Interaction betweenPlectranthus barbatusherbal tea components and human serum albumin and lysozyme: Binding and activity studies

Abstract

Abstract. Anti-cholinesterase and antioxidant active constituents of Plectranthus barbatus aqueous extract were found in plasma of rats after its administration -rosmarinic acid, luteolin and apigenin. The aim of the present work is to determine if the extract components can interact with human plasma proteins, namely albumin and lysozyme. Protein intrinsic fluorescence analysis showed that the plant phenolic compounds may bind to albumin, the main transport protein in plasma, and to lysozyme. The estimated thermodynamic parameters suggest that the main intermolecular interaction is hydrophobic association. FTIR analysis of the protein amide bands showed that the plant extract components do not alter the secondary structure of either albumin or lysozyme, however the rate of hydrogen-deuterium exchange suggests that tertiary structure changes might have occurred. An increase of hydrogen deuterium exchange suggests that rosmarinic acid may bind to the fatty acid binding sites in albumin, while luteolin and apigenin may bind to the drug binding sites. The plant extract components also inhibit lysozyme activity with IC 50 values around 100 µM. Therefore P. barbatus herbal tea, rosmarinic acid, luteolin and apigenin interact and may be transported by albumin and lysozyme. The inhibition of lysozyme activity may be an additional mechanism for its anti-inflammatory activity.

Evaluation of Bioactive Metabolites and Antioxidant-Rich Extracts of Amaranths with Possible Role in Pancreatic Lipase Interaction: In Silico and In Vitro Studies

“…Their quenching rate constant (Kq) and binding constant (Ka) were reported as Lg −1 and Lg −1 s −1 only (Table 5), and therefore, the mechanism of quenching was not clear. The decrease in Kq with increasing temperature (310 to 330 K) showed that the static complex formation might initiate that quenching (Figure 5) [75,76]. On the other side, the fluorescence quenching by betahistine, and orlistat were clearly static as the magnitudes of Kq were of order 10 13 which were much higher than the maximum collision quenching constant, i.e., 2.0 × 10 10 LM −1 s −1 [76].…”

“…The extracts used for fluorescence experiments were in their crude forms (mix of a variety of compounds with different affinity for PPL). Therefore, their degrees of fitness for apparent quenching were acceptable (ranging from 0.87 to 0.99) [75]. Table 5 reported the various parameters of binding affinity calculated from these plots for each extract and compound.…”