Polyamine-Drug Conjugates: Do They Boost Drug Activity?

Over the past two decades, the strategy of conjugating polyamine tails with bioactive molecules such as anticancer and antimicrobial agents, as well as antioxidant and neuroprotective scaffolds, has been widely exploited to enhance their pharmacological profile. Polyamine transport is elevated in many pathological conditions, suggesting that the polyamine portion could improve cellular and subcellular uptake of the conjugate via the polyamine transporter system. In this review, we have presented a glimpse on the polyamine conjugate scenario, classified by therapeutic area, of the last decade with the aim of highlighting achievements and fostering future developments.

A Comprehensive Review on Steroidal Bioconjugates as Promising Leads in Drug Discovery

Ever increasing unmet medical requirements of the human race and the continuous fight for survival against variety of diseases give birth to novel molecules through research. As diseases evolve, different strategies are employed to counter the new challenges and to discover safer, more effective, and target-specific therapeutic agents. Among several novel approaches, bioconjugation, in which two chemical moieties are joined together to achieve noticeable results, has emerged as a simple and convenient technique for a medicinal chemist to obtain potent molecules. The steroid system has been extensively used as a privileged scaffold gifted with significantly diversified medicinal properties in the drug discovery and development process. Steroidal molecules are preferred for their rigidness and good ability to penetrate biological membranes. Slight alteration in the basic ring structure results in the formation of steroidal derivatives with a wide range of therapeutic activities. Steroids are not only active as such, conjugating them with various biologically active moieties results in increased lipophilicity, stability, and target specificity with decreased adverse effects. Thus, the steroid nucleus prominently behaves as a biological carrier for small molecules. The steroid bioconjugates offer several advantages such as synergistic activity with fewer side effects due to reduced dose and selective therapy. The steroidal bioconjugates have been widely explored for their usefulness against various disorders and have shown significant utility as anticancer, anti-inflammatory, anticoagulant, antimicrobial, insecticidal/pesticidal, antioxidant, and antiviral agents along with several other miscellaneous activities. This work provides a comprehensive review on the therapeutic progression of steroidal bioconjugates as medicinally active molecules. The review covers potential biological applications of steroidal bioconjugates and would benefit the wider scientific community in their drug discovery endeavors.

Bis(cholyl)-based chloride channels with oxalamide and hydrazide selectivity filters

We report the development of supramolecular bis(cholyl) ion channels by using oxalamide and hydrazide as selectivity filters. The hydrazide system displayed superior chloride transport activity than oxalamide via the formation...

Rapid Self-Healing and Thixotropic Organogelation of Amphiphilic Oleanolic Acid-Spermine Conjugates

Natural and abundant plant triterpenoids are attractive starting materials for the synthesis of conformationally rigid and chiral building blocks for functional soft materials. Here, we report the rational design of three oleanolic acid-triazole-spermine conjugates, containing either one or two spermine units in the target molecules, using the Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction. The resulting amphiphile-like molecules 2 and 3, bearing just one spermine unit in the respective molecules, self-assemble into highly entangled fibrous networks leading to gelation at a concentration as low as 0.5% in alcoholic solvents. Using step-strain rheological measurements, we show rapid self-recovery (up to 96% of the initial storage modulus) and sol ⇔ gel transition under several cycles. Interestingly, rheological flow curves reveal the thixotropic behavior of the gels. To the best of our knowledge, this kind of behavior was not shown in the literature before, neither for a triterpenoid nor for its derivatives. Conjugate 4, having a bolaamphiphile-like structure, was found to be a nongelator. Our results indicate that the position and number of spermine units alter the gelation properties, gel strength, and their self-assembly behavior. Preliminary cytotoxicity studies of the target compounds 2-4 in four human cancer cell lines suggest that the position and number of spermine units affect the biological activity. Our results also encourage exploring other triterpenoids and their derivatives as sustainable, renewable, and biologically active building blocks for multifunctional soft organic nanomaterials.

Synthesis and biological evaluation of aza-crown ether–squaramide conjugates as anion/cation symporters

Aim: Anion/cation symport across cellular membranes may lead to cell apoptosis and be developed as a strategy for new anticancer drug discovery. Methodology: Four aza-crown ether–squaramide conjugates were synthesized and characterized. Their anion recognition, anion/cation symport, cytotoxicity and probable mechanism of action were investigated in details. Conclusion: These conjugates are able to form ion-pairing complexes with chloride anions and facilitate the transmembrane transport of anions via an anion/cation symport process. They can disrupt the cellular homeostasis of chloride anions and sodium cations and induce the basification of acidic organelles in live cells. These conjugates exhibit moderate cytotoxicity toward the tested cancer cells and trigger cell apoptosis by mediating the influx of chloride anions and sodium cations into live cells.

Synthesis of a dimeric 3α-hydroxy-7α,12α-diamino-5β-cholan-24-oate conjugate and its derivatives, and the effect of lipophilicity on their anion transport efficacy

A dimeric 3α-hydroxy-7α,12α-diamino-5β-cholan-24-oate conjugate and its derivatives were synthesized, and lipophilicity was found to significantly affect their anion transport efficacy.

Highly efficient anion transport mediated by 1,3-bis(benzimidazol-2-yl)benzene derivatives bearing electron-withdrawing substituents

1,3-Bis(benzimidazol-2-yl)benzene exhibits potent anionophoric activity through a process of anion exchange with a minor level of proton/anion symport. Modification of 1,3-bis(benzimidazol-2-yl)benzene with strong electron-withdrawing substituents, such as trifluoromethyl and nitro groups, leads to up to 789-fold increase in the activity. The benzimidazolyl-NH fragments, the relative position and the number of the benzimidazolyl groups on the central phenyl scaffold play an essential role in the transport.

Does lipophilicity affect the effectiveness of a transmembrane anion transporter? Insight from squaramido-functionalized bis(choloyl) conjugates

Lipophilicity was found to have little effect on the effectiveness of squaramido-functionalized bis(choloyl) conjugates.

Toward transmembrane anionophores based on rigid bis(choloyl) conjugates: reversal of the ion selectivity by appended polyamines

A bis(polyamine)-appending rigid linker-tethered bis(choloyl) conjugate was synthesized as a potent anionophore with high selectivity for iodide over the other monoanionic ions.