Periwinkles form the plant genus Vinca, of which the lesser periwinkle and the greater periwinkle are the two members. They are also a form of dogbane, known for its alkaloid properties. Periwinkles are of interest to the medical profession due to their biosynthesis of a number of alkaloids that are used to protect themselves from bacteria and are also toxic to the herbivores that would otherwise eat them.
Many other plants produce alkaloids, perhaps the best known being poppy, that produces the alkaloid opium that is the precursor to heroin. The alkaloids of the periwinkle, however, have a much more beneficial use for mankind in their action on certain types of cancer such as Hodgkin’s disease, and also on the flow of blood to the brain.
The components of the periwinkle include vinblastine, which is used in the treatment of Hodgkin’s lymphoma, and it is the only plant known to produce the alkaloid, although only in very small quantities after synthetic seeding. This involves introducing modified tryptamines to the plant so that they produce the desired alkaloid, although only in quantities of 0.002% of the weight of the plant. Although small, this is still less expensive that synthesizing the alkaloid in a chemical plant rather than a biological one!
Chemists are now seeking more readily synthesizable alternative forms of the alkaloid that have the same effect, again using the periwinkle as a botanical chemical factory to provide them with a lead as to possible synthetic routes. However, it is for the application of another alkaloid of this amazing little plant that we are more concerned with here.
In addition to vinblastine, the periwinkle produces the alkaloid vincamine, a type of tryptamine that can be extracted from the leaves of the lesser periwinkle, the Vinca minor. This periwinkle has been used through the ages as an invigorating tonic and as an astringent to treat bleeding gums and sores in the mouth. Vincamine promotes the aerobic glycolysis that is essential to cerebral health.
Normal glycolysis, or the conversion of glucose to energy in the mitochondria of the cells of the body, occurs best in the absence of oxygen (anaerobic glycolysis). However, the brain produces up to and over 90% more energy through aerobic glycolysis in the presence of oxygen than through anaerobic. Hence one of the needs for such a rich supply of oxygenated blood being needed by the brain. As people grow older, or their brain tissue becomes damaged, then the supply of blood can be reduced and more and more anaerobic glycolysis is switched on. This results in an increasing loss of brain energy and hence brain function. Vincamine can reverse this effect, or at least maintain the status quo, and so enable people to maintain their brain function for longer.
It is also what is known as a vasodilator, and dilates the blood vessels in the brain allowing a greater blood flow. It is known to be beneficial in relation to tasks requiring focused concentration such as mathematical problem solving, and has also been found effective in the treatment of people with poor memory.
Vinpocetine (ethyl apovincaminate) is a derivative of vincamine, obtained by slightly modifying the molecule to produce a commercial form of the alkaloid. This possesses all of the beneficial effects of its precursor, including its positive effects on memory, believed to be due to the stimulation of serotonin production that improves the rate at which the brain can process information. Tinnitus, or ringing in the ears that has severely reduced the quality of life of so many people, can also be treated with vinpotecine.
Its vascodilation effect is thought to be through its action as a phosphodeaterase 1 (PDE1) inhibitor that results in an improvement in the plasticity of neurons. The mechanism is complex, but the end result is an improvement in the cognitive abilities of the subject. This is supplemented by the effect of vinpocetine on the calcium levels in the blood vessels. This renders them more plastic in much the same way that some anti-hypertension treatments work to reduce blood pressure by increasing the plasticity of the blood vessels by modification of their calcium levels. It can also reduce the viscosity of the blood through its action on the “stickiness” of leucocytes and so allow the blood to run more freely through the capillaries of the brain.
These effects have been demonstrated through double blind studies, and there is little doubt that vinpocetine helps to maintain a healthy cerebral circulation. So let’s have a recap on its various effects, and then finish with a summary of the conditions that the alkaloid can be used to treat or improve. The theory and biochemistry behind these effects is known, but is complex, but here are the major actions:
a) It improves blood flow by modifying the calcium content of the blood vessels and so improves their elasticity, hence allowing a freer movement of blood. In effect it helps the blood vessels to dilate easier.
b) It inhibits the enzyme PDE1 and by doing so helps to restore the elasticity of neurons in aging brain cells, allowing them to relax more and operate more effectively.
c) It promotes aerobic glycolysis, and so the rate at which the mitochondria of brain cells produce ATP (adenosine triphosphate) that is the chemical manifestation of energy.
d) It helps to maintain a good supply of glucose and oxygen in the brain to allow (c) to occur.
Not all of these may be separate effects, but the outcome is an improvement in conditions such as short term memory loss, dementia and other conditions associated with a reduction in the blood supply to the brain including Menière’s syndrome and vertigo. There is also evidence that it helps with hearing problems, macular degeneration of the eye, and fatigue.
It is a supplement that should be taken by the elderly to help with age-related memory problems, but has also been found to be beneficial in normal healthy people. The periwinkle extract Vinpocetine has been shown to have benefits, largely through an increase in the blood flow to the brain, and will be of use to anybody suffering from conditions that can be related to a deficiency in their cerebral blood supply.