Ugi Adducts as Novel Anti-austerity Agents against PANC-1 Human Pancreatic Cancer Cell Line: A Rapid Synthetic Approach.

Pancreatic cancer cells have an inherent tolerance to withstand nutrition starvation, allowing them to survive in hypovascular tumor microenvironments that lack of sufficient nutrients and oxygen. Developing anti-cancer agents that target this tolerance to nutritional starvation is a promising anti-austerity strategy for eradicating pancreatic cancer cells in their microenvironment. In this study, we employed a chemical biology approach using the Ugi reaction to rapidly synthesize new anti-austerity agents and evaluate their structure-activity relationships. Out of seventeen Ugi adducts tested, Ugi adduct 11 exhibited the strongest anti-austerity activity, showing preferential cytotoxicity against PANC-1 pancreatic cancer cells with a PC50 value of 0.5 µM. Further biological investigation of Ugi adduct 11 revealed a dramatic alteration of cellular morphology, leading to PANC-1 cell death within 24 h under nutrient-deprived conditions. Furthermore, the R absolute configuration of 11 was found to significantly contribute to the preferential anti-austerity ability toward PANC-1, with a PC50 value of 0.2 µM. Mechanistically, Ugi adduct (R)-11 was found to inhibit the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway preferentially under nutrition starvation conditions. Consequently, Ugi-adduct (R)-11 could be a promising candidate for drug development targeting pancreatic cancer based on the anti-austerity strategy. Our study also demonstrated that the Ugi reaction-based chemical engineering of natural product extracts can be used as a rapid method for discovering novel anti-austerity agents for combating pancreatic cancer.

Mechanistic Insights into a DMSO-Perturbing Inhibitory Assay of Hyaluronidase.

A hyaluronic acid-degrading enzyme (hyaluronidase; HAase) is involved in tumor growth and inflammation, and consequently, HAase inhibitors have received recent attention as potential pharmaceuticals. Previous studies have discovered a wide range of inhibitors; however, unfortunately, most of them are dissimilar to the original ligand hyaluronic acid, and their mode of inhibition remains ambiguous or seems promiscuous. This situation presents an urgent need for readily available and highly reliable assay systems identifying the promiscuous inhibitory properties of HAase inhibitors. We have previously proposed a unique method to identify promiscuous nonspecific binding inhibitors of HAase by using the DMSO-perturbing effect. Here, to obtain mechanistic insights into the DMSO-perturbing assay, we studied the addition effect of 11 water-compatible chemicals on HAase inhibitory assay. Intriguingly, the perturbing property was found to be highly specific to DMSO. Furthermore, kinetic analyses described characteristic description of the perturbing property of DMSO: DMSO displayed entropy-driven interactions with HAase, whereas nonperturbing agents such as ethanol and urea exhibited enthalpy-driven interactions. The enthalpy-driven tight interactions of ethanol and urea with HAase would lead to the irreversible denaturation of the enzymes, while the entropy-driven weak interactions caused structural and catalytic perturbation, generating nonproductive but nondenatured states of enzymes, that are key species of the perturbation assay. With these mechanistic understandings in hand, the present assay will enable rapid and reliable identification of HAase inhibitors with certain pharmaceutical potential.

Synthesis of natural product hybrids by the Ugi reaction in complex media containing plant extracts.

Plant extracts are rich in a wide variety of molecules with diverse biological activities. Chemical engineering of plant extracts has provided a straightforward and simultaneous synthetic route for artificial molecules derived from plant products. This study achieved the synthesis of 13 natural product-like molecules by the Ugi multicomponent reaction using plant extracts as substrates. In particular, the engineering of a mixture of plant extracts demonstrated a unique synthetic route to a series of natural product hybrids, whereby otherwise unencountered naturally occurring molecules of different origins were chemically hybridized in complex media. Even though these reactions took place in complex media containing plant extracts, the well-designed process achieved a good conversion efficiency (~ 60%), chemoselectivity, and reproducibility. Additionally, some of the Ugi adducts exhibited promising inhibitory activity toward protease.