Protective effects of Quercus acuta Thunb. fruit extract against UVB-induced photoaging through ERK/AP-1 signaling modulation in human keratinocytes

Background Quercus acuta Thunb. (Fagaceae) or Japanese evergreen oak is cultivated as an ornamental plant in South Korea, China, Japan, and Taiwan and used in traditional medicine. The acorn or fruit of Quercus acuta Thunb. (QAF) is the main ingredient of acorn jelly, a traditional food in Korea. Its leaf was recently shown to have potent xanthine oxidase inhibitory and anti-hyperuricemic activities; however, there have been no studies on the biological activity of QAF extracts. Solar ultraviolet light triggers photoaging of the skin, which increases the production of reactive oxygen species (ROS) and expression of matrix metalloproteinase (MMPs), and destroys collagen fibers, consequently inducing wrinkle formation. The aim of this study was to investigate the effect of water extracts of QAF against UVB-induced skin photoaging and to elucidate the underlying molecular mechanisms in human keratinocytes (HaCaT). Methods In this study, we used HPLC to identify the major active components of QAF water extracts. Anti-photoaging effects of QAF extracts were evaluated by analyzing ROS procollagen type I in UVB-irradiated HaCaT keratinocytes. Antiradical activity was determined using 2,2-diphenyl-1-picrylhydrazyl and 2,20-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) assays. The expression of MMP-1 was tested by western blotting and ELISA kits. QAF effects on phosphorylation of the MAPK (p38, JNK, and ERK) pathway and transcription factor AP-1, which enhances the expression of MMPs, were analyzed by western blots. Results We identified two major active components in QAF water extracts, gallotannic acid and ellagic acid. The QAF aqueous extracts recovered UVB-induced cell toxicity and reduced oxidative stress by inhibiting intracellular ROS generation in HaCaT cells. QAF rescued UVB-induced collagen degradation by suppressing MMP-1 expression. The anti-photoaging activities of QAF were associated with the inhibition of UVB-induced phosphorylation of extracellular signal-regulated kinase (ERK) and activator protein 1 (AP-1). Our findings indicated that QAF prevents UVB-induced skin damage due to collagen degradation and MMP-1 activation via inactivation of the ERK/AP-1 signaling pathway. Overall, this study strongly suggests that QAF exerts anti-skin-aging effects and is a potential natural biomaterial that inhibits UVB-induced photoaging. Conclusion These results show that QAF water extract effectively prevents skin photoaging by enhancing collagen deposition and inhibiting MMP-1 via the ERK/AP-1 signaling pathway.

Quercus acuta Thunb. (Fagaceae) and Its Component, Isoquercitrin, Inhibit HSV-1 Replication by Suppressing Virus-Induced ROS Production and NF-κB Activation

HSV-1 is a neurotropic virus that replicates lytically during acute infection and establishes latency in peripheral neurons. Currently, the clinically approved compounds for the prevention of HSV-1 infection include acyclovir and penciclovir; however, long-term use of the drug is associated with serious side effects, and drug-resistant strains often appear. Therefore, it is important to find a safe and novel antiviral agent for HSV-1 infection. Quercus acuta Thunb. (Fagaceae) (QA) is widely distributed as an ornamental and dietary plant in Korea, Taiwan, China, and Japan. Thus far, the effects of QA extract and its active ingredients are known to have antioxidant, antibacterial, and anti-inflammatory activity, but studies of possible antiviral effects have not been reported. We studied the antiviral effects and molecular mechanism of QA after HSV-1 infection at the cellular level. We confirmed that QA suppresses ROS expression after HSV-1 infection and also suppresses inflammatory cytokine expression through inhibition of NF-кB activity. In addition, we found that QA increases the phosphorylation activity of IRF3 through induction of TBK1 activity during HSV-1 infection. QA exhibits an antiviral effect, and we confirmed through UPLC-DAD-mass spectrometer (MS)/MS analysis that it contains five main components: catechin, chlorogenic acid, fraxin, isoquercitrin, and taxifolin. Of these, isoquercitrin was confirmed to exhibit an antiviral effect on SK-N-SH cells through ICP27 inhibition. Overall, our results suggest that QA is a novel inhibitor with antiviral effects against HSV-1 infection and may be used specifically to prevent and treat of herpes simplex virus encephalitis infection.

