Total Phenolic, Flavonoids Contents, and Antioxidant Activities in The Stems and Rhizomes of Java Cardamom as Affected by Shading and N Fertilizer Dosages

Abstract

Java cardamom is an herbal medicinal plant known as the "queen of spices." This research aims to determine the influence of shading and nitrogen fertilizer dose on the total phenolics, flavonoids, and antioxidant activity of Java cardamom stems and rhizomes. The study employed a split-plot design with two factors: the level of shading (0, 25, 50, and 75%) as the main plot and the dosage of nitrogen (N) fertilizer (0, 0.9, and 1.36 g polybag-1) as the subplots. Twelve months after planting, the rhizome and stem dried powder were extracted using the sonication-maceration technique with ethanol as the solvent. The 75% shading affected the more outstanding production of total phenolics (1.65 ± 0.59 mg GAE g-1 DW), DPPH antioxidant (4.95 ± 0.50 µmol TEAC g-1 DW), and FRAP antioxidant (8.94 ± 2.56 µmol TEAC g-1 DW) activities of the rhizomes cultivated with 0 g/polybag N in comparison to the stems of the plants. Contrary to phenolics and antioxidant activities, total flavonoids cultivated at 0% shading with 1.36 g polybag-1 N of the stems increased concentration than the rhizomes. The results indicated that the 75% shading affected the Java cardamom rhizome's phenolic content and antioxidant activities.