**2.1.1 Statistical analysis**

Principal components analysis (PCA) was applied to the population study. The analysis was performed using the NTSYS-pc 2.11w (Numerical Taxonomy and Multivariate Analysis System) designed by Rohlf (1998).

Basic data matrix was prepared considering 700 absorbance values (quantitative variable) of each analysed sample (53 extracts in total).

Before PCA the data were pre-processed with normalization to unit area technique (Beebe et al., 1998).
