The amount of total polyphenols, measured by Folin-Ciocalteu method, was expressed as pyrogallol equivalent and ranged from 174.76±0.74 mg/g dry extract (de) (in P. americana fruit) to 786.70±1.78 mg/g de (in A. fruticosa leaves) . The highest level of total polyphenols was found in A. fruticosa leaves, followed by A. fruticosa fruit. The total flavonoids content in the extracts was expressed as mg hyperoside equivalent and varied from 15.88 ± 0.12 mg/g de (in P. americana fruit) to 32.19 ± 0.29 mg/g de (in A. fruticosa leaves). The results demonstrated that flavonoids generally were showing higher content in leaves than in fruits. The least quantity of total polyphenols and flavonoids was found in P. americana fruit. The content of total hydroxycinnamic derivatives was expressed as rosmarinic acid equivalent and was found in A. fruticosa fruits (153.55 ± 1.11 mg/g de), leaves (132.25 ± 5.49 mg/g de) and P. americana leaves (23.63 ± 0.39 mg/g de) .
Contents of total polyphenols, flavonoids, and hydroxycinnamic derivatives in A. fruticosa and P. americana
Radical scavenging activity, ferric reducing antioxidant power and AChE inhibitory potential of studied invasive plants were compared with those of BHT and are presented in . Methanol extract from A. fruticosa
fruit demonstrated the highest antioxidant (DPPH-, ABTS-, FRAP) and acetylcholinesterase inhibitor activity. The DPPH- and ABTS- radical scavenging activity decreased in order: A. fruticosa
9.83 μg/mL and 2.90 μg/mL) > A. fruticosa
11.23 μg/mL and 2.93 μg/mL) > BHT (IC50
64.76 μg/mL and 17.70 μg/mL) > P. americana
88.79 μg/mL and 18.43 μg/mL) > P. americana
412.06 μg/mL and 112.49 μg/mL, respectively). Previous investigation revealed significant DPPH radical scavenging of Phytolacca
berries growing native in Iran with IC50
62.0 ± 2.1 μg/mL.[4
] Differences between quoted and current data are probably due to lower content of flavonoids in our sample and differences in the methods used.
DPPH, ABTS-radical scavenging, FRAP and AChE inhibitory activities of A. fruticosa and P. americana
In contrast to A. fruticosa, P. americana fruit did not manifest any FRAP and acetylcholinesterase inhibition activity. FRAP and acetylcholinesterase inhibition properties was demonstrated by A. fruticosa fruit (642.95 ± 3.95 μg TE/mg de; 48.86 ± 0.55%) and leaves (508.81 ± 1.75; 25.43 ± 0.16). The results obtained revealed the potential importance of the presence of hydroxycinnamic derivatives for the antioxidant and AChE inhibitory properties of plants. FRAP activity of A. fruticosa was found to be higher compared to the control BHT (30.50±0.24 μg TE/mg de), nevertheless the species demonstrated lower acetylcholinesterase inhibition activity than the positive control Galanthamine hydrobromide with an IC50 of 0.15 μg/mL.
In the present study, the inhibition of lipid peroxidation of the extracts (1 mg/mL) was determined in linoleic acid system using the FTC method . During linoleic acid peroxidation, peroxides were formed and these compounds oxidized Fe2+ to Fe3+. The Fe3+ ion formed a complex with SCN-, which had a maximum absorbance at 500 nm. Thus, a high absorbance value was an indication of high peroxide formation during the emulsion incubation. The presence of antioxidants in the mixture minimizes the oxidation of linoleic acid and reduces absorption, respectively. The highest significant diminution was demonstrated by A. fruticosa fruit followed by P. americana fruit. However, the antioxidant activity of studied species was slightly less effective than that of BHT, all of them inhibited lipid peroxidation compared to the control.
Antioxidant activity of A. fruticosa and P. americana in linoleic acid system
Generally, it is known that total polyphenols (a wide class of components including phenolic acids, catechins, flavonols, and anthocyanins) are highly correlated with antioxidant activity.[19
]. The analysis of the correlation between the total phenolic compounds, flavonoids and hydroxycinnamic derivatives content and antioxidant activities showed significant dependence in the case of DPPH, free radical neutralizing properties, FRAP activity, and the total phenolic compounds and hydroxycinnamic derivatives (r = -0.999, r = 0.998; r = -0.990, r = 0.986, respectively). It should be also noted that positive correlations were between inhibition of acetylcholinesterase activity and content of total polyphenols (r = 0.91) and total hydroxycinnamic derivatives (r = 0.946) .
Correlation between total phenolics, flavonoids, and hydroxycinnamic derivatives content and antioxidant activity of A. fruticosa and P. americana