Chemometric Analysis of ATR-FTIR Spectra for Extract Screening in Caulerpa spp.

This study investigated the use of Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) as a cost-effective analytical approach for screening the bioactivity of green algal extracts. Samples of five Caulerpa species—C. ashmeadii, C. paspaloides, C. cupressoides, C. verticillata, and C. prolifera—were collected from Dzilam, Yucatán, Mexico, across seven seasonal campaigns. Sequential extraction was performed using solvents of increasing polarity: hexane, dichloromethane, acetone, and methanol. After solvent evaporation, extracts were analyzed via ATR-FTIR, and Total Phenolic Content (TPC) and Trolox Equivalent Antioxidant Capacity (TEAC) were quantified. Statistical analysis (PERMANOVA) revealed that the type of solvent accounted for most of the variance (61.6%), while species and collection date contributed minimally. Infrared (IR) band assignments highlighted functional groups associated with lipids, such as terpenes, and carbohydrates. K-means clustering enabled the subdivision of less polar extracts, notably grouping numerous samples from C. verticillata. Classification models comparing full-spectrum and IR band datasets showed that Partial Least Squares Discriminant Analysis (PLS-DA) with full-spectrum data achieved the best performance. TPC showed a positive correlation with absorption at 1730.8 cm⁻¹, which is associated with ester-containing metabolites. Although ATR-FTIR effectively distinguished extraction solvents, it was less sensitive to subtle biological variation among Caulerpa. However, the method remains a practical tool for rapid screening, with spectral data supporting solvent-based classification. Reduction of salt content prior to extraction may minimize interference in both FTIR measurements and biological assays.