The phase behaviors
of systems containing saturated phosphatidylcholine
(PC) and plant steroids can be important for designing new alternative
delivery methods. In our previous studies, we found that even a small
amount of β-sitosteryl sulfate (PSO4) significantly
affects the phase behavior, hydration properties, and liposomal properties
of pure saturated phosphatidylcholines [KafleA.
Kafle, A.
Colloids Surf., B20181615966
KafleA.
Kafle, A.
J. Oleo
Sci.20186715111519]. In
the current paper, we are reporting the phase behavior of a more complex
system consisting of hydrogenated soy lecithin (HLC), which is useful
as a carrier in drug delivery systems or in cosmetics, and PSO4. HLC, which is composed of phosphatidylcholine (PC), phosphatidylethanolamine
(PE), phosphatidic acid (PA), and lysophosphatidylcholine (LPC), demonstrated
a versatile phase behavior. The PC component of HLC was found to separate
from the PE and PA components as a result of nonideal mixing. At room
temperature, these two domains represented two distinct gel phases
denoted Lβ1 and Lβ2. The Lβ1 phase selectively underwent transition into the liquid crystalline
phase (Lα) at a lower temperature than Lβ2. Upon addition of PSO4, at room temperature, the PC fraction
gradually converted into the liquid-ordered (Lo) phase,
while the (PE + PA) fraction remained unaffected. When heated above
60 °C, the whole material converted into the liquid crystalline
phase. The observed fluidizing effect of PSO4 on HLC can
find applications in preparing vehicles for moisture or drugs in cosmetic
and pharmaceutical formulations.