商品描述

The phytosterol revolution

What are phytosterols?

Phytosterols (or plant sterols) are natural compounds commonly found in plants. Cholesterol plays a significant role in stabilizing human cell membranes,and phytosterols play the same role in plants.Cholesterol is the most common sterol in plants. Over 40 sterols have been identified in plants, including b-sitosterol, stigmasterol and campesterol. The human body cannot produce phytosterols, and food is its only source. In western diets, an average of 250 mg of phytosterols are consumed per day, derived from cereals, vegetables, fruit and especially vegetable oils.
This is similar to the amount of cholesterol consumed (about 300 mg per day). All sterols share identical structures, differing only in their side chains (see fig. 1). Surprisingly, these minor differences result in major differences in biological function.
Another sub-category, which is less common in plants, is phytostanols. These are completely saturated forms of phytosterols. We usually consume less phytostanols (about 25 mg per day), which are found mainly in grains.

An elevated level of serum cholesterol is a well-known risk factor for coronary heart disease. Most strategies for lowering serum cholesterol require special diets and/or use of drugs. The possibility of lowering cholesterol levels by consuming foods enriched with natural ingredients is most attractive.

Phytosterolsdiscussion extract and analysis:

Abstract:

In recent years the phytosterols of the plant because of have many physiology functions and once more cause the very big value.It lies in reducing the cholesterol(total cholesterol and the low density fat egg white cholesterol) aspect contain obvious effect, and is found to have the bane of repressing the cardiovascular disease on the animal research.In regard to its chemistry structure, the Phytosterols and cholesterol(cholesterol) are very similar, its difference lies in the dissimilarity that pays the key up structure and the carbon few amount.The Phytosterols extracts many with lye solve and low pole organic melting agent of method, but still may cause it is the mistake of the content measurement because of the structural factor in the plant.The function that matches with the sour water solution can increase the phytosterols amount of examination, it may be because the phytosterols and other materials,such as fatty acids,carbohydrate etc. organic functions key, knot, and cause to examine the blind spot on the instrument. Phytosterols' difference in the total and solid content of the dissimilarity plant originates the solid is existed in the form in the plant originally, and extract up of processing, Examine in the content up, solid is many to analyze with the GC or the GC-MS.GC to the wreath form structure on solid ascend of replace , the position dissimilarity of a key, it there will be to be detained time differently.In phytosterols familiar sitosterols,sitostanols and Δ 5-the avenasterol all has the good separation result, matching with the GC-MS to take in to confirm the its structure and the information that provide and did not know the compound in times before, is one good phytosterols content examination.The GC is often been used for the measurement of the first step, confirming quantitative analysis in the pure degree and the living creature body of the solid .

To examine whether phytosterols in polyunsaturated oils account for their differential action on lipid metabolism compared with monounsaturated oils, 16 normolipidemic individuals consumed three 10-day experimental diets containing corn oil

DESCRIPTION

Phytosterols (also see Phytostanols and Beta-Sitosterol), widely found in the plant kingdom, are chemically similar to cholesterol. Cholesterol, however, only occurs in animals and is not found in plants. The cylclopentanoper- hydrophenanthrene ring structure of the sterol molecule is common to all sterols; the differences are primarily in the structure of the side chains.

Phytosterols are present in the diet. Typical daily dietary intakes of phytosterols range from 100 to 300 milligrams. It is higher in vegetarians. There are over 40 phytosterols, but beta-sitosterol is the most abundant one, comprising about 50% of dietary phytosterols. The next most abundant phytosterols are campesterol (about 33%) and stigmasterol (about 2 to 5%). Other phytosterols found in the diet include brassicasterol, delta-7-stigmasterol and delta-7-avenasterol.

(high in polyunsaturated fatty acids and phytosterols), olive oil (high in monounsaturated fatty acids and low in phytosterols), or olive oil supplemented with phytosterols given at twice the level naturally found in corn oil (high in monounsaturated fatty acids and phytosterols). Plasma total cholesterol concentrations after both the olive oil and the olive oil–phytosterol treatments were higher (P < 0.001) than those after the corn oil treatment. Olive oil treatment resulted in greater (P < 0.05) plasma LDL-cholesterol and triglyceride concentrations compared to corn oil treatment. Addition of the phytosterol mixture to the olive oil diet resulted in suppression of the significant differences in LDL-cholesterol and triglyceride concentrations between corn and olive oil. Free cholesterol fractional synthetic rates determined by deuterium incorporation were lower (P < 0.05) with olive oil treatment compared to corn oil treatment; the significance of this difference was abolished with the addition of phytosterols to the olive oil diet.

Phytosterols constitute the largest nontriacylglycerol component of refined vegetable fats . They act within the intestine to reduce cholesterol absorption and lower LDL-cholesterol concentration without being absorbed themselves . Studies with properly formulated phytosterols showed that 300 mg phytosterols in a single dose, or 830 mg phytosterols/d, may have important effects on cholesterol metabolism. These doses suggested to us that natural dietary phytosterols might also be physiologically active when compared with estimates of 100–500 mg phytosterols/d (or per 100 g fat) in the general diet. We chose corn oil as a source of natural phytosterols because vegetable oils have much higher concentrations of phytosterols than do nonfatty vegetable foods and because corn oil is one of the richest sources of phytosterols among commonly used commercial oils. Our hypothesis was that cholesterol absorption during the consumption of test meals that contained corn oil would increase after corn oil phytosterols were removed.

