dyslipidemia can be defined as the elevation of cholesterol , triglycerides , and low - density lipoprotein ( ldl ) cholesterol serum levels while maintaining low serum levels of high - density lipoprotein ( hdl ) cholesterol . this imbalance is considered a high - risk factor for inducing atherosclerosis and cardiovascular diseases ( cvd ) . cvd is now considered the most common cause of death in both western and eastern countries . traditionally , natural remedies were used to overcome such imbalance in lipids metabolism and are claimed to be useful in controlling hyperlipidemia and associated pathologies . plants such as artichoke ( cynara scolymus ) is an important component of the mediterranean diet and it is rich in bioactive phenolic compounds , inulin , fibers , and minerals . it has been used to treat dyspepsia mainly because of its choleretic effect that is associated with increased bile formation . in addition , artichoke extract has been found to exhibit antioxidant properties in cultured endothelial cells and monocytes   and has lipid lowering properties [ 3 , 68 ] . curcuma longa , commonly known as turmeric , is a rhizomatous perennial plant from the family zingiberaceae [ 9 , 10 ] . curcumin has been identified as the principle active component of turmeric that is responsible for many pharmacological properties   including anti - inflammatory , powerful antioxidant activity , and cancer - preventive properties . also , it lowers blood glucose and glycated hemoglobin levels by lowering oxidative stress in diabetic rats [ 14 , 15 ] . it lowers serum cholesterol levels in diet induced hyperlipidemia   and triglycerides in alcohol induced toxicity . it also increases cholesterol fecal excretion   and induces changes in gene expression involved in cholesterol homeostasis . prickly pear cactus ( opuntia ficus - indica ) is a tree like cactus from the family cactaceae . the dried leaves of prickly pear cactus have been considered as one of the functional food by embracing essential ingredients , such as amino acids , taurine , carbohydrates , vitamin c , minerals , and soluble fibers . prickly pear owns well - known antidiabetic and lipid lowering properties . also , it is very useful in obesity , alcohol - induced hangover , colitis , diarrhea , and benign prostatic hypertrophy ( bph ) . many uses of cladodes ( leaves ) of cactus pear have been reported and utilized for their hypolipidemic properties [ 21 , 24 , 25 ] . evidence showed that cactus pear reduces cholesterol levels in human and modify ldl composition . garlic ( allium sativum ) from the family alliacae is used as spice and medicinal herb . it is used as raw , cooked , dried , and in form of tablets . numerous studies suggest that garlic can normalize serum lipids , enhances fibrinolytic activity , and reduces blood pressure . the successful use of herbal combinations in treating or managing diseases or conditions over a single herb [ 29 , 30 ] has led us to evaluate the antidyslipidemic properties of the combination of the above natural extracts versus each one alone in two different hyperlipidemic models . furthermore , in order to study the mechanism of action of each constituent , each product was tested in inhibiting the activity of hmg - coa reductase enzyme . the long - term objective of this study , however , is enhancing the use of these natural extracts in lowering serum levels of cholesterol , ldl and triglycerides , and increasing serum hdl in order to reduce cvd and their adverse consequences . pluronic f-127 , cholesterol and cholic , acid were obtained from sigma - aldrich , usa . corn oil and atorvastatin were supplied by the jordanian pharmaceutical manufacturing company ( jpm ) . artichoke leaves powdered extract ( > 2.5% caffeolquinic acid ) was purchased from finzelberg , germany ; cactus dried leaves ( > 35% edible fibers ) from bioserae , france ; common turmeric extract ( curcumins > 97.5% ) from xi'an tianxing natural bio - products co ltd , china , garlic powder extract ( alliin > 3.4% ) from flachsmann , canada . the natural extracts were used as supplied and no attempts were carried to evaluate their compositions . experiments were carried out on adult spargue dawley ( sd ) male rats weighing ( 200250  g ) . the animals were housed in an air - conditioned environment under a daily photoperiod 12  h light/12  h dark cycle and received standard chow and tap water ad libitum . animals were kept for 2 weeks to allow acclimatization to the animal facility before starting the experiments . all experiments on animals were performed following the standards of european community council directive of november 24 , 1986 ( 86/609/eec ) . the study protocol was revised and approved ( 9/2008 ) by the ethical committee of the faculty of pharmacy and medical sciences , university of petra , amman , jordan . pluronic f-127 is a nontoxic , hydrophilic nonionic surfactant that is administered parenterally in rodents to induce reversible hyperlipidemia [ 3234 ] . pluronic f-127 solution was prepared by dissolving the corresponding dose in cold normal saline and kept in the refrigerator