Phytosterol synthesis, effect

The increased accumulation of anthocyanins in hypocotyls of mevinolin-treated radish seedlings ( 9) certainly does not simply reflect the routing away of acetate units from sterois (cf. Figure 1) but also reflects a more general response of plants upon treatment with chemicals (95). Inhibitors (see also below) affecting later steps in phytosterol synthesis seem to affect various other products of the isoprenoid pathway before and after squalene formation (95). Secondary effects of such growth... 

Effect of inhibitors affecting late steps in phvtosterol synthesis on growth of radish seedlings. HMG-CoA reductase and enzymes catalyzing late steps of phytosterol synthesis are... 

It remains to be seen what effect will be demonstrated by the brassinosteroids on the mammalian system, if any. If one accepts the thesis that the animal steroids had their genesis in a common phytosterol ancestor and that certain mechanisms evolved in the animal system for steroid production, the question then arises as to what responses are elicited in the mammalian system when it is challenged with select brassinosteroids. Another way of asking the question is, do the brassinosteroids have any medicinal value Until now, limited quantities have precluded such examinations, but because synthesis is becoming more efficient the day cannot be far off for pharmaceutical evaluations if, in fact, they have not been tested already. 

The original structure of brassinosteroids and the requirement for reference compounds and sufficient amounts of brassinosteroids for biological studies has tremendously stimulated the synthesis of such phytohormones and their analogues up till now.2-4- 9 63 Much efforts have especially been focussed to developing convenient and effective methods for constructing the brassinosteroid side chain with (22R,23/ )-diol function, which is essential for a high bioactivity.63 Starting from suitable phytosterol precursors with a A22 double bond the alkyl... 

Finally, since the absorption of cholesterol is reduced by PS, this reduction would lead to a compensatory increase in de novo synthesis of cholesterol [71]. Indeed, cholesterol biosynthesis is upregulated after consumption of diets containing phytosterols, although this increment is insufficient to offset the beneficial effects of phytosterol [28, 49, 77]. 

The cholesterol-lowering properties of phytosterols were first demonstrated in the early 1950s by Peterson (1951), who fed cholesterol and plant sterols to chicks and found that soy sterols inhibited the increase in cholesterol concentration otherwise induced by cholesterol feeding. Shortly afterwards, Poliak (1953) showed the same effect in humans, to whom he administered 5-10 g of crude sitosterol daily for up to 8 months. In similar studies in rabbits, he observed that sitosterol was poorly absorbed and that, if present in excess, it blocked the absorption of cholesterol and prevented atherosclerosis. Poor absorption and lack of any endogenous synthesis of sitosterol in humans were subsequently demonstrated by Salen et al. (1970). 

This effect may be due to the high level of PUFA, which is supported by evidence that com oil is more effective than olive oil in lowering LDL-cholesterol because com oil has higher PUFA (58.7 g/100 g oil) than olive oil (8.4 g/100 g oil) (Howell et al., 1998 Dupont et al., 1990). Com oil has a plant sterols content of 128 mg/lOOOkcal vs. 66 mg/lOOOkcal for olive oil, and these plant sterols can reduce cholesterol absorption from the gut which in turn lowers body pools and enhances synthesis rate through de-suppression of cellular hydroxy-methylglutaryl-CoA reductase activity (Howell et al., 1998 Maki, et al., 2015). This is supported by a recent human study that the hypocholesteremic effect of com oil is connected with the high amount of phytosterols (Wagner et al., 2001). 

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