The content of vitamin C, beta-carotene, and total carotenoids was 69.77, 45.68, and 65.08 mg/100 g, respectively. To investigate the antioxidant capacity, bitter melon leaves were extracted using various concentrations of ethanol (60, 80, or 100%). Highest content of total polyphenols (18.07 mg gallic acid equivalent/g) and flavonoids (4.53 mg cathechin equivalent/g) was found in the 100% ethanolic extract of the leaves (E100). Also, the E100 extract showed the highest levels of 2,2'azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and α-α-diphenyl-β-picrylhydrazyl (DPPH) free radical scavenging activities. Reducing power was also the highest (39.21 mg Trolox equivalent/g) in E100 extract. The E100 extract effectively inhibited lipid peroxidation by 91.45% compared to the control group. Also, the E100 extract showed a cytoprotective effect against oxidative stress in HepG2 cells and decreased the generation of intracellular reactive oxygen species. These results suggest that bitter melon leaves could be regarded as a potential source of natural antioxidants.

In this study, biotin (vitamin B7) contents of frequently consumed foods in Korea were determined by using immunoaffinity column in conjunction with high-performance liquid chromatography (HPLC). The biotin contents of 24 foods of plant origin and 27 foods of animal origin were selected. The highest biotin contents in frequently consumed foods of plant origin were found in red beans (Huinguseul; 11.475 μg/100 g). On the other hand, biotin was not detected in any varieties of sorghum. For frequently consumed foods of animal origin, salted pollack roe (7.486 μg/100 g) showed the highest biotin content. However, beef and fish contained less biotin. All biotin analyses were conducted under analytical quality control. The limits of detection and limits of quantification of biotin were 0.007 and 0.023 μg/100 g, respectively, and the accuracy/recovery percentage was 95.35-105.02%. The precision values were 4.041% (repeatability) and 3.835% (reproducibility). Taken together, our data provide reliable data on the biotin contents of frequently consumed foods in Korea.

The purpose of this study was to evaluate the antioxidant and hepatocyte protective effects of guava (Psidium guajava L.) leaves cultivated in Korea. The contents of the total polyphenol of the extract was 271.57 mg gallic acid equivalent (GAE)/ g residue. Antioxidant activities of leaf extract were evaluated by examining the free radical scavenging ability. 2,2'-azinobis-( 3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and α-α-diphenyl-β-picrylhydrazyl (DPPH) free radical scavenging activities of the extract were 1133.23 mg trolox equivalent antioxidant capacity (TEAC)/g residue and 721.68 mg TEAC/g residue, respectively. The hepatocyte protective effect of guava leaf extract was examined in HepG2 cells. Against tert-butyl hydroperoxide (TBHP), the viability of HepG2 cells were increased by the treatment of leaf extract. In addition, guava leaf extract led to the inhibition of reactive oxygen species (ROS) generated in HepG2 cells. The leaf extract increased the activity of glutathione (GSH), glutathione reductase (GR), and glutathione peroxidase (GPx) against oxidative stress. These results suggested that guava leaves might be regarded as a potential source natural antioxidant and a hepatoprotective material.

The purpose of this study was to evaluate the antioxidant and anti-adipogenic activities of Ligularia stenocephala (L. stenocephala) extract. The contents of the total polyphenol of the extract was 55.950 mg GAE/g residue. Antioxidant activities of L. stenocephala were evaluated by free radical scavenging ability and a reducing power test. 2,2'azino-bis- (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and α-α-diphenyl-β-picrylhydrazyl (DPPH) free radical scavenging activities of the extract were approximately 90% and 70%, respectively. Reducing power of the extract was 258.833 mg TE/g residue. The anti-adipogenic activity of L. stenocephala extract was examined in 3T3-L1 cells. During adipocyte differentiation, the 3T3-L1 cells were treated both with and without the extract. L. stenocephala extract suppressed the lipid accumulation in a concentration-dependent manner in the 3T3-L1 cells. The L. stenocephala extract inhibited the expression of peroxisome proliferator activated receptor γ (PPARγ) and adipocyte protein 2 (aP2) proteins, compared with control adipocytes. These results indicate that L. stenocephala could be regarded as a potential source natural antioxidant and an anti-obesity agent.