Privileged 1,2,4-Oxadiazoles in Anticancer Drug Design: Novel 5- Aryloxymethyl-1,2,4-oxadiazole Leads for Prostate Cancer Therapy

Discovery of PIM-1 kinase inhibitors based on the 2,5-disubstituted 1,3,4-oxadiazole scaffold against prostate cancer: Design, synthesis, in vitro and in vivo cytotoxicity investigation

PIM-1 kinases play an established role in prostate cancer development and progression. This research work tackles the design and synthesis of new PIM-1 kinase targeting 2,5-disubstituted-1,3,4-oxadiazoles 10a-g&11a-f, and investigation thereof as potential anti-cancer agents through in vitro cytotoxicity assay followed by in vivo studies along with exploration of this chemotype's plausible mechanism of action. In vitro cytotoxicity experiments have disclosed 10f as the most potent derivative against PC-3 cells (IC₅₀ = 16 nM) compared to the reference drug Staurosporine (IC₅₀ = 0.36 μM), also eliciting good cytotoxicity against HepG2 and MCF-7 cells (IC₅₀ = 0.13 and 5.37 μM, respectively). Investigating PIM-1 kinase inhibitory activity of compound 10f revealed an IC₅₀ of 17 nM paralleled to that of Staurosporine (IC₅₀ = 16.7 nM). Furthermore, compound 10f displayed an antioxidant activity eliciting a DPPH inhibition ratio of 94% as compared to Trolox (96%). Further investigation demonstrated that 10f induced apoptosis in treated PC-3 cells by 43.2-fold (19.44%) compared to 0.45% in control. 10f also disrupted the PC-3 cell cycle by increasing the cell population at the PreG1-phase by 19.29-fold while decreasing the G2/M-phase by 0.56-fold compared to control. Moreover, 10f affected a downregulation of JAK2, STAT3 and Bcl-2 and upregulation of caspases 3, 8 and 9 levels that activated the caspase-dependent apoptosis. Finally, in vivo 10f-treatment caused a significant increase in tumor inhibition by 64.2% compared to 44.5% in Staurosporine treatment of the PC-3 xenograft mouse model. Additionally, it improved the hematological, biochemical parameters, and histopathological examinations compared to control untreated animals. Finally, docking of 10f with the ATP-binding site of PIM-1 kinase demonstrated good recognition of and effective binding to the active site. In conclusion, compound 10f represents a promising lead compound that merits further future optimization for controlling prostate cancer.

Exploration of electronic properties, radical scavenging activity and QSAR of oxadiazole derivatives by molecular docking and first-principles approaches

Eight new oxadiazole derivatives were designed then geometries for ground state were optimized through Density Functional Theory (DFT) at B3LYP/6-31G** level. Single electron transfer mechanism has been studied to understand the antioxidant ability of the oxadiazole derivatives. Then molecular electrostatic potential and quantitative structure–activity relationship (QSAR) was probed. Additionally, we shed light on different molecular descriptors, e.g., electrophilicity(ω), electronegativity(χ), electrophilicity indices(ωi), hardness(η), softness(S) and chemical potential(μ).The smaller value of ionization potential for 5a is showing that it might be efficient antioxidant candidate. The electrophilic reactive sites in 2a, 3a, 4a, 5a and 7a derivatives might be a good choice for reactivity that would be advantageous to improve the biological activity. The polar surface area of 3a, 4a and 5a derivatives was found < 60 A² which is enlightening that these drugs might be suitable as orally active and for brain penetration. First-principles calculations and molecular docking results revealed that 5a would lead to superior antioxidant activity.

Bioactive Compounds from Marine Heterobranchs

The natural products of heterobranch molluscs display a huge variability both in structure and in their bioactivity. Despite the considerable lack of information, it can be observed from the recent literature that this group of animals possesses an astonishing arsenal of molecules from different origins that provide the molluscs with potent chemicals that are ecologically and pharmacologically relevant. In this review, we analyze the bioactivity of more than 450 compounds from ca. 400 species of heterobranch molluscs that are useful for the snails to protect themselves in different ways and/or that may be useful to us because of their pharmacological activities. Their ecological activities include predator avoidance, toxicity, antimicrobials, antifouling, trail-following and alarm pheromones, sunscreens and UV protection, tissue regeneration, and others. The most studied ecological activity is predation avoidance, followed by toxicity. Their pharmacological activities consist of cytotoxicity and antitumoral activity; antibiotic, antiparasitic, antiviral, and anti-inflammatory activity; and activity against neurodegenerative diseases and others. The most studied pharmacological activities are cytotoxicity and anticancer activities, followed by antibiotic activity. Overall, it can be observed that heterobranch molluscs are extremely interesting in regard to the study of marine natural products in terms of both chemical ecology and biotechnology studies, providing many leads for further detailed research in these fields in the near future.

