Effect of Methyl Jasmonate and Plant Growth Promoting Rhizobacteria (PGPR) on Antioxidant Potential and Metabolomic Profiles of Zingiberaceae Rhizomes

The rhizomes of Zingiberaceae plants are used as cooking spices, medicines, cosmetics and beverage ingredients. Zingiberaceae rhizomes have the potential to be immunostimulants, antioxidants and immunomodulators. Antioxidants are chemical compounds that bind free oxygen radicals and prevent free radicals from damaging healthy cells. This research aimed to analyze the antioxidant potential and metabolomic compounds of the rhizomes of the Zingiberaceae tribe using GC-MS after the application of the elicitor methyl jasmonate and Plant Growth Promoting Rhizobacteria (PGPR). Experimental method research with stages: 1) Collection of rhizomes of the Zingiberaceae family, Genus Curcuma; 2) Preparation of experimental land and fertilization with Petroganik organic fertilizer, 3) Planting Curcuma rhizomes; 4) Application of elicitor methyl jasmonate 60 ppm at 25 and 50 days after planting (DAP), 5) Application of PGPR 10 mL/L water at 30 and 60 DAP. Antioxidant activity testing using a spectrophotometer with DPPH solution. Metabolomic profile analysis using GC-MS. The GC-MS results, 3 with the highest area (%) of Curcuma xanthorrhiza rhizomes, obtained 18 metabolite compounds, namely 1-Naphthaleneethanol, Ethyl orthoformate and Cyclopentanol. The GC-MS results of Curcuma longa rhizomes obtained 17 metabolite compounds: Turmerone, Curlone and Acetylene. The GC-MS results of Curcuma caesia rhizomes obtained 21 metabolite compounds: Isoprene, Imidazol-4-one and 3-ethenyl-3-ethylcyclopentanone. The GC-MS results of Curcuma zedoria rhizomes yielded 15 metabolite compounds, namely 3,4,5-trimethylphenol, Naphthalene, and Acetic acid. Based on the DPPH test, the IC50 values mg/L ± SD (category) for the control group were Curcuma xanthorrhiza 51.02 ± 4.53 (strong), Curcuma longa 124.06 ± 3.71 (medium), Curcuma zedoria 112.46 ± 3.145 (medium), and Curcuma caesia 154.18 ± 3.629 (weak). The IC50 values (mg/L) for the treatment group were Curcuma xanthorrhiza 31.50 ± 3.373 (very strong), Curcuma longa 97.20 ± 2.940 (strong), Curcuma zedoria 88.18 ± 2.924 (strong), and Curcuma caesia 143.69 ± 3.500 (medium). The results of the t-test, between the control and treatment groups of Curcuma xanthorrhiza, Curcuma longa, Curcuma zedoria (sig. 0.001), Curcuma caesia (sig. 0.004), sig value <0.05, then it is stated that the IC50 value between the control and treatment groups is different. Application of methyl jasmonate and PGPR elicitors increased antioxidant potential.