overnight for complete dissolution . twenty - four hours before the experiment , only water was offered to the rats . treated groups ( n = 8/time point ) received a single intraperitoneal ( i.p ) injection of 300  mg / kg of pluronic f-127 . the controls were injected with normal saline only . during the 48  h of the experiment , blood samples at 0 , 4 , 12 , 24 , and 48  h were drawn . at each time point , rats were sacrificed under anesthesia and blood samples were directly collected from the heart . high - fat diet consisted of standard diet mixed with 10% corn oil , 1% cholesterol , and 0.2% cholic acid . for this method of induction , rats were divided in two groups ; group 1 : control , fed with the normolipidemic diet , and group 2 : fed with the cholesterol based formula . blood samples were taken directly from the heart and processed as previously described .   to investigate the effect of the natural extracts to prevent the elevation of blood lipids , animals were divided into 8 groups with eight rats in each group . each group received daily either water , atorvastatin 10  mg / kg , artichoke leaves extract 26  mg / kg , turmeric 80  mg / kg , prickly pear leaves ( ppl ) 22  mg / kg , garlic 17  mg / kg , combination 1 ( artichoke , turmeric , and ppl ) , or combination 2 ( artichoke , turmeric , ppl , and garlic ) . these doses correspond to the human recommended daily doses of 1.8 , 5.6 , 1.5 , and 1.2  g / day for artichoke , turmeric , ppl , and garlic , respectively [ 6 , 18 , 35 , 36 ] . at the beginning of each experiment , rats were treated orally using an intragastric tube and they had free access to water and normal diet . in pluronic f-127 induced hyperlipidemia , rats were divided into 9 groups ( n = 6/group ) . , rats were orally treated with the previously described doses and had free access to water and normal diet . twenty - four hours before the last sample treatment , hyperlipidemia was induced using a single i.p injection of 300  mg / kg pluronic f-127 after 24  h fasting . group 1 was injected with normal saline only . at the end of the experiment , blood samples were collected from the hearts , centrifuged and kept at 20c until analysis . in high - fat diet modeland after 14 days of treatment , rats were switched to be fed with high - fat diet ( 10% corn oil , 1% cholesterol , and 0.2% cholic acid ) along with the treatment . at the last day of the study , all animals were kept fasting ( except for water ) for 24  h before blood samples were collected directly from the heart and processed as previously described . serum total cholesterol , triglycerides , and ldl were determined by enzymatic method using analyticon biotechnologies ag , germany kits , while hdl was measured by using labkit , chemelex , s.a . the absorbance was measured at 546  nm wavelength using ra-50 chemistry analyzer , technicon , usa . the effect of the natural extracts on the activity of hmg - coa reductase was assayed using an enzymatic assay kit from sigma - aldrich , usa . data obtained were analyzed by anova followed by dunnett as post hoc test using spss program , version 17 . administration of pluronic f-127 led to very high serum levels of triglycerides , cholesterol , and ldl , but not hdl in rats ( figure 1 ) . after 4  h , the increase in cholesterol and ldl was not significant as it is compared to the control , while triglycerides level increased significantly ( p < 0.05 ) . the increase in serum lipid levels continued till it reached a peak level at 24  h and plateaued for 48  h following the injection ( p < 0.0001 ) . however , the elevation in triglyceride level was much higher than cholesterol and ldl ( figure 1 ) . giving high - fat diet to rats for 10 days , on the other hand , resulted in a significant increase in serum cholesterol , ldl , ldl / hdl ratio , and triglycerides ( p < 0.001 , 0.001 , 0.001 , and 0.05 , resp . ) ( table 1 ) . a two - week treatment of ppl and garlic extracts prior to a single i.p injection of 300  mg / kg pluronic f-127 resulted in decreasing significantly serum ldl levels ( p < 0.05 ) ( table 2 ) . however , turmeric , ppl , and both combinations resulted in decreasing ldl / hdl ratios significantly ( p < 0.05 , 0.001 ) . atorvastatin , on the other hand , did not cause any significant effect on serum lipid levels induced by pluronic administration ( table 2 ) .   treating the rats for 2 weeks either with a single product or with different combinations and then giving them high - fat diet for only 10 days ( with the treatment ) gave the following results : none of the single product changed the level of any serum lipid profiles ; the first combination ( artichoke , turmeric and ppl ) and the second one ( artichoke , turmeric , ppl and garlic ) lowered cholesterol and ldl levels by 812% ; decreased significantly serum triglycerides , ldl / hdl ratio , and increased significantly hdl levels ( p < 0.0001 ) ( figure 2 ) . on the other hand , atorvastatin decreased significantly serum cholesterol , ldl levels ( p < 0.05 ) , ldl / hdl ratio ( p < 0.0001 ) , triglycerides ( p < 0.0001 ) , and increased significantly hdl levels ( p < 0.0001 ) .   