Nuclear factor erythroid-2 related factor 2 (Nrf2) is a vital transcription factor that regulates the anti-oxidative defense system. Previous reports suggested that the expression of the Nrf2 gene can be regulated by epigenetic modifications. The potential epigenetic effect of taxifolin (TAX), a potent cancer chemopreventive agent, in skin cancer chemoprotection is unknown. In this study, we investigated how Nrf2 is epigenetically regulated by TAX in JB6 P+ cells. TAX was found to inhibit the 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced colony formation of JB6 P+ cells. TAX induced antioxidant response element (ARE)-luciferase activity in HepG2-C8 cells and up-regulated mRNA and protein levels of Nrf2 and its downstream genes heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase 1 (NQO1), in JB6 P+ cells. Furthermore, bisulfite genomic sequencing revealed that TAX treatment reduces the methylation level of the first 15 CpGs sites in the Nrf2 promoter. Western blotting showed that TAX inhibits the expression levels of DNA methyltransferase (DNMT) and histone deacetylase (HDAC) proteins. In summary, our results revealed that TAX can induce expression of Nrf2 and its downstream target genes in JB6 P+ cells by CpG demethylation. These finding suggest that TAX may exhibit a skin cancer preventive effect by activating Nrf2 via an epigenetic pathway.

A rapid and sensitive LC-MS/MS method based on the Triple Quad system has been developed and validated for the determination and pharmacokinetics of taxifolin and its nanodispersion in rat plasma. Taxifolin plasma samples along with butylparaben (internal standard) were pre-treated by liquid-liquid extraction with ethyl acetate, and then separated on a SB-C₁₈ RRHD column (150 mm × 2.1 mm × 1.8 μm) using isocratic elution with a run time of 3.0 min. The mobile phase was acetonitrile–water (90:10, v/v) containing 5 mM ammonium acetate at a flow rate of 0.4 mL/min. Quantification of taxifolin was performed by the electrospray ionization tandem mass spectrometry in the multiple reaction monitoring (MRM) mode with negative atmospheric ionization at m/z 303.0→285.0 for taxifolin and 193.1→92.0 for I.S., respectively. The calibration curve of taxifolin showed good linearity over a concentration range of 5.0–4280 ng/mL with a correlation coefficient of 0.9995. The limit of quantification (LLOQ) was 5.0 ng/mL. Intra-day, inter-day precision and accuracy (percent relative to standard deviation) were all within 8% at three concentration levels. A total recovery of taxifolin and I.S. was beyond 75%. The present LC-MS/MS method was successfully applied to pharmacokinetic studies of taxifolin after intravenous administration of taxifolin, oral administration of its physical mixture and nanodispersion. The absolute bioavailability of taxifolin was calculated as 0.75% for taxifolin nanodispersion and 0.49% for taxifolin, respectively.

Thin-layer chromatography (TLC) bioautography is an evolving technology that integrates the separation and analysis technology of TLC with biological activity detection technology, which has shown a steep rise in popularity over the past few decades. It connects TLC with convenient, economic and intuitive features and bioautography with high levels of sensitivity and specificity. In this study, we discuss the research progress of TLC bioautography and then establish a definite timeline to introduce it. This review summarizes known TLC bioautography types and practical applications for determining antibacterial, antifungal, antitumor and antioxidant compounds and for inhibiting glucosidase, pancreatic lipase, tyrosinase and cholinesterase activity constitutes. Nowadays, especially during the COVID-19 pandemic, it is important to identify original, natural products with anti-COVID potential compounds from Chinese traditional medicine and natural medicinal plants. We also give an account of detection techniques, including in situ and ex situ techniques; even in situ ion sources represent a major reform. Considering the current technical innovations, we propose that the technology will make more progress in TLC plates with higher separation and detection technology with a more portable and extensive scope of application. We believe this technology will be diffusely applied in medicine, biology, agriculture, animal husbandry, garden forestry, environmental management and other fields in the future.

Three new germacrane-type sesquiterpenoids, heishuixiecaoline A–C (compounds 1–3), were isolated along with ten known compounds 4–13 from fraction of Valeriana amurensis roots and rhizomes effective against Alzheimer’s disease (AD). The structures of 1–3 were elucidated on the basis of their spectroscopic data. We also investigated the protective effect of compounds 1–13 on the neurotoxicity of PC12 cells induced by amyloid-beta (Aβ_25–25), respectively. As a result, germacrane-type sesquiterpenoids 1–4 and lignans 5–7 were seen to afford protection against Aβ-induced toxicity in PC 12 cells. This study will contribute to revealing the chemical basis for the therapeutic effect of V. amurensis against AD.

A rapid, simple and sensitive ultra-performance liquid chromatography-electrospray-ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) method was developed and validated for the simultaneous determination of aesculin, aesculetin, fraxetin, fraxin and polydatin in beagle dog plasma for the first time. Plasma samples were pretreated by protein precipitation with methanol. Chromatographic separation was performed on an Acquity UPLC HSS T3 C18 column (2.1 mm × 100 mm, 1.8 μm) with gradient elution at a flow rate of 0.4 mL/min, using a mobile phase consisting of 0.1% formic acid (A) and acetonitrile (B). The analytes and IS were detected by multiple reaction monitoring (MRM) via negative ion mode with ion transitions of m/z 339.1–m/z 176.8 for aesculin, m/z 176.8–m/z 88.9 for aesculetin, m/z 206.8–m/z 192.1 for fraxetin, m/z 369.1–m/z 206.9 for fraxin, m/z 389.1–m/z 227.0 for polydatin and m/z 415.2–m/z 295.1 for puerarin. This method was validated according to the FDA guidelines and the results met the requirements of analysis. The calibration curves of analytes were linear with correlation coefficients more than 0.9980. The intra- and inter-day precisions were less than 15% and the accuracy was within ±15%. The maximum plasma concentration (Cmax) of aesculin, aesculetin, fraxetin, fraxin and polydatin was 46.75 ± 7.46, 209.9 ± 57.65, 369.7 ± 48.87, 67.04 ± 12.09 and 47.14 ± 12.04 ng/mL, respectively. The time to reach the maximum plasma concentration (Tmax) was 1.32 ± 0.38 h for aesculin, 1.03 ± 0.27 h for aesculetin, 0.94 ± 0.23 h for fraxetin, 0.83 ± 0.18 h for fraxin and 1.15 ± 0.15 h for polydatin. The results indicated that the absorption of aesculin might be slow in beagle dog plasma. This method was successfully applied for pharmacokinetics in beagle dog plasma after oral administration of the extracts of Ledum palustre L. at a dosage of 0.27 g/kg.