Hypercholesterolemia is a known major risk factor in the development of athereosclerosis [29, 32, 51]. This circumstance is caused by internal homeostasis due to foods consumed. The hypercholesterolemia may be related to high cholesterol diet or regular saturated fatty acids intake . The incidence of Chronic Heart Disease (CHD) remains high despite blood pressure being controlled in hypertensive patients. Thus, in hypercholesterolemia patient’s LDL (Low Density Lipoprotein) concentration increases, and the lipoprotein is more aged and more susceptible to oxidative modifications than LDL from healthy subjects . These patients have been diagnosed with disability of LDL excreation and very low LDL receptor activity. The most potent inhibitors of cellular cholesterol synthesis are inhibitors of 3-hydroxy-3-methyglutaryl coenzyme A (HMG-CoA) reductase and consequently elevated the cellular LDL receptors synthesis, resulting in significant reduction of plasma LDL levels. .
1.1.1. Relation of hypercholesterolemia with atherosclerosis
Atherosclerosis is the disease caused by accumulation of foam cells originated from the monocytes which are transformed into macrophages that engulf excessive oxidized lipoprotein cholesterol. There was an increased foam cell formation which leads to intimal thickening after migration of smooth muscle cells to the intima and lamellar calcification under the endothelium. Finally a typical plaque characterized (Voet and Voet, 1990). The lumen of the arteries was narrowed and high blood pressure induced. The formation of plaque occurrs internally and raises the risk of cardiovascular diseases (CVDs) and strokes while remaining asymptomatic.
Cholesterol is an important component and needed in development of metabolism cell, but the excess of cholesterol content in serum could be problematic. Preclinical and clinical studies have shown that high cholesterol diet is regarded as a main factor in the development of hypercholesterolemia, atherosclerosis and ischemic heart disease . The cholesterol content in hypercholesterolemia cases produced extremely high risk agents such as oxygen free radicals in serum as well as erythrocytes, platelets and endothelial cells. The elevation of total serum cholesterol and LDL cholesterol along with generation of reactive oxygen species (ROS) play a key role in the development of coronary artery disease and atherosclerosis.
In term of mechanism, these vascular problems of atherosclerosis, hypercholesterolemia and hypertension are all correlated to each other. The formation of plaque is associated with a period of time and relies on homeostasis of each individual in dealing with good cholesterol (HDL: high-density lipoprotein) and bad cholesterol (LDL).
Today, strategies and remedies are available to combat CVDs. Even though changing life style with appropriate dietary intake remains the first line of defence advocated by the healthcare workers, drug treatment is still widely used because of the rapid effect especially in treating severe cases . Hence, most research today focuses on screening and identifying compounds exhibiting anti-hypercholesterolemic properties.
To date, several cholesterol lowering medications were discovered and used singly or in combination to lower the LDL cholesterol and triglycerides, a type of fats in the blood that also increases the risk of atherosclerosis. Concomitantly increase of HDL cholesterol often offers protection from CVDs . These types of drug include, bile acid binding resins, cholesterol absorption inhibitor, combination cholesterol absorption inhibitor and statins such as ezetimibe-simvastatin, fibrates, niacin and omega-3 fatty acids. However, almost all the anti-hypercholesteromia drugs have been reported as having various adverse effects . Several side effects such as constipation, nausea, diarrhea, stomach pain, cramps, muscle soreness, pain and weakness are reported; while more severe side-effects such as facial and neck flushing, nausea, vomiting, diarrhea, gout, high blood sugar etc. are also known. The side effects of statin and niacin are similar to each other. In addition, adverse drug reactions are always encountered in multiple diseases treated with a number of drugs. If hypercholesterolemia is accompanied by other diseases, these diseases may have an impact on the response of the body to anti-hypercholesterolemia drugs and the metabolic processes of the body may be affected negatively. Later on, increased dosages may be required, which in turn would only worsen the cholesterol medication drugs. The search for cholesterol lowering medication has now turned to complementary traditional medicine. However, the traditional use of herbs in lowering cholesterol is often not verified scientifically. On the other hand, even if proven effective, such herbs should be investigated on their mechanisms of action.
1.1.2. Mushrooms as medicinal-functional food against hypercholesterolemia
Medicinal mushrooms have been scientifically proven to be safe, efficacious, and novel anti-hypercholesterolemia therapeutic agents of natural source. An abundance of scientific research and studies on medicinal mushrooms or edible mushrooms shed light on them as functional food due to their broad spectrum of therapeutic efficacy beside culinary demand .
