ATR-FTIR spectral fingerprinting and Chemometric classification of Labisia pumila varieties with exploratory screening of herbal products.
ATR-FTIR spectroscopy combined with chemometric analysis can differentiate between varieties of Labisia pumila, but its clinical application is not established.
Where it sits
this study against the rest of the vip (vasoactive intestinal polypeptide) corpusSummary and findings
This study measured the spectral fingerprints of Labisia pumila varieties using ATR-FTIR spectroscopy and chemometric analysis. A total of 310 spectra were acquired from authenticated materials and commercial herbal products. The study aimed to differentiate between cultivated L. pumila var. alata and var. pumila based on their spectral characteristics.
Abstract
Labisia pumila (syn. Marantodes pumilum), an important medicinal herb in Southeast Asia, exhibits compositional variability that complicates authentication of raw materials and related herbal products. In this study, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy combined with chemometric analysis was applied as a rapid and non-destructive approach for differentiating authenticated cultivated L. pumila var. alata and var. pumila materials, and plant parts, with exploratory screening of related commercial herbal medicinal products (HMPs). A total of 310 ATR-FTIR technical replicate spectra were acquired from authenticated raw materials collected from multiple locations in Peninsular Malaysia and from solid commercial HMP contents. The fingerprint region of 1646-720 cm<sup>-1</sup> provided the most informative spectral variation for sample discrimination. Principal component analysis (PCA), hierarchical cluster analysis (HCA), and partial least squares-discriminant analysis (PLS-DA) were used to evaluate spectral classification. PCA and HCA supported separation between L. pumila var. alata and var. pumila based on discriminative spectral features in the fingerprint region, while PCA additionally revealed clustering patterns associated with leaf and stem-root tissues. The final PLS-DA model, developed using the 273-variable fingerprint-region subset (1646-720 cm<sup>-1</sup>) of the 490 VIP-selected variables from Savitzky-Golay first-derivative spectra, classified authenticated cultivated L. pumila var. alata and var. pumila raw materials based on their ATR-FTIR spectral fingerprints (R<sup>2</sup>Y = 0.894, Q<sup>2</sup> = 0.894). Additional grouped leave-one-source-material-out validation correctly classified all 120 held-out spectra and all 12 cultivated source materials, while Y-randomization testing supported that the observed class separation was unlikely to be due to random class assignment. Commercial HMPs were subsequently projected onto the calibrated model as an exploratory prediction set to assess potential applicability to market samples. These findings demonstrate that ATR-FTIR spectral fingerprinting, combined with chemometric analysis, provides a cultivated-reference screening workflow for differentiating medicinally relevant L. pumila varieties and plant parts, with potential application in exploratory screening of commercial HMPs.
Background
This paper addresses the authentication of Labisia pumila, a medicinal herb with compositional variability that complicates the validation of raw materials and herbal products. Previous methods for authentication may not have been rapid or non-destructive. The application of ATR-FTIR spectroscopy combined with chemometric analysis offers a potential solution for differentiating between varieties and parts of the plant.
Methods
The study utilized ATR-FTIR spectroscopy to acquire 310 technical replicate spectra from authenticated L. pumila var. alata and var. pumila, as well as from commercial herbal medicinal products. Principal component analysis (PCA), hierarchical cluster analysis (HCA), and partial least squares-discriminant analysis (PLS-DA) were employed to evaluate spectral classification. The analysis focused on the fingerprint region of 1646-720 cm^-1.
Results
The primary endpoint was the classification accuracy of the PLS-DA model, which achieved R²Y = 0.894 and Q² = 0.894. The model correctly classified all 120 held-out spectra and all 12 cultivated source materials. The PCA and HCA analyses supported the separation of L. pumila varieties based on spectral features.
Interpretation
The findings indicate that ATR-FTIR spectral fingerprinting can effectively differentiate between L. pumila varieties, aligning with previous literature on the use of chemometric methods for plant authentication. However, while the statistical significance is noted, the clinical relevance remains uncertain due to the lack of direct implications for therapeutic use. Limitations such as the sample size and potential biases in sourcing may affect the robustness of the conclusions.
Key findings
- 310 ATR-FTIR technical replicate spectra acquired from multiple locations in Peninsular Malaysia.
- Fingerprint region of 1646-720 cm^-1 provided the most informative spectral variation for sample discrimination.
- Final PLS-DA model classified authenticated cultivated L. pumila var. alata and var. pumila with R²Y = 0.894, Q² = 0.894.
- Leave-one-source-material-out validation correctly classified all 120 held-out spectra and all 12 cultivated source materials.
- Y-randomization testing supported that observed class separation was unlikely due to random class assignment.
Limitations
- small n=310 spectra may not represent all varieties
- limited to specific locations in Peninsular Malaysia
- exploratory nature of commercial HMP assessment
- no long-term follow-up or clinical outcomes reported