Bioactive properties of Chamaerops humilis L.: antioxidant and enzyme inhibiting activities of extracts from leaves, seeds, pulp and peel

Abstract

In this work we evaluated methanolic extracts from different parts (leaves, seeds, fruit peel and pulp) of Chamaerops humilis L. for antioxidant activity and the ability to inhibit enzymes linked with neurodegenerative diseases: acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and tyrosinase (TYR). The total content of phenolics, flavonoids and condensed tannins was also determined. The antioxidant and inhibitory activities of the extracts varied significantly according to the tissue. Seed extracts showed the greatest ability to scavenge DPPH (IC₅₀ = 81.28 µg mL⁻¹) and ABTS (1440.42 µmol_TE ${{\text{g}}^{-1}}_{\text{extract}}$) and to reduce iron (1142.46 µmol_AAE ${{\text{g}}^{-1}}_{\text{extract}}$). Seed and peel extracts strongly inhibited AChE (IC₅₀ = 660.16 and 653.68 µg mL⁻¹, respectively) and BChE (IC₅₀ = 304.86 and 701.54 µg mL⁻¹, respectively). The strongest inhibition of TYR was achieved by the seed and pulp extracts (268.97 and 279.99 µg mL⁻¹, respectively). The highest levels of phenolics and condensed tannins were found in the seed extract (1564.88 µmol_GAE ${{\text{g}}^{-1}}_{\text{extract}}$ and 170.00 µmolc_E ${{\text{g}}^{-1}}_{\text{extract}}$, respectively) whereas the leaf extract was the richest in flavonoids (139.88 µmol_QE ${{\text{g}}^{-1}}_{\text{extract}}$). HPLC-DAD analysis indicated the presence of flavonoids and phenolic acids (hydroxycinnamic acids) in the leaf and pulp extracts. A high correlation was found between the total condensed tannins content and the antioxidant and enzyme inhibition activities, suggesting these compounds are responsible for the biological activity of the extracts. Overall, our results indicate that C. humilis extracts may provide a new and alternative source of agents for medical and industrial applications.