however , keeping the rats under high - fat diet for another 25 days ( i.e. , 5 weeks in total ) resulted in a drop of serum cholesterol level in the control group that abolishes the significance effect of atorvastatin on cholesterol level . however , all the natural extracts , except for ppl , and atorvastatin resulted in a significant decrease in triglycerides levels ( p < 0.010.0001 ) ( table 3 ) . the decrease in ldl level was also significant for all groups ( p < 0.050.01 ) except for atorvastatin . treatment with turmeric and ppl increased hdl levels significantly ( p < 0.01 ) , ( table 3 ) . moreover , all the treatments decreased significantly ldl / hdl ratio ( p < 0.050.0001 ) . the effect of the natural extracts on the activity of hmg - coa reductase is given in figure 3 . using three different concentrations for each product and for atorvastatin , as a positive control , resulted in that atorvastatin 's three concentrations significantly inhibited the activity of the enzyme ( p < 0.050.01 ) . artichoke 's and ppl 's highest concentrations also inhibited the enzyme 's activity significantly ( p < 0.05 ) . although garlic did not have a significant effect on the activity of the enzyme , it is obvious that its inhibitory effect is concentration dependent . on the other hand , turmeric did not have a significant effect on the enzyme 's activity , at the used concentrations . in order to understand the relationship between disorders in cholesterol metabolism and atherogenesis and to test possible treatments for the reduction of serum lipid levels , various models are found to induce hyperlipidemia in rats [ 2 , 37 ] . as intrinsic inducer , the surfactant pluronic produces massive but reversible hyperlipidemia in rodents after acute administration [ 34 , 38 ] . this rise in circulating lipoproteins levels is caused by modifications in a number of biochemical pathways that is involved in lipoprotein metabolism , mainly an increase in serum triglycerides due to the direct inhibition of lipoprotein lipase which is the enzyme responsible for triglycerides degradation [ 31 , 33 ] . the increase in serum cholesterol is potentially due to indirect activation of hmg - coa reductase that is responsible for cholesterol de novo synthesis [ 31 , 39 ] . using this extreme model of hyperlipidemia induction , ppl , and garlic decreased significantly serum ldl levels whereas the combination 1 and 2 resulted in decreasing ldl / hdl ratio as well as ppl and turmeric extracts . preadministration of atorvastatin , on the other hand , did not prevent the changes induced by pluronic administration indicating that the increase in serum cholesterol in such model may not be due to indirect activating hmg - coa reductase and/or the latter has a minor role .   as extrinsic inducer , 10-day high - fat diet caused a significant increase in serum cholesterol and ldl , triglycerides levels and decreased hdl . pretreating the rats for 14 days with any of the single products did not prevent or decrease serum lipid profiles . on the other hand , the combinations artichoke , turmeric and ppl or artichoke , turmeric , ppl , and garlic decreased significantly serum triglycerides level , and ldl / hdl ratio ; increased significantly hdl , and also mildly lowered cholesterol and ldl levels by 812% , respectively . thus , such natural extracts combination for long - term use would give more significant normalization of dyslipidemia . when the high - fat diet continued for longer period ( 5 weeks ) , it did not increase the total serum cholesterol level but increased serum ldl and decreased hdl levels . it has been noticed that after 710 days of high - fat diet feeding , serum cholesterol , triglyceride , and ldl levels increased significantly in comparison to baseline levels . during the next 4 weeks of high - fat diet feeding to rats , it was noticed that the level of serum cholesterol and triglycerides started to decrease in the control group as well as the treated groups but the ratio of ldl / hdl stayed significantly high . this could be explained by that long - term high - fat diet induces saturation in cholesterol synthesis inside hepatocytes , and thus ldl receptor expression is reduced justifying high ldl serum concentrations [ 37 , 40 ] . in addition , long - term treatment of plant sterol with cholesterol might reduce intestinal cholesterol absorption [ 41 , 42 ] but this would be noticed after long - term treatment . ( 2000 ) have reported that the artichoke extract significantly lowered cholesterol and ldl ( 18.5% and 22.9% , resp . ) , in a randomized double - blinded placebo - control trial in which 143 hypercholesterolemic patients received either 1800  mg / day of the extracts or matched placebo for six weeks [ 6 , 8 ] . in this study , artichoke leaves extracts significantly lowered serum triglycerides , ldl , and ldl / hdl ratio . these modulations are attributed partially to inhibiting hmg - coa reductase as seen herein and by others . we have shown herein that turmeric decreased significantly serum triglyceride , ldl , ldl / hdl ratio , and increased