To allow for the most direct comparison between purified corn oil triacylglycerol and commercial corn oil, we developed a method to remove both free and esterified phytosterols from bulk corn oil by using the principle of competition for adsorption to silica. We then compared cholesterol absorption in human subjects on 2 occasions after otherwise sterol-free test meals that contained 30–35 g of a corn oil preparation and deuterated cholesterol tracer. The concentration of the tracer cholesterol was quantified in plasma after each test by using a sensitive, negative-ion, mass spectroscopic procedure. We determined the effect on cholesterol absorption of commercial corn oil, purified corn oil, and purified corn oil with added corn oil phytosterols.

Beta-sitosterol differs from cholesterol by the presence of an ethyl group at the 24th carbon position of the side chain. In the case of campesterol, this position is occupied by a methyl group. Chemically, the phytosterols are classified as 4-desmethylsterols of the cholestane series. Beta-sitosterol has the following chemical structure:

Phytosterols are potentially atherogenic like cholesterol, but except in the rare genetic disorders, sitosterolemia and cerebrotendinotic xanthomatosis, they are not. This is because so little of the phytosterols are absorbed. On the other hand, phytosterols can lower cholesterol levels. As early as 1951, it was shown that phytosterols lowered cholesterol in chickens, and subsequently they were found to lower cholesterol in humans. Recently, functional foods containing phytosterols have become available. These functional foods are in the form of margarines, spreads and salad dressings. In the case of most of these products, phytosterols are found esterified with long-chain fatty acids. These phytosterols are derived from soybean oil and are mainly beta-sitosterol, campesterol and stigmasterol.

Phytosterols are also known as plant sterols and, owing to their large sitosterol content, are sometimes called sitosterol. Phytosterols are virtually insoluble in aqueous media and are poorly soluble in lipid media. Esterification of phytosterols with long-chain fatty acids increases their lipid solubility.

ACTIONS AND PHARMACOLOGY

ACTIONS:

Phytosterols have cholesterol-lowering activity.

MECHANISM OF ACTION:

The mechanism of the cholesterol-lowering activity of phytosterols is not fully understood. Phytosterols appear to inhibit the absorption of dietary cholesterol and the reabsorption (via the enterohepatic circulation) of endogenous cholesterol from the gastrointestinal tract. Consequently, the excretion of cholesterol in the feces leads to decreased serum levels of this sterol. Phytosterols do not appear to affect the absorption of bile acids.

It is believed that phytosterols displace cholesterol from bile salt micelles. Another proposed mechanism is the possible inhibition of the rate of cholesterol esterification in the intestinal mucosa.

PHARMACOKINETICS:

Supplemental esterified phytosterols, following ingestion, undergo hydrolysis in the small intestine, catalyzed by such enzymes as cholesterol esterase, to yield the phytosterols beta-sitosterol, campesterol and stigmasterol. Of course, unesterified phytosterols do not undergo hydrolysis. About 5% of the ingested beta-sitosterol and about 15% of the campesterol are absorbed and transported via the portal circulation to the liver where some fraction of these phytosterols is glucuronidated. The phytosterols are excreted either in the free or glucuronidated form mainly via the biliary route.

INDICATIONS AND USAGE:

Phytosterols may be indicated for the management of hypercholesterolemia.

RESEARCH SUMMARY:

Phytosterols have been compared with phytostanols to assess their relative efficacy in lowering total cholesterol and LDL-cholesterol. These studies confirm that both are effective in lowering these lipids. A recent review concluded that plant sterols and stanols, in the studies analyzed, reduce, on average, total cholesterol by 10% and LDL-cholesterol by 13%. They have no significant effect in either HDL-cholesterol or triglycerides.

Clinical Studies* Indicate PhytoSterols and Sterolins Boost Immunity:

In nature, the function of Plant Cholesterol is to bolster an under-active immune system and, at the same time, turn off an overactive immune system. Taking both sterols and sterolins helps to balance the cells of the immune system so that they can function optimally. Scientists have long been searching for a drug that could effectively balance the T-cells, strengthening the immune system against disease yet preventing the body from destroying itself. The answer, as always, has been provided by nature. By enhancing only the function of the TH-1 cells and not the TH-2 helper cells, PhytoSterols/Sterolins may provide that crucial balance. There are hundreds of vegetables and fruits that contain Phytosterols/sterolins. Testing has been conducted using various plant fats from several sources. Plant fats have been found to be effective in balancing immune response. To date, the plant fatty acids/lipids, sterols/sterolins, have been found to be helpful in cases of autoimmune diseases like lupus and multiple sclerosis as well as infectious such as HIV, tuberculosis and hepatitis C.

