Isolation, Characterization, and Determination of Antioxidative Activity of Oligomeric Procyanidins from the Seedpod of Nelumbo nucifera Gaertn.

The procyanidins of nonedible parts of lotus (Nelumbo nucifera Gaertn.) were determined for the first time. The procyanidins of lotus seedpod were extracted with Me2CO/H2O and purified by Sephadex LH-20 column chromatography, with a purity of >98%. ESI-MS analysis showed that the main molecular weight distribution of procyanidins ranged from 291 to 1155, with M + H peak values of 291.1, 579.2, 731.2, 867.2, 1019.4, and 1155.3, respectively. This indicates that the extract contains monomers, dimers, and tetramers of procyanidins, in which the amounts of dimers are greatest, and catechin and epicatechin are the base units. 1H NMR and 13C NMR spectra confirmed that two to four monomers are linked through C4−C8 (or C6) bonds. The effects of the procyanidins on lipid autoxidation, lipoxygenase activities, and free radical scavenging were also studied. The results showed that 0.1% procyanidins have a strong antioxidant activity in a soybean oil system, better than BHT at the same concentration; inhibited lipoxygenase activity by >90% at a concentration of 62.5 μg/mL, with an IC50 value of 21.6 μg/mL; and had IC50 inhibitory values rate to •OH of 10.5 mg/L and a scavenging effect on O2•- of 17.6 mg/L. Keywords: Lotus seedpod; procyanidins; antioxidant