Hyeon Ji Yeo’s research while affiliated with Chungnam National University and other places

Background: Tissue culture is an important strategy for metabolite accumulation in plants. Moreover, adventitious roots can produce high levels of phytochemicals. Actinostemma lobatum is consumed as a medicinal plant in South Korea, China, India, and Thailand. In this study, we aimed to identify the effects of darkness and light on metabolic changes and antioxidant activity in the adventitious roots of A. lobatum. Methods and Results: To confirm metabolic changes and antioxidant activity, adventitious roots of A. lobatum were grown under appropriate conditions and separated into dark and light treatment groups. Light conditions were found to more significantly influence the accumulation of natural pigments, such as chlorophyll a [0.136 ± 0.001 ㎎·g-1 dry weight (DW)] and total carotenoids (0.047 ± 0.001 ㎎·g-1 DW), than dark conditions (0.072 ± 0.001 ㎎·g-1 DW and 0.026 ± 0.003 ㎎·g-1 DW, respectively). Moreover, the light treatment group had substantially high contents of total phenolic, flavonoid, and rutin compounds (11.273 ± 0.291 gallic acid equivalent (GAE)·㎎·g-1 DW, 9.943 ± 0.28 quercetin equivalent (QE)·㎎·g-1 DW, and 2.136 ± 0.491 ㎎·g-1 DW, respectively). These results revealed that light stimulates the accumulation of secondary metabolites, such as phenolics and flavonoids, and enhances antioxidant activity in the adventitious roots of A. lobatum. Conclusions: Light conditions can considerably influence the production of health-beneficial metabolites in the adventitious roots of A. lobatum. This provides an understanding of metabolism in adventitious roots for further experimental studies on environmentally sustainable plant secondary metabolite production. In this study, we show that suitable root cultures have the potential to be used as supplements in the pharmaceutical and nutraceutical industries.

Background: Scutellaria baicalensis is a traditional medicinal plant that is rich in bioactive flavonoids, the accumulation of which can be impacted by environmental factors, including salinity. We aimed to determine the effects of different sodium chroride (NaCl) concentrations on the growth, flavonoid biosynthesis, and antioxidant activity of S. baicalensis hairy root cultures. Methods and Results: We examined the effects of NaCl at various concentrations (0, 30, 50, 100, 200, and 300 mM) on biomass production, flavonoid content, and antioxidant properties of S. baicalensis hairy roots and found that biomass production was impaired by salinity, with 50 mM NaCl significantly reducing the biomass. High performance liquid chromatography of flavonoids at different salinity levels indicated high levels of baicalin, baicalein, and wogonin at an NaCl concentration of 100 mM (moderate salinity-induced metabolic activation). Flavonoid synthesis was inhibited under high salinity conditions (200 mM - 300 mM NaCl); under these conditions, some flavonoids were undetectable. Higher radical scavenging and redox potentials were detected at an NaCl concentration of 100 mM, with lower IC50 values in DPPH and ABTS, and reducing power antioxidant assays (compared to control conditions). Conclusions: These results emphasize the importance of moderate salt stress in promoting bioactive compound production by S. baicalensis, providing information on its potential for cultivation under stress-adapted conditions and practical applications for medical use.

