Beyond Total Phenolics: Antioxidant and α-Amylase Inhibitory Profiles of Foeniculum Vulgare Extracts and Solvent Fractions

Abstract

This study investigated the bioactivity profiles of Foeniculum vulgare extracts and fractions obtained from different geographical origins and extraction conditions. Extraction yield, total phenolic content (TPC), total flavonoid content (TFC), DPPH radical-scavenging activity, FRAP reducing capacity, and α-amylase inhibitory activity were evaluated, and the relationships among these parameters were further explored using Pearson correlation and principal component analysis (PCA). The results revealed marked variability among the investigated samples. TPC and TFC showed a relatively strong positive correlation (r = 0.695), whereas their associations with α-amylase inhibition were weak (r = −0.323 and −0.298, respectively), indicating that total phenolic and flavonoid contents alone did not adequately explain the enzyme-inhibitory response. Distinct antioxidant profiles were also observed between DPPH and FRAP assays; notably, FME exhibited high reducing capacity (FRAP = 0.900 TEAC) and strong radical-scavenging activity (DPPH-EC₅₀ = 0.0495), while showing only 6% α-amylase inhibition. In contrast, DMD, SMD, and FMD displayed the highest α-amylase inhibitory activities, with values of 23.84%, 20.50%, and 18.65%, respectively. PCA provided an integrated view of these relationships, with the first two components explaining 65.442% of the total variance and revealing distinct associations among quantitative phenolic/flavonoid descriptors and biological responses. Overall, the findings demonstrate that F. vulgare extracts and fractions possess diverse and assay-dependent bioactivity profiles, and that their biological properties cannot be predicted solely from global phenolic or flavonoid abundance. Fractions exhibiting promising combined antioxidant and α-amylase inhibitory properties may therefore represent suitable candidates for further chemical characterization and identification of the metabolites underlying the observed activities.