Interaction Between Phenolic Compounds and Lipase: The Influence of Solubility and Presence of Particles in the IC₅₀ Value

Abstract

Obesity is one of the principal human health problems and one of the main treatments against it is the inhibition of pancreatic lipase, the main responsible enzyme of lipid digestion. For that purpose, previous studies have tested several phenolic compounds against lipase, without considering their aggregation behavior in aqueous solutions. Because of this, the present study focuses on understanding how the solubility and the presence of particles affect the IC value of the interaction between lipase and phenolic compounds present in beverages like fruit juices and teas. Therefore, the inhibitory capacity against pancreatic lipase and the aggregate formation of 9 phenolic compounds (quercetin, rutin, myricetin, catechin, epigallocatechin gallate, cyanidin, caffeic acid, chlorogenic acid, and vanillic acid) were analyzed. The results obtained together with the solubility data from literature were treated by principal component analysis and indicate that the IC value does not correlate with the solubility or aggregate formation of the phenolic compounds. However, the IC values of phenolic compounds which aggregate during the assay conditions have low reproducibility. This study shows that the aggregate formation of phenolic compounds plays an important role during in vitro assays for pancreatic lipase inhibition and should be considered in future experiments as it can lead to false positive results. In terms of particle formation, the flavonoids investigated in this study are more prone to aggregation compared to the phenolic acids.

Interaction between myricetin aggregates and lipase under simplified intestinal conditions

“…The increased optical density displayed in Figure 1 shows that myricetin can form aggregates in aqueous solutions, as reported previously (26) and that the optical density increases with increasing myricetin concentration. For the data obtained in water,it is possible to see that for 600 and 1000 µM of myricetin, there is a significant change in the optical density (with respect to the blank), indicating that after two hours myricetin aggregates were detected at those concentrations.…”

“…From table 2 we can see that the size of the small myricetin aggregates is in the range of a few nm. Large myricetin aggregates were previously detected by dynamic light scattering (DLS) (26, 29), but the use of separation with AF4 allowed for the detection of smaller myricetin aggregates without the interference of large aggregates. The myricetin-lipase aggregates are somewhat large but remain in a size range <10 nm.…”

Interaction of quercetin and epigallocatechin gallate (EGCG) aggregates with pancreatic lipase under simplified intestinal conditions

“…For example, it has been reported that quercetin and epigallocatechin gallate (EGCG) act as pancreatic lipase inhibitors, binding to the enzyme near the active site [16,17]. Nevertheless, findings have suggested that flavonoids can form aggregates and that they are able to inhibit several unrelated enzymes [18,19]. McGovern et al (2003), have proposed that flavonoids can reversibly sequester some enzymes instead of binding to them in specific sites [20].…”

“…Our previous study suggests that the presence of flavonoid aggregates affects the reproducibility of pancreatic lipase assays [18], but their mechanism of action as aggregates is still unknown. Since it is likely that the ingested flavonoids are present in the human digestive track as aggregates, we hypothesize that the interaction with pancreatic lipase follows an additional mechanism besides molecular inhibition.…”

“…For that reason, the present study focusses on studying the interaction of two well-known flavonoids and pancreatic lipase under simplified intestinal conditions. Based on our previous study, we chose quercetin and EGCG, two flavonoids found in teas and fruits in high concentrations, and that can form aggregates in aqueous solutions [18,19,21] 2. Material and methods…”