ANTI-OXIDATIVE ACTIVITY IN THE LIPOPHILIC FRACTION OF SWEET POTATO TUBERS

Anti-oxidative activities in the lipophilic fraction of 10 sweet potato cultivars with white to yellow flesh were examined by 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and lipid peroxyl based on inhibition of 2,2’-azobis (2,4-dimethylvaleronitrile) (AMVN)-initiated peroxidation of methyl linoleate.
The lipophilic fraction exhibited anti-oxidative activity with a correlation between ABTS radical scavenging activity and lipid peroxyl radical scavenging activity, and the activity was not related to the content of yellow pigments.
To identify the components related to the anti-oxidative activity, the lipophilic fraction was analyzed by thin-layer chromatography (TLC) and successive immersion in 1,1-diphenyl-2-picrylhydrazyl (DPPH) solution (TLC-DPPH method). A strong DPPH radical scavenging band was detected, and the band migrated differently from those of yellow pigments.
Anti-oxidative components in the band were purified by preparative TLC and preparative HPLC. They were identified by means of EI-MS and ¹H and ¹³C NMR as p-coumaric acid hexadecyl (p-CAHD) and p-coumaric acid octadecyl (p-CAOD). The contents of the p-coumaric acid esters were highly correlated with the anti-oxidative activity in the lipophilic fraction.
From these results, the main anti-oxidative components in the lipophilic fraction are p-coumaric acid esters with long alkyl chains, and these would act as anti-oxidants together with hydrophilic polyphenolics in sweet potato tubers.

XXVII International Horticultural Congress – IHC2006: International Symposium on The Role of Postharvest Technology in the Globalisation of Horticulture

K. Ishiguro, M. Yoshimoto, M. Suzuki, S. Yahara

Ipomoea batatas, lipophilic anti-oxidant, radical scavenging, p-coumaric acid hexadecyl, p-coumaric acid octadecyl

https://doi.org/10.17660/ActaHortic.2008.768.77