Biophysical characterization of the interaction of bovine serum albumin with anticancer sipholane triterpenoid from the Red Sea sponge

Red Sea Sponge Callyspongia siphonella Extract Induced Growth Inhibition and Apoptosis in Breast MCF-7 and Hepatic HepG-2 Cancer Cell Lines in 2D and 3D Cell Cultures

Introduction

The increasing incidence of cancer diseases necessitates the urgent exploration of new bioactive compounds. One of the trends in drug discovery is marine sponges which is gaining significant support due to the abundant production of natural pharmaceutical compounds obtained from marine ecosystems. This study evaluates the anticancer properties of an organic extract from the Red Sea sponge Callyspongia siphonella (C. siphonella) on HepG-2 and MCF-7 cancer cell lines.

Methods

C. siphonella was collected, freeze-dried, and extracted using a methanol-dichloromethane mixture. The extract was analyzed via Liquid Chromatography-Mass Spectrometry. Cytotoxic effects were assessed through cell viability assays, apoptosis detection, cell cycle analysis, mitochondrial membrane potential assays, scratch-wound healing assays, and 3D cell culture assays.

Results

Fifteen compounds were identified in the C. siphonella extract. The extract showed moderate cytotoxicity against MCF-7 and HepG-2 cells, with IC50 values of 35.6 ± 6.9 μg/mL and 64.4 ± 8 μg/mL, respectively, after 48 hours of treatment. It induced cell cycle arrest at the G2/M phase in MCF-7 cells and the S phase in HepG-2 cells. Apoptosis increased significantly in both cell lines, accompanied by reduced mitochondrial membrane potential. The extract inhibited cell migration, with notable reductions after 24 and 48 hours. In 3D cell cultures, the extract had IC50 values of 5.1 ± 2 μg/mL for MCF-7 and 166.4 ± 27 μg/mL for HepG-2 after 7 days of treatment, showing greater potency in MCF-7 spheres compared to HepG-2 spheres.

Discussion and Conclusion

The anticancer activity is attributed to the bioactive compounds. The C. siphonella extract's ability to induce apoptosis, disrupt mitochondrial membrane potential, and arrest the cell cycle highlights its potential as a novel anticancer agent. Additional research is required to investigate the underlying mechanism by which this extract functions as a highly effective anticancer agent.

Detailed Experimental and In Silico Investigation of Indomethacin Binding with Human Serum Albumin Considering Primary and Secondary Binding Sites

The interaction of indomethacin with human serum albumin (HSA) has been studied here considering the primary and secondary binding sites. The Stern–Volmer plots were linear in the lower concentration range of indomethacin while a downward curvature was observed in the higher concentration range, suggesting the presence of more than one binding site for indomethacin inside HSA due to which the microenvironment of the fluorophore changed slightly and some of its fraction was not accessible to the quencher. The Stern–Volmer quenching constants (KSV) for the primary and secondary sites were calculated from the two linear portions of the Stern–Volmer plots. There was around a two-fold decrease in the quenching constants for the low-affinity site as compared to the primary binding site. The interaction takes place via a static quenching mechanism and the KSV decreases at both primary and secondary sites upon increasing the temperature. The binding constants were also evaluated, which show strong binding at the primary site and fair binding at the secondary site. The binding was thermodynamically favorable with the liberation of heat and the ordering of the system. In principle, hydrogen bonding and Van der Waals forces were involved in the binding at the primary site while the low-affinity site interacted through hydrophobic forces only. The competitive binding was also evaluated using warfarin, ibuprofen, hemin, and a warfarin + hemin combination as site markers. The binding profile remained unchanged in the presence of ibuprofen, whereas it decreased in the presence of both warfarin and hemin with a straight line in the Stern–Volmer plots. The reduction in the binding was at a maximum when both warfarin and hemin were present simultaneously with the downward curvature in the Stern–Volmer plots at higher concentrations of indomethacin. The secondary structure of HSA also changes slightly in the presence of higher concentrations of indomethacin. Molecular dynamics simulations were performed at the primary and secondary binding sites of HSA which are drug site 1 (located in the subdomain IIA of the protein) and the hemin binding site (located in subdomain IB), respectively. From the results obtained from molecular docking and MD simulation, the indomethacin molecule showed more binding affinity towards drug site 1 followed by the other two sites.

