Secondary metabolites of Java cardamom leaves extract function under shading and nitrogen doses¹

Metabólito secundário do extrato de folhas de cardamomo de Java em função de sombreamento e doses de nitrogênio

HIGHLIGHTS:

The use of 75% shade was recommended to produce the maximum content of phenolics and flavonoids and antioxidant activity.

Without shading, 2,2-diphenyl picrylhydrazyl (DPPH) antioxidant activity was higher.

Compounds 1.8-Cineole and 5-Hydroxy-3,7,4’-trimethoxyflavone were the dominant metabolite extracts of Java cardamom leaves.

ABSTRACT

Java cardamom is a species of herbal medicinal plant endemic to West Java, Indonesia, that has been used for a long time in traditional medicine. The effects of shading and nitrogen doses on the Gas Chromatography-Mass Spectrometry (GC-MS) profile, total phenolic and flavonoid contents, and antioxidant activity in the ethanol extract of Java cardamom leaves were investigated in this study. The experiment was conducted using a split-plot scheme with three replicates. The main plot constituted shading (without, 25, 50, and 75%), and the sub-plot comprised nitrogen doses (control, 0.9, and 1.36 g nitrogen fertilizer per polybag). GC-MS analysis found 27 compounds in the ethanol extract of Java cardamom leaves. The compounds 1.8-Cineole (36.87%) and 5-Hydroxy-3,7,4’-trimethoxyflavone (18.83%) had the highest concentrations in the combination of 25% shade with 0.9 g N fertilizer per polybag and 50% shade with 1.36 g N fertilizer per polybag. The highest total phenolic content (1.26 mg gallic acid equivalent g^-1 dry weight), flavonoid content (3.42 mg quercetin equivalent g^-1 dry weight), and ferric reducing antioxidant power (FRAP) antioxidant activity (5.80 μmol Trolox equivalent antioxidant capacity g-1 dry weight) were found with 75% shade. Metabolites 1-Methyl-4-isopropyl-cis-3-hydroxycyclohex-1-ene-6-one, 4-propoxy-catechol, cyclohexane, tert-pentyl-, cis-p-Menth-2,8-dienol, cis-carveol, and cis-p-mentha-1(7),8-dien-2-ol were responsible for antioxidant activity in the ethanol extract of Java cardamom leaves. Shade of 75% is recommended to produce optimal antioxidant activity and phenolic and flavonoid content from Java cardamom leaf extract.

Key words:
Amomum compactum Soland Ex. Maton; abiotic stress; antioxidant; GC-MS; polyphenols