Screening of mammalian DNA polymerase and topoisomerase inhibitors from Garcinia mangostana L. and analysis of human cancer cell proliferation and apoptosis

β-Mangostin targets and suppresses glioma via STING activation and tumor-associated microglia polarization

Glioma, a common and highly malignant central nervous system tumor, markedly influences patient prognosis via interactions with glioma-associated macrophages. Previous research has revealed the anticancer potential of β-mangostin, a xanthone derivative obtained from the mangosteen fruit. This research investigated the role of β-mangostin on microglia in the glioma microenvironment and evaluated the efficacy of β-mangostin combined with anti-PD-1 antibody (αPD-1) in glioma-bearing mice. The results showed that, β-mangostin attenuated M2 polarization in BV2 cells and promoted M1-related interleukin (IL)-1β and IL-6 secretion, thereby inhibiting glioma invasion. In addition, β-mangostin improved the anti-glioma effects of αPD-1 and increased CD8+T cell and M1-type microglia infiltration. Mechanistically, β-mangostin bound to the stimulator of interferon genes (STING) protein, which is crucial for the anti-tumor innate immune response, and promoted STING phosphorylation in microglia, both in vivo and in vitro. These results provide insights into its mode of action and supporting further investigation into β-mangostin as a therapeutic agent.

Bioactivities of β-mangostin and its new glycoside derivatives synthesized by enzymatic reactions

Beta-mangostin is a xanthone commonly found in the genus Garcinia. Unlike α-mangostin, to date, there have only been a few studies on the biological activity and derivatization of β-mangostin. In this study, two novel glycosylated derivatives of β-mangostin were successfully synthesized via a one-pot enzymatic reaction. These derivatives were characterized as β-mangostin 6-O-β-d-glucopyranoside and β-mangostin 6-O-β-d-2-deoxyglucopyranoside by TOF ESI/MS and 1H and 13C NMR analyses. Beta-mangostin showed cytotoxicity against KB, MCF7, A549 and HepG2 cancer cell lines, with IC50 values ranging from 15.42 to 21.13 µM. The acetylcholinesterase and α-glucosidase inhibitory activities of β-mangostin were determined with IC50 values of 2.17 and 27.61 µM, respectively. A strong anti-microbial activity of β-mangostin against Gram-positive strains (Bacillus subtilis, Lactobacillus fermentum and Staphylococcus aureus) was observed, with IC50 values of 0.16, 0.18 and 1.24 µg ml-1, respectively. Beta-mangostin showed weaker activity against Gram-negative strains (Salmonella enterica, Escherichia coli and Pseudomonas aeruginosa) as well as Candida albicans fungus, with IC50 and MIC values greater than the tested concentration (greater than 32 µg ml-1). The new derivatives of β-mangostin showed weaker activities than those of β-mangostin, demonstrating the important role of the hydroxyl group at C-6 of β-mangostin in its bioactivity.

The purple mangosteen (Garcinia mangostana): Defining the anticancer potential of selected xanthones

The purple mangosteen (Garcinia mangostana) is a popular Southeast Asian fruit that has been used traditionally for its health promoting benefits for years. Unique to the mangosteen are a class of phytochemicals known as xanthones that have been reported to display significant anti-cancer and anti-tumor activities, specifically through the promotion of apoptosis, targeting of specific cancer-related proteins, or modulation of cell signaling pathways. α-Mangostin, the most abundant xanthone isolated from the mangosteen, has received substantial attention as it has proven to be a potent phytochemical, specifically as an anticancer agent, in numerous different cancer cell studies and cancer animal models. While the mechanisms for these anticancer effects have been reported in many studies, lesser xanthones, including gartanin, β-mangostin, γ-mangostin, garcinone C, and garcinone E, and mangosteen extracts from the pericarp, roots, rind, and stem show promise for their anticancer activity but their mechanisms of action are not as well developed and remain to be determined. Mangosteen products appear safe and have been well tolerated in human clinical trials where they show antioxidant activity, though their clinical anticancer activity has not yet been evaluated. This review summarizes the work that has been done to explore and explain the anticancer and antitumor activities of α-mangostin, lesser xanthones, and mangosteen extracts in vitro, in vivo, and in humans in various cancers.

β-Mangostin inhibits the metastatic power of cervical cancer cells attributing to suppression of JNK2/AP-1/Snail cascade

β-Mangostin is a natural mangostin with potent anticancer activity against various cancers. In this study, we further explored the anticancer activity of β-mangostin on cervical cancer cells. β-Mangostin did not affect cell viability and cell cycle distribution in HeLa and SiHa cells; however, it dose-dependently inhibited the migration and invasion of both the human cervical cancer cell lines. In addition, we observed that β-mangostin suppressed the expression of integrin αV and β3 and the downstream focal adhesion kinase/Src signaling. We also found that Snail was involved in the β-mangostin inhibited cell migration and invasion of HeLa cell. Then, our findings showed that β-mangostin reduced both nuclear translocation and messenger RNA expression of AP-1 and demonstrated that AP-1 could target to the Snail promoter and induce Snail expression. Kinase cascade analysis and reporter assay showed that JNK2 was involved in the inhibition of AP-1/Snail axis by β-mangostin in HeLa cells. These results indicate that β-mangostin can inhibit the mobility and invasiveness of cervical cancer cells, which may attribute to the suppression of both integrin/Src signaling and JNK2-mediated AP-1/Snail axis. This suggests that β-mangostin has potential antimetastatic potential against cervical cancer cells.

