Triterpenoids and sterols

ANTITUMOR-PROMOTING AND ANTIINFLAMMATORY ACTIVITIES OF TRITERPENOIDS AND STEROLS FROM PLANTS AND FUNGI... 

INHIBITORY EFFECTS OF TRITERPENOIDS AND STEROLS ON PRIMARY SCREENING ASSAYS FOR ANTITUMOR-PROMOTERS... 

ANTI-INFLAMMATORY AND ANTI-ALLERGIC ACTIVITIES OF TRITERPENOIDS AND STEROLS... 

The concept that inflammation and carcinogenesis are related phenomena has been the subject of many studies that have attempted to link these two processes in a mechanistic fashion [94-99]. In connection with this, as is evident in some triterpenoids such as oleanolic acid (142), glycyrrhetic acid (147), and ursolic acid (210) in Table 2, those possessing anti-inflammatory activity in various experimental models exhibited antitumor-promoting activity as well. This suggests that most of the other anti-inflammatory triterpenoids and sterols listed in Table 2 might have antitumor-promoting properties which have not been evaluated, yet. 

Table 2. Triterpenoids, and Sterols and Their Oxygenated Derivatives from Plants and Fungi and the Bioassay Systems in which the Compounds Exhibited Inhibitory Activities... 

Triterpenoids occur in hardwood parenchyma resin, and closely related sterols are also present in softwoods (Fig. 5-6). Sterols typefied by the abundant /3-sitosterol, mostly have a hydroxyl group in the C-3 position. They also appear as the alcohol component in fatty acid esters (waxes). Triterpenoids and sterols are sparingly soluble substances contributing to pitch problems in pulping and paper making. Some trees contain polyterpenes and their derivatives known as polyprenols. Betulaprenols, present in birch wood, belong to this category of substances (Fig. 5-7). 

Inhihitory effects of triterpenoids and sterols on human immunodeficiency virus-1 reverse transcriptase. Lipids 5 507-512. 

Phytochemistry The plant contains terpenoids and diterpenoids (salvin, salvifolin, salvicin, salvicinin, salvicinolide, and salvicinolin, etc.), as well as flavonoids (rutin, etc.), triterpenoids, and sterols (Nurmukhamedova et al. 1985, 1986 Sagitdinova et al. 1992,1994 Eshbakova et al. 1997 Eshbakova and Saidkhodzhaev 2001). 

Hacettepe Universitesi EczacrUk Fakultesi Dergisi 11 29-36 Eshbakova KA, Saidkhodzhaev At (2001) Triterpenoids and sterols from three species of Pulicaria. Chem Nat Compd 37(2) 196-197 Eshbakova KA, Sagitdinova GV, Levkovich MG, Rasulev BE, Abdullaev ND, Malikov VM (1997) Diterpenoids of Pulicaria salviifolia IV. Structures of salvicinolide and salvidnohn. Chem Nat Compd 33(4) 458-461... 

Triterpenoids and sterols Roburic acid, a-amyrin, oleanolic acid, P-sitosterol, P-sitosterol-3-O-gentiobioside, daucosterol, stigmasterol... 

Genetic analysis indicates that two of the 10 sad mutants of A. strigosa that we isolated represent different mutant alleles at the Sadi locus.6 These mutants accumulate radiolabelled 2,3-oxidosqualene but not p-amyrin when the roots are fed with 14C-labelled precursor mevalonic acid, suggesting that the triterpenoid pathway is blocked between 2,3-oxidosqualene and P-amyrin.34 The roots of these mutants also lack detectable P-amyrin synthase activity, but, like the wild type and the other mutants, are unimpaired in cycloartenol synthase (CS) activity and sterol biosynthesis.34 The transcript levels for AsbASl are substantially reduced in roots of sadl mutants, while AsCSl transcript levels are unaffected,35 suggesting that the sadl mutants are either mutated in the AsbASl gene itself or in a gene involved in its regulation. 

Translocate movement of a substance within a plant from one site to another. Transpiration transport of water by plants from soils to the atmosphere, whereby water is released through pore-like structures (stomata) in the leaves to the atmosphere. Triglyceride composed of three fatty acids bonded to a glycerol (C3 alcohol). Triterpenoids a large group of natural compounds which typically include steroids and sterols. 

Six isoprene units combine to give a molecular formula C30H4g for the triterpenes. Their derivatives - the triterpenoids - include sterols (found in all plant and animal cells), steroids (many hormones) and saponins (important plant products). 

The lipophilic fraction, extractable with nonpolar solvents (ethyl ether, dichloromethane, etc.) consists mainly of fats, waxes, terpenes and terpenoids, and higher aliphatic alcohols (cf. Sections 5.3.1 and 5.3.2). Terpenes, resin acids, and sterols are located in the resin canals present in the bark and also occur in the cork cells and in the pathological exudate (oleore-sin) of wounded bark. Triterpenoids are abundant in bark /3-sitosterol occurs in waxes, as an alcohol component, and the cork cells in the outer bark (periderm) of birch contain large amounts of betulinol (cf. Fig. 5-6). 

Further work in the phylum Echinodermata shows a variable ability to biosynthesize steroids. In the class Holothuroidea and Echinoidea, the representatives examined could synthesize squalene but not triterpenoids or sterols from acetate. However, several examples from the class Asteroidea were able to synthesize squalene, lanosterol, and other steroids. In the later stages of steroid metabolism it was shown that cholesterol was converted into cholest-7-enol via cholestanol. 

Substances capable of interaction with ROS are claimed to play an important role in the prevention of cancer. Some compoimds of the unsaponifiable fraction from virgin oil (oleuropein, tyrosol, sterols and triterpenoids) were assayed to determine their cytostatic activity in McCoy cells (originated from synovial fluid from a patient suffering degenerative arthritis) [92]. Oleuropein and the sterol+triterpenoid fraction potently inhibited cell growth at 6 Xg/ml (83 and 89% respectively), a concentration recommended by the protocols of the National Cancer Institute of USA [93]. IC50 for oleuropein and sterol+terpenoid fraction was 4.4 and 0.11 ig/ml, respectively. Tyrosol exhibited lower inhibition IC50 was 10 pg/ml. 

Similarly squalene is the biosynthetic precursor of many triterpenoids and, thus, occurs widely in organisms. Cholesterol, like hexadecanoic acid, is a constituent of the cell membranes of many different families of organisms, with the notable exception of bacteria. It acts as a rigidifier in cell membranes. It is a prominant sterol of many algae and land plants, and is often the only sterol component of copepods. Tocopherols are held to play an important role in photosynthetic processes. Hence, they are abundant in many... 

Our initial structure-activity studies were not designed to reveal bulk importance but to discriminate the specificty for molecular groups (3B -OH, length of side chain, etc) in sterol-controlled growth and reproduction. We found (Fig. ] ) that a variety of sterols and "sterol-like compounds, ie., triterpenoids, added to the cultures at lOppm stimulate growth (1.6.7.24), although only specific sterols induced oospore production (1.50-53). The lack of activity was not due to uptake per se (2,6). 

Cycloartenol is an important type of stanol found in plants. The biosynthesis of cycloartenol starts from the triterpenoid squalene. It is the first precursor in the biosynthesis of other stanols and sterols, referred to as phytostanols and phytosterols in photosynthetic organisms and plants. The identities and distribution of phytostanols and phytosterols is characteristic of a plant species. One notable product of cycloartenol biosynthesis is the triterpenoid lanosterol. 

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