Interaction of the Glycoalkaloid Tomatine with DMPC and Sterol Monolayers Studied by Surface Pressure Measurements and Brewster Angle Microscopy

Abstract

The interaction of the glycoalkaloid tomatine with monolayers of dimyristoylphosphatidylcholine (DMPC) and cholesterol, as well as other selected sterols, has been investigated using surface pressure measurements at constant area and Brewster angle microscopy (BAM). The interaction of tomatine with sterol monolayers is found to vary with the structure of the sterol. The interaction of tomatine with cholesterol-containing monolayers results in a surface pressure increase accompanied by the appearance of a mottled texture. Morphological changes are observed that suggest the formation of tomatine-cholesterol complexes that aggregate at the water-air interface. No morphology change observable by BAM is observed for monolayers containing epicholesterol, suggesting that the stereochemistry of hydrogen bonding between the sterol and the sugar units on tomatine is of particular significance. Strong interactions are observed with cholestanol- and coprostanol-containing monolayers, and BAM reveals formation of spiked aggregates upon interaction with 7:3 mole ratio DMPC/coprostanol mixed monolayers. More modest surface pressure changes are observed for cholestenone- and epicoprostanol-containing monolayers. A much smaller surface pressure increase is observed when tomatine is injected beneath a pure DMPC monolayer.

Protective effect of dietary tomatine against dibenzo[a,l]pyrene (DBP)‐induced liver and stomach tumors in rainbow trout

“…The mechanism(s) of the anticarcinogenic effect of tomatine remain to be investigated. Tomatine is known, however, to bind to cholesterol in the digestive tract [9,32] a) Mortality is defined as the number of trout that died during the 4-week exposure divided by the number of trout per tank. The only reported mortalities, 2%, were for the doses of 100 and 1000 ppm of tomatine.…”

A DSC and FTIR spectroscopic study of the effects of the epimeric cholestan-3-ols and cholestan-3-one on the thermotropic phase behavior and organization of dipalmitoylphosphatidylcholine bilayer membranes: Comparison with their 5-cholesten analogs

“…Comparative monolayer film studies of sChol and Chol and of their binary or ternary mixtures with various phospholipids and SpMs are particularly numerous, probably in part because sChol is often used in place of Chol because the presence of the double bond in the latter makes it susceptible to oxidation at the air/water interface. The general consensus of these studies is that sChol and Chol exhibit comparable limiting areas/molecule and collapse pressures in pure sterol films and condense monolayers of various phospholipids to a similar degree (Demel et al, 1972;Ghosh and Tinoco, 1972;Grauby-Heywang and Turlet, 2007;Kodama et al, 2004;Lancelot and Grauby-Heywang, 2007;Lintker et al, 2009;Radhakrishnan and McConnell, 2000;Stine et al, 2006;Stottrup and Keller, 2006). In contrast, only a relatively few comparative biophysical studies of the effects of sChol and Chol incorporation into lipid bilayer model membranes have been carried out.…”

Evaluation of the Structure–Activity Relationship of Rifabutin and Analogs: A Drug–Membrane Study

“…[18] Therefore, these lipid aggregates may result from the interaction between CHOL and phosphatidylcholine CHEMPHYSCHEM ARTICLES www.chemphyschem.org molecules. [45] The observed condensed domains are probably due to the formation of aggregates of CHOL with saturated PC, since CHOL selectively interacts with saturated chains even in a mixed-chain environment.…”

“…[35] On the other hand, the monolayers of CHOL are characterized by the appearance of small brighter spots on a fluid background. [45,46] It is well-known that CHOL molecules can undergo tight packing with phosphatidylcholines, which results in the formation of domains in the membranes and liquid-ordered phases in artificial systems. [34] Therefore, before compression of the monolayer it is possible to observe the existence of "elliptic vacuoles", which are attributed to the coexistence of two phases ( Figure 3, marked with arrows).…”