Changes in antioxidative activity and flavonoid composition of the extracts from aerial parts of buckwheat during growth period

The DPPH radical-scavenging activities and polyphenol contents of methanolic extracts from aerial parts of buckwheat (Fagopyrum esculentum Moench) during growth period were investigated. The total polyphenols in the extracts decreased from germination to 15 days after, but thereafter, it increased up to the 23rd day at early in the flowering time. Although the change in the DPPH radical-scavenging activitiy was similar to that of the total polyphenol content, the activity on the 23 rd day was similar to or higher than that on the first. Whereas the HPLC pattern of the extracts during the early stage of development showed five main peaks including rutin, the number of peaks decreased with increasing days, and only rutin was detected on and after the 19th day. UV spectra of the peaks detected in the HPLC chromatogram of the extracts of buckwheat seedlings, revealed that they contained four flavonoid compounds except for rutin. Two peaks of the chromatogram, which were not detected by an electrochemical detector at +300mV, were identified as vitexin and isovitexin by comparison with HPLC data of the isolated compounds from buckwheat hulls, Other two peaks, which were detected by electrochemical analysis, were isolated by Sephadex LH-20 chromatography, preparative HPLC with ODS and a polymer based column. They were identified as orientin and isoorientin by NMR and FAB-MS spectrometric data. The contents of these flavonoid compounds were abundant in buckwheat seedlings along with rutin.