Vegetation structure and distribution characteristics of Symplocos prunifolia, a rare evergreen broad-leaved tree in Korea

Background In Korea, Symplocos prunifolia Siebold. & Zucc. is only found on Jeju Island. Conservation of the species is difficult because little is known about its distribution and natural habitat. The lack of research and survey data on the characteristics of native vegetation and distribution of this species means that there is insufficient information to guide the management and conservation of this species and related vegetation. Therefore, this study aims to identify the distribution and vegetation associated with S. prunifolia. Results As a result of field investigations, it was confirmed that the native S. prunifolia communities were distributed in 4 areas located on the southern side of Mt. Halla and within the evergreen broad-leaved forest zones. Furthermore, these evergreen broad-leaved forest zones are themselves located in the warm temperate zone which are distributed along the valley sides at elevations between 318 and 461 m. S. prunifolia was only found on the south side of Mt. Halla, and mainly on south-facing slopes; however, small communities were found to be growing on northwest-facing slopes. It has been confirmed that S. prunifolia trees are rare but an important constituent species in the evergreen broad-leaved forest of Jeju. The mean importance percentage of S. prunifolia community was 48.84 for Castanopsis sieboldii, 17.79 for Quercus acuta, and 12.12 for Pinus thunbergii; S. prunifolia was the ninth most important species (2.6). Conclusions S. prunifolia can be found growing along the natural streams of Jeju, where there is little anthropogenic influence and where the streams have caused soil disturbance through natural processes of erosion and deposition of sediments. Currently, the native area of S. prunifolia is about 3300 m2, which contains a confirmed population of 180 individual plants. As a result of these low population sizes, it places it in the category of an extremely endangered plant in Korea. In some native sites, the canopy of evergreen broad-leaved forest formed, but the frequency and coverage of species were not high. Negative factors that contributed to the low distribution of this species were factors such as lacking in shade tolerance, low fruiting rates, small native areas, and special habitats as well as requiring adequate stream disturbance. Presently, due to changes in climate, it is unclear whether this species will see an increase in its population and habitat area or whether it will remain as an endangered species within Korea. What is clear, however, is that the preservation of the present native habitats and population is extremely important if the population is to be maintained and expanded. It is also meaningful in terms of the stable conservation of biodiversity in Korea. Therefore, based on the results of this study, it is judged that a systematic evaluation for the preservation and conservation of the habitat and vegetation management method of S. prunifolia should be conducted.

Analysis of the Active Constituents and Evaluation of the Biological Effects of Quercus acuta Thunb. (Fagaceae) Extracts

We evaluated the antioxidant and antibacterial activity of hexnane, ethyl acetate, acetone, methanol, ethanol, and water extracts of the Quercus acuta leaf. The antioxidant properties were evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, reducing power, and total phenolic content. Antibacterial activity was assessed against general infectious pathogens, including antibiotic-resistant clinical isolates. The methanolic extract showed the highest DPPH radical scavenging activity and total phenolic content, while the reducing power was the highest in the water extract. The ethyl acetate extract showed the best antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) strains. Additionally, it displayed antibacterial activity against Staphylococcus aureus KCTC1928, Micrococcus luteus ATCC 9341, Salmonella typhimurium KCTC 1925, Escherichia coli KCTC 1923, and eight MRSA strains. These results present basic information for the possible uses of the ethanolic and ethyl acetate extracts from Q. acuta leaf in the treatment of diseases that are caused by oxidative imbalance and antibiotic-resistant bacterial infections. Six active compounds, including vitamin E, which are known to possess antioxidant and antibacterial activity, were identified from the extracts. To the best of our knowledge, this is the first study that reports the chemical profiling and antibacterial effects of the various QA leaf extracts, suggesting their potential use in food therapy or alternative medicine.

In Vitro and In Vivo Studies on Quercus acuta Thunb. (Fagaceae) Extract: Active Constituents, Serum Uric Acid Suppression, and Xanthine Oxidase Inhibitory Activity

Quercus acuta Thunb. (Fagaceae) (QA) is cultivated as a dietary and ornamental plant in China, Japan, South Korea, and Taiwan. It has been widely used as the main ingredient of acorn tofu, a traditional food in China and South Korea. The aim of this study was to determine in vitro and in vivo xanthine oxidase (XO) inhibitory and antihyperuricemic activities of an ethyl acetate extract of QA leaf (QALE) and identify its active phytochemicals using gas chromatography-mass spectrometry (GC-MS) and liquid chromatography (LC) systems. The QALE was found to possess potent in vitro antioxidant and XO inhibitory activities. In vivo study using hyperuricemic mice induced with potassium oxonate demonstrated that the QALE could inhibit hepatic XO activity at a relatively low oral dose (50 mg/kg) and significantly alleviate hyperuricemia to a similar extent as allopurinol. Several active compounds including vitamin E known to possess XO inhibitory activity were identified from the QALE. To the best of our knowledge, this is the first study that reports the active constituents and antihyperuricemic effect of QA, suggesting that it is feasible to use QALE as a food therapy or alternative medicine for alleviating hyperuricemia and gout.