Phenolic constituents, antioxidant and α-amylase inhibitory activities of Pulicaria vulgaris growing in Tunisia: an in vitro and in silico study

The present research aimed to establish the polyphenolic profile and to appraise the antioxidant and anti-α-amylase activities of the EtOAc and BuOH extracts from the aerial parts of Pulicaria vulgaris. Total phenolics and flavonoids of both extracts were quantified. A total of 4 and 19 polyphenolic compounds were identified in the EtOAc (major component: methylcatechin: 261.51 ± 0.03 g kg−1) and BuOH extracts (major component: 1,3-O-caffeoylquinic acid:12.95 ± 0.12 g kg−1), respectively, by HPLC-PDA/ESI-MS analysis. P. vulgaris extracts showed interesting in vitro antioxidant properties. The EtOAc and BuOH extracts exhibited an α-amylase inhibitory action (IC50 values of 10.0 and 7.5 μgmL−1, respectively). It has been shown that the EtOAc extract produced an uncompetitive inhibition against α-amylase, while the BuOH extract inhibited this enzyme in mixed manner. The molecular docking analysis of the major constituents of BuOH extract showed a low binding energy, a correct mode of interaction in the active pocket of the enzyme, and an ability to interact with the key residues of glycosidic cleavage (GLU-230 and ASP-206), which can explain the strong inhibitory effect of α-amylase established by the BuOH extract. This is the first report on the polyphenolic composition, antioxidant and anti-α-amylase activities of the extracts from the aerial parts of P. vulgaris.