In this study, antioxidant activities of two macroalgae, Eucheuma sp. J.Agardh and Laminaria sp., J.V.Lamouroux used as food supplements were investigated. The antioxidant activity, free radical scavenging activity, the total content of phenolics, flavonoids and condensed tannins in extracts were determined. The IC50 values of the extracts of Eucheuma sp. and Laminaria sp. on DPPH scavenging activity was 2.26±0.03 mg/g and 2.63±0.03 mg/g of extract, respectively. The maximum total phenolic (5.31±0.04 mg GAE/g Ext.) were determined. According to our results, all extracts exhibited low radical scavenging activity when compared to the standards used, i.e. -tocopherol and butylated hydroxytoluene (BHT) with the inhibition percentage in the range of 48.45±0.06% (Eucheuma sp.) – 58.49±0.03% (Laminaria sp.). The highest flavonoid content was measured as 18.78±0.10 mg rutin/g of extract in Laminaria sp. The condensed tannins were not detected in Eucheuma sp. However, this value was measured as 6.24±0.60 mg CE/g of extract for Laminaria sp. According to our results, Eucheuma sp. and Laminaria sp., which are commercially sold in medicinal herb stores, are good sources of antioxidant components because of their phenolic and flavonoid contents.

In this study, the antioxidant activities and biochemical characteristics of Ulva rigida (Ulvophyceae) and Arthrospira platensis (Cyanophyceae) were determined. The extracts from two seaweed species were evaluated for their free radical scavenging activity, using the 1,1-diphenyl-2-picrylhydrazyl hydrate (DPPH) method, their total phenolic, flavonoid, and condensed tannin contents, through Folin–Ciocalteu, Quettier-Deleu, and Price methods, respectively. The extracts of two seaweeds showed a low free radical scavenging capacity in comparison with commercial antioxidant BHT (butylated hydroxytoluene), and vitamin C. The extract of U. rigida demonstrated greater antioxidant potential with a low IC50 (3.76±0.02 mg/g Ext.). The total phenolic contents were ranged from 2.21±0.08 (U. rigida) to 8.59±0.62 (A. platensis) mg GAE/g of extract. The highest flavonoid content was found in A. platensis as 22.70±0.65 mg rutin/g of extract. The contents of condensed tannin were measured 3.01±0.11 mg CE/g of extract for A. platensis and 3.76±0.06 mg CE/g of extract for U. rigida. According to results obtained, U. rigida and A. maxima possess antioxidant activity and could be used in for future applications in medicine, functional foods, and agriculture.

The genus Achillea (Yarrow)is one of the most important medicinal plants. Nowadays, different medicinal functions of yarrow such as spasmolytic, choleretic, treatment of wounds and anti-inflammatory activities, make it as an important medicinal plant. The purpose of this study was to determine the antioxidant activity of aqueous (AAE) and methanol (AME) extracts from the plant Achillea santolinoides L. (A. santolinoides L.) aerial parts in vitro. Quantitative evaluation of polyphenols, flavonoids and tannins were determined using Folin-Ciocalteu reagent, aluminum chloride (AlCl3) and Bate Smith methods, respectively. Antioxidant activity was carried out using ABTS radical scavenging, alkaline DMSO superoxide radical scavenging and cupric reducing antioxidant capacity (CUPRAC). The obtained results showed that the highest content in total phenolic, flavonoids and tannins was found in the AME with values of 210.78±0.001 µg GAE/mg Dw, 21.18±0.025 µg QE/mg DW and198.73±0.014µg TAE/mg DW, respectively. For the in vitro antioxidant activity, AME had the strongest ABTS and DMSO alkaline radical scavenging activity (IC50= 6.74±0.16 µg/mL and 15.13±0.92 µg/mL, respectively) and the CUPRAC reducing with A0.50 of 76.56±2.35 µg/mL. The results of the present study confirm the use of the genus Achillea in the treatment of various diseases as a powerful antioxidant.