Chemical Analysis and Biological Activities of Extracts Isolated from Symbiotic L. japonicus Plants.

Plants produce a wide variety of secondary metabolites, including compounds with biological activities that could be used for the treatment of human diseases. In the present study, we examined the putative production of bioactive molecules in the legume plant Lotus japonicus, which engages into symbiotic relationships with beneficial soil microorganisms. To monitor the production of secondary metabolites when the plant develops beneficial symbiotic relationships, we performed single and double inoculations with arbuscular mycorrhizal fungi (AMF) and nitrogen-fixing Rhizobium bacteria. Plant extracts from non-inoculated and inoculated plants were chemically characterized and tested for anti-proliferative, apoptotic, and anti-inflammatory effects on human HEK-293 cells. Both shoot and root extracts from non-inoculated and inoculated plants significantly reduced the HEK-293 cell viability; however, a stronger effect was observed when the root extracts were tested. Shoot and root extracts from Rhizobium-inoculated plants and shoot extracts from AMF-inoculated plants showed apoptotic effects on human cells. Moreover, both shoot and root extracts from AMF-inoculated plants significantly reduced TNFα-induced NF-κB transcriptional activity, denoting anti-inflammatory activity. These results suggest that symbiotic L. japonicus plants are enriched with metabolites that have interesting biological activities and could be further explored for putative future use in the pharmaceutical sector.

A Reliable Enantioselective Route to Mono-Protected N1-Cbz Piperazic Acid Building Block.

The chiral N1-Cbz, N2-H derivative of the piperazic acid monomer is a valuable building block in the total synthesis of natural products, comprising this nonproteinogenic amino acid. In that context, we wish to report an improved synthetic protocol for the synthesis of both (3R)- and (3S)-piperazic acids bearing the carboxybenzyl protecting group (Cbz) selectively at the N1 position. Our method builds on previously reported protocols, circumventing their potential shortcomings, and optimizing the ultimate selective deprotection at the N2 position, thus, offering an efficient and reproducible pathway to suitably modified piperazates in high optical purity.

APD-Containing Cyclolipodepsipeptides Target Mitochondrial Function in Hypoxic Cancer Cells.

The natural product family of macrocyclic lipodepsipeptides containing the 4-amido-2,4-pentadienoate functionality possesses intriguing cytotoxic selectivity toward hypoxic cancer cells. These subpopulations of cancer cells display increased metastatic potential and resistance to chemo- and radiotherapy. In this paper, we present studies on the mechanism of action of these natural products in hypoxic cancer cells and show that this involves rapid and hypoxia-selective collapse of mitochondrial integrity and function. These events drive a regulated cell death process that potentially could function as a powerful tool in the fight against chemo- and radiotherapy-resistant cancer cells. Toward that end, we demonstrate activity in two different mouse tumor models.

Pharmacophore Mapping of Thienopyrimidine-Based Monophosphonate (ThP-MP) Inhibitors of the Human Farnesyl Pyrophosphate Synthase.

The human farnesyl pyrophosphate synthase (hFPPS), a key regulatory enzyme in the mevalonate pathway, catalyzes the biosynthesis of the C-15 isoprenoid farnesyl pyrophosphate (FPP). FPP plays a crucial role in the post-translational prenylation of small GTPases that perform a plethora of cellular functions. Although hFPPS is a well-established therapeutic target for lytic bone diseases, the currently available bisphosphonate drugs exhibit poor cellular uptake and distribution into nonskeletal tissues. Recent drug discovery efforts have focused primarily on allosteric inhibition of hFPPS and the discovery of non-bisphosphonate drugs for potentially treating nonskeletal diseases. Hit-to-lead optimization of a new series of thienopyrimidine-based monosphosphonates (ThP-MPs) led to the identification of analogs with nanomolar potency in inhibiting hFPPS. Their interactions with the allosteric pocket of the enzyme were characterized by crystallography, and the results provide further insight into the pharmacophore requirements for allosteric inhibition.

Total Synthesis and Biological Evaluation of Rakicidin†A and Discovery of a Simplified Bioactive Analogue.

We report a concise asymmetric synthesis of rakicidin A, a macrocyclic depsipeptide that selectively inhibits the growth of hypoxic cancer cells and stem-like leukemia cells. Key transformations include a diastereoselective organocatalytic cross-aldol reaction to build the polyketide portion of the molecule, a highly hindered ester fragment coupling reaction, an efficient Helquist-type Horner-Wadsworth-Emmons (HWE) macrocyclization, and a new DSC-mediated elimination reaction to construct the sensitive APD portion of rakicidin A. We further report the preparation of a simplified structural analogue (WY1) with dramatically enhanced hypoxia-selective activity.

The amido-pentadienoate-functionality of the rakicidins is a thiol reactive electrophile--development of a general synthetic strategy.

We demonstrate that a unique class-defining functionality (mc-APD) found in macrocyclic natural products with potent anti-cancer activity, imparts these compounds with electrophilic reactivity. The mc-APD group represents an interesting structural hybrid between canonical biologically relevant Michael-acceptors. Further, a novel thiol-elimination method for preparation of the mc-APD group is outlined.

Ester coupling reactions--an enduring challenge in the chemical synthesis of bioactive natural products.

In this review we investigate the use of complex ester fragment couplings within natural product total synthesis campaigns. We first outline the different biosynthetic and chemical strategies for performing complex ester couplings and on this mechanistic background we then present and discuss a collection of successful examples from the literature.

Steroidal cardiac Na+/K+ ATPase inhibitors exhibit strong anti-cancer potential in vitro and in prostate and lung cancer xenografts in vivo.

Sodium potassium pump (Na(+)/K(+)ATPase) is a validated pharmacological target for the treatment of congestive heart failure. Recent data with inotropic drugs such as digoxin & digitoxin (digitalis) suggest a potent anti-cancer action of these drugs and promote Na(+)/K(+)ATPase as a novel therapeutic target in cancer. However, digitalis have narrow therapeutic indices, are pro-arrhythmic and are considered non-developable drugs by the pharmaceutical industry. On the contrary, a series of recently-developed steroidal inhibitors showed better pharmacological properties and clinical activities in cardiac patients. Their anti-cancer activity however, remained unknown. In this study, we synthesized seventeen steroidal cardiac inhibitors and explored for the first time their anti-cancer activity in vitro and in vivo. Our results indicate potent anti-cancer actions of steroidal cardiac inhibitors in multiple cell lines from different tumor panels including multi-drug resistant cells. Furthermore, the most potent compound identified in our studies, the 3-[(R)-3- pyrrolidinyl]oxime derivative 3, showed outstanding potencies (as measured by GI50, TGI and LC50 values) in most cells in vitro, was selectively cytotoxic in cancer versus normal cells showing a therapeutic index of 31.7 and exhibited significant tumor growth inhibition in prostate and lung xenografts in vivo. Collectively, our results suggest that previously described cardiac Na(+)/K(+)ATPase inhibitors have potent anti-cancer actions and may thus constitute strong re-purposing candidates for further cancer drug development.

Organocatalytic asymmetric domino Michael-Henry reaction for the synthesis of substituted bicyclo[3.2.1]octan-2-ones.

The first organocatalytic asymmetric reaction between 1,4-cyclohexanedione and nitroalkenes has been studied, affording bicyclo[3.2.1]octane derivatives containing four continuous stereogenic centres. The products were obtained through a domino Michael-Henry process as a single diastereoisomer with excellent enantioselectivities.