Purification and Identification of Novel Antioxidant Peptides from Enzymatic Hydrolysate of Ginkgo biloba Seed Proteins

Abstract

Ginkgo biloba seed proteins were hydrolyzed using alkali protease and pepsin to obtain antioxidant peptides. Ginkgo biloba antioxidant peptides (GKAPs) were separated by Sephadex G-25 and Sephadex G-10 gel filtration chromatography. The GKAP B3 exhibited highest antioxidant activity. B3 peptide was separated by reversed-phase high-performance liquid chromatography (RP-HPLC), and 2 peptides with good antioxidant activity, i.e., GKAPs C8 and C9, were obtained. The molecular weight and amino acid sequences of the peptides were identified by Liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS). The results showed that the molecular mass of GKAP C8 was 452.21 Da and the amino acid sequence was YVGD (Tyr-Val-Gly-Asp), while the molecular mass of GKAP C9 was 988.49 Da and the amino acid sequence was LGNTDYAVH (Leu-Gly-Asn-Thr-Asp-Tyr-Ala-Val-His). GKAPs C8 and C9 exhibited good free radical-scavenging effect and inhibited the autoxidation of the linoleic acid system.Keywords: Ginkgo biloba seed protein, antioxidant peptide, radical scavenging activity, amino acid sequence *To whom correspondence should be addressed. E-mail: sxwucaie@163.com IntroductionIn China, Ginkgo biloba seeds are widely used in traditional medicines and foods. It is rich in vitamin C, riboflavin, carbohydrates, proteins, and many other nutrients (Son and Kim, 1998). The protein content of Ginkgo biloba seed is around 10% (dry mass). Ginkgo biloba seed protein is considered to be a high-quality protein and exhibits strong antioxidant properties (Huang et al., 2010;Zhou et al., 2012). The protein polypeptide chain contains various functional areas that are considered bioactive with respect to antioxidant property. When a protein polypeptide chain was hydrolyzed enzymatically, functional groups within the chain were exposed, and they can exhibit different biological activities (Meisel, 1997;Meisel and Bockelmann, 1999). In recent years, peptides generated from various species including animal and plant sources have been found to possess good antioxidant activity. For example, peptides ACGT and ATAGT from Tibpia frame protein (Fan et al., 2012), peptide LEELEEELEGCE from Bullfrog skin (Qian et al., 2008b), LPHSGY from Alaska Pollock protein hydrolysate (Je et al., 2005), NADFGLNGLEGLA from Giant squid, and LKQELEDLLEKQE from Oyster protein hydrolysate have been reported to possess antioxidant activity (Qian et al., 2008a;Rajapakse et al., 2005). In these studies, the antioxidant activity of peptides was evaluated by scavenging free radicals by in vitro assays using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, hydroxyl (•OH) radical, superoxide anion radical (•O 2 ), and determination of antioxidant capacity in linoleic acid system. However, there are few reports on antioxidant peptides from Ginkgo biloba seed peptides. In this research, Ginkgo biloba seed protein was hydrolyzed with alkaline protease 2709 and pepsin to obtain antioxidant peptides. The antioxidant activity of antioxidant peptides were evaluated b...

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“…Their antioxidant potential, expressed as half maximal inhibitory concentrations (IC 50 ), differed depending on the assay applied to measure the activity. Hence, the IC 50 values were at 0.47, 0.51, and 0.53 mg·cm −3 for the YVGD peptide and at 0.46, 0.51, and 0.66 mg·cm −3 for the LGNTDYAVH peptide when measured with DPPH, hydroxyl (·OH), and ·O 2 free radical scavenging activity assays, respectively (Wu and others ).…”

“…Wu and others () hydrolyzed Ginkgo biloba seed proteins using alkaline protease 2709 (Beijing Donghua Qiangsheng Biotechnology Co., Ltd, China) and pepsin (Shanghai Yuanju Biological Technology Co., Ltd., China) to produce the following peptides: YVGD and LGNTDYAVH. Their antioxidant potential, expressed as half maximal inhibitory concentrations (IC 50 ), differed depending on the assay applied to measure the activity.…”