鹿児島大学 · 医歯学総合研究科

研究キーワードACE inhibitory phytochemicals・moringa oleifera・Salacia extracts・taro quality・natural food colorants・capsaicinoids・tea catechins・functional food chemistry

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• Kajiya K., Inokuchi H., Sakakibara Y., Takamatsu H., Yamanouchi H. . Preventive and inhibitory effects of Salacia on sustained contraction of vascular smooth muscle cells and characterization2026 · 記述言語： 日本語 出版者・発行元： Biochemistry and Biophysics Reports Sustained contraction of vascular smooth muscles can abruptly restrict blood flow, leading to ischemia. While mild, prolonged contractions may cause dizziness and migraines, severe vasoconstriction (vasospasm) can result in cerebral or myocardial infarction and may be fatal. Sphingosylphosphorylcholine (SPC) is a known inducer of pathological sustained contraction that occurs independently of Ca²⁺-dependent mechanisms. Although lipid-soluble dietary compounds have been reported to inhibit SPC-induced contractions, their clinical utility is limited by poor suitability for aqueous formulations and a tendency to accumulate in membranes and adipose tissue. In this study, we sought to identify water-soluble compounds that selectively inhibit pathological sustained contraction without impairing Ca²⁺-dependent vascular contraction. We focused on Salacia , a medicinal plant extensively studied for its metabolic effects, but whose vascular actions remain poorly characterized. Extracts from both aboveground (stems and trunks) and belowground (roots) parts of Salacia , applied either before or during SPC exposure, significantly inhibited SPC-induced sustained contraction. The active compounds were identified as 3,4-dihydroxybenzoic acid (3,4-DHBA), trans -3-, trans -4-, and trans -5-caffeoylquinic acids (CQAs), ortho -hydroxybenzoic acid ( o -HBA), and para -HBA ( p -HBA). Inhibitory potency followed the order 3,4-DHBA ≈ CQA > HBA. Notably, 3,4-DHBA and CQAs readily permeated vascular endothelial cells to reach smooth muscle, and their inhibitory effects were synergistically enhanced when 3,4-DHBA was present in excess. These findings suggest that water-soluble compounds from Salacia may prevent or attenuate SPC-induced vasospasm and its associated severe vascular diseases. DOI： 10.1016/j.bbrep.2026.102530 Scopus PubMed
• Yamanouchi H., Minami Y., Kajiya K. . Evaluation and validation of angiotensin-converting enzyme inhibitory activity of moringa oleifera, quercetin, and isoquercetin: A comparative study of fl2025 · 担当区分： 筆頭著者 記述言語： 英語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： Food Research International Moringa oleifera, known for its nutritional benefits and biological functions, such as antihypertensive effects, has cultivated in Japan. However, there is limited information available on moringa cultivated in Japan. Cardiovascular diseases, including ischemic heart disease and stroke, cause many deaths worldwide each year, with hypertension being the most significant risk factor. This study investigated the inhibitory activity of angiotensin-converting enzyme (ACE), which is one of the blood pressure elevation mechanisms, aiming to identify the active compounds in moringa leaves cultivated in Kagoshima prefecture, Japan (Kagoshima-moringa). Additionally, we evaluated the potential overestimation of the ACE inhibitory activity when measured using the fluorescence method. The ACE inhibitor compounds in the methanol-rich extract of Kagoshima-moringa were purified, and mass, aglycone, and glycoside analyses suggested isoquercetin as one of the active compounds. ACE inhibitory activity was evaluated using a fluorescent derivatization method with o-phthalaldehyde (OPA). However, the inhibitory effect of isoquercetin may have been overestimated, as the OPA fluorescence measurement indicated that isoquercetin could inhibit fluorescence readings. Therefore, the absorbance method was performed, revealing that captopril demonstrated similar inhibitory activity, whereas Kagoshima-moringa extracts showed low activity. These results indicate that the ACE inhibitory activity of flavonoids, or samples rich in flavonoids, may be overestimated when assessed by the fluorescence method using OPA. Hence, evaluating ACE inhibitor activity requires the careful selection of measurement methods; multiple activity measurement methods should be used if possible. The study underscores the importance of appropriate measurement methods for evaluating ACE inhibitory activity, guiding future research practices. DOI： 10.1016/j.foodres.2025.115768 Scopus PubMed
• Yamanouchi H., Tokimura K., Miura N., Ikezawa K., Onjo M., Minami Y., Kajiya K. . Effects of flooding cultivation on the composition and quality of taro (Colocasia esculenta cv. Daikichi)2021 · 担当区分： 筆頭著者 記述言語： 英語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： Journal of the Science of Food and Agriculture BACKGROUND: Taro (Colocasia esculenta cv. Daikichi) is believed to be one of the earliest cultivated tuber crops and it is a staple food in many parts of the world. The mother corm and side cormels (daughter and granddaughter tubers) form the major consumed parts; however, the former is rarely preferred. Taro is mainly cultivated using either unflooded or flooding cultivation, under dryland-rainfed and wetland-irrigated conditions, respectively. Although flooding cultivation has several advantages, such as lower risk of diseases, weeds, and insect pests, contributing to increased tuber yield, its effects on the quality characteristics of the tubers are largely unknown. In this study, the effects of controlled flooding cultivation on the quality of mother corm and side cormels were investigated. Their taste, color, physical properties, antioxidant activity, and starch, oxalic acid, nitrate ion, arabinogalactan (AG)/AG protein (AGP), γ-aminobutyric acid (GABA), and total polyphenol content was compared with those under unflooded cultivation. RESULTS: Flooding cultivation increased polyphenol levels and antioxidant activity and decreased oxalate, nitrate ion, GABA, and AG/AGP levels. Flooding cultivation also reduced the harshness and increased the hardness and stickiness of steamed mother corm paste, generally discarded under unflooded cultivation, thus rendering it suitable for consumption. CONCLUSION: Controlled flooding cultivation has economic advantages and the potential to improve the quality of cultivated taro. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. DOI： 10.1002/jsfa.11469 Scopus PubMed
• Kawasoe H., Wakamatsu M., Hamada S., Arata Y., Nagayoshi K., Uchida R., Yamashita R., Kishita T., Yamanouchi H., Minami Y., Kajiya K. . Analysis of natural colourant extracted from the pericar2020 · 記述言語： 英語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： LWT The pericarp of passion fruit is typically discarded before consumption. We aimed to demonstrate that pigments extracted from the pericarp could be used as natural colourants. We focused on the stability of the dyes in response to heat, light, and storage, which is the most pressing problem associated with natural colourants. The stability of the pigment in solutions was affected by certain factors. However, colour measurements confirmed that for test samples in powder form or those covered by a coloured commercial plastic bag or light shield, the pigments remain stable with no noticeable colour change. The pigment extracted from the pericarp included anthocyanins such as cyanidin-3-glucoside, peonidin-3-glucoside, callistephin, and cyanidin-3-rutinoside, which have 3-O-glycoside bonding of the C-ring. They were not found in the passion fruit pulp or seeds. The colour value of the pigment was lower than that of the same amount of red cabbage dye or purple sweet potato dye, which are typically used in food manufacturing. The pigment extracted from passion fruit pericarp was used to dye processed food such as jelly, which was coloured pink to red depending on the amount of pigment used. The passion fruit pericarp could be used as a low-cost natural red colourant. DOI： 10.1016/j.lwt.2020.110412 Scopus

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