Screening of the antioxidant properties of crude extracts of six selected plant species from the Canary Islands (Spain)

The extracts of six common plants from the Canary Islands were screened for their antioxidant activities and compared with several phenolic compounds of natural origin (quercetin, catechin, rutin and gentisic acid) and synthetic (butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT)). The in vitro antioxidant activity determined by using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method revealed that Plantago major L., Artemisia canariensis (Bess.) Lessing and Bidens aurea (Dryand.) Sherff exerted greater activity than the other plants (90.9%, 89.0% and 88.2% inhibition rate, respectively). The most active plants were Bidens aurea (Dryand.) Sherff and Plantago major L. (9.5 and 7.2 trolox mu mol equivalents), when the cupric ion reducing antioxidant capacity assay (CUPRAC) was used. All the plants species exhibited higher antioxidant capacities than the synthetic antioxidants BHA and BHT. Among the natural phenolic compounds, gentisic acid was the most active. However, two of the plant extracts showed higher antioxidant activity than any other of the pure compounds studied, even than that of gentisic acid. The use of reversed phase high performance liquid chromatography (RP-HPLC) allowed the identification of the natural phenolic constituents listed above in Bidens aurea (Dryand.) Sherff and Plantago major L. extracts. Catechin and quercetin were the most prominent phenolic compounds. The presence of phenolic compounds in the plant extracts and their high antioxidant activities underline their phytomedicinal potentials. These plants may be exploited in the production of health foods and as an antioxidant carrier in the food and pharmaceutical industries.