The interactions of human and bovine serum albumins (HSA and BSA) with various drugs and nanomaterials receive great attention in the recent years owing to their significant impact in the biomedical field. Although there are various techniques available for studying such interactions, fluorescence spectroscopy is the most appealing one due to its high sensitivity and straightforwardness. Detailed information about the interactions of drugs and nanomaterials with serum can be deducted from a mass of information accumulated by the fluorescence quenching studies. The present review emphasizes the interaction of various nanomaterials, antibiotics, anticancer drugs, anti-inflammatory agents, dyes, flavonoids, and certain noxious materials with HSA and BSA. In particular, we focus on the interactions of serum albumin with nanomaterials having different size and stabilizing agents with various receptors. This review helps in understanding the structural features of drugs/nanomaterials crucial for not only their affinity for serum albumin but also their optimum pharmacological activities.

Binding of serum albumins with bioactive substances – Nanoparticles to drugs

Apigenin (4',5,7-trihydroxyflavone, 5,7-dihydroxy-2-(4-hydroxyphenyl)-4H-1-benzopyran-4-one) is a flavonoid found in many fruits, vegetables, and herbs, the most abundant sources being the leafy herb parsley and dried flowers of chamomile. Present in dietary sources as a glycoside, it is cleaved in the gastrointestinal lumen to be absorbed and distributed as apigenin itself. For this reason, the epithelium of the gastrointestinal tract is exposed to higher concentrations of apigenin than tissues at other locations. This would also be true for epithelial cancers of the gastrointestinal tract. We consider the evidence for actions of apigenin that might hinder the ability of gastrointestinal cancers to progress and spread. Apigenin has been shown to inhibit cell growth, sensitize cancer cells to elimination by apoptosis, and hinder the development of blood vessels to serve the growing tumor. It also has actions that alter the relationship of the cancer cells with their microenvironment. Apigenin is able to reduce cancer cell glucose uptake, inhibit remodeling of the extracellular matrix, inhibit cell adhesion molecules that participate in cancer progression, and oppose chemokine signaling pathways that direct the course of metastasis into other locations. As such, apigenin may provide some additional benefit beyond existing drugs in slowing the emergence of metastatic disease.

Apigenin and its impact on gastrointestinal cancers.

The relationship between the structural properties of natural polyphenols and their affinities for α-amylase were investigated by fluorescence titration analysis. The binding process with α-amylase was strongly influenced by the structural differences of the compounds under study. For instance, the methylation of the hydroxyl group in flavonoids increased their binding affinities for α-amylase by 2.14 to 7.76 times. The hydroxylation on rings A, B, and C of flavonoids also significantly affected their affinities for α-amylase. The glycosylation of isoflavones and flavanones reduced their affinities for α-amylase and the glycosylation of flavones and flavonols enhanced their affinities for α-amylase. Hydrogenation of the C2C3 double bond of flavonoids decreased the binding affinities. The galloylated catechins had higher binding affinities with α-amylase than non-galloylated catechins and the pyrogallol-type catechins had higher affinities than the catechol-type catechins. The presence of the galloyl moiety is the most decisive factor. The glycosylation of resveratrol decreased its affinity for α-amylase. The esterification of gallic acid significantly reduced the affinity for α-amylase. The binding interaction between polyphenols and α-amylase was mainly caused by hydrophobic forces.

Interaction of natural polyphenols with α-amylase in vitro: molecular property-affinity relationship aspect.

Apigenin loaded nanoparticle delayed development of hepatocellular carcinoma in rats

Flavonoids are a class of plant secondary metabolites and among thousands of flavonoids few are considered as dietary flavonoids. Serum albumin (SA), the most abundant protein in plasma, functions as the most important carrier of vital drugs, including dietary flavonoids. The binding affinity of dietary flavonoids to SA is demonstrated to be governed by structure–affinity relationship (SAR) and its bioavailability. The present review summarizes the interactions of flavonoids categorized as flavanol, flavonol, flavone, isoflavone, flavanones, and anthocyanidins with SAs (bovine serum albumin and human serum albumin) in light of SAR. The key findings are: (1) the position and degree of hydroxylation highly influence the affinity of flavonoids to SAs, (2) glycosylation decreases and substitution of methoxy group increases the affinity of flavonoids for SAs, (3) catechin gallates have higher binding affinity to SAs than catechins and gallocatechins, (4) inorganic metal ions modulate the binding affinity of fl...

A review on structure-affinity relationship of dietary flavonoids with serum albumins.

CdTe quantum dots (QDs) improve the affinities of baicalein and genistein for human serum albumin in vitro.

Much of the bioactivities of Citrus flavanones significantly appear to impact blood and microvascular endothelial cells. It is essential to investigate the interaction between Citrus flavanones and serum albumin to verify the effect of flavanone structures on the distribution and transportation in blood. The interactions between flavonoids and proteins have attracted great interest among researchers. The work in here mainly concerns about the binding interaction between Citrus flavanones and human serum albumin (HSA) in vitro. The methoxylation of tangeretin improved the affinity for HSA by 100 times. The 2,3-double bond in conjugation with a 4-oxo group plays an important role for the affinity for HSA. The affinity of apigenin for HSA is about 10,000-times higher than that of naringenin. It was found that the hydroxylation on position 3' of flavonol significantly improves the binding affinity for HSA. The affinity of quercetin (3', 4') for HSA is about 100-times higher than that of kaempferol (4'). The hydroxylation on position 3' of flavone slightly improves the binding affinity for HSA. The affinity of luteolin for HSA is about 1.38-times higher than that of apigenin. The values of log10(Ka) are proportional to the number of binding sites (n), which confirms the method used here is suitable to study the interaction between Citrus flavanones and HSA.

Hui Cao

Papers

CdTe quantum dots (QDs) improve the affinities of baicalein and genistein for human serum albumin in vitro.

Binding Citrus flavanones to human serum albumin: effect of structure on affinity