Albumin protein as an effective carrier for the protection of (-)-epigallocatechin-3-gallate and suppression of heme toxicity

The health-promoting function of bioactive polyphenols in vitro and in vivo is usually restrained by their low stabilities, which might be counteracted by the use of protein as carriers for these compounds. Demonstration of the binding mechanism of protein-ligand complex is important for the encapsulation and protection of bioactive compounds. In this study, human serum albumin (HSA) was used to investigate its binding characteristic to (−)-epigallocatechin-3-gallate (EGCG, the main component of catechins in green tea), in the presence of free heme (an inducer for cytotoxicity) by multi-spectroscopic analysis and molecular docking. The free radical scavenging capability of bioactive EGCG was retained in the albumin-ligand complex relative to free flavonoid. Albumin-diligand complex (HSA-EGCG-heme) was successfully formed when EGCG and heme was added to protein solution. The toxicity of heme in vascular endothelial cells was declined in the HSA-diligand complex comparison with those of free heme or HSA-heme complex, where the stability of EGCG during storage was improved in the HSA-diligand complex comparison with that in the free EGCG. Our results demonstrate the possibility and advantage of designing albumin protein-based carriers for the protection of active flavonoid and suppression of heme toxicity during their biomedical applications.