Xanthone-rich extract from Gentiana dinarica transformed roots and its active component norswertianin induce autophagy and ROS-dependent differentiation of human glioblastoma cell line

Research Progress of Natural Small-Molecule Compounds Related to Tumor Differentiation

Tumor differentiation is a therapeutic strategy aimed at reactivating the endogenous differentiation program of cancer cells and inducing cancer cells to mature and differentiate into other types of cells. It has been found that a variety of natural small-molecule drugs can induce tumor cell differentiation both in vitro and in vivo. Relevant molecules involved in the differentiation process may be potential therapeutic targets for tumor cells. Compared with synthetic drugs, natural small-molecule antitumor compounds have the characteristics of wide sources, structural diversity and low toxicity. In addition, natural drugs with structural modification and transformation have relatively concentrated targets and enhanced efficacy. Therefore, using natural small-molecule compounds to induce malignant cell differentiation represents a more targeted and potential low-toxicity means of tumor treatment. In this review, we focus on natural small-molecule compounds that induce differentiation of myeloid leukemia cells, osteoblasts and other malignant cells into functional cells by regulating signaling pathways and the expression of specific genes. We provide a reference for the subsequent development of natural small molecules for antitumor applications and promote the development of differentiation therapy.

Xanthones Production in Gentiana dinarica Beck Hairy Root Cultures Grown in Simple Bioreactors

The hairy root clones of Gentiana dinarica cl-B, cl-D, cl-3, and cl-14 were cultivated in parallel in diverse simple bioreactors, including temporary immersion systems RITA^® (TIS RITA^®), bubble column bioreactors (BCB), and Erlenmeyer flasks (EF), and evaluated for biomass production and xanthone content. The obtained results showed that TIS RITA^® and BCB containing ½ MS medium with 4% sucrose provided equally good growth conditions in which the majority of the clones displayed the higher percentage of dry matter (DM%), and xanthones norswertianin-1-O-primeveroside (nor-1-O-prim) and norswertianin production than those cultivated in EF. Thin and well branched hairy root clone cl-B grown in BCB for 7 weeks was superior regarding all growth parameters tested, including growth index (19.97), dry weight (2.88 g), and DM% (25.70%) compared to all other clones. Cl-B cultured in TIS RITA^® contained the highest amount of nor-1-O-prim (56.82 mg per vessel). In BCB with constant aeration, cl-B accumulated the highest norswertianin content reaching 18.08 mg/vessel. The optimized conditions for cultivation of selected G. dinarica hairy root clones in highly aerated TIS RITA^® and BCB systems contribute to the development of bioreactor technology designed for the large scale commercial production of xanthones nor-1-O-prim and norswertianin.

Antioxidant and anticancer potentials of edible flowers: where do we stand?

Edible flowers are attracting special therapeutic attention and their administration is on the rise. Edible flowers play pivotal modulatory roles on oxidative stress and related interconnected apoptotic/inflammatory pathways toward the treatment of cancer. In this review, we highlighted the phytochemical content and therapeutic applications of edible flowers, as well as their modulatory potential on the oxidative stress pathways and apoptotic/inflammatory mediators, resulting in anticancer effects. Edible flowers are promising sources of phytochemicals (e.g., phenolic compounds, carotenoids, terpenoids) with several therapeutic effects. They possess anti-inflammatory, anti-diabetic, anti-microbial, anti-depressant, anxiolytic, anti-obesity, cardioprotective, and neuroprotective effects. Edible flowers potentially modulate oxidative stress by targeting erythroid nuclear transcription factor-2/extracellular signal-regulated kinase/mitogen-activated protein kinase (Nrf2/ERK/MAPK), reactive oxygen species (ROS), nitric oxide (NO), malondialdehyde (MDA) and antioxidant response elements (AREs). As the interconnected pathways to oxidative stress, inflammatory mediators, including tumor necrosis factor (TNF)-α, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), interleukins (ILs) as well as apoptotic pathways such as Bcl-2-associated X protein (Bax), Bcl-2, caspase and cytochrome C are critical targets of edible flowers in combating cancer. In this regard, edible flowers could play promising anticancer effects by targeting oxidative stress and downstream dysregulated pathways.

