(slightly erythema). In two of these rabbits, the irritation
disappeared within 1 hour after applying the liposome
formulation, and in the third, it disappeared in
6 days. None of the rabbits had oedema formation on
skin applied with the liposome formulation, whereas
the skin of all rabbits applied with the 2% w/v Roselle
extract showed well defined erythema and very slightly
oedema after one hour. Moreover, the aqueous extract
solution had still showed an effect on rabbit skin (very
slightly erythema) right until the end of observation
period (14 days).
Discussion
The water extract of Hisbiscus sabdariffa Linn
(Roselle) is a strong free radical scavenger. It shows
similar activity to BHT in the DPPH radical scavenging
assay. With the EC50 value of 8.45 + 0.35 mg/mL, Roselle
extract can be considerate as one of the important
sources for natural antioxidants. The active components
of Roselle extract are polyphenolic compounds
especially anthocyanin(8-13). High linear correlation is
found between the antioxidant capacity of Roselle
extract and the anthocyanin contents. This result
indicates that anthocyanins are one of major class of
components that contribute to antioxidant capacity in
Roselle extracts. Since anthocyanin is only stable in
acidic solutions, the extract should be formulated in an
acidic vehicle, but this acid solution may cause skin
irritation and allergy. In addition, due to the hydrophilic
nature of the constituents in Roselle extracts, they may
not be able to penetrate into the lipophilic structure of
the stratum corneum, an important protective barrier
on the outer surface of the skin. Therefore, liposome
technology was applied to overcome these problems.
In this study, the liposomes have been prepared by the
modified ethanol injection technique to avoid the use
of organic solvents such chloroform which are no
longer permitted in cosmetic products. The entrapment
efficiency of liposome depends on the ratio and total
amount of the lipid components. In fact, surface charge,
vesicle type and size of liposomes can be affected by
the structural lipid components as well as the process