Results
Roselle was extracted by boiling their fresh
calyxes in water for 15 minutes and then dried under
vacuum at 40°C for 8-10 hours. The dried extracts of
Roselle were attractively red in color with a typical odor
of Roselle. The yield (based on the dried extract) was
4.1% by weight of fresh calyces. The extract had
antioxidant activity (EC50) at the concentration of 8.45
+ 0.35 mg/mL which was similar to antioxidant activity
of the standard compound, BHT (EC50 = 9.14 + 0.42 mg/
mL). The amount of total monomeric anthocyanin
pigments, calculated as cyaniding-3-glucoside in mg/g
of dried Roselle extract was found to be 3.46 + 0.12
(n = 6). A linear relationship between the monomeric
anthocyanin content in Roselle extract and its DPPH
activity was observed with the correlation coefficient
(r2
) of 0.9525 as shown in Fig. 1.
Roselle extract (10% w/v) was incorporated in
the formulations of liposome with various ratios of lipid
composition and total lipid contents. All formulations
were determined for their physicochemical properties
including particle size and entrapment efficiency.
The differences of lipid components, or ratios of
phospholipids and cholesterol, or surfactants gave
liposomes with different entrapment efficacy.
Moreover, as the total lipid contents were increased,
the entrapment efficacy of liposomes increased (Table
2). At the total lipid level of 200 mmole/mL, the liposome
composed of SPC gave higher entrapment efficiency
(76%) than those composed of EPC. Therefore, the
liposome formulations of SPC were selected for further
studied on the effect of surface charged (Table 3). All
formulations of liposome containing Roselle extract
appeared as the pink colloidal suspensions with the
lipid vesicular size in range of 0.218-1.234 mm (Table 2
and 3). The formulations containing Tween 80 afforded
liposomes with greater ease, and gave smaller vesicular
size than those containing cholesterol because the latter
formulations were more viscous. The uses of both
positive and negative surface charge agents were able