Isolation and Identification of an Antioxidant Substance from Heated Onion (Allium cepa L.)

The objectives of this study were to identify antioxidant substance in heated onion. The isolation of active compound was performed in three steps: silica gel column chromatography, preparative TLC, and preparative HPLC. The structure of the purified compound was determined using spectroscopic methods, i.e., ultraviolet, mass spectrometry, $^1H$-NMR, $^{13}C$-NMR, and DEPT. The antioxidant activities of isolated compound were evaluated and compared with $\alpha$-tocopherol, ascorbic acid, and butylated hydroxytoluene (BHT) using DPPH and ABTS assay. The isolated compound was identified as 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one(DDMP). The DPPH radical-scavenging activity ($IC_{50}$) of the DDMP was in the following order: ascorbic acid (45.3 ${\mu}g/mL$)>$\alpha$-tocopherol (69.2 ${\mu}g/mL$)>DDMP (241.6 ${\mu}g/mL$)>BHT (268.0 ${\mu}g/mL$). In addition, DDMP showed strong ABTS radical-scavenging activity of 569.0 mg AA eq/g.

열처리 양파로부터 항산화물질의 분리동정

열처리한 양파 착즙액의 ethyl acetate 분획물로부터 항산화물질을 분리 동정하기 위하여 1, 2차 silica gel column chromatography, preparative TLC 및 HPLC를 이용하여 항산화활성 물질을 분리 정제하였다. GC/MSD, $^1H$-NMR 및 $^{13}C$-NMR spectrum 결과로부터 구조 동정한 결과 분리된 물질은 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one(DDMP)으로 확인되었다. DDMP의 항산화활성의 $IC_{50}$값은 241.6 ${\mu}g/mL$이었으며, vitamin E의 69.2 ${\mu}g/mL$와 C의 45.3 ${\mu}g/mL$보다는 낮은 활성을 보였고 BHT의 268.0 ${\mu}g/mL$보다는 높은 활성을 보였지만 유의적인(p>0.05) 차이는 나타나지 않았다. 추후 DDMP를 기능성물질로 활용하기 위하여 다양한 생리활성 평가가 필요할 것으로 생각된다.