Hawthorn (Crataegus oxyacantha) is a European thorny shrub that is often found in hedgerows, hence its alternative name hedgethorn. Its trimmed presence in hedgerows hides its usual size, with the hawthorn three being able to reach heights of around 10 meters. Hawthorn is interesting nutritionally because both its blossom (flowers) and its berries can be used medicinally to treat various forms of cardiovascular disease, including atherosclerosis, angina, congestive heart failure and high blood pressure. The ability of hawthorn to treat cardiovascular disease is thought to relate to the presence of high concentrations of flavonoids in its berries, leaves and blossoms. In particular the berries and flowers are rich sources of the blue, red and purple anthocyanin group of flavonoids, a feature that is common to all berries including grapes. Anthocyanins have been shown to have particularly beneficial effects against the development of cardiovascular disease, possibly because they are strong antioxidants but may also regulate gene function.
The antioxidant activity of hawthorn flavonoids is interesting, because one of the known effects is an ability to raise cellular levels of other antioxidants. In particular, anthocyanins may raise tissue levels of vitamin C and reduced glutathione. This occurs because the anthocyanins can partake in some of the chain quenching reactions normally undertaken by vitamin C or glutathione and in this regard spare the latter and thus boost tissue levels. The flavonoids and their associated higher concentrations of vitamin C may improve the synthesis and integrity of collagen. As collagen is required for the correct formation of healthy blood vessels, flavonoids may help stabilise the vasculature, improve healing rates of micro adhesions, and improve elasticity. The antioxidant effects of anthocyanins may also increase the production of nitric oxide in the endothelial cells of the arteries and this may allow for correct dilation in response to blood flow, thus facilitating normal blood pressure regulation, preventing hypertension.
The antioxidant effects of flavonoids in hawthorn berries and flowers are also likely involved in combating systemic inflammation. Inflammation is increasingly being seen as part of the aetiology of cardiovascular disease, with the end product of the inflammatory process being an increase in the production of free radicals and subsequent tissue damage. Hawthorne anthocyanins, like most dietary flavonoids, may reduce inflammation and thus decrease one of the factors required for the development of lesions in the arteries that may ultimately contribute to atherosclerosis. The flavonoids in hawthorn berries and flowers have also been shown to increase the force of contraction in heart muscle. This effects was however not due to an improvement in blood flow to the heart, but was suspected to be caused by interactions of the flavonoids with particular enzymes in the heart muscle tissue (such as cyclic AMP phosphodiesterase), the result of which was to cause greater energy concentrations within the heart cells. This makes hawthorn a useful treatment for congestive heart failure.