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Articles by E. Djauhari
Total Records ( 2 ) for E. Djauhari
  I. Batubara , L.K. Darusman , T. Mitsunaga , M. Rahminiwati and E. Djauhari
  The aim of this study is to screen whitening agent potency of 45 Indonesian plant materials from 35 species. All plant materials were extracted with methanol and 50% ethanol which resulted to 90 extracts. The methods for screening is based on tyrosinase inhibitor potency using mushroom tyrosinase and antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH). Scoring method was used to identify the best extract as whitening agent. Out of 90 extracts, merbau (Intsia palembanica) methanol and 50% ethanol extracts are the most potent extracts as tyrosinase inhibitor (for monophenolase and diphenolase). Their IC50 values are not significantly different with kojic acid as positive control. Based on antioxidant activity, merbau methanol extract (IC50: 3.87 μg mL-1) is the best antioxidant together with kayu putih (Melaleuca cajuputi) ethanol 50% extract (IC50: 5.76 μg mL-1) and Rhizopora sp. methanol extract (IC50: 5.90 μg mL-1). Their IC50 values are not significantly different with (+)-catechin (IC50: 2.94 μg mL-1) as positive control. In conclusion, merbau methanol extract is the most potent extract as whitening agent based on scoring data from its tyrosinase inhibitory and antioxidant activities.
  L.K. Darusman , I. Batubara , T. Mitsunaga , M. Rahminiwati , E. Djauhari and K. Yamauchi
  Intsia palembanica is the most potential plant having tyrosinase inhibitor over 30 Indonesian plants that have been searched. It’s active compound namely (-)-robidanol, (+)-epirobidanol and 4’-dehydroxyrobidanol had been identified and showed the tyrosinase inhibitory activity. The study aims to obtain the kinetic enzyme inhibition type of the three active compounds. About 3 g of I. palembanica methanol extract was fractionated using n-hexane soluble part, ethyl-acetate soluble part and aqueous soluble part. Compounds were isolated for the most active part (ethyl-acetate soluble part) by silica gel column chromatography. Purification of fractions was performed using preparative High Performance Liquid Chromatography (HPLC). Kinetic inhibition against tyrosinase on monophenolase and diphenolase were analyzed by Lineweaver-Burk plot. The results showed that three active compounds showed different kinetic inhibition type on monophenolase and diphenolase. The kinetic characteristics of (-)-robidanol, the most active inhibitor, on monophenolase were Km increased and Vmax did not changed while on diphenolase were Vmax decreased and Km did not change. In conclusion, (-)-robidanol is a competitive inhibitor for monophenolase and a non-competitive inhibitor for diphenolase. The kinetic data is useful for further research on mechanism of action of the whitening agent that will be formulated.
 
 
 
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