Comparative Analysis of Volatile Compounds and Biochemical Activity of Curcuma xanthorrhiza Roxb. Essential Oil Extracted from Distinct Shaded Plants

Abstract

The application of shade during plants' growth significantly alters the biochemical compounds of the essential oil (EO). We aimed to analyze the effect of shade on the volatile compounds and biochemical activities of EO extracted from Curcuma xanthorrhiza Roxb. (C. xanthorrhiza) plants. Four shading conditions were applied: no shading (S0), 25% (S25), 50% (S50), and 75% shade (S75). The volatile compounds of EO extracted from each shaded plant were analyzed by gas chromatography-mass spectrometry. The antioxidant, antibacterial, and antiproliferative activities of EO were also investigated. We found that shade application significantly reduced the C. xanthorrhiza EO yield but increased its aroma and bioactive compound concentration. α-curcumene, xanthorrhizol, α-cedrene, epicurzerenone, and germacrone were found in EO extracted from all conditions. However, β-bisabolol, curzerene, curcuphenol, and γ-himachalene were only detected in the EO of S75 plants. The EO of the shaded plants also showed higher antioxidant activity as compared to unshaded ones. In addition, the EO extracted from S75 exerted higher antiproliferative activity on HeLa cells as compared to S0. The EO extracted from S0 and S25 showed higher antibacterial activity against Gram-positive bacteria than kanamycin. Our results suggest that shade applications alter the composition of the extractable volatile compounds in C. xanthorrhiza, which may result in beneficial changes in the biochemical activity of the EO.

Keywords: Curcuma xanthorrhiza Roxb.; antibacterial; anticancer; antioxidant; essential oil.

Figure 1

(a) The workflow of essential oil extraction from C. xanthorrhiza Roxb. rhizomes. (b) Yield (% v/w) of C. xanthorrhiza essential oil. Extraction was performed in 3 independent plants, with statistical analysis by one-way ANOVA followed by Tukey’s post hoc test, *** p < 0.001. S0, no shade; S25, 25% shade; S50, 50% shade; S75, 75% shade.

Figure 2

Chemical compositions of C. xanthorrhiza Roxb. essential oil. (a) Pie chart displaying the groups of secondary metabolites in C. xanthorrhiza essential oil from 4 shading conditions detected by GC-MS. (b) Heatmap displaying the abundance of 64 compounds detected by GC-MS in C. xanthorrhiza essential oil from each shade condition. Three replicates of EO extraction were pooled and subjected to chemical compound analysis.

Figure 3

Antioxidant activity of C. xanthorrhiza Roxb. essential oil measured by DPPH and FRAP assays. n = 3, statistical analysis by one-way ANOVA followed by Tukey’s post hoc test, * p < 0.05, ** p < 0.01, *** p < 0.001. S0, no shade; S25, 25% shade; S50, 50% shade; S75, 75% shade. DPPH, 2,2′-diphenyl-1-picrylhydrazyl; DW, dry weight; FRAP, ferric reducing antioxidant power; TE, Trolox equivalent; DW: dry weight.

Figure 4

Antiproliferative activity of C. xanthorrhiza Roxb. essential oil (4 µg/mL) measured in vero (left), MCF-7 (middle), or HeLa (right) cells. n = 3, statistical analysis by one-way ANOVA followed by Tukey’s post hoc test, ** p < 0.01, *** p < 0.001. S0, no shade; S25, 25% shade; S50, 50% shade; S75, 75% shade. Doxo: doxorubicin (0.2 µg/mL).

Figure 5

Antibacterial activity of C. xanthorrhiza Roxb. essential oil (4 µg/mL) tested against S. aureus (left) or E. coli (right). n = 3, statistical analysis by one-way ANOVA followed by Tukey’s post hoc test, */# p < 0.05, ### p < 0.001. * Analysis was performed by using S0 as reference. # Analysis was performed by using KS as reference. S0, no shade; S25, 25% shade; S50, 50% shade; S75, 75% shade. KS: kanamycin sulfate (1 mg/mL).