The original term “functional food” has been defined by Martirosyan (1992) as “a natural or processed food that contains known biologically-active compounds which when in defined quantitative and qualitative amounts provides a clinically proven and documented health benefit, and thus, an important source in the prevention, management and treatment of chronic diseases of the modern age”.
Medicinal Mushrooms (macrofungi), mostly members of the class Basidiomycetes fulfil the requirement of functional foods. Recently, they have become increasingly attractive as functional foods for their potential beneficial effects on human health. Hence, the food industry is especially interested in cultivating these mushrooms. The wild edible mushrooms have gained their reputation as health food due to their geographical origin in natural unpolluted environment. Nonetheless the cultivation of medicinal mushrooms using modern technology and the quality of the extracted product are crucial factors determining them as functional-medicinal food.
A plethora of potent therapeutic components in medicinal mushrooms such as fibers, phytosterols, saponins, polyphenols, flavanoids, terpenes and polysaccharides confer antihypercholesterolemic, antioxidant and anti-atherosclerotic properties .
The intensive study of  reported the hypocholesterolemic effect of the mushroom fruiting bodies and several types of these extracts exhibited different mechanisms of action, such as impairing dietary cholesterol absorption or inhibiting the endogenous cholesterol metabolism. Other reports showed that medicinal mushrooms are rich in chitin (dietary fibre) and specific β-glucans which may inhibit cholesterol absorption by increasing the faecal excretion of bile acids and reducing the amount of serum LDL-cholesterol [19, 28].
Among the most studied mushroom species are
The objectives of this article are to review the possible anti-hypercholesterolemic mechanisms of some putative bioactive compounds extracted from well known medical mushrooms particularly
2. Selective mushrooms as anti-hypercholesterolemia agent
As fungal wall constituents, bioactive polyglycans (polysaccharides), such as β-glucans in
Triterpenes are relatively simple molecules which are easy to isolate and quantify. They can be used as a measure of the quality of different
Triterpenes are produced in the fruiting body. They can also be induced in the mycelial mat on solid medium (Nishitoba
The bitter taste of
3. Mechanism on different biomedical application of
There are many studies on
Excretion of second metabolism products of the mushroom are used for self protection in extremely severe environment condition. The second metabolism products of
3.1. Mechanism of inhibitory effect of ganoderic acid on HMG-CoA reductase
Previous research by  focused on the oxygenated lanostanoid triterpenes isolated from
These mushroom triterpenes inhibited histamine release from rat mast cells. Compound VI with 7-oxo and 15 α-hydroxy groups at 40 μM showed highly potential inhibition of cholesterol synthesis from [24,25-3H]-24,25-dihydrolanosterol (18 µM). This encouraging result was obtained by testing 24, 25-dihydrolanosterol on rat hepatic subcellular 10,000 xg supernatant fraction. The triterpene involved is ganoderic acid C methyl ester. Its derivative is synthesized by a complicated reaction included the yield of tri β-methoxyethoxymethyl ether (MEM) derivative under Wolff-Kishner condition to allow the 7-oxo-11-deoxo derivative further decarboxylation and deprotection of the hydroxyl group. The whole structure of compound VI has no functional group in the side chain and has both 7-oxo and 15 α-hydroxy groups on the same skeleton and showed potent inhibitory effect compared with other derivatives with carboxyl groups at the side chain.
Compound I and II showed the other derivatives with oxo group at C-23 and decarboxyl compounds at the side chain had moderate inhibitory effects. Derivatives of compond IV and V has carboxyl group at C-25 in the side chain showed almost no inhibitory effect. These results provided an excellent clue and fundamental of specific side of triterpenes on the discovery of other
Figure 2 showed the statins as HMG-CoA reductase inhibitor drug playing its key role in the pathway of blocking the biosynthesis mevalonate from the HMG-CoA. The mechanism involved the statin by interrupting the structure of HMG-CoA reductase binding to NADPH in HMG-CoA to produce mevalonate. Therefore the metabolic pathway that produces cholesterol and other isoprenoids has terminated.
Akira Endo and his group discovered statins in 1976, and these HMG-CoA reductase inhibitors showed competitive effect on inhibiting HMG reductase due to their very close molecular structure to HMG-CoA. The use of statins is able to reduce the blood cholesterol levels significantly as HMG reductase is the first committed enzyme in the sequence of cholesterol synthesis cumulative process. However, since mevalonic acid (MVA) is a common precursor for many isoprenoids, blocking of MVA formation may induce undesired side effects besides inhibiting sterol synthesis. More specific inhibition of cholesterol synthesis may be attained by inhibition at some later stage of cholesterol synthesis. In this case, lanosterol was chosen in the ganoderic acid test as it originally converts from squalene by squalene oxido-cyclase at the end of cholesterol synthesis (Figure 2).
