Screening of growth inhibitors for epithelial-mesenchymal transition-induced cells by TGF-ß from plant-based sources identified the active compound hydroxychavicol from Piper bitle.

Epithelial-mesenchymal transition (EMT) has recently been associated with cancer invasion, metastasis, and resistance. In our previous study, we discovered nanaomycin K, a natural growth inhibitor for EMT-induced Madin Darby canine kidney (MDCK) cells, from the cultured broth of actinomycetes. However, the screening method was undeveloped, because the activity of nanaomycin K was discovered accidentally. In this study, we established a screening method by analyzing the characteristics of nanaomycin K in MDCK cells. Nanaomycin K showed the characteristic growth inhibitory activity on MDCK cells cultured under four conditions: medium containing dimethyl sulfoxide, SB431542, TGF-ß, and a mixture of SB431542 and TGF-ß. The activity was stronger in TGF-ß-treated cells than in DMSO-treated cells. In the mixture of SB431542 and TGF-ß-treated cells, the activity of nanaomycin K was suppressed. The anti-cancer agents, mitomycin C, cisplatin, and staurosporine, lacked the characteristics as that of nanaomycin K for these four treatment conditions. Since these four conditions distinguish between the effects of nanaomycin K and other anti-cancer agents in EMT-induced cells, the screening method was established. Among the 13,427 plant extracts tested, Piper betle leaf extract displayed growth inhibitory activity against EMT-induced cells. Through the purification of the extract via bio-guided fractionation, hydroxychavicol was isolated as an active compound. The cytotoxic activity of hydroxychavicol was stronger in EMT-induced MDCK cells than in control cells. However, its cytotoxic activity was suppressed in EMT-inhibited cells. Furthermore, hydroxychavicol exhibited same activity against SAS cells (human squamous cell carcinoma of the tongue). Thus, we have successfully established a screening method for growth inhibitors of EMT-induced cells and have discovered an inhibitor from plant-based sources.

Phenanthroindolizine alkaloids from Boehmeria sieboldiana leaves exhibit cytotoxicity against human cancer cell lines.

To explore useful natural compounds from indigenous medicinal plants, the cytotoxic properties from a methanolic extract of Boehmeria sieboldiana leaves against human cancer cell lines were isolated in the present study. After purification of the extract, seco-dehydroantofine B (1) together with two known phenanthroindolizine alkaloids, seco-dehydroantofine A (2) and septicine (3), were isolated. The structure of seco-dehydroantofine B was elucidated by performing comprehensive one- and two-dimensional nuclear magnetic resonance spectroscopy and high-resolution electrospray ionization mass spectrometry. The cytotoxicity of these compounds against five human tumor cell lines was evaluated. Compound 3 exhibited anti-tumor activity at IC50 values of 50.0, 66.9, 50.0, and 153.7 µM against MKN1, SAS, HL-60, and THP-1 cells, respectively.

Toxicity of Jegosaponins A and B from Styrax japonica Siebold et al. Zuccarini in Prostate Cancer Cells and Zebrafish Embryos Resulting from Increased Membrane Permeability.

(1) Background: Screening of medicinal herbs is one of the most powerful approaches to identifying novel therapeutic molecules against many human diseases. To avoid potential harmful effects during medicinal use, toxicity testing is necessary in the early stages of drug discovery. The objective of this study was to identify the cytotoxic mechanisms of jegosaponin A and B from Styrax japonica Siebold et al. Zuccarini; (2) Methods: We screened Japanese medicinal herb extracts using PC-3 prostate cancer cells and found that a methanol extract isolated from the unripe fruit of Styrax japonica Siebold et al. Zuccarini (SJSZ) had an inhibitory effect on cell viability. We further performed fractionation assays with PC-3 cells and identified the bioactive compounds using LC/MS and NMR analysis. We clarified the toxic mechanisms of these compounds using PC-3 cells and zebrafish embryos; (3) Results: We identified two active molecules, jegosaponin A and jegosaponin B, in the inhibitory fractions of the methanol extract. These jegosaponins are toxic to zebrafish embryos during the early developmental stage. Jegosaponin A and B showed strong haemolytic activity in sheep defibrinated blood (EC50 = 2.1 µM, and 20.2 µM, respectively) and increased the cell membrane permeability in PC-3 cells and zebrafish embryos, which were identified using a membrane non-permeable DRAQ7, a fluorescent nucleus staining dye; (4) We identified the cytotoxic compounds jegosaponin A and B from SJSZ, which we showed to exhibit cell membrane disruptive properties using cell- and zebrafish-based testing.

Endotoxin Contamination and Reaction Interfering Substances in the Plant Extract Library.

Endotoxin is an unintentional contaminant that has numerous activities and can affect various biological experiments using cells. In this study, we measured the endotoxin activity of samples from a plant extract library (PEL) and determined their degrees of contamination. Endotoxin was detected in approx. 48% (n = 139) and approx. 4% (n = 5) of field-collected and crude drug samples, respectively, and in concentrations >5.0 EU/mL in some samples. The concentrations of endotoxin that affect cells in vitro vary depending on the target cell type. Although the degree of contamination varied in the present study, it was considered to have little effect on the cell experiments. More than 150 PEL samples had problems with reaction courses or recovery rates of Limulus amoebocyte lysate (LAL) tests. In the LAL tests, using three plant extracts [Sanguisorba officinalis L. (Rosaceae), Oenothera biennis L. (Onagraceae), and Lythrum salicaria L. (Lythraceae)], the polyphenolic compounds in the plant extracts affected LAL test and their effects differed depending on the plant species. When the 16 single polyphenol compounds were added to the LAL tests, the compounds with caffeoyl and pyrogallol moieties were found to affect the LAL reaction course and recovery rate. Furthermore, none of the compounds had any effects at concentrations of 1 µM. Because the plant extracts contained analogs of various polyphenolic compounds, they were presumed to actually act synergistically. Our findings demonstrated that attention must be paid to the recovery rate and reaction process of LAL tests with samples containing polyphenolic compounds.