Changes in Antioxidant Activities in Leaves and Stems of <i>Forsythia saxatilis</i> var. <i>lanceolata</i> Kept under Different Light Conditions

Abstract

The purpose of this study was to analyze changes in antioxidant activities in the leaves and stems of Forsythia saxatilis var. lanceolata kept under different light conditions and to provide basic data for functional new materials. The antioxidant concentrations in growth third-year F. saxatilis var. lanceolata leaves after cutting were higher than those in the stem at 68.8 mg CGE / 100 g FW (total anthocyanins), 7405.0 mg CE / 100 g FW (total flavonoids), and 4231.2 mg GAE / 100 g FW (total phenolics). The antioxidant activity was also higher at 294.3 mg VCE / 100 g FW (DPPH radical scavenging). As a result of the correlation between antioxidant concentration and activity, total anthocyanins showed no correlation with other factors, but total flavonoids and total phenolics were found to have an r value of 0.753 in the significance level of 0.05 to each other, and total flavonoids and total phenolics were highly correlated with the DPPH radical scavenging activity (r = 0.753 and 0.698 at the 0.05 level, respectively). These results suggest that the total phenolic level of F. saxatilis var. lanceolata mostly comprises total flavonoids and that total flavonoids and total phenolics contribute to the antioxidant activity. An analysis of F. saxatilis var. lanceolata three years after cutting and growing under different light conditions (shade: 42.83 umol･m-2 ･s-1 PPFD, sunny: 788.39 umol･m-2･s-1 PPFD) showed that antioxidant concentrations and activities were higher in plants cultivated under sunny conditions. The chlorophyll content was also found to be higher in leaves from plants grown under sunny conditions. These results suggest that the phenolic compounds and vitamin C are synthesized during the photosynthesis process. Therefore, the antioxidant contents and activities of the leaves of F. saxatilis var. lanceolata grown under sunny conditions were higher than those of plants grown under the “shade” conditions. Thus, it was determined that F. saxatilis var. lanceolata has a high potential for antioxidant materials. It is considered that F. saxatilis var. lanceolata leaves grown under sunny conditions are highly likely to be used as a functional material owing to their high antioxidant concentration and activities than those grown under “shade” conditions.