Anticancer activity of benzoxazole derivative (2015 onwards): a review

Background

According to the report published recently by the World Health Organization, the number of cancer cases in the world will increase to 22 million by 2030. So the anticancer drug research and development is taking place in the direction where the new entities are developed which are low in toxicity and are with improved activity. Benzoxazole and its derivative represent a very important class of heterocyclic compounds, which have a diverse therapeutic area. Recently, many active compounds synthesized are very effective; natural products isolated with benzoxazole moiety have also shown to be potent towards cancer.

Main text

In the last few years, many research groups have designed and developed many novel compounds with benzoxazole as their backbone and checked their anticancer activity. In the review article, the recent developments (mostly after 2015) made in the direction of design and synthesis of new scaffolds with very potent anticancer activity are briefly described. The effect of various heterocycles attached to the benzoxazole and their effect on the anticancer activity are thoroughly studied and recorded in the review.

Conclusion

These compiled data in the article will surely update the scientific community with the recent development in this area and will provide direction for further research in this area.

1,2,4-Oxadiazole-5-ones as analogues of tamoxifen: synthesis and biological evaluation

A series of 2,3,4-triaryl-substituted 1,2,4-oxadiazole-5-ones have been prepared as fixed-ring analogues of tamoxifen (TAM), a drug inhibitor of Estradiol Receptor (ER) used in breast cancer therapy, by an efficient synthetic protocol based on a 1,3-dipolar cycloaddition of nitrones to isocyanates. Some of the newly synthesized compounds (14d-f, 14h and 14k) show a significant cytotoxic effect in a human breast cancer cell line (MCF-7) possessing IC50 values between 15.63 and 31.82 μM. In addition, compounds 14d-f, 14h and 14k are able to increase the p53 expression levels, activating also the apoptotic pathway. Molecular modeling studies of novel compounds performed on the crystal structure of ER reveal the presence of strong hydrophobic interactions with the aromatic rings of the ligands similar to TAM. These data suggest that 1,2,4-oxadiazole-5-ones can be considered analogues of TAM, and that their anticancer activity might be partially due to ER inhibition.

Pharmacokinetic evaluation, molecular docking and in vitro biological evaluation of 1, 3, 4-oxadiazole derivatives as potent antioxidants and STAT3 inhibitors

1, 3, 4-Oxadiazole derivatives (4a–5f) were previously synthesized to investigate their anticancer properties. However, studies relating to their antioxidant potential and signal transducer and activator of transcription (STAT) inhibition have not been performed. We investigated previously synthesized 1, 3, 4-oxadiazole derivatives (4a–5f) for various radical scavenging properties using several in vitro antioxidant assays and also for direct inhibition of STAT3 through molecular docking. The data obtained from various antioxidant assays such as 2, 2,-diphenyl-1-picrylhydrazyl radical (DPPH), nitric oxide, hydrogen peroxide, and superoxide anion radical revealed that among all the derivatives, compound 5e displayed high antioxidant activities than the standard antioxidant L-ascorbic acid. Additionally, the total reduction assay and antioxidant capacity assay further confirmed the antioxidant potential of compound 5e. Furthermore, the molecular docking studies performed for all derivatives along with the standard inhibitor STX-0119 showed that binding energy released in direct binding with the SH2 domain of STAT3 was the highest for compound 5e (-9.91kcal/mol). Through virtual screening, compound 5e was found to exhibit optimum competency in inhibiting STAT3 activity. Compound 5e decreased the activation of STAT3 as observed with Western blot. In brief, compound 5e was identified as a potent antioxidant agent and STAT3 inhibitor and effective agent for cancer treatment.

Synthesis and antioxidant activity of 1,3,4-oxadiazoles and their diacylhydrazine precursors derived from phenolic acids

Eight 1,3,4-oxadiazoles and eight of their diacylhydrazine precursors were synthesized and examined for their antioxidative potential using different tests.