Synthesis of 2’,4’-dihydroxy-3,4-dimethoxychalcone and in vitro test of its sunscreen activity has been carried out. The research was started by synthesizing 2,4-dihydroxyacetophenone through Friedel-Crafts acylation from resorcinol. Glacial acetic acid was used as acylating agent and ZnCl2 as catalyst. Recrystalization was done using HCl:aquades (1:11) to purify the product. Product of acetophenone was then reacted with 3,4-dimethoxybenzaldehyde in the presence of KOH 40% through Claisen-Schmidt condensation to collect 2’,4’-dihydroxy-3,4-dimethoxychalcone. The synthesis was done by constant stirring for 48 hours at room temperature. The mixture was acidified using HCl 10% until the solid was formed. Then the solid obtained was recrystalized using methanol. Product of 2’,4’-dihydroxy-3,4-dimethoxychalcone was then diluted using ethanol to a range of concentration from 2 ?g/mL to 40 ?g/mL. The maximum absorbance of the solution was first measured using spectrophotometer UV-Vis at wavelength 200-400 nm. The wavelength was used to measure the absorbance of all solutions. The absorbances werethen used to count the SPF (Sun Protecting Factor) values. Structures of both products were analysed using spectrometer IR, GC-MS, and 1H-NMR. Spectrophotometer UV-Vis was used to analyse the structure of chalcone product as well.Yellowish-orange solid was obtained from the first synthesis.The yield was 38,05% and its melting point was 141-144 oC. It was confirmed as 2,4-dihydroxyacetophenone. Brownish-yellow solid was collected from the second synthesis. The yield was 19,94% and its melting point was 195-199 oC. It was confirmed as 2’,4’-dihydroxy-3,4-dimetoxychalcone. Maximum absorbance of this chalcone was reached at 276 nm (UV-C) and 370 nm (UV-A)so that it could be used as sunscreen anti UV-C and anti UV-A. Yet the absorbance measurement of all solutions was done at 370 nm because UV-C radiation was absorbed by ozone layer at atmosphere. Minimum protection (SPF 2-12) was reached from 12 ?g/mL. Moderate protection (SPF 12-30) was reached at 40 ?g/mL.

Kata Kunci : 2,4-dihydroxyacetophenone; chalcone; sunscreen; Sun ProtectingFactor