เอกสารการประชุมวิชาการและเสนอผลงานวิจัย มหาวิทยาลัยทักษิณ ครั้งที่ 19 2552 - page 968

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The emulsion prepared by the beaker method; two phases of substances would be separately heat to
70°C. Then mixed the two phases together with continuing stirring until the mixture cooled down and congealed at
room temperature. The cream with pH 5.5 then was attained.
The percutaneous absorption of caffeine from Emulsions was studied by Franz diffusion model, which
followed the experiment of Songkro et al., 2003. Full thickness skins of newborn pigs, weighing 1.4-1.8 kg, was
prepared, cut into 4.5x4.5 cm2 pieces, placed in phosphate buffer pH 7.4 and hydrated at room temperature for 1
hour before use. The receptor compartment of the modified Franz diffusion cell was filled with 11 ml of phosphate
buffer (0.1 M, pH 7.4), which was continuously stirred. The modified Franz diffusion cell was placed in a
circulating water bath with magnetically stirred at 300 rpm that maintained a constant temperature of the receptor
fluid at 37 oC. One gram of each formulation was put in a donor compartment, spread on the surface of the skin.
Sample in the receptor compartment was withdrawn at 0.5, 1, 2, 4, 8, 10, 12, and 24 hours and collected in the vial
for caffeine content analysis by HPLC method calibration with standard caffeine curve. An equal volume of fresh
phosphate buffer would be immediately added to the receptor solution after each sampling. All experiments were
repeated three times.
After 24 hours, the caffeine content on the donor side surface was washed 10 times with 1 ml each of
fresh receptor liquid, and the excess washing liquid was absorbed on cotton swabs. Then all the obtained washing
liquid was collected in the vial and analyzed the caffeine content by HPLC method calibration with standard
curve. The full thickness skin was cut into small pieces with a scalpel and collected in a vial, homogenized with
acetonitrile, centrifuged 15,000 g for 5 min room temperature, and filtered through cellulose acetate filter; pore
size of 0.2 ôm (Sartorius, AG, Germany). The filtrate then was analyzed by HPLC method and calibration with
standard curve. (Bolzinger et al. 2008)
The HPLC analysis method modified from the method of Potard et al. (1999) using HPLC analysis.
The condition of HPLC analysis would be a reversed phase column (RP8 4.6x250 mm–5 ôm) and UV detector
working at 271 nm wavelength. The mobile elution solvent was water/ acetonitrile/ acetic acid (85:15:1 v/v, pH
2.5). The solvent flow rate is 1 mL/ min at 35°C.
The amount of caffeine in various part of the skin was analyzed, and calculated using arithmetic mean
± S.D. triplicate done, and then plotted against time. Statistical comparisons were made using analysis of variance
(ANOVA, single factor). A difference was considered with significant at p d 0.05.
Results and discussions
The transfer of caffeine through full thickness skin by Franz diffusion cell method, from the two types
of emulsions was first assessed and compared. The results were shown in Fig. 1. After 24 hr exposure, amount of
caffeine diffused from oil in water (o/w) emulsion through the full thickness skin was 75.75 ± 24.84 ôg/ml while
caffeine diffused from water in oil (w/o) emulsion through the full thickness skin was 35.07 ± 6.05 ôg/ml. Now