Abstract

Light plays a crucial part in the growth of plants, and ensuring appropriate illumination may impact on the antioxidant qualities of the medicinal plant Curcuma xanthorrhiza (Roxb.). This study investigated the effect of different shade levels (0, 25, 50 and 75%) on the concentration of polyphenol antioxidants in C. xanthorrhiza rhizomes using a randomized complete group design with a single factor. Colorimetric assays were employed to measure the phenolic (TPC) and flavonoid (TFC) content and the antioxidant capacity of the samples using four methods: DPPH, FRAP, ABTS and CUPRAC. The rhizomes were extracted using 80% ethanol through sonication. The research discovered that applying shade treatment improved the polyphenol content, with plants under 25% shade displaying the highest levels, a 15% increase in TPC, and a 16% increase in TFC compared to plants that did not receive shade treatment. This plant also exhibited more potent antioxidant activity when grown in shaded conditions. Furthermore, a positive correlation was observed between TPC and TFC with antioxidant capacity, particularly with FRAP, with correlation coefficients of 0.51 and 0.53, respectively. Chemometric analysis, including Hierarchical Clustering Analysis (HCA) and Principal Component Analysis (PCA), confirmed that shade significantly affects the polyphenol antioxidants of C. xanthorrhiza. Therefore, shade treatment can be a viable method to enhance the growth and antioxidant potential of C. xanthorrhiza rhizomes, offering potential health benefits.