Exploration of the binding between cuminol and bovine serum albumin through spectroscopic, molecular docking and molecular dynamics methods

Cuminol (4-Isopropylbenzyl alcohol), found in the essential oils of several plant sources, is an important constituent of several cosmetics formulations. The interaction of cuminol with model plasma protein bovine serum albumin was studied in this paper. The experimental studies were mainly carried out using fluorescence spectrophotometry aided with UV visible and CD spectroscopies. Intrinsic fluorescence measurements showed that there was a weak binding between cuminol and BSA. The mechanism of binding involved static quenching with around 1:1 binding. The binding was chiefly supported by hydrophobic forces although a little contribution of hydrogen bonding was also found in the interaction and the values of enthalpy change were negative with positive entropy change. The secondary structure of BSA didn't change significantly in presence of low concentrations of cuminol, however, partial unfolding of the former taken place when the concentration of the latter increased. Molecular docking analyses showed cuminol binds at the intersection of subdomains IIA and IIIA, i.e. its binding site is in between Sudlow sites I and II. Molecular dynamics simulations results have shown that BSA forms a stable complex with cuminol and the structure of the former didn't change much in presence of later. Communicated by Ramaswamy H. Sarma.

New cytotoxic polyacetylene alcohols from the Egyptian marine sponge Siphonochalina siphonella

Three new polyacetylenic alcohols, siphonellanols A-C (1-3), together with two known polyacetylenic alcohols (4-5), were isolated from the CHCl₃-soluble fraction of the methanolic extract of the marine sponge Siphonochalina siphonella, collected in Egypt. The structures of 1-3 were determined by spectroscopic analyses of their 1D-, 2D-NMR, and MS spectra and by comparisons with reported data. The cytotoxicity assay revealed that 1-3 exhibited moderate cytotoxic activities against a human cervical cancer cell line (HeLa), a human breast cancer cell line (MCF-7), and a human lung cancer cell line (A549) with IC₅₀ values ranging from 25.9 to 69.2 μM.

Spectroscopic and computational evaluation on the binding of safranal with human serum albumin: Role of inner filter effect in fluorescence spectral correction

For determining the pharmacological properties of medicinal compounds, their binding with serum albumins is very crucial. Herein, we have selected safranal, a major constituent of saffron which is known to retain a number of medicinal properties including antioxidant, anti-inflammatory, tumoricidal, anti-genotoxic, and anti-aging activities; and studied its mechanism of binding with human serum albumin at physiological pH using various spectroscopic methods along with computational approach using molecular docking. A change in the difference UV-visible spectrum of HSA in presence of safranal was found which is due to the complex formation. Owing to the strong absorption of safranal at the fluorescence excitation wavelength of HSA (295 nm) and in the whole range of emission, the fluorescence spectra of HSA in presence of safranal were corrected for the inner filter effect. After the correction the spectra were free from the safranal absorption effect and it was found that addition of safranal causes the quenching of HSA fluorescence and a blue shift of the emission maximum which are attributed to the binding of safranal to the protein and dominance of hydrophobic forces in the interaction, respectively. It was evident from the comparison of observed and corrected fluorescence spectra that before correction there was a large red shift while after correction appearance of blue shift was occurred. The involvement of hydrophobic interaction was also found from the extrinsic fluorescence measurements using ANS dye as well as from the analyzed thermodynamic parameters. Safranal was found to partially induce the secondary structure of HSA as construed from the CD measurements. The size of the HSA was also decreased as evident from the DLS and RLS measurements. Both site marker studies and molecular docking simulations suggested that the primary binding site of the safranal in the HSA is Sudlow's site 1 located in the subdomain IIA. Hydrophobic interaction provides the major contribution to the binding forces along with a little amount of hydrogen bonding.

Comprehensive insight into the binding of sunitinib, a multi-targeted anticancer drug to human serum albumin

Binding studies between a multi-targeted anticancer drug, sunitinib (SU) and human serum albumin (HSA) were made using fluorescence, UV-vis absorption, circular dichroism (CD) and molecular docking analysis. Both fluorescence quenching data and UV-vis absorption results suggested formation of SU-HSA complex. Moderate binding affinity between SU and HSA was evident from the value of the binding constant (3.04×10⁴M^-1), obtained at 298K. Involvement of hydrophobic interactions and hydrogen bonds as the leading intermolecular forces in the formation of SU-HSA complex was predicted from the thermodynamic data of the binding reaction. These results were in good agreement with the molecular docking analysis. Microenvironmental perturbations around Tyr and Trp residues as well as secondary and tertiary structural changes in HSA upon SU binding were evident from the three-dimensional fluorescence and circular dichroism results. SU binding to HSA also improved the thermal stability of the protein. Competitive displacement results and molecular docking analysis revealed the binding locus of SU to HSA in subdomain IIA (Sudlow's site I). The influence of a few common ions on the binding constant of SU-HSA complex was also noticed.

Acridone in a biological nanocavity: detailed spectroscopic and docking analyses of probing both the tryptophan residues of bovine serum albumin

AD initially gets hooked to Trp 212 housed in domain IIA, inducing conformational changes in the protein and paving the way for the ligand to reach Trp 134 located in domain IB.