3.1.2. Comparison of structure of statins and ganoderic acid derivatives
These renowned drugs have been studied for their functional anti-hypercholesterolemic mechanism as a model for preliminary comparison of undefined natural products based on the results of the laboratory and the spectroscopy elucidation of their structure. Therefore the highest percentage of similarity of both compound structures implied similar highest effectiveness. This theory has been validated when the structure of HMG-CoA and the binding site of competitor lovastatin drug in HMG-CoA reductase inhibition was compared (figure 3).
The active side of lovastatin is circled in box, while the structure site of the ganoderic acid derivatives automatically refers to the site chain for comparison. The important difference is statin inhibited the earlier stage of cholesterol formation whereby ganoderic acid inhibited at the late stages of cholesterol formation. Figure (4a) showed that lavostatin has 5 carbons in aromatic ring when the reaction of carboxyl group and the hydroxyl group occurred. The active sites mostly rely on the double bond of oxide group and the beta hydroxyl group. The position of both active sites is separated and impossible to react intra-molecularly. Conversely the site chain of ganoderic acid derivatives (figure 4b) is aliphatic whereby the position of carboxyl group and double bond could possibly interact. Compound IV and V (in figure 1) has close double bond at C-23 and 24 and this contribute to instability. Structure of figure (VI) shows that it is a potent inhibitor but is surprisingly without any carboxyl and double bond at the site chain. Its competitor effect could be due to the interaction of C-7 and C-15 with the binding site of 24, 25-dihydrolanosterol. The binding site of ganoderic acids with 24, 25-dihydrolanosterol is essentially similar to ganoderic acid and hence no side effect to the patient will result.
3.2. Mechanism as angiotensin converting enzyme inhibitor in rennin angiotension-aldosterone system
The other mechanism that could apparently be involved is the inhibition of angiotensin converting enzyme (ACE) in renin-angiotensin system. This system is indirectly related to hypercholesterolemia. Atherosclerosis is the main contributory factor in this case but it may result in high blood pressure due to the narrowing of lumen of blood arteries. Therefore the regulatory mechanism of blood pressure by vasoconstriction and vasodilation may attenuate the hypercholesterolemia impact.
 identified five novel lanostane triterpenes, namely ganoderal A; ganoderols A and B; ganoderic acids K and S in the methanolic extract. These compounds were tested for their ACE inhibitory effect by a modification of the method described by Friedland and Silverstein (1976) and expressed in terms of IC50 (the amount of samples needed to inhibit 50% of ACE activity). All the newly discovered lanostane triterpenes showed IC50 of the order of 10-5 M which is considered potent. However, the earlier reported ganoderic acid F (figure 5) achieved the highest inhibitory effect with IC50 of 4.7 x 10-6 M.
In 2012, Abdullah
3.2.1. Mechanism of Renin-Angiotensin System (RAS) of
The RAS is important for the aldosterone hormone system in kidneys and lung. Consequently, the blood pressure and water (fluid) balance is regulated.
Briefly, when the blood volume is low in the circulation, this scenario would be sensed by the juxtaglomerular cells at the afferent arterioles of the renal glomeruli  in kidneys and concurrently activate the prorenin which converts to renin directly into circulation. Plasma rennin hydrolyzes its substrate, angiotensinogen released by the liver to produce a decapeptide known as angiotensin I, which is then rapidly converted to an octapeptide, angiotensin II, by a circulating angiotensin-converting enzyme found in the lungs. Angiotensin II is a potent vasoconstrictor peptide that stimulates the cells of the zona glomerulosa of adrenal cortex to produce aldosterone  and  which causes blood vessels to constrict, resulting in increased blood pressure. When the re-intake of sodium and water in the kidneys tubules is caused by Aldosterone, the body fluid eventually increases resulting in increase of blood pressure. .
