Oxocarbon Acids and their Derivatives in Biological and Medicinal Chemistry.

The biological and medicinal chemistry of the oxocarbon acids 2,3- dihydroxycycloprop-2-en-1-one (deltic acid), 3,4-dihydroxycyclobut-3-ene-1,2-dione (squaric acid), 4,5-dihydroxy-4-cyclopentene-1,2,3-trione (croconic acid), 5,6-dihydroxycyclohex- 5-ene-1,2,3,4-tetrone (rhodizonic acid) and their derivatives is reviewed and their key chemical properties and reactions are discussed. Applications of these compounds as potential bioisosteres in biological and medicinal chemistry are examined. Reviewed areas include cell imaging, bioconjugation reactions, antiviral, antibacterial, anticancer, enzyme inhibition, and receptor pharmacology.

Water-solubility croconic acid-bisindole dye with morpholine ring for tumor NIRF/PA imaging and photothermal therapy activated by lysosome pH-response.

A novel croconic acid-bisindole dye CR-630 with a morpholine ring showed good water-solubility and obvious lysosome-targeting. The protonation of the nitrogen atom in the indole and lysosome-targeting of morpholine ring let it exhibit stronger pH-responsive NIR/PA imaging and photothermal effect in the lysosome acidic microenvironment (pH 4.0-5.5) than in the tumor acidic microenvironment. In the animal study, compound CR-630 could NIRF/PA image in the tumor tissues in 1.5-2.0 h, effectively inhibit the growth of the tumor, and even ablate the tumor at the drug dose of 1 mg/kg. It also demonstrated good biosafety. This study gives a new idea to develop water-solubility organic dyes with lysosome targeting, stronger pH-responsive NIRF/PA imaging and PTT for breast cancer.

NIR absorptive croconic acid/quercetin/CaO2 nanoplatform for tumor calcium overload therapy combined mild photothermal therapy.

With excellent biocompatibility, stable chemical and optical properties, small organic molecules-based agents have always been a research hotspot in cancer photothermal therapy (PTT). In this work, a novel croconic acid-based molecule (CR) was designed and synthesized as an ideal photothermal agent (PTA), which showed abundant near-infrared (NIR) light absorption, high photothermal conversion ability, and excellent photothermal stability. By loading CR and quercetin (Qu) in CaO2, and coated with DSPE-PEG2000, a multifunctional theranostic nanoparticle (CCQ) was successfully prepared for calcium overloading mitochondrial metabolism inhibition synergetic mild PTT. Upon entering tumor microenvironment, CCQ can produce abundant H2O2 and a large amount of calcium ions, which lead to the imbalance of calcium concentration in the internal environment of tumor cells and induced mitochondrial apoptosis. With the existence of Qu, CCQ can effectively inhibit the expression of heat shock proteins (Hsp) during the PTT process, which weaken the heat resistance of tumors, ablate tumors at lower temperature (~45 °C), and reduce the damage to normal tissues. Guided by photoacoustic imaging (PAI), CCQ showed excellent multimodal therapeutic effect of tumors. This study provided a novel CR organic molecule-based theranostic nanoplatform that can be used to treat tumors via calcium overload therapy synergetic PTT at safe temperatures, which has promising potential for the future clinical cancer treatment.

Evidence of cluster formation of croconic acid with Ag, Au and Cu cages, enhancement of electronic properties and Raman activity.

Investigation of the adsorption properties croconic acid (CCA) with metal clusters (mC: Ag, Au and Cu) are reported using DFT method. CCA is found to form stable cluster with transition metal clusters of copper, silver and gold. The drug-cluster complexaton energy is slightly more for the copper nanocluster-drug complex. Non-covalent interaction analysis indicated that strong interactions and weak van der Waal interaction is present between drug and metal clusters. Dipole moment of the drug-gold cluster is found to be higher than that of the other systems. SERS studies demonstrates improved Raman signals for multiple wavenumbers of all CCA-metal cluster complexes. Mulliken charge analysis show that all CCA oxygen atom's charge changes due to the interactions with the mCs. Clustering of CCA with metal cages enhances the medicinal properties and the metal nanoclusters will act as a drug carrier of CCA.