FT-IR fingerprinting analysis for classification of West Sumatra small ginger (<i>Zingiber officinale</i> Roscoe) essential oil and its antioxidant activity

Abstract

Due to its essential oil content, the community utilises the small ginger rhizome as traditional medicine and spices. This study aims to compare the antioxidant activity of small ginger essential oil (SGEO) from six different altitudes in West Sumatra and then categorise the SGEO using FTIR spectroscopic and chemometric analysis. Fresh rhizome of small ginger was extracted by hydrodistillation method. Antioxidant activity was evaluated using DPPH, ABTS, FRAP, and inhibition of erythrocyte hemo lysis by H₂O₂. The SGEO has a golden yellow colour with a distinctive ginger odour. The yield was between 0.1- 0.2%; the refractive index was 1.4860-1.4880, the optical rotation value was - 30.3207°, and specific gravity was 0.80-0.95 g/mL. The data was analysed using one-way ANOVA at a 95% significance level. The FTIR spectra revealed the typical peak at 2923 cm^-1, corresponding to terpene hydrocarbons. The results showed that the six essential oils had weak antioxidant activity with an IC₅₀ value >200 μg/mL and a FRAP value < ascorbic acid (positive control). PCA analysis showed that the SGEO from lowland and highland regions could be classified based on the 200-400 cm^-1 fingerprint area. The hierarchical clustering analysis (HCA) dendrogram showed 3 clusters of SGEO (I; Ampek Angkek, II; Paninjauan, Sitiung, III; Koto laweh, Kinali, Lunang). Altitude plays little or no role in the FTIR fingerprint properties of small ginger essential oils. The essential oils exhibited weak antioxidant activity.