3.2.2. ACE inhibitor
Interrupting the RAS effectively control the constriction of blood vessels. When the arteries are confronted with the problem of narrowing lumen caused by the formation of plaque in hypercholesterolemia, the treatment of using ACE inhibitor or compound that blocks the activity of ACE could reduce some risk drastically via vasodilation. Most of the synthetic pharmaceutical drug for the treatment of hypertension has no curative effect, and in fact needs prolonged administration for congestive heart failure protection. These types of drugs are usually used in combination with other medication and are usually well-tolerated by most individuals. Nevertheless, side effects such as cough, headache, drowsiness, weakness, abnormal taste (metallic or salty taste), rash are very common. By testing the active ingredient(s) in
3.2.3. Comparative structure of ACE inhibitor captopril and ganoderic acid F
Captopril (figure 5) is a ACE inhibitor used for the treatment of hypertension and some types of congestive heart failure. Captopril plays its role in blocking the conversion of angiotensin I to angiotensin II. Both captopril and ganoderic acid F are highly active ACE inhibitor. In term of structure, captopril contains a side chain with 3 carbons with different functional groups and an aromatic ring formed with 4 carbons and a nitrogen atom as the main attachment to the side chain. The molecule is small with a molecular weight of 217 Daltons. In contrast, ganoderic acid F is a natural product. Its structure is huge with 7 carbons at the side chain attached to the main skeleton which contains 4 aromatic rings. Its molecular weight is 2.6 times more than captopril. Both compounds have the carboxyl, ketone and methyl functional groups except captopril which, in addition has a sulphate group at the tail. There is no sulphate and nitrogen atom in ganoderic acid F.
Comparison of the molecular structure cannot really ascertain the effectiveness of both compounds in term of anti-hypertension or indirectly on anti-hypercholesterol activity. In addition, there are many other differences in term of their configurations and binding site of both compounds. Moreover, there could be many other factors influencing the mechanism of RAS system. As the comparison is based on the isolated and characterized
3.3. Mechanism of inhibition of oxidative damage
Extracts prepared from either mycelial or fruiting body of
(1 6) or (1 3)-β-D-glucans from
Many synthetic chemicals such as phenolic compounds are found to be strong radical scanvengers but they usually have side effects . Most of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activities of
3.3.1. The mechanism of scavenging DPPH radicals
Crude hot water extract of
3.3.2. Inhibition of Lipid Peroxidation (LPO)
LPO is regarded as one of the basic mechanisms of cellular damage caused by free radicals . The relationship between LPO and hypercholesterolemia is well recognized. A cholesterol rich diet results in increased LPO by the induction of free radical production . Hypercholesterolemia and lipid peroxidation are believed to be critically involved in development of atherosclerosis .
3.3.3. Reducing power
 reported xanthan and methylcellulose showed hardly any hydrogen donating activity compared with the very huge activity of ascorbic acid.  also reported that weak relationship was found between monosaccharide composition and reducing ability. In fact the non-polysaccharide components of the
3.3.4. Chelating ability on ferrous ions
The molecular masses of the polysaccharide fractions are important for the chelating ability . The ferrous ions chelating ability of polysaccharides extract of
3.4. Mechanism of inflammation — Hepatoprotective effect
Total triterpenes extract from
These data indicated that peptides and ganoderic acids which have been isolated from
However the other experiments revealed administration of
The liver is the main organ of detoxification and is the site of metabolic conversion of endogenous and exogenous compounds. Another major function of the liver is to synthesize bile acids from cholesterol and to secrete these compounds from the hepatocytes into the intestine, thereby generating bile flow and facilitating dietary fat emulsification and absorption . The studies on hepatoprotective effect of
3.4.1. Mechanism of hepatoprotective effect of Ganoderma extract
Whatever substrates are involved, the basic of this mechanism is promoting the release of SODs into the blood stream. Kurt and Stefan (2014) reported that plasma clearance of human extracellular-superoxide dismutase C (EC-SOD C) in rabbits was initiated in the liver which contained the most 125I-EC-SOD C, followed by kidney, spleen, heart, and lung. This scenario shows that almost all 125I-EC-SOD C in the organs was deposited on endothelial cell surfaces and was not associated with any other tissue cell surfaces, or present within the cells. .
Pathology studies on the hepatocytes that the SODs are a family of metalloenzymes which need mineral copper as integral component. About 50−80% copper absorption is maximal in the duodenum and may be absorbed from the stomach. Within the intestinal mucosal cells, copper can react with metallothionein, a sulfhydryl group-rich protein that binds copper through the formation of mercaptide bonds. Factors affecting copper absorption include gender, the chemical form and certain dietary constituents.
The rich and multi nutrient ingredient of ganoderma extract has provided sufficient natural supplement in enhancing the liver metabolism. Besides beta-glucan, coumarin, mannitol, and alkaloids, triterpenes isolated from
There are three types of SODs in eukaryotic cells catalysing the same reaction. They are copper and zinc-containing SOD (CuZnSOD) exists in cytosol, an manganese-containing SOD (MnSOD) which is encoded in the nucleus, synthesized in the cytosol and imported post-translationally into the mitochondrial matrix, and an extracellular CuZnSOD.