Background Scutellaria baicalensis roots contain root-specific flavones (baicalin, baicalein, and wogonin) exhibiting strong biological effects. Hence, this plant is considered the best plant material for hairy root system applications. Results In this study, we obtained hairy roots, which are considered natural genetically modified organisms, from S. baicalensis leaves in vitro using wild Agrobacterium rhizogenes (A. rhizogenes) R1000 and investigated the effects of postharvest wounding treatment on their flavone production and in vitro antimicrobial properties. Hairy roots were exposed to wounding stress, and the levels of baicalin, baicalein, and wogonin were determined using high-performance liquid chromatography (HPLC). We found that the levels of these flavones in S. baicalensis hairy roots increased after 6, 12, 24, 48, 72, and 96 h of exposure in a time-dependent manner. In particular, the highest production of three flavones was reported after exposure to 96 h of wounding stress. Furthermore, the expression levels of genes involved in root-specific flavone pathways (SbPAL1, SbPAL2, SbPAL3, SbCCL7, SbCHS2, SbCHI, SbFNS2-2, SbCYP82D1.1, and SbF8H) were determined at two time points (control and after 96 h of exposure). Expression levels of SbPAL1, SbCHS2, SbCHI, and SbCYP82D1.1 were significantly increased following exposure to wounding stress. Antimicrobials were observed with seven normal pathogens, two multidrug-resistant pathogens, and one pathogenic yeast. Moreover, the inhibition zone sizes of these bacteria were larger in the wounded S. baicalensis hairy roots with higher levels of baicalin, baicalein, and wogonin than in those with lower levels of these flavones. In addition to antimicrobial activities, the wounded hairy roots exhibited stronger anti-inflammatory and antioxidant activities than the controls. Conclusions Our results indicate that postharvest wounding treatment is a good strategy to increase flavone production and enhance the antibacterial activity of S. baicalensis hairy root cultures. Graphic Abstract

Beech mushrooms (Hypsizygus marmoreus) are edible mushrooms commercially used in South Korea. They can be classified into white and brown according to their pigmentation. This study analyzed the metabolites and biological activities of these mushrooms. Specifically, 42 metabolites (37 volatiles, two phenolics, and three carbohydrates) were quantified in white beech mushrooms, and 47 (42 volatiles, two phenolics, and three carbohydrates) were detected in brown mushrooms. The major volatiles detected were hexanal, pentanal, 1-hexanol, and 1-pentanol. Brown mushrooms contained higher levels of hexanal (64%) than white mushrooms (35%), whereas white mushrooms had higher levels of pentanal (11%) and 1-pentanol (3%). Most volatiles were more abundant in white mushrooms than in brown mushrooms. Furthermore, brown beech mushrooms had a higher phenolic content than white mushrooms. Biological assays revealed that both types of mushroom demonstrated anti-microbial activities against bacterial and yeast pathogens and weak DPPH scavenging activity. The extracts from both mushrooms (50 μg/mL) also exhibited strong anti-inflammatory properties. Brown mushroom extracts showed higher antioxidant, anti-microbial, and anti-inflammatory properties than white mushroom extracts. This study reported that the differences in phenotype, taste, and odor were consistent with the metabolite differences between white and brown beech mushrooms, which have high nutritional and biofunctional values.

Background: The peptidyl-prolyl isomerase (PIN1) plays a vital role in cellular processes, including intracellular signaling and apoptosis. While oxidative stress is considered one of the primary mechanisms of pathogenesis in brain ischemic injury, the precise function of PIN1 in this disease remains to be elucidated. Objective: We constructed a cell-permeable PEP-1–PIN1 fusion protein and investigated PIN1’s function in HT-22 hippocampal cells as well as in a brain ischemic injury gerbil model. Methods: Transduction of PEP-1–PIN1 into HT-22 cells and signaling pathways were determined by Western blot analysis. Intracellular reactive oxygen species (ROS) production and DNA damage was confirmed by DCF-DA and TUNEL staining. Cell viability was determined by MTT assay. Protective effects of PEP-1-PIN1 against ischemic injury were examined using immunohistochemistry. Results: PEP-1–PIN1, when transduced into HT-22 hippocampal cells, inhibited cell death in H2O2-treated cells and markedly reduced DNA fragmentation and ROS production. This fusion protein also reduced phosphorylation of mitogen-activated protein kinase (MAPK) and modulated expression levels of apoptosis-signaling proteins in HT-22 cells. Furthermore, PEP-1–PIN1 was distributed in gerbil hippocampus neuronal cells after passing through the blood–brain barrier (BBB) and significantly protected against neuronal cell death and also decreased activation of microglia and astrocytes in an ischemic injury gerbil model. Conclusions: These results indicate that PEP-1–PIN1 can inhibit ischemic brain injury by reducing cellular ROS levels and regulating MAPK and apoptosis-signaling pathways, suggesting that PIN1 plays a protective role in H2O2-treated HT-22 cells and ischemic injury gerbil model.