Antioxidant vitamins promote anticancer effects on low-concentration methotrexate-treated glioblastoma cells via enhancing the caspase-3 death pathway

Vitamin C and vitamin E are well-known antioxidant vitamins, both of which are also applied as adjunct treatments for cancer therapy. Methotrexate (MTX) is a clinical drug that is used widely for rheumatoid arthritis and cancer treatment. Human glioblastoma multiforme (GBM) is an aggressive malignant brain tumor; the mean survival time for GBM patients is <2 years with traditional therapies. Developing and investigating novel treatments are important for clinical GBM therapy. Therefore, the aim of this study was to investigate whether combined treatment with vitamin C/E and MTX can display anticancer activities on GBM. Our studies showed that MTX displays anticancer effects on GBM in a dose-dependent manner, while vitamins C and E are not cytotoxic to glioblastoma. Importantly, this study showed that vitamins C and E can promote anticancer effects on low-concentration methotrexate-treated glioblastoma. Additionally, this study suggested that MTX alone or combined with vitamins C/E inhibits GBM cell growth via the caspase-3 death pathway.

Genus Gentiana: A review on phytochemistry, pharmacology and molecular mechanism

ETHNOPHARMACOLOGICAL RELEVANCE

As the largest genus of Gentianaceae family, the Gentiana genus harbors over 400 species, widely distributed in the alpine areas of temperate regions worldwide. Plants from Gentiana genus are traditionally used to treat a wide variety of diseases including easing pain dispelling rheumatism, and treating liver jaundice, chronic pharyngitis and arthritis in China since ancient times. In this review, a systematic and constructive overview of the traditional uses, phytochemistry, molecular mechanisms, toxicology and pharmacological activities of the researched species of genus Gentiana is provided.

MATERIALS AND METHODS

The used information in this review is based on various databases (PubMed, Science Direct, Wiley online library, Wanfang Data, Web of Science) through a search using the keyword "Gentiana" in the period of 1981-2019. Besides, other ethnopharmacological information was acquired from Chinese herbal classic books and Chinese pharmacopoeia 2015 edition.

RESULTS

The plants from Gentiana genus have a long tradition of various medicinal uses in Europe and Asia. Phytochemical studies showed that the main bioactive components isolated from this genus includes iridoids xanthones and flavonoids. These compounds and extracts isolated from this genus show a wide range of protective activities including hepatic protection, gastrointestinal protection, cardiovascular protection, immunomodulation, joint protection, pulmonary protection, bone protection and reproductive protection. Molecular mechanism studies also indicated several potential therapeutic targets in the treatment of certain diseases by plants from this genus. Besides, natural products from this plant show no significant animal toxicity, cytotoxicity or genotoxicity.

CONCLUSION

This review summarized the traditional medicinal uses, phytochemistry, pharmacology, toxicology and molecular mechanism of genus Gentiana, providing references and research tendency for plant-based drug development and further clinical studies.

In Vivo Screening of Xanthones from Garcinia oligantha Identified Oliganthin H as a Novel Natural Inhibitor of Convulsions

Epilepsy is a chronic neurological disorder, characterized by recurrent, spontaneous, and transient seizures, and affects more than 70 million people worldwide. Although two dozen antiepileptic drugs (AEDs) are approved and available in the market, seizures remain poorly controlled in one-third of epileptic patients who are suffering from drug resistance or various adverse effects. Recently, the xanthone skeleton has been regarded as an attractive scaffold for the discovery and development of emerging anticonvulsants. We had isolated several dihydroxanthone derivatives previously, including oliganthin H, oliganthin I, and oliganthin N, whose structures were similar and delicately elucidated by spectrum analysis or X-ray crystallographic data, from extracts of leaves of Garcinia oligantha. These xanthone analogues were evaluated for anticonvulsant activity, and a novel xanthone, oliganthin H, has been identified as a sound and effective natural inhibitor of convulsions in zebrafish in vivo. A preliminary structure-activity relationship analysis on the relationship between structures of the xanthone analogues and their activities was also conducted. Oliganthin H significantly suppressed convulsant behavior and reduced to about 25% and 50% of PTZ-induced activity, in 12.5 and 25 μM treatment groups (P < 0.01 and 0.001), respectively. Meanwhile, it reduced seizure activity, velocity, seizure duration, and number of bursts in zebrafish larvae (P < 0.05). Pretreatment of oliganthin H significantly restored aberrant induction of gene expressions including npas4a, c-fos, pyya, and bdnf, as well as gabra1, gad1, glsa, and glula, upon PTZ treatment. In addition, in silico analysis revealed the stability of the oliganthin H-GABAA receptor complex and their detailed binding pattern. Therefore, direct interactions with the GABAA receptor and involvement of downstream GABA-glutamate pathways were possible mechanisms of the anticonvulsant action of oliganthin H. Our findings present the anticonvulsant activity of oliganthin H, provide a novel scaffold for further modifications, and highlight the xanthone skeleton as an attractive and reliable resource for the development of emerging AEDs.

