Identification of bioactive secondary metabolites in citronella grass leaves (Cymbopogon nardus L.) against Curvularia andropogonis

Citronella grass (Cymbopogon nardus) is an essential oil-producing plant. The essential oils consist of geraniol and citroneal whose production is affected by plant health. The production of citronella grass decreases (harvest loss) due to red spot disease caused by Curvulaia andropogonis infection which also affects the bioactive composition of secondary metabolites. Defense signal responses are also generated using plant defense pathways which result in compounds used for counterattacking plant invasions. The purpose of this study was to determine the secondary metabolites of C. nardus attacked by C. andropogonis. This research used HPLC to analysis citronellol and geraniol C. nardus with normal, wound and infected treatment. The Gas Chromatography-Mass Spectrometry (GCMS) method was used to detect metabolites profiles in normal treatment, injury, and infection, and then analyzed based on metabolite groups and metabolic pathways. The result of this study indicated that the citronellol in normal treatment sample was higher, namely 102.003mg/L compared to the wound treatment, which was 100.120mg/L and the infected treatment, which was 89.356mg/L. Likewise for geraniol in the normal treatment of 20.065mg/L, which is greater than the wound treatment, which was 19.245 mg/L and the infected, which was 15.765mg/L. There were 12 types of metabolites based on chemical grouping including alkaloids, carboxylic acids, fatty acids, flavonoids, nucleic acids, phenolics, terpenoids, alcohols, aldehydes, amino acids, heterocyclic compounds, and carbohydrates. The highest metabolites were found in carboxylic acid. Metabolic pathways resulted carboxylic acids which came from 2-Oxocaboxylic acid metabolism, and phenolics came from the biosynthesis of secondary metabolites, which were highest in carbohydrate metabolism. In conclusion, almost all metabolites and metabolic pathways increase in the infection treatment which was significant with the results of citronellol and geranioldecreased so that the overall content of bioactive secondary metabolites decreased.