serum hdl level . although turmeric effect on serum cholesterol was not significant , it decreased its level by 12% . the hypocholesterolemic effect of turmeric has been widely investigated . in rats fed high - cholesterol diet for 7 days , arafa ( 2005 ) investigated the hypolipidemic effect of curcumin ( 0.5% w / w ) when added to diet and reported that curcumin decreased cholesterol by 21% and ldl by 42.5% , while hdl level was increased by 50% . another report has shown that curcumin decreased total cholesterol in serum by 12% and increased hdl by 29% in human subjects after oral administration of 0.5  g / day of curcumin . in healthy human volunteers receiving 500  mg / day curcumin for 7 days , serum cholesterol was lowered by 11.63% and hdl level was increased by 29% . the mechanism by which curcumin affects lipid levels is not related to hmg - coa inhibition but could be due to an increase in the activity of hepatic cholesterol-7a - hydoxylase thereby enhancing cholesterol catabolism . other mechanisms of turmeric may include increasing cholesterol fecal excretion , inducing changes in gene expression involved in cholesterol homeostasis   and through a local effect on cholesterol absorption . prickly pear dried leaves significantly decreased serum cholesterol , ldl levels , and ldl / hdl ratio and significantly increased serum hdl levels . although its effect on triglycerides level was not significant , ppl decreased serum triglycerides by 23.5% . many authors mentioned that the cladodes of opuntia ficus indica are utilized for their hypolipidemic properties [ 21 , 24 , 25 ] . rodriguez - fragoso also clarified that pectin is able to alter hepatic cholesterol metabolism without affecting cholesterol absorption . ppl at a dose of 1.6  g / meal given to 42 females above 45 years increased serum hdl levels and decreased triglycerides and ldl levels . in the current study , ppl significantly inhibited the activity of hmg - coa reductase and was concentration dependent . various extracts of garlic have been shown to lower serum cholesterol , triglycerides , and ldl in rodents and humans [ 26 , 46 ] . chetty studied the effect of 2% dietary garlic given to rats fed 1% cholesterol with olive oil . the results indicated a significant decrease in total serum cholesterol and ldl with an increase in hdl levels . many authors stated that garlic exert its antihyperlipidemic effect by inhibiting hmg - coa reductase and thus inhibit hepatic cholesterol biosynthesis [ 28 , 36 , 47 ] . in our study , although garlic did not have a significant effect on the activity of the enzyme , it is obvious that its inhibitory effect is concentration dependent ( figure 3 ) . other mechanisms include inhibiting intestinal cholesterol absorption and enhancing cholesterol turnover to bile acids [ 36 , 48 ] . since treating or managing dyslipidemia requires a life - long use of antihyperlipidemic drugs , it is necessary to use a combination of natural extracts that exert a similar outcome with multi - mechanism of action and have less adverse events . such combination can be used alone as prophylactic , a booster to a known antihyperlipidemic drugs , or as life - long phytopharmaceuticals . as presented herein , neither of the artichoke leaves extract , turmeric extract , prickly pear dried leaves , and garlic extract showed any effect on short - term treatment in high - fat diet model but the combination effect to normalize dyslipidemia is additive . thus using the combination of artichoke leaves extract , turmeric extract , prickly pear dried leaves , and garlic extract for short - term , as well as long - term , treatment can prevent dyslipidemia ; partially through inhibiting hmg - coa reductase .
the successful use of herbal combinations in managing diseases or conditions over a single herb has lead us to evaluate the anti - dyslipidemic properties of the combination of the artichoke leaves extract , turmeric extract , prickly pear dried leaves ( ppl ) and garlic extract versus each one alone in two different hyperlipidemic animal models . a two - week treatment of each of the natural extracts , combination 1 ( artichoke , turmeric and ppl ) or combination 2 ( artichoke , turmeric , ppl and garlic ) prior to a single intraperitoneal injection of pluronic f-127 resulted in decreasing significantly serum ldl levels by garlic and ppl extracts and serum ldl / hdl ratios by turmeric , ppl , combination 1 and 2 . in a 10-day high fat diet model , only the combination 1 and 2 lowered serum cholesterol , ldl by 812% , decreased significantly triglycerides , ldl / hdl ratio ; and increased significantly hdl ( p < 0.0001 ) . 
 however , a long term treatment of each natural product for 7 weeks resulted in decreasing significantly serum ldl levels and ldl / hdl ratio ( p < 0.050.0001 ) . 
 furthermore , only artichoke and ppl inhibited significantly hmg - coa reductase activity ( p < 0.05 ) . in conclusion , 
 short term , as well as long term , treatment using the combination of artichoke , turmeric , ppl and garlic extract prevents dyslipidemia ; partially through inhibiting hmg - coa reductase .