The extract of artichoke (Cynara scolymus) has the ability to reduce total serum cholesterol and LDL and to improve the LDL=HDL ratio.22 New methods of action are continually being explained. While one study suggested a different method of action from the well-known one of lowering cholesterol by increasing its excretion in bile (and listed chemical contents that were thought to be responsible), another study suggested that inhibiting gastric emptying may lower cholesterol. Because of botanical medicines' ability to work via several different biochemical pathways to achieve the same result, the newer research covered in this article does not negate the idea that artichoke acts as a cholagogue.
The results of a study to determine the lipid-lowering effects of artichoke suggest that this occurs via an indirect modulation of hydroxymethylglutaryl-CoA-reductase activity.23 Furthermore, this study investigated many of artichoke's main active constituents and revealed that cynaroside and, more specifically, its aglycone luteolin were most responsible for inhibition, while chlorogenic acid was less effective and caffeic acid, cynarin, and dicaffeoylquinic acids exerted little hypocholesterolemic influences. A methanol-derived extract from artichoke leaves was able to suppress triglyceride elevation in mice that were fed large amounts of olive oil; these active compounds were determined to be both sesquiterpenes (cynaropicrin, aguerin B, and grosheimin) and three newly discovered sesquiterpene glycosides (cynarascolosides A, B, and C).24 Inhibition of gastric emptying was also shown to contribute to the antihyperlipidemic activity in this study. The side effects of this plant are minimal, with flatulence being the most-often reported consequence.25 No other internal side effects are mentioned in the literature but one external one—allergic contact dermatitis—did occur; this was attributed to cynaropicrin.26 The body of research for artichoke is fairly small at this time; however, it contains positive support for use of this plant as a reliable lipid-lowering agent.
A yellow pigment compound derived from the spice turmeric (Curcuma longa), curcumin, and its structurally related compounds (curcuminoids) produce several pharmacologic effects including anti-inflammatory, antioxidative, hypocholesterolemic, and anti-carcinogenic activities. Precise mechanisms for the previously mentioned actions have not been elucidated fully. The anti-inflammatory and anti-carcinogenic properties are believed to be mediated, in part, to curcumins' ability to down-regulate NFkB activation and by activation of the NRF-2 receptor, which activates the antioxidant response element on DNA. Curcumin also down-regulates the expression of COX-2, a gene regulated by NFkB.27 Curcuminoids are thought to exert a lipid-lowering effect, possibly as a result of alterations in fatty-acid metabolism.28 Wistar rats who were fed a high-fat diet for four weeks, then placed on a diet containing curcumin (5 g=kg of body weight), had decreased serum levels of cholesterol and triglycerides, with increases in apolipoprotein A. This effect remained for an additional two weeks' post-diet alteration.29 There are several studies demonstrating similar effects on animal lipid models, but human studies are infrequent. Based on these models, however, curcumin may be a useful tool in helping to prevent or manage atherosclerotic diseases.
Tocotrienols, a particular form of vitamin E, have been shown to effectively reduce elevated cholesterol levels. One study showed that hypercholesterolemic subjects supplemented with 200 mg gamma-tocotrienol per day showed decreased serum cholesterol by 31% during a four-week period.30 The delta and gamma isomers found in tocotrienols are effective at lowering cholesterol due to the substitution and location of methyl groups at the head region of the molecule. Tocotrienols positively affect lipid levels by suppressing the activity of HMG-CoA reductase.31 Tocotrienols have also been shown in humans to significantly reduce aortic systolic blood pressure and induce a 9.2% improvement in total antioxidant status as well.32
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