Indole oligomers from a marine sponge-associated bacterium Psychrobacter sp

Vegetable-derived indole enhances the melanoma-treating efficacy of chemotherapeutics

Food-drug interaction is an important but overlooked issue. For example, little is known concerning whether or not the chemotherapy of cancers is affected by the well-defined dietary chemicals such as 2-(indol-3-ylmethyl)-3,3'-diindolylmethane (LTr1) derived from daily consumed cruciferous vegetables. This work, inspired by the described melanogenesis reduction by certain indoles, presents that LTr1 mitigates the melanogenesis and thus potentiates the in vitro and in vivo anti-melanoma effectiveness of different chemotherapeutic agents including dacarbazine, vemurafenib, and sorafenib. In B16 melanoma cells, LTr1 was shown to inhibit the melanogenesis by acting towards the regulatory (R) subunit of protein kinase A (PRKAR1a) associated with the phosphorylation of cAMP-response element binding protein (CREB). This allows LTr1 to reduce the expression of melanogenesis-related enzymes such as tyrosinase (TYR), tyrosinase-related protein 1 (TYRP1), and tyrosinase-related protein 2 (TYRP2). Furthermore, LTr1 was addressed to bind to the aryl hydrocarbon receptor (AhR) and up-regulate the expression of CYP1A1 encoding cytochrome P450 1A1, leading to the escalation of reactive oxygen species (ROS) level. The increased ROS generation promotes the cysteine-to-cystine transformation to inhibit the pheomelanogenesis in melanomas. Collectively, the work identifies LTr1 as a new melanogenesis inhibitor that modulates the PKA/CREB/MITF and AhR/CYP1A1/ROS pathways, thereby providing a new option for (re)sensitizing melanomas to chemotherapeutics.

Anti-osteoclastogenic Effects of Indole Alkaloids Isolated from Barley (Hordeum vulgare Var. Hexastichon) Grass

As part of our continuous program to identify new potential candidates for controlling osteolytic bone diseases from natural products, the alkaloid fraction of barley (Hordeum vulgare var. hexastichon) grass (HVA) significantly inhibited RANKL-induced osteoclast formation and protected mice from LPS-induced bone loss. A phytochemical investigation of HVA afforded nine indole alkaloids, including one new compound [hordeumin A (1)] and eight known analogues (2-9). Of them, four (1, 2, 4, and 5) were anti-osteoclastogenic compounds. Of these four, compound 5 significantly suppressed RANKL-induced osteoclast formation, actin ring formation, and bone resorption in a concentration-dependent manner. It also suppressed the RANKL-induced NF-κB and MAPK signaling pathways and the activation of c-Fos and NFATc1. Compound 5 also reduced the expression levels of osteoclast-specific marker genes, including TRAP, CtsK, DC-STAMP, OSCAR, and MMP9. Our findings suggest that HVA and its alkaloid constituents could be valuable candidates for the prevention and treatment of osteolytic bone diseases.

Post-ingestion conversion of dietary indoles into anticancer agents

There are health benefits from consuming cruciferous vegetables that release indole-3-carbinol (I3C), but the in vivo transformation of I3C-related indoles remains underinvestigated. Here we detail the post-ingestion conversion of I3C into antitumor agents, 2-(indol-3-ylmethyl)-3,3^′-diindolylmethane (LTr1) and 3,3^′-diindolylmethane (DIM), by conceptualizing and materializing the reaction flux derailing (RFD) approach as a means of unraveling these stepwise transformations to be non-enzymatic but pH-dependent and gut microbe-sensitive. In the upper (or acidic) gastrointestinal tract, LTr1 is generated through Michael addition of 3-methyleneindolium (3MI, derived in situ from I3C) to DIM produced from I3C via the formaldehyde-releasing (major) and CO₂-liberating (minor) pathways. In the large intestine, ‘endogenous’ I3C and DIM can form, respectively, from couplings of formaldehyde with one and two molecules of indole (a tryptophan catabolite). Acid-producing gut bacteria such as Lactobacillus acidophilus facilitate the H⁺-promotable steps. This work updates our understanding of the merits of I3C consumption and identifies LTr1 as a drug candidate.

Biological and Chemical Diversity of Marine Sponge-Derived Microorganisms over the Last Two Decades from 1998 to 2017

Marine sponges are well known as rich sources of biologically natural products. Growing evidence indicates that sponges harbor a wealth of microorganisms in their bodies, which are likely to be the true producers of bioactive secondary metabolites. In order to promote the study of natural product chemistry and explore the relationship between microorganisms and their sponge hosts, in this review, we give a comprehensive overview of the structures, sources, and activities of the 774 new marine natural products from sponge-derived microorganisms described over the last two decades from 1998 to 2017.

Cytotoxic Natural Products from Marine Sponge-Derived Microorganisms

A growing body of evidence indicates that marine sponge-derived microbes possess the potential ability to make prolific natural products with therapeutic effects. This review for the first time provides a comprehensive overview of new cytotoxic agents from these marine microbes over the last 62 years from 1955 to 2016, which are assorted into seven types: terpenes, alkaloids, peptides, aromatics, lactones, steroids, and miscellaneous compounds.

Marine natural products

Covering: 2010. Previous review: Nat. Prod. Rep., 2011, 28, 196. This review covers the literature published in 2010 for marine natural products, with 895 citations (590 for the period January to December 2010) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1003 for 2010), together with the relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.