Phloroglucinol Benzophenones and Xanthones from the Leaves of Garcinia cowa and Their Nitric Oxide Production and α-Glucosidase Inhibitory Activities

Five new compounds-two phloroglucinol benzophenones, garciniacowones F (1) and G (2), and three xanthones, garciniacowones H (3), I (4), and J (5)-together with seven known xanthones (6-12) were isolated from the fresh leaves of Garcinia cowa. Their structures were elucidated by detailed analysis of NMR and MS data. Compounds 1 and 2 are phloroglucinol benzophenones containing a polyprenylated bicyclo[3.3.1]nonane ring system, while compounds 3-5 are rare xanthones having farnesyl (3 and 5) and geranylgeranyl (5) units at C-8. Compounds 1, 3, 4, 7, 8, and 10 exhibited inhibitory effects on NO production in LPS-induced RAW264.7 macrophage cells with IC₅₀ values ranging from 5.4 to 18.6 μM. Compounds 4 and 8 had α-glucosidase inhibitory activities with IC₅₀ values of 15.4 and 11.4 μM, respectively, which were more potent than that of the acarbose control.

β-mangostin suppresses human hepatocellular carcinoma cell invasion through inhibition of MMP-2 and MMP-9 expression and activating the ERK and JNK pathways

β-mangostin is a dietary xanthone that has been reported to have the anticancer properties in some human cancer cell types. However, the antimetastatic effect and molecular mechanism of β-mangostin action in human hepatocellular carcinoma (HCC) cells remain unknown. In this study, we found that β-mangostin did not induce cytotoxicity in human HCC cells (SK-Hep-1, Huh-7 and HA22T/VGH cells). β-mangostin could inhibit migration and invasion of human HCC cells. Meanwhile, β-mangostin significantly decreased the protein activities and expression of matrix metalloproteinase (MMP)-2 and MMP-9 via increasing the activation of MEK1/2, ERK1/2, MEK4 and JNK1/2 signaling pathways. Furthermore, using specific inhibitor for ERK1/2 (PD98059) and JNK1/2 (JNKII) significantly restored the expression of MMP-2/-9 and invasion by β-mangostin treatment in Huh-7 cells. In addition, β-mangostin effectively restored the protein levels and transcription activity of MMP-2 and MMP-9 in siERK or siJNK-transfected Huh-7 cells, concomitantly with promotion on cell migration and invasion. Taken together, these findings are the first to demonstrate the antimetastatic activity of β-mangostin against human HCC cells, which may act as a promising therapeutic agent for the treatment of HCC.

Medicinal properties of mangosteen (Garcinia mangostana L.): A comprehensive update

Garcinia mangostana L. (Clusiaceae) is a tropical tree native to Southeast Asia known as mangosteen which fruits possess a distinctive and pleasant taste that has granted them the epithet of "queen of the fruits". The seeds and pericarps of the fruit have a long history of use in the traditional medicinal practices of the region, and beverages containing mangosteen pulp and pericarps are sold worldwide as nutritional supplements. The main phytochemicals present in the species are isoprenylated xanthones, a class of secondary metabolites with multiple reports of biological effects, such as antioxidant, pro-apoptotic, anti-proliferative, antinociceptive, anti-inflammatory, neuroprotective, hypoglycemic and anti-obesity. The diversity of actions displayed by mangosteen xanthones shows that these compounds target multiple signaling pathways involved in different pathologies, and place them as valuable sources for developing new drugs to treat chronic and degenerative diseases. This review article presents a comprehensive update of the toxicological findings on animal models, and the preclinical anticancer, analgesic, neuroprotective, antidiabetic and hypolipidemic effects of G. mangostana L. extracts and its main isolates. Pharmacokinetics, drug delivery systems and reports on dose-finding human trials are also examined.

DNA Repair in Despair-Vitamin D Is Not Fair

The role of vitamin D as a treatment option for neoplastic diseases, once considered to have a bright future, remains controversial. The preclinical studies discussed herein show compelling evidence that Vitamin D Derivatives (VDDs) can convert some cancer and leukemia cells to a benign phenotype, by differentiation/maturation, cell cycle arrest, or induction of apoptosis. Furthermore, there is considerable, though still evolving, knowledge of the molecular mechanisms underlying these changes. However, the attempts to clearly document that the treatment outcomes of human neoplastic diseases can be positively influenced by VDDs have been, so far, disappointing. The clinical trials to date of VDDs, alone or combined with other agents, have not shown consistent results. It is our contention, shared by others, that there were limitations in the design or execution of these trials which have not yet been fully addressed. Based on the connection between upregulation of JNK by VDDs and DNA repair, we propose a new avenue of attack on cancer cells by increasing the toxicity of the current, only partially effective, cancer chemotherapeutic drugs by combining them with VDDs. This can impair DNA repair and thus kill the malignant cells, warranting a comprehensive study of this novel concept. J. Cell. Biochem. 117: 1733-1744, 2016. © 2016 Wiley Periodicals, Inc.