Polyphenol-Mediated Autophagy in Cancer: Evidence of In Vitro and In Vivo Studies

One of the hallmarks of cellular transformation is the altered mechanism of cell death. There are three main types of cell death, characterized by different morphological and biochemical features, namely apoptosis (type I), autophagic cell death (type II) and necrosis (type III). Autophagy, or self-eating, is a tightly regulated process involved in stress responses, and it is a lysosomal degradation process. The role of autophagy in cancer is controversial and has been associated with both the induction and the inhibition of tumor growth. Autophagy can exert tumor suppression through the degradation of oncogenic proteins, suppression of inflammation, chronic tissue damage and ultimately by preventing mutations and genetic instability. On the other hand, tumor cells activate autophagy for survival in cellular stress conditions. Thus, autophagy modulation could represent a promising therapeutic strategy for cancer. Several studies have shown that polyphenols, natural compounds found in foods and beverages of plant origin, can efficiently modulate autophagy in several types of cancer. In this review, we summarize the current knowledge on the effects of polyphenols on autophagy, highlighting the conceptual benefits or drawbacks and subtle cell-specific effects of polyphenols for envisioning future therapies employing polyphenols as chemoadjuvants.

Gentiana clusii Perr.&Song.: Enhanced production of secondary metabolites by in vitro propagation

Shoot and root in vitro culture of endemic European species Gentiana clusii was established for the first time. The effects of different concentrations of benzyl adenine (BA), 6-phurphurylaminopurine (KIN), indole-3-butyric acid (IBA) and naphthalene acetic acid (NAA) on shoot propagation and rooting of G. clusii were investigated. The optimal in vitro conditions for shoot propagation and long-term maintenance were achieved using woody plant medium (WPM) supplemented with 0.5 mg l^-1 KIN, and subsequent application of IBA at 0.5 mg l^-1 significantly improved rooting of these shoots. Root culture was established from excised root tips cultured in ½ MS liquid media with increasing concentrations of IBA (0.1-1.0 mg l^-1). A high root growth rate and considerable biomass yield were obtained by addition of 1.0 mg l^-1 IBA. HPLC analysis revealed that in vitro culture considerably promoted the production of secondary metabolites in G. clusii. The selected protocol for shoot propagation (WPM + 0.5 mg l^-1 KIN) increased the content of sweroside, gentiopicrin and norswertianin-1-O-primeveroside (N-1-P) for more than 2-fold compared with the wild plants. IBA promoted N-1-P and norswertianin production in root cultures; their contents were enhanced 6.4- and 18.6-fold, respectively, compared with the wild plants. The extract of these roots displayed the highest antioxidant capacity (IC₅₀ = 66.57 μg ml^-1). The established shoot and root propagation protocols facilitate in vitro conservation of G. clusii, and provides a promising tool for the large scale production of valuable secoiridoids and xanthones.

Astrocytes autophagy in aging and neurodegenerative disorders

Astrocytes can serve multiple functions in maintaining cellular homeostasis of the central nervous system (CNS), and normal functions for autophagy in astrocytes is considered to have very vital roles in the pathogenesis of aging and neurodegenerative diseases. Autophagy is a major intracellular lysosomal (or its yeast analog, vacuolar) clearance pathways involved in the degradation and recycling of long-lived proteins, oxidatively damaged proteins and dysfunctional organelles by lysosomes. Current evidence has shown that autophagy might influence inflammation, oxidative stress, aging and function of astrocytes. Although the interrelation between autophagy and inflammation, oxidative stress, aging or neurological disorders have been addressed in detail, the influence of astrocytes mediated-autophagy in aging and neurodegenerative disorders has yet to be fully reviewed. In this review, we will summarize the most up-to-date findings and highlight the role of autophagy in astrocytes and link autophagy of astrocytes to aging and neurodegenerative diseases. Due to the prominent roles of astrocytic autophagy in age-related neurodegenerative diseases, we believe that we can provide new suggestions for the treatment of these disorders.