of preparation(28). It is found in our study that the most
suitable formulation for the Roselle liposome composes
of SPC: Tween 80: DA (84: 16: 2.5 weight ratio, 200
mmole/mL of total lipid).
Since the Roselle extract consists of several
highly polar phenolic compounds, the feasibility of
liposomes as a transport delivery system for such
hydrophilic substances into the skin was examined.
For this purpose, in vitro skin permeation studies were
performed using modified Franz diffusion cells and pig
skin as the skin model. The antioxidant activity of the
Roselle extract chemical constituents delivered by the
liposome formulation into the receptor cell was tested
to reflect the skin permeation of the antioxidant
constituents. The results of these studies have
revealed that the antioxidant activity of the Roselle
extract components delivered by the liposomes
was higher than that penetrated from its aqueous
solutions. These results imply significant transdermal
transportation of the hydroplilic Roselle extract
constituents by the liposome formulations.
The skin permeability of the active
antioxidants in Roselle extract containing liposomes
can be explained by the size of liposomes. A small
particle size might assist the deep penetration and
distribution of the drugs(29). The intercellular space
between corneocytes of the skin is about 0.1 mm(30).
Nevertheless, the liposome particles with larger size
than the intercellular space can also be absorbed,
since the elasticity of liposomal membrane allows the
extrusion of liposomes through this gap(29). In addition,
the incorporation of surfactant into the liposomes could
also enhance the skin permeation due to the mechanism
of additive effect with possible synergism (surfactants
or ethanol with phosphatidylcholine)(31,32). The in vitro
skin permeation of antioxidant components of the
Roselle liposomal preparations supported the evidence
that liposomes could delivery the active components
of the Roselle extracts into the skin. The optimum
miscibility of liposomes with the lipid bilayer of stratum
cornoun might facilitate the release of active compound
from formulation and transport of active compound
through skin(28).
The Roselle extract aqueous solution is red in
color and highly acidic (pH 2.0), it causes high skin
irritation and is therefore unsuitable for skin care
products. By entrapping the extract or its consti tuents
inside the vesicles, liposomes can remarkably reduce
the skin irritation of the aqueous extract and make it
more suitable for cosmetic use. Additionally, the
liposome formulations help skin maintain a good state
of health due to their moisturizing effects.