The flavonoids of sea buckthorn (mainly from fruit pulp and in the leaves) and the oils of sea buckthorn (primarily in the seeds, but also in the fleshy part of the fruit) are the two items specially extracted for medicinal use. e.g., mainly isorhamnetin, quercetin glycosides, and kaempferol; these are the same flavonoids as found in Ginkgo biloba Important Therapeutic Uses of Sea Buckthorn

 
 
 
 

Research on pharmacological effects of seabuckthorn

Effects of Flavonoids

Flavonoids, together with other antioxidants, constitute two lines of defense in protecting cells against injury owing to oxidation of LDL. At the LDL level, they inhibit LDL oxidation due to their free radical scavenger activity; at the cellular level, they protect the cells directly, i.e., by increasing their resistance against the cytotoxic effect of oxidized LDL. Furthermore, recent studies indicate that flavonoids can prevent the expression of adhesion and chemoattractant molecules

Many drugs based on Seabuckthorn products are registered and prepared in china like Seabuckthorn “ Xindakang” a flavonide from the residues left from squeezed juice of fruits. The drug because of its potency in curing heart diseases is very well received internationally and its value was 8.0million US Dollars in 1996 (Rongsen, 1998).

Quercetin

Quercetin acts as an antihistamine and has anti-inflammatory properties. As an antioxidant, it protects LDL cholesterol ("bad" cholesterol) from becoming damaged. A variety of evidence indicates that quercetin possesses potent antioxidant properties. Cardiologists believe that damage to LDL cholesterol is an underlying cause of heart disease. Quercetin blocks an enzyme that leads to accumulation of sorbitol, which has been linked to nerve, eye, and kidney damage in those with diabetes. However, no human research has demonstrated these actions of quercetin in people with diabetes patients.

Quercetin is widely distributed in the plant kingdom and is the most abundant of the flavonoid molecules.
Isorhamnetin

To investigate the effects of isorhamnetin 3,7-di-O-beta-D-glucopyranoside (isorhamnetin diglucoside), on oxidative stress due to diabetes mellitus, in vivo and in vitro studies were carried out.

Furthermore, lipid peroxidation in blood, liver, and kidney associated with diabetes mellitus declined after the administration of isorhamnetin. These results suggest that isorhamnetin diglucoside is metabolized in vivo by intestinal bacteria to isorhamnetin and that isorhamnetin plays an important role as an antioxidant.

Keampferol

Keampferol is a strong antioxidant and helps to prevent oxidative damage of our cells, lipids and DNA. Kaempferol seems to prevent arteriosclerosis by inhibiting the oxidation of low density lipoprotein and the formation of platelets in the blood. Studies have also confirmed that kaempferol acts as a chemopreventive agent, which means that it inhibits the formation of cancer cells.

The flavonoids kaempferol and quercetin seems to act synergistically in reducing cell proliferation of cancer cells, meaning that the combined treatments with quercetin and kaempferol are more effective than the additive effects of each flavonoid. This was a conclusion from a study by ML Ackland et al (In Vivo, Feb 2005) titled "Synergistic antiproliferative action of the flavonols quercitin and kaempferol in cultured human cancer cell lines"".

Effects of flavonoids on the arterial wall

Little information about the in vivo effects of flavonoids on the arterial wall is available. Recently, the chronic oral administration of quercetin, the main dietary flavonoid, has been shown to exert potent antihypertensive effects in both spontaneously hypertensive rats (SHR) and chronic nitric oxide deficient rats. After 5 weeks of treatment, quercetin improved aortic endothelium-dependent relaxation to acetylcholine and tended to reduce the media:lumen ratio in mesenteric vessels from SHR. These effects were associated with a reduced oxidant status due to the antioxidant properties of the drug (4). Quercetin prevented endothelium-dependent vasoconstriction induced by acetylcholine secondary to TXA2 release in aortae, and also renal vascular lesion (hyaline and proliferative arteriopathy) in chronic NO-deficient rats (5).

Metabolism and other biological properties of flavonoids
 

The fluorescence of quercetin and other flavonols can not only be used to identify the protein targets in vital cells but also to monitor flavonoid metabolism in the cell since the major relevant metabolites of quercetin are not fluorogenic.

The metabolic activity can be monitored in the fluorescence microscope and quantified using flow cytometry. The quercetin metabolism in human leukaemia cells (HL-60) is very rapid and little quercetin is left in the cells after only 1 hour of culture in quercetin-free medium. In contrast, apoptotic cells retain their fluorescence for prolonged periods of time.

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