Objective: The objective of the present study was to measure antioxidant activity and to evaluate the phytochemical constitution of Helichrysum lacteum growing in Algeria.
Methods: The structure elucidation of the isolated compounds was performed by spectroscopic methods. Antioxidant activity of the extracts the crude extracts (PE, EtOAc, and n-BuOH) and pure compound (noryangonin (3)) was investigated by 5 methods, including DPPH free radical scavenging activity, reducing power and ferric thiocyanate methods, hydrogen peroxide scavenging capacity, and total antioxidant activity by phosphomolybdate assay.
Results: The chemical investigation of the EtOAc extract of the aerial parts of H. lacteum led to the isolation of two flavonoids, astragalin (1) and isoquercitrin (2), together with a styryl pyrone, noryangonin (3), and a cyclobutane dimer, achyrodimer C (4) as well as two triterpenoid compounds, β-sitosterol (5) and oleanolic acid (6). The highest phenolic and flavonoid contents were detected in the ethyl acetate extract. Noryangonin exhibited the highest antioxidant activity than those of the references and all the tested extracts, with a value of IC50 at 1.45±0.44 μg/mL in DPPH scavenging. In hydrogen peroxide scavenging essay, the results revealed that EtOAc extract exhibited the highest percent inhibition (63.15 %) as compared to the ascorbic acid (63.36 %) at the concentration of 100 μg/mL. In the phosphomolybdenum method, the EtOAc extract showed the strongest activity (36.85±0.02 μg EAA/mg ex) as compared to those of n-BuOH and PE extracts.
Conclusion: The antioxidant property shown in these findings needs further investigation, especially with the pure compound (3).
Keywords: Helichrysum lacteum, flavonoid, NMR, antioxidant activity, ascorbic acid, ferric thiocyanate.