ATR-FTIR Spectral Profiling and PCA of Red Ginger (Zingiber officinale var. rubrum) from Java, Indonesia

Abstract

Background: Red ginger (Zingiber officinale var. rubrum) is a herbal plant widely used in traditional medicine due to its various bioactive compounds, which are influenced by geographical and agroclimatic conditions. Objectives: This study aimed to distinguish the Fourier Transform Infrared (FTIR) spectral profiles of red ginger in Java, Indonesia using Principal Component Analysis (PCA). Methodology: Red ginger samples from six regions, namely Jatinangor, Ciamis, Trenggalek, Bogor, Sumedang, and Wonogiri, were dried, ground, and analysed using ATR-FTIR in the wavenumber range of 4000-400 cm?¹. The transmittance data were processed using PCA in XLSTAT. Dry weight loss was determined using an oven at 105°C to evaluate the water content of the medicinal plants. Results: The results of dry weight loss showed an average value ranging from 9.24% to 11.96%. Samples from Ciamis (11.76%), Sumedang (11.96%), Trenggalek (10.84%), and Bogor (10.15%) exceeded the required standard limit (<10%), while the other samples met the standard requirements. FTIR spectral analysis revealed the presence of O–H, C–H, C=O, C=C, and C–O functional groups associated with gingerol and shogaol compounds. PCA analysis showed that two principal components, PC1 and PC2, explained 96.798% of the total variation in the data. The score plot showed sample clustering by geographical origin, with Jatinangor, Trenggalek, and Bogor exhibiting relatively similar spectral characteristics, whereas Sumedang, Ciamis, and Wonogiri showed distinct profiles. Contribution analysis showed that Ciamis and Wonogiri contributed mostly to the formation of PC1, while Ciamis and Sumedang contributed significantly to PC2. PCA is used to distinguish the spectral profiles of red ginger based on the regional origin of the tested samples as an initial overview for explanation without a validated classification model. Conclusions: This study demonstrated that the combination of ATR-FTIR and PCA is an effective, rapid method for differentiating the spectral profiles of red gingers by geographical origin.