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Sasaki K.,University of Tsukuba | Han J.,University of Tsukuba | Shimozono H.,Kagoshima Prefectural Institute of Food Processing and Utilization | Villareal M.O.,University of Tsukuba | Isoda H.,University of Tsukuba
Journal of Agricultural and Food Chemistry | Year: 2013

The effects of caffeoylquinic acid (CQA)-rich purple sweet potato (PSP) extract, with (PSPEa) or without (PSPEb) anthocyanin, on the improvement of spatial learning and memory of senescence-accelerated prone mouse strain (SAMP) 8 was determined. SAMP8 was treated with 20 mg/kg/day of PSPEa or PSPEb for 30 days. The effect on spatial learning and memory and the molecular mechanism of this effect were determined in vivo (SAMP8) and in vitro (SH-SY5Y cells). PSPEa or PSPEb reduced the escape latency time of SAMP8 by 17.0 ± 8.0 and 14.2 ± 5.8 s (P < 0.01), respectively. PSPEa administration induced an overexpression of antioxidant-, energy metabolism-, and neuronal plasticity-related proteins in the brain of SAMP8. Additionally, PSPEa and PSPEb increased the cell viability by 141.6 and 133% as compared to Aβ1-42-treated cells. These findings suggest that PSP rich in CQA derivatives with or without anthocyanidine had a neuroprotective effect on mouse brain and can improve the spatial learning and memory of SAMP8. © 2013 American Chemical Society. Source

Shimada Y.,Kagoshima Prefectural Institute of Food Processing and Utilization | Kume T.,Kagoshima Prefectural Institute of Food Processing and Utilization | Ishiguro K.,Japan National Agricultural Research Center | Kura R.,Japan National Agricultural Research Center | And 2 more authors.
Nippon Shokuhin Kagaku Kogaku Kaishi | Year: 2010

Large-scale extraction of polyphenols from sweet potato tops was analyzed for its applicability in industry. The sweet potato cultivar "Koganesengan" was chosen because its tops generate the majority of its sweetness during Shochu brewing and starch production. The yield of the hot-water extract at 95°C was 219 g (dry weight) from 100 kg (fresh weight) of sweet potato tops, giving a 34.1% recovery of polyphenols from the dried powder. The extract was composed of 49.9% caffeoylquinic acid (CQA) derivatives. HPLC analysis revealed three mono CQAs (3-, 4-, and 5-CQAs), three diCQAs (3, 4-, 3, 5-, and 4, 5-diCQAs), and 3, 4, 5triCQA. The 1,1-diphenyl-2- picrylhydrazyl radical-scavenging activity of the extract was 75.2% that of commercial chlorogenic acid. Source

Ishiguro K.,Japan National Agriculture and Food Research Organization | Sameshima Y.,Kagoshima Prefectural Institute of Food Processing and Utilization | Kume T.,Kagoshima Prefectural Institute of Food Processing and Utilization | Ikeda K.-I.,Kagoshima Prefectural Institute of Food Processing and Utilization | And 2 more authors.
Food Chemistry | Year: 2012

We have investigated angiotensin I-converting enzyme (ACE) inhibitory activity in an enzyme digest of sweetpotato protein, the antihypertensive effect of the digest in spontaneously hypertensive rats (SHR), and the identification of an ACE inhibitory peptide. Protein was prepared from squeezed juice of sweetpotato by isoelectric focusing precipitation. Three kinds of proteases were selected for effective protein digestion. The digest, sweetpotato peptide (SPP), exhibited strong ACE inhibitory activity (IC 50: 18.2 μg/ml). SPP was orally administered by gavage to SHR at a dose of 100 mg/kg or 500 mg/kg. The systolic blood pressure and the diastolic blood pressure were measured at 0 (before administration), 2, 4, 8, and 24 h after administration. A dose-dependent decrease in systolic blood pressure in SHR was observed after oral administration of SPP. Significant differences between SPP-administered rats and control rats were observed 4 and 8 h after administration in the 500 mg/kg-administered group and 8 h after administration in the 100 mg/kg-administered group. Diastolic blood pressure also decreased in the SPP-administered groups, although the difference between SPP-administered rats and control rats was not significant. These results suggest that SPP may be useful in the prevention or treatment of hypertension. Peptides with ACE inhibitory activity were purified from SPP by absorption chromatography and preparative HPLC using an ODS column. The amino acid sequences of isolated peptides were I-T-P, I-I-P, G-Q-Y and S-T-Y-Q-T; their ACE inhibitory activities (IC 50) were 9.5 μM, 80.8 μM, 52.3 μM and 300.4 μM, respectively. In conclusion, I-T-P is a novel, strong ACE inhibitory peptide. © 2011 Elsevier Ltd. All rights reserved. Source

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