FIGURE1:

Mean (± SEM) reduction in plasma hexadeuterated cholesterol tracer concentration after consumption of corn oil sterols. Cholesterol absorption was determind in paired test meals comparing 1 of 3 phytosterol-containing corn oil preparations with purified sterol-free corn oil: unpurified corn oil compared with purified corn oil and purified corn oil containing 150 or 300 mg added corn oil sterols compared with purified corn oil. Plasma hexadeuterated cholesterol concentrations after purified corn oil ingestion were 0.557, 0.655, and 0.512 mmol/mol natural cholesterol in the 3 groups, respectively. *P < 0.05. **P 0.01.

Although previous work has shown that extracted, concentrated phytosterols given as a dietary supplement reduce serum cholesterol concentration , there has been no evidence that the smaller amounts of phytosterols found in vegetable foods are bioactive. In the present study, we found that the natural concentrations of dietary phytosterols in corn oil, taken in amounts that might be consumed in some recommended diets at 40% of energy, have a substantial effect on the efficiency of intestinal cholesterol absorption. To show this, we took advantage of previous work showing that inhibitors of cholesterol absorption can have prominent effects during single-meal tests that can be quantitated by using nonradioactive, hexadeuterated cholesterol as an oral tracer followed by measurement of the plasma enrichment by using a sensitive mass spectrometric technique. We further decreased the test variability by using a standard meal that was free of sterols, except for phytosterols, in the corn oil preparations and hexadeuterated cholesterol tracer. The magnitude of the observed effect on acute cholesterol absorption, a 38% increase in cholesterol absorption after the removal of corn oil phytosterols and a 28% reduction from the increased baseline after their readdition, was prominent and quite similar to reported reductions of 30–43% in cholesterol absorption efficiency with the administration of maximum effective doses of phytosterols and phytostanols in other studies. Thus, we believe it likely that phytosterols in natural foods, such as corn oil, meaningfully regulate circulating cholesterol concentration.

Corn oil phytosterols appear to have good bioavailability because a dose of only 150 mg in a test meal had a measurable effect on cholesterol absorption. This is similar to the low effective dose range of phytosterols emulsified with lecithin and suggests that corn oil phytosterols become active during intraluminal digestion of the triacylglycerol. For reference, the mean phytosterol intake in a free-living group of middle-aged Finnish men was 279 mg/d . This same study found a significant, inverse correlation between fecal phytosterols and percentage cholesterol absorption. Our work suggests that this correlation may be due to a causal relation with dietary phytosterols contained in vegetable oils and perhaps other foods.

Sterol-free resynthesized oils were used in a previous study of 3 hyperlipidemic subjects, but unfortunately the experimental design did not allow any conclusions to be drawn about the effects of endogenous sterols on cholesterol metabolism . Early investigators also attempted to remove sterols and other nonsaponifiables from vegetable oils by vacuum distillation, but a complete separation was never achieved, rendering the studies difficult to interpret . In our experience, the purification of oils by vacuum distillation resulted in poor removal of sterol esters (which have the same volatility as triacylglycerol) and unacceptable, heat-related degradation of unsaturated fatty acids. Our method of saturation adsorption to silica allows for the preparation of purified oils without extreme heat in sufficient quantities for clinical investigation so that the effects of natural oil phytosterols can be reinvestigated.

The limitations of the present study should be recognized. We have used only single meal tests, and chronic effects on LDL, although expected, have not yet been verified. It was shown previously that reducing serum cholesterol concentrations by use of phytosterols and neomycin appears to be closely related to a reduction in the percentage of cholesterol absorption . Our sterol-free test meals are not typical of recommended diets but do allow for the discovery of potential phytosterol effects hidden in natural baseline diets. Finally, we measured only the efficiency of cholesterol absorption rather than the absolute amount, which depends on endogenous biliary cholesterol secretion.

Nevertheless, our results have implications for the mechanism of action of dietary vegetable fats on lipoprotein concentrations. The substantial effect on the efficiency of intestinal cholesterol absorption shown here indicates that we cannot necessarily attribute all of the effects of vegetable oils to fatty acid structure. It is possible that both unsaturated fatty acids and phytosterols contribute to the beneficial effects of vegetable oils. For example, unsaturated oils increase hepatic LDL receptor activity, decrease LDL production, and increase LDL clearance . Although potential mechanisms for the involvement of fatty acids in this process are speculative, these actions are exactly what is anticipated from the known effect of phytosterols to reduce the delivery of dietary and biliary cholesterol to the liver . Thus, future work needs to focus on the independent contributions of phytosterol content and fatty acid structure to the regulation of LDL concentration. Dietary studies need to report explicitly the phytosterol content of the fats used. This will require the preparation of new and more accurate food tables because current knowledge of phytosterol intake on a population level is limited.

There are also implications for the industrial manufacturing process. The phytosterol content of oils is not fixed but can be considerably affected by the refining process. For example, there can be a 20-fold concentration of phytosterols in steam distillates removed from commercial oils during physical refining . If phytosterols are important to the natural diet, refining processes need to be optimized to remove the smallest feasible amount of phytosterols while producing acceptable products.

The present study and the work of many other investigators strongly suggest that phytosterols may be more important in human physiology than previously appreciated and may allow us an additional means to reduce cholesterol concentrations and prevent atherosclerotic disease.