The sweet chestnut (Castanea sativa) is a medium to large-sized medicinal tree of the beech family, with large sawtooth-edged leaves and edible nuts, traditionally used in respiratory complaints.
Medicinal effects
The sweet chestnut is widely known for its nutritious fruits, but it has much more to offer as a medicinal tree. While sweet chestnut fruits have long been used as a food both for humans and animals, the medicinal value of the tree was also understood in classical times. Dioscorides identified its astringent and tonic characteristics. Chestnut flower honey was appreciated by the Romans for its pleasant and mildly bitter taste, and was also used for dressing wounds, burns and skin ulcers. Culpeper recommended dried powdered peeled sweet chestnuts in honey for a cough. The leaves have been used in many ethnobotanic formulations against colds, whooping cough, diarrhoea, as well as for skin complaints and infections.
Overall the sweet chestnut offers significant astringent and antibacterial effects. The leaves are antitussive, astringent, anti-inflammatory and expectorant. The chestnut flowers have anti-oxidant activity. The fruits, or chestnuts, offer dietary fibre and are high in unsaturated fatty acids. Sweet chestnuts can provide a nutritious diet element for people with coeliac disease, as a source of carbohydrate, protein and other essential nutrients which is gluten-free.
Growing
The sweet chestnut may have originated in the eastern Mediterranean and was then cultivated in southern Europe and Asia. Now it is widely naturalised from north Africa to southern Scandinavia. It flowers in July and the fruits ripen in October. The catkins hold both male and female flowers and are pollinated by bees. Chestnuts form inside spiny husks. Trees grown from seed may take 30 years to begin to produce these fruits. Mature trees have deeply grooved bark which curls up and around the trunk. Many sweet chestnut cultivars exist, over 100 are known. Although the plant is hardy, the young growth in spring can be damaged by frost. The tree prefers well-drained soil in a sunny position and can grow in poor or acid soil. It is resistant to drought. Warm dry summers are needed to ripen fruit in UK. Sweet chestnut can be readily coppiced or pollarded, and a planting density of 590 per acre has been reported. This plant will probably do better with global warming. C. mollissima is the Chinese chestnut, growing to about 25 m high. The American sweet chestnut is C. dentata. However Chinese chestnut has been affected by blight and introduction of this species in USA is the reason why American chestnuts are now almost extinct in the wild. Note that the sweet chestnut is not related to the horsechestnut (Aesculus hippocastanum) which has an inedible nut.
Harvesting
The leaves are picked in June and July and used fresh or dried. The nuts are ready when they fall to the ground in September-November, they can be de-husked and used immediately, frozen for up to 6 months or dried.
Research studies
The whole medicinal tree contains polyphenolics and is strongly anti-oxidant according to recent research studies. The leaves contain tannins and are rich in pentacyclic terpenes, ursene and oleanene derivatives. Chestnut bark is high in ellagitannins, with antiatherogenic, anti-thrombotic, anti-inflammatory, and antiangiogenic properties and antioxidant activity. The nuts contain starch, free sugars, proteins, vitamins and minerals, as well as polyphenolics, gallic and ellagic acids, ellgitannins such as castalgin and vescalagin. Traditional use against skin and bacterial infections is supported by the research finding that the leaf extracts have antibacterial activity, helping to block infection by Staphylococcus aureus. Some recent research studies are looking into the potential antibacterial and antioxidant applications for the leaf and husks offering a use for the byproducts of sweet chestnut production.
Ways to use
The dried leaves can be infused as a tea in the proportion of 25 g to 500 ml of water. This can be taken in bronchitis and coughs.
The tannin-rich leaves can be used as an infusion for sore throat.
Chestnut flour can be used for making gluten-free pancakes and pasta dishes.
References
Cerulli A, Napolitano A, Hošek J, et al. (2021) Antioxidant and in vitro preliminary anti-inflammatory activity of Castanea sativa (Italian cultivar ‘Marrone di Roccadaspide’ PGI) burs, leaves, and chestnuts extracts and their metabolite profiles by LC-ESI/LTQOrbitrap/MS/MS. Antioxidants (Basel) 10(2): 78.
Chiarini A, Micucci M, Malaguti M, et al. (2013) Sweet chestnut (Castanea sativa Mill.) bark extract: Cardiovascular activity and myocyte protection against oxidative damage. Oxidative Medicine and Cellular Longevity 2013: 71790.
Donno DBG, Mellano MG, Bonvegna L, et al.(2014) Castanea spp. buds as a phytochemical source for herbal preparations: Botanical fingerprint for nutraceutical identification and functional food standardisation. Sci Food Agric 94(14): 2863-2873.
Howkins C (2003) Sweet chestnut: history, landscape, people. Addlestone, Surrey: Published by the author.
Quave CL, Lyles JT, Kavanaugh JS, et al. (2015) Castanea sativa (European chestnut) leaf extracts rich in ursene and oleanene derivatives block Staphylococcus aureus virulence and pathogenesis without detectable resistance. PLoS One 10(8): e0136486.
Schink A, Neumann J, Leifke AL, et al. (2018) Screening of herbal extracts for TLR2- and TLR4-dependent anti-inflammatory effects. PLoS ONE 13(10): e0203907.
