柑橘類類黃酮類的結構與生理機能

Structure and Health-Promoting Properties of Citrus Flavonoids

類黃酮是對人體有生理效益的植物二次代謝物，其種類繁多，包括：黃酮醇（flavonol）、黃酮（flavone）、黃烷酮（flavonone）、和異黃酮（isoflavone）。柑橘屬植物含有多量類黃酮，這是柑橘類苦味的主要來源，其所含類黃酮主要為黃烷酮，還有少量的黃酮醇及黃酮。柑橘的類黃酮類與種的關係密切，從66種柑橘類及近緣種內含類黃酮種類的分析結果，與田中長三郎氏（Tanaka）的柑橘型態分類系統可有相當好的對應。柑橘類之類黃酮主要具有的生理機能包括抗氧化、抗癌、抗發炎，其對心血管疾病的治療有助益，並可提高特定藥物的藥效。類黃酮的抗氧化力主要決定於C6-C3-C6的三環結構中，第三環或稱為B環上的OH基數目，不具OH基者抗氧化力較弱，具一個OH基者以上則顯著提高；若B環上含有兩個OH基，則鄰位（ortho-，3'-4'）比間位（meta-，2'，4'）抗氧化力強；當B環上OH基數相同時，又以A、C環上含有較多OH基者具較強抗氧化力。由於類黃酮的強抗氧化力，因此在抗癌及抗炎方面具有效能。柑橘的類黃酮類的含量，除了隨品種而異外，尚與果實發育階段及栽培管理有密切關係。 Flavonones, flavones, and flavonols are the flavonoids exist in Citrus. Twenty-four flavonoids have been found in 66 Citrus spices and near-citrus relatives. There is a close correspondence between the result of analyzing 66 Citrus species and relatives with flavonoids contents and Tanaka's classification system. Flavonoids are a widely distributed group of polyphenolic compounds with health-related properties, which are based on their antioxidant activity. These properties provide the resistence to oxidation, cancer, and flammation; the enhancement of curative effects in cardio vascular therapy, and the raise of bioavailability of some drugs. The antioxidant capacity of any flavonoid will be determined by a combination of the O-dehydroxyl structure in the B-ring, a hydroxyl group at position 3 in the C-ring and more hydroxyl groups in the A-ring. Some Citrus flavonoids have been used directly as drugs in anti-inflammation and cardiovascular therapeutic efficacy. Naringin, one of the major flavonoids in grapefruit, can increase the bioavailability of coumarin by interacting with grapefruit juice. In addition, early foliar spray treatments containing gibberellic acid (GA3) significantly lower the strength of bitterness of flavonoids naringin in fruit tissues.