Neuroblastoma is the most common extracranial solid tumor found in children and survival rate is extremely meager. HDAC8, a class I zinc-dependent enzyme, is a potential drug target for treatment of neuroblastoma and T cell lymphoma. Most of the HDAC8 inhibitors discovered till date contains a hydroxamic acid group which acts as a zinc binding group. The high binding affinity to the zinc and other ions results in adverse effects. Also, the non-selective inhibition of HDACs cause a variety of side effects. The objective of this is to identify structurally diverse, non-hydroxamate, novel, potential and selective HDAC8 inhibitors. A number of five featured pharmacophore hypotheses were generated using 32 known selective HDAC8 inhibitors. The hypotheses ADDRR.4 were selected for building 3D QSAR model. This model has an excellent correlation coefficient and good predictive ability, which was employed for virtual screening of Phase database containing 4.3 × 10⁶ molecules. The resultant hits with fitness score >1.0 were optimized using in-silico ADMET (absorption, distribution, metabolism, excretion, and toxicity) and XP glide docking studies. On the basis of pharmacophore matching, interacting amino acid residues, XP glide score, more affinity towards HDAC8 and less affinity towards other HDACs, and ADME results five hits- SD-01, SD-02, SD-03, SD-04 and SD-05 with new structural scaffolds, non-hydroxamate were selected for in vitro activity study. SD-01 and SD-02 were found to be active in the nanomolar (nM) range. SD-01 had considerably good selectivity for HDAC8 over HDAC6 and SD-02 had marginal selectivity for HDAC6 over HDAC8. The compounds SD-01 and SD-02 were found to inhibit HDAC8 at concentrations (IC₅₀) 9.0 nM and 2.7 nM, respectively.

The side effects associated with conventional anti-cancer therapies call for safer and more effective alternatives. Flavonoids are a class of polyphenolic compounds well documented to possess antioxidant, anti-inflammatory, and anticancer properties. This study investigates the bioactivity of three flavonoids, namely Luteolin, Naringenin, and Scutellarin, with a focus on identification and validation of their molecular targets in human breast cancer. Potential targets were screened using the ePharmaLib database, followed by in silico structure-based pharmacophore mapping and molecular docking. Further confirmation was achieved through in vitro biochemical assays and cell-based studies. HDAC4 and HDAC8 assays validated the enzyme inhibitions of flavonoids, particularly Luteolin. In breast cancer cell lines, apoptosis was induced by flavonoids, as viewed by fluorescence microscopy and flow cytometry. Among these, Luteolin exhibited the most potent cytotoxicity. Antioxidant activity assays showed that luteolin and Scutellarin strongly scavenged radicals similar to quercetin. Naringenin and Luteolin significantly enhanced catalase activity. In THP-1-derived macrophages, all three flavonoids significantly suppressed LPS-induced inflammation with reduced expression of pro-inflammatory cytokines at both RNA and protein levels. Collectively, results clearly pinpoint that Luteolin, Naringenin, and Scutellarin may be explored as therapeutic possibilities since they exhibit strong anticancer, antioxidant, and anti-inflammatory properties.