Anthraquinone Glycosides PDF

Anthraquinone Glycosides Anthraquinone Glycosides are oxygenated derivatives of pharmacological importance that are used as laxatives or cathartics, anti-inflammatory, antibacterial, antifungal and also as natural dyes. These glycosides are present in such drugs as cascara sagrada, frangu...

Anthraquinone Glycosides Anthraquinone Glycosides are oxygenated derivatives of pharmacological importance that are used as laxatives or cathartics, anti-inflammatory, antibacterial, antifungal and also as natural dyes. These glycosides are present in such drugs as cascara sagrada, frangula, aloe, rhubarb and senna. A- Aglycones: Forms of Anthracene derivatives in Plants: The activity decreases as oxidation level increase. B- Dimeric Anthracene derivatives: They are derived from two anthracene units connected by covalent C-C bond through C-10. 1) Homo-Dianthrones: The two anthrone moieties are similar. e.g. Sennidins A&B and their corresponding glycosides Sennosides A&B. They are all formed of two Rhein monomers. The A group are (l)-form while the B group are meso compounds with zero optical rotation. 2) Hetero-Dianthrones: The two anthrone moieties are different. e.g. Sennidins C&D and their corresponding glycosides Sennosides C&D. They are all formed of one Rhein and one Aloe- emodin monomers. The C group are (l)-form while the D group are meso compounds with zero optical rotation. Without sugar moiety, free anthraquinones exhibit little therapeutic activity. The sugar is essential because it serves to transport the aglycone to the site of action in the large intestine. Anthraquinone group are interchangeable to each other either by oxidation or reduction as shown below:  Mechanism of action The anthraquinone and related glycosides are stimulant cathartics and exert their action by increasing the tone of the smooth muscle in the wall of the colon and stimulate the secretion of water and electrolytes into the large intestine. The drugs of choice are cascara sagrada, frangula and senna. Aloe and rhubarb are not recommended because they are irritant. Numbering system and nomenclature Numbering can be started from any corner provided that we give the substituent the smallest number. plants containing anthraquinone glycosides 1-Senna Senna or senna leaves consist of the dried leaves of Cassia acutifolia, known in commerce as Alexandria senna (Fam:Fabaceae). Active constituents: are dimeric glycosides whose aglycons are composed of aloe-emodin and/or rhein. Those are sennosides A and sennosides B (major constituents) which are stereoisomers whose aglycones are rhein dianthrone. And sennosides C and D (minor contents) which composed of one molecule of rhein and one of aloe- emodin. ▪ The C-C bond protect the anthrone from oxidation. Uses: as cathartics.  glucose glucose sennosides A and B R: COOH sennosides C and D R: CH2OH 2- Cascara Sagrada bark Cascara sagrada or rhamnus purshiana is the dried bark of Rhamnus purshianus (Fam: Rhamnaceae). It should be aged for at least one year before use in medicinal preparations to lose its griping properties it is stored in order to change the reduced form which has drastic griping action into the corresponding oxidized form which has less griping action. Active constituents: 1- cascarosides A&B (glycosides of barbaloin) 2- cascarosides C&D (glycosides of chrysaloin which is deoxy barbaloin) 3- Frangula Frangula bark is the dried bark of Rhamnus frangula. Its laxative effect is due to the presence of anthraquinone glycosides. Again like cascara , the bark should be aged a year or more before its use for medicinal preparations. Consist of: 1- Frangulin (frangula emodin rhamnoside). 2.Glucofrangulin (frangula emodin glucorhamnoside). 4- Aloe Aloe or aloes is the dried juice of the leaves of Aloe barbadensis (Fam:Liliaceae). Active constituents Aloe contains a number of anthraquinone glycosides, the principal ones are (Barbaloin )aloins A and B. The C-linked glucose at C-10 protect anthrones from oxidation. The active constituents of aloe vary qualitatively and quantitatively according to the species from which the drug is obtained. Uses: As a cathartic by acting on the large intestine. The fresh juice has been used in the treatment of burns and other skin irritations. The extracted gel could be blended with a special lanolin base. The ointment is recommended for the treatment of sunburn, deep thermal burns and radiation burns. It can be used to relief pain, itching and tend to minimize keratosis and ulceration. 4-Rhubarb Rhubarb ,rheum or Chinese rhubarb consists of the dried rhizome and root of rheum officinal (Fam: polygonaceae). Active constituents: The principal constituents of medicinal rhubarbs are rhein anthrones. Uses: Rhubarb has been used as cathartics.