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.^{3, 4, 5} A double-blind study found that vincamine can help people with Alzheimer’s disease,⁶ while one open study did not.⁷ 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.⁸ 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).⁹ 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.¹⁰ One review of the use of vinpocetine in people who have suffered strokes found that the only double-blind study did not show efficacy,¹¹ though previous uncontrolled studies have suggested there might be a benefit.^{12, 13}

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.¹⁴ 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.^{15, 16} 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.