Basically 90% of the cell’s oxygen is consumed by MnSOD at the mitochondria matrix. Thus mitochondria are sensitive to oxidative damage, especially inducible by environment oxidative stress. Most probability due to mitochondria are lack of histones and an efficient DNA repair .
The SODs are playing their role in the initial stage of cellular anti-oxidant defense by the dismutation of the superoxide radical into hydrogen peroxide and molecular oxygen. Superoxide is the one-electron reduction product of molecular oxygen.
There are two possible equations of SOD-catalysed dismutation of superoxide where the oxidation state of the metal cation oscillates between n and n+1. The half-reactions could be written as :
The H2O2 will be disproportionating to H2O and O2 by catalase which is excreted from hepatocytes to complete the oxygen radical detoxification process 
The mechanisms of the hepatoprotective effects of
3.5. Mechanism on immunostimulation with
Many bioactive components in
Of great interest is the discovery of β-D-glucan receptors on the surface of a number of white blood cells (leukocytes, monocytes, macrophages, natural killer (NK) cells, and other lymphocytes) in animals and humans [17, 22]. The broad stimulatory effects of
 reported activation of T-cell by administering
3.6. Mechanism —
Ganoderma lanostane-type triterpenes as potent Farnesoid-X-Receptor (FXR) agonists
 reported the application of
The relevance of FXR as bile acid (BA) activated receptor was illustrated with regard to the treatment of atherosclerosis and its counter-regulatory role in immunity and inflammation. FXR exhibits a regulating function in many endogenous pathways. Its active site contains specific features which are well-characterized. These important characteristics have contributed to the attractiveness of this nuclear receptor as an atypical drugable target for the development of novel therapaeutic agents which may be effective in the prevention and treatment of, including, the metabolic syndrome, dyslipidemia and atherosclerosis. Chenodeoxycholic acid (CDCA) and other BA are natural ligands for FXR.
A dose-dependent FXR-inducing activity showed the EC50 of the most active lanostanes identified from
3.6.1. Comparative molecular structure of active lanostanes and CDCA
Four of the compounds have the basic molecular structure with 3 benzene rings and a penta ring, and the side chain is completely different (Figure 6). In term of number of carbon, ergosterol peroxide has the higher number of carbons at the side chain which is 4 carbons more than CDCA. The other two compounds contain same number of carbon. Ergosterol peroxide has 4 methyl groups at the side chain excluding hydroxyl group. The rest contain at least a hydroxyl group at the side chain with the possibility of intermolecular bond forming. Only ergosterol peroxide and ganoderiol F formed double bond at their side chain but at different position. This is important as double bond is favoured in binding and activating the compound. The position of double bond of ergosterol peroxide is ideal compared with ganoderiol F, because there is no other functional group beside the double bond. There is a carbonyl group at the side chain of CDCA compared with others. This interpretation is comparable with the possible mechanism of inhibition of HMG-CoA reductase by ganoderic acid derivatives, as the compound with carboxyl group at the side chain has lower inhibitory potential. In the component of aromatic ring, the position of carbon 7 determines the activity of the compound. In this case, ergosterol peroxide showed double bond within carbon 6 and 7. Ganodermanontriol and ganoderiol F formed double bond at carbon 7 but within carbon 8 and both compounds have another double bond of which the configuration is not as stable as ergosterol peroxide and CDCA. The interesting point is, only ergosterol peroxide showed the binding of oxygen between carbon 5 and 8 which stablises the compound and equivalent the active side of double bond between carbon 6 and 7 in the ring.
Farnesoid X receptor (FXR; NR1H4) plays a role in the pathogenesis of cardiovascular disease . It is a ligand-induced transcriptional activator and is expressed at high level in liver, intestine, kidney, adrenal glands, and also in the vasculature. It targets the enterohepatic recycling and detoxification of BA. When activated, FXR translocates to the cell nucleus, forms a heterodimer with retinoid-X-receptor and binds to hormone response elements on DNA, which produces either repression or an up regulation of gene transcription. The resulting mechanisms are affected by antagonist or agonist character of the respective ligand .
On the other hand, both (
These mechanisms are possibly valid due to the promising results by comparing the treated and the control group. The activity of isolated compounds mentioned herein is very convincing and the working mechanisms mentioned above are involved. However, it is likely more than one mechanism may interplay. The method of extracting the bioactive compounds or the fraction used is closely related to the anti-hypercholesterolemia effect. There are several factors that may influence the possible mechanisms. The effective dosage of
Synthetic anti-hypercholesterolemia drug works by affecting an array of intermediate precursors which could be important for health. Therefore the side effect of such drug would be more severe than someone taking a mixture of active components present in