齲蝕原因菌に対する柿蔕抽出成分の抗菌効果  [in Japanese] Antibacterial Effects of Diospyros Kaki Thunb. Extract against Cariogenic Bacteria  [in Japanese]

齲蝕は世界的に最も頻度の高い口腔疾患の一つであるとともに,Streptococcus mutansを代表とする齲蝕原因菌による内因性疾患であることが明らかにされている.近年,健康に対する認識の向上とともに自然食品への関心が高まり,それらの健康への効用ならびに薬効作用が注目されている.柿(Diospyros Kaki Thunb.)は,日本古来より果実としてなじみの深い食品であるとともに生薬としても用いられ,抗酸化作用,抗炎症作用,抗菌作用などのいくつかの生物学的活性を有する.今回,われわれは抗吃逆剤として用いられてきた柿の蔕(へた)を乾燥した柿蔕(してい, Kaki Calyx)の抽出成分に着目した.本研究の目的は,より有効な齲蝕予防を行うために柿蔕抽出成分であるウルソール酸およびオレアノール酸の抗菌作用について,in vitro実験において調べることである.検討の結果,以下の知見が得られた.1. S. mutansに対する最小発育阻止濃度は,ウルソール酸において60μg/ml,オレアノール酸において120μg/mlであった.2. Actinomyces viscosusに対する最小発育阻止濃度は,ウルソール酸において30μg/ml,オレアノール酸において60μg/mlであった.3. ウルソール酸ならびにオレアノール酸の抗菌作用は,S. mutansおよびA. viscosusのresting cellに対して殺菌的であった.4. ウルソール酸ならびにオレアノール酸は,S. mutans PS-14(c)株産生粗glucosyltransferaseのショ糖依存性非水溶性グルカン合成活性を顕著に阻害した.以上のことより,柿蔕抽出成分であるウルソール酸およびオレアノール酸は齲蝕原因菌に対して顕著な殺菌作用が認められ,抗齲蝕作用を有することが示唆された.

It has been so far clarified that caries is an endogenous disease due to carious pathogens represented by Streptococcus mutans (S. mutatis) and so on. With the growing recognition of the benefits to public health in recent years, natural foods are now highlighted with special reference to their effects on the human health in addition to their pharmacological actions. Japanese persimmons (Diospyros Kaki Thunb.) have been used as an herbal medicine in Japan with several biological activities, including antioxidant, anti-inflammatory and antimicrobial actions. In the present study, therefore, we focused on the components extracted from Kaki Calyx, a dried persimmon's calyx, which has been used as an anti-hiccup agent. The purpose of this study was to examine the antimicrobial actions of ursolic acid and oleanolic acid, both of which were extracted from Kaki Calyx, in an in vitro experiment in order to find a more efficient tool for the prevention of caries. The following conclusions were obtained. 1. The minimum inhibitory concentration against S. mutans was revealed to be 60μg/ml for ursolic acid and 120μg/ml for oleanolic acid. 2. The minimum inhibitory concentration against A. viscosus was revealed to be 30μg/ml for ursolic acid and 60μg/ml for oleanolic acid. 3. The antibacterial activities of ursolic and oleanolic acids were both found to have a bactericidal action against resting cells of S. mutans and A. viscosus. 4. Both ursolic and oleanolic acids markedly inhibited water insoluble glucan synthesis from sucrose by the crude glucosyltransferase of S. mutans PS-14(c). In conclusion, it was suggested that ursolic acid as well as oleanolic acid, both being a component extracted from Kaki Calyx, have antibacterial activity against cariogenic bacteria with an expected anti-carious effect.