Pakchoi (Brassica rapa subsp. chinensis) is one of the most widely consumed vegetables in Asian countries, and it is high in secondary metabolites. The availability, quantity, and quality of light play a critical role in the growth and development of plants. In this study, we investigated the effect of LEDs (light-emitting diodes; white, blue, red, and red + blue) on anthocyanin, glucosinolates, and phenolic levels in red pakchoi baby leaves. On the 24th day after sowing (DAS), red baby pakchoi leaves were harvested, and shoot length, root length, and fresh weight were measured. Among the different LED treatments, there was no significant difference in shoot length, whereas the highest root length was achieved in the red + blue LED treatment (23.8 cm). The fresh weight also showed a significant difference among the different LED treatments. In total, 12 phenolic and 7 glucosinolate individual compounds were identified using high-performance liquid chromatography (HPLC) analysis. The highest total glucosinolate (2937 μg/g dry wt) and phenolic (1589 μg/g dry wt) contents were achieved in baby leaves exposed to red + blue light. Similarly, the highest contents of total anthocyanins (1726 μg/g dry wt), flavonoids (4920 μg/g dry wt), and phenolics (5900 μg/g dry wt) were achieved in the red + blue treatment. Plants exposed to red + blue LED light showed the highest accumulation of anthocyanin, glucosinolates, and phenolic compounds. For antioxidant activity, DPPH (2,2-diphenyl-1-picrylhydrazylradical) free radical scavenging, ABTS (2,2-azinobis (3-ethylbenzothiazoline)-6-sulfonic acid) radical scavenging, and reducing power assays were performed, and the antioxidant activity of red pakchoi baby leaves grown under red + blue LED light was found to be the best. The metabolic profiling of the identified metabolites revealed distinct separation based on the secondary metabolites. This research will be helpful for farmers to choose the best LED light combination to increase the secondary metabolic content in pakchoi plants.

Light-emitting diodes (LEDs) are regarded as an effective artificial light source for producing sprouts, microgreens, and baby leaves. Thus, this study aimed to investigate the influence of different LED lights (white, red, and blue) on the biosynthesis of secondary metabolites (glucosinolates, carotenoids, and phenolics) and the biological effects on kale microgreens. Microgreens irradiated with white LEDs showed higher levels of carotenoids, including lutein, 13-cis-β-carotene, α-carotene, β-carotene, and 9-cis-β-carotene, than those irradiated with red or blue LEDs. These findings were consistent with higher expression levels of carotenoid biosynthetic genes (BoPDS and BoZDS) in white-irradiated kale microgreens. Similarly, microgreens irradiated with white and blue LEDs showed slightly higher levels of glucosinolates, including glucoiberin, progoitrin, sinigrin, and glucobrassicanapin, than those irradiated with red LEDs. These results agree with the high expression levels of BoMYB28-2, BoMYB28-3, and BoMYB29 in white- and blue-irradiated kale microgreens. In contrast, kale microgreens irradiated with blue LEDs contained higher levels of phenolic compounds (gallic acid, catechin, ferulic acid, sinapic acid, and quercetin). According to the total phenolic content (TPC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) inhibition assays, the extracts of kale microgreens irradiated with blue LEDs had slightly higher antioxidant activities, and the DPPH inhibition percentage had a positive correlation with TPC in the microgreens. Furthermore, the extracts of kale microgreens irradiated with blue LEDs exhibited stronger antibacterial properties against normal pathogens and multidrug-resistant pathogens than those irradiated with white and red LEDs. These results indicate that white-LED lights are suitable for carotenoid production, whereas blue-LED lights are efficient in increasing the accumulation of phenolics and their biological activities in kale microgreens.