There are two classes of active compounds in lesser periwinkle--alkaloids and tannins. The major alkaloid is known as vincamine. A closely related semisynthetic derivative of vincamine most widely used as medicine is known as ethyl-apovincaminate or vinpocetine. It has vasodilating, blood thinning, and memory-enhancing actions. It has been shown in double-blind studies to help alleviate a type of dementia known as vascular dementia, in which the arteries supplying blood to the brain develop atherosclerotic plaques.22, 23, 24 A double-blind study found that vincamine can help people with Alzheimer's disease,25 while one open study did not.26 Vinpocetine has also been found to prevent the decline in short-term memory induced by the anti-anxiety benzodiazepine drug flunitrazepam in one preliminary study.27 Further study is needed to determine whether vinpocetine would be a helpful adjunct to use of benzodiazepines.
One double-blind study found that high amounts of vinpocetine (60 mg per day) could have a beneficial effect on hearing loss due to aging (presbyacusis).28 A preliminary study concluded that supplementation with ethyl-apovincaminate (a vinca alkaloid) may reduce symptoms of tinnitus (ringing in the ears) due to impaired blood flow to the inner ear.29 One review of the use of vinpocetine in people who have suffered strokes found that the only double-blind study did not show efficacy,30 though previous uncontrolled studies have suggested there might be a benefit.31, 32
Vinpocetine tends to act as a calcium-chelating agent. One uncontrolled study found that use of vinpocetine for 3 to 12 months could eliminate calcium buildup in people undergoing dialysis.33 Further research is needed to determine whether this could be helpful in other conditions associated with excess calcium, or whether vinpocetine might interfere with calcium's beneficial actions.
One double-blind and one preliminary study have found that brovincamine, a compound closely related to vinpocetine, was helpful in people with chronic glaucoma.34, 35 Until studies have been conducted using actual vinpocetine, it is unknown whether it would be as effective as brovincamine.
Crude periwinkle also contains tannins. These make it a mild astringent. It may relieve pain from canker sores or sore throats, according to traditional use. Clinical trials have not been conducted to confirm this.