Seasonal Variations in Total Antioxidant Capacity and Total Phenolics Content of Leaves of <i>Phyllostachys<i> Taxa Using Different Extraction Methods
András NEMÉNYI | Éva STEFANOVITSNÉ-BÁNYAI | Szonja Szimóna BURJÁN | Zoltán PÉK | Attila HEGEDŰS | Csaba GYURICZA | Lajos HELYES
Changes in total phenolic content (TP) and total antioxidant capacity (AC) during the vegetation period (April-November) were analysed in <i>Phyllostachys aureosulcata </i>f.<i> aureocaulis (PAA), P. flexuosa (PF), P. humilis (PH), P. sulphurea </i>var.<i> sulphurea (PSS). </i>Different extraction methods were compared: infusion or decoction with water or aqueous methanol. The highest significant value for TP was measured in the case of infusion at 90 °C for 5 min, which lead to the highest value for AC. During the vegetation period the highest values of TP were measured in April and May in the case of <i>PAA</i> (409.5; 314.9 and 258.7; 119.0 μg GA/ml) and <i>PH</i> (388.4; 411.6 and 252.9; 253.3 μg GA/ml). There was a clear trend in the changes of TP, with high values in April and November and a peak during August-September. Similar to TP, the highest values of AC were measured in April and May in <i>PH </i>(519.7; 566.3 and 513.5; 510.4 μg AA/ml) and <i>PAA</i> (534.5; 337.8 and 394.9; 275.4 μg AA/ml). We compared the change of TP in all taxa with stress index values derived from daily maximum and minimum air temperature, cumulative precipitation plus irrigation and cumulative evapotranspiration values. A close correlation R<sup>2</sup> = 0.32 (p=0.001) was found between stress index values and the change in TP of all taxa. The correlation is even closer R<sup>2</sup> = 0.52 (p=0.001) with <i>PF, PH </i>and<i> PSS</i>. Our results with <i>PAA</i> can be explained by possible inter/intra-specific differences in freeze tolerance and cold-acclimation.
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