Optimization and Formulation of Gold Nanoparticle Preparations Using Temulawak (Curcuma Xanthorrhiza) Extract

Abstract

Background: Temulawak (Curcuma xanthorrhiza) contains flavonoids, phenolics, and curcuminoids which possess strong antioxidant and brightening activity, but its application in cosmetics is limited by low water solubility resulting in poor bioavailability. Gold nanoparticles (AuNPs) offer a promising delivery system due to their biocompatibility and stability. However, conventional AuNP synthesis often requires chemical reducing agents that may leave toxic residues. Plant-based biosynthesis using temulawak extract offers a safer alternative, yet optimization studies remain limited. Objective: To optimize and formulate the use of temulawak extract as a natural bioreducing agent to synthesize AuNPs. Methods: Temulawak extract solution was prepared by macerating dried temulawak in 40C aquabidest for 6 hours, while polyvinyl alcohol (PVA) solution was prepared by dissolving PVA in 60C aquabidest for 24 hours. Gold nanoparticles were synthesized using 1 mM HAuCl4 with varying volumes and concentrations of temulawak extract and PVA solution. Ultrasonication was applied to initiate nanoparticle formation. Characterisation included visual observation of colour changes and aggregation, transmittance, particle size, polydispersity index (PDI), and zeta potential. The collective qualitative and quantitative data will then be analysed using Microsoft Excel to identify the most optimal AuNPs formula. Results: The results demonstrated successful AuNP formation, where amongst all formulations, F2 containing 15% temulawak extract and 2% PVA, exhibited the most favourable physicochemical characteristics, including stable colouration from transparent yellow to purple without visible aggregation, relatively stable transmittance values, particle sizes below 200 nm, low PDI values, and zeta potential values approaching the stability threshold throughout the 4-week observation period. Conclusion: In conclusion, temulawak extract demonstrated potential as a natural bioreducing agent for green AuNP synthesis. Further studies are recommended to conduct additional stability testing and advanced characterisation analysis such as FTIR and SEM-EDX.