Steroid hormones plants

First obtained from Physosligma venenosum (Calabar bean) and is readily isolated from many plant sources where it often co-occurs with sitosterol. It has served as a starting substance for the synthesis of steroid hormones. 

Some plant and animal steroids occur in large quantities and can be used as inexpensive starting materials for pharmaceutically useful steroid hormones (see table 22). 

The major problem in such conversions is the degradation of the branched carbon side-chain on C-17 which is present in all abundant steroids and lacking in all steroid hormones. The most important starting material used in industry today is diosgenin from the Mexican dioscorea plant. It is degraded by the method of Marker to 16-dehydropregnenolone in 45% total yield. This compound is a key substance in the production of several hormones with anabolic, catabolic, and sexual effects. 

Terpenes (and terpenoids) are further classified according to the number of 5-carbon units they contain. Thus, monoterpenes are 10-carbon substances biosynthesized from two isoprene units, sesquiterpenes are 15-carbon molecules from three isoprene units, diterpenes are 20-carbon substances from four isoprene units, and so on. Monoterpenes and sesquiterpenes are found primarily in plants, but the higher terpenoids occur in both plants and animals, and many have important biological roles. The triterpenoid lanosterol, for example, is the precursor from which all steroid hormones are made. 

Sinee steroid hormones can only be obtained in small quantities direetly from mammals, attempts were made to synthesize them fiom plant sterols whieh ean be obtained eheaply and economically in large quantities. However, all adrenoeortieal steroids are eharaeterized by the presence of an oxygen at position 11 in the steroid nueleus. Thus, although it is easy to hydroxylate a steroidal eompound it is extremely diffieult to obtain site-specific hydroxylation, so that many of the routes used for synthesizing the desired steroid are lengthy, complex and eonsequently expensive. This problem was... 

Brassinosteroids (BR) are a group of plant steroid hormones that help to regulate many aspects of plant growth and development. Several P450s have been... 

Plant sterols such as sitosterol and camposterol, as by-products from vegetable oils at prices of about 15 kg-1, are also important starting materials for the production of steroid hormones. A new application is the cholesterol lowering property of these sterols esterified with fatty acids (with a production of about 10000 t a 1). They can be found in the margarine Becel pro-active of Unilever. A Finnish equivalent is Benecol, which contains stands such as sitostanol and campostanol, sterols having the 5,6-double bound hydrogenated, also esterified with fatty adds [33]. 

Donath J, Boland W (1994) Biosynthesis of acyclic homoterpenes in higher plants parallels steroid hormone metabolism. J Plant Physiol 143 473 78... 

Many plants contain estrogenic compounds. Estrone (Fig. 11.11) is found in seeds of date palms, pomegranates, and apples, and estriol in willow. These may be merely by-products of sterol metabolism, or serve a particular function. Harborne (1993) proposed that plants synthesize steroid hormones to deter feeding by mammals. Estrogenic compounds in plants are thought to upset the delicate hormone balance of mammals. 

Isoprenoids that have hormonal and signaling functions form an important group. These include steroid hormones (1 = 6) and retinoate (the anion of retinoic acid 1 = 3) in vertebrates, and juvenile hormone (1 =3) in arthropods. Some plant hormones also belong to the isoprenoids—e.g., the cytokinins, absci-sic acid, and brassinosteroids. 

The three most important groups of steroids are the sterols, bile acids, and steroid hormones. Particularly in plants, compounds with steroid structures are also found that are notable for their pharmacological effects—steroid alkaloids, digitalis glycosides, and saponins. 

Ecdysone is the steroid hormone of the arthropods. It can be regarded as an early form of the steroid hormones. Steroid hormones with signaling functions also occur in plants. 

Cholesterol is a soft waxy substance that is a steroidal alcohol or sterol. It is the most abundant steroid in the human body and is a component of every cell. Cholesterol is essential to life and most animals and many plants contain this compound. Cholesterol biosynthesis occurs primarily in the liver, but it may be produced in other organs. A number of other substances are synthesized from cholesterol including vitamin D, steroid hormones (including the sex hormones), and bile salts. Cholesterol resides mainly in cell membranes. 

The kinds of compounds that elicit signals in plants are similar to certain signaling molecules in mammals (Fig. 12-28). Instead of prostaglandins, plants have jas-monate instead of steroid hormones, brassinosteroids. 

In addition to these major processes, many other chemical events also occur. Mitochondria concentrate Ca2+ ions and control the entrance and exit of Na+, K+, dicarboxylates, amino acids, ADP, P and ATP, and many other substances.16 Thus, they exert regulatory functions both on catabolic and biosynthetic sequences. The glycine decarboxylase system (Fig. 15-20) is found in the mitochondrial matrix and is especially active in plant mitochondria (Fig. 23-37). Several cytochrome P450-dependent hydroxylation reactions, important to the biosynthesis and catabolism of steroid hormones and... 

Terpenoids are structurally based on the isoprenoid (C5) unit and include monoterpenoids, sesquiterpenoids, diterpenoids, triterpenoids, steroids and carotenoids. These compounds can be further modified to generate greater structural complexity. Thus the saponins are surface active amphiphiles deriving from the glycosylation of steroid (C27) or triterpenoid (C30) entities. Plant triterpenoids with very specific biochemical effects include those that mimic the effects of mammalian steroid hormones or of insect developmental hormones. 

Owing to periodic fluctuations in the price of diosgenin. alternative law materials such as solasodinc have been used for the synthesis of steroid drugs. In the U.S., the plant sterols stigmasterol and /3-sitosterol arc a significant raw material for the synthesis of antiinflammatory glucocorLicuids and other steroid hormones. 

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