ISOLATION OF ANTIOXIDANT COMPOUNDS FROM TURK’S CAP (MALVAVISCUS ARBOREUS CAV.) LEAVES

• Main Author: Kristiana, Syela
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/40088
• Institution: Institut Teknologi Bandung

Turk’s cap (Malvaviscus arboreus Cav., Malvaceae) leaves have been reported for having antioxidant activity which is potential to be used as medicine, however, the antioxidant activity and isolates of the leaves have not been investigated yet. Therefore, this research was conducted to determine the antioxidant activity of ethanolic extract, fractions and isolates from Turk’s cap leaves and to determine the chemical structures of the isolates. The crude drug was characterized, screened for its phytochemicals and extracted by reflux method using ethanol. The ethanolic extract was monitored and fractionated by liquid-liquid extraction using n-hexane and ethyl acetate in a row and n-hexane, ethyl acetate and aqueous ethanol fractions were obtained which later were further monitored. Antioxidant activity of the extract and three fractions were tested quantitatively and qualitatively using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity method. The chosen active fraction was further purified using reverse phase preparative thin layer chromatography and the obtained isolates were tested for their purity and qualitative and quantitative antioxidant activity and were also characterized and identified. Based on phytochemical screening result, the crude drug and extract contained flavonoids, phenols and steroid/triterpenoids. At concentration of 200 µg/mL, ethanolic extract had DPPH free radical scavenging activity value of 11.14%, meanwhile, n-hexane, ethyl acetate and aqueous ethanol fractions had DPPH free radical scavenging activity values of 5.37%, 46.16% and 14.26% respectively. The ethyl acetate fraction which had the strongest scavenging activity, was further purified using reverse phase preparative thin layer chromatography and five active isolates were obtained. The result of quantitative antioxidant activity test of isolates showed that the five isolates had inhibition percentages between 1- 5% at concentration 50 µg/mL. The isolates obtained from ethyl acetate fractions were isolate 7 which was suspected to be 7,4’-dihydroxyflavone, isolate 8 and 10 which were suspected to be flavone-7-O-glycosides, isolate 9 which was suspected to be 4’-hydroxyflavone-7-O-glycoside and isolate 11 which was suspected to be substituted flavonol with 7-O-glycoside. The extract and three fractions had weak activity as antioxidants in scavenging against DPPH. Isolate 7, 8, 9 and 10 were suspected to be flavones, meanwhile, isolate 11 was suspected to be substituted flavonol. The five isolates had low antioxidant activity potential. iv