54-399: An acorn is the nut of an oak tree. Acorn or ACORN may also refer to: Acorn The acorn is the nut of the oaks and their close relatives (genera Quercus , Notholithocarpus and Lithocarpus , in the family Fagaceae ). It usually contains a seedling surrounded by two cotyledons (seedling leaves), enclosed in a tough shell known as the pericarp, and borne in
108-585: A coffee substitute , particularly when coffee was unavailable or rationed. The Confederates in the American Civil War and Germans during World War I (when it was called Ersatz coffee), which were cut off from coffee supplies by Union and Allied blockades respectively, are particularly notable past instances of this use of acorns. Acorns are a traditional food of many indigenous peoples of North America, and long served an especially important role for Californian Native Americans , where
162-589: A chemical structure formed by attachment of an aromatic benzenoid ( phenyl ) ring to a hydroxyl (-OH) group (hence the -ol suffix). The term "polyphenol" has been in use at least since 1894. The term polyphenol is not well-defined, but it is generally agreed that they are natural products with "several hydroxyl groups on aromatic rings " including four principal classes: "phenolic acids, flavonoids, stilbenes, and lignans". The White–Bate-Smith–Swain–Haslam (WBSSH) definition characterized structural characteristics common to plant phenolics used in tanning (i.e.,
216-445: A cup-shaped cupule . Acorns are 1–6 cm ( 1 ⁄ 2 – 2 + 1 ⁄ 2 in) long and 0.8–4 cm ( 3 ⁄ 8 – 1 + 5 ⁄ 8 in) on the fat side. Acorns take between 5 and 24 months (depending on the species) to mature; see the list of Quercus species for details of oak classification, in which acorn morphology and phenology are important factors. The word acorn (earlier akerne , and acharn )
270-466: A large family of naturally occurring phenols . They are abundant in plants and structurally diverse. Polyphenols include phenolic acids , flavonoids , tannic acid , and ellagitannin , some of which have been used historically as dyes and for tanning garments . The name derives from the Ancient Greek word πολύς ( polus , meaning "many, much") and the word ‘phenol’ which refers to
324-458: A large influence on small rodents in their habitats , as large acorn yields help rodent populations to grow. Large mammals such as pigs, bears, and deer also consume large amounts of acorns; they may constitute up to 25% of the diet of deer in the autumn. In Spain, Portugal and the New Forest region of southern England, pigs are still turned loose in dehesas (large oak groves ) in
378-682: A large, diverse group of compounds, making it difficult to determine their biological effects. They are not considered nutrients , as they are not used for growth, survival or reproduction, nor do they provide dietary energy . Therefore, they do not have recommended daily intake levels , as exist for vitamins , minerals , and fiber . In the United States, the Food and Drug Administration issued guidance to manufacturers that polyphenols cannot be mentioned on food labels as antioxidant nutrients unless physiological evidence exists to verify such
432-439: A long time, much as squirrels do. In years that oaks produced many acorns, Native Americans sometimes collected enough acorns to store for two years as insurance against poor acorn production years. After drying in the sun to discourage mould and germination , acorns could be cached in hollow trees or structures on poles to keep them safe from mice and squirrels. Stored acorns could then be used when needed, particularly during
486-559: A minimum of 20–30 m (70–100 ft) from the parent tree . Many animals eat unripe acorns on the tree or ripe acorns from the ground, with no reproductive benefit to the oak, but some animals, such as squirrels and jays serve as seed dispersal agents. Jays and squirrels that scatter-hoard acorns in caches for future use effectively plant acorns in a variety of locations in which it is possible for them to germinate and thrive. Even though jays and squirrels retain remarkably large mental maps of cache locations and return to consume them,
540-548: A molecule at the core of naturally occurring phenolic compounds of varying sizes, is itself not a polyphenol by the WBSSH definition, but is by the Quideau definition. The raspberry ellagitannin , on the other hand, with its 14 gallic acid moieties (most in ellagic acid-type components), and more than 40 phenolic hydroxyl groups, meets the criteria of both definitions of a polyphenol. Other examples of compounds that fall under both
594-575: A qualification and a Dietary Reference Intake value has been established – characteristics which have not been determined for polyphenols. In the European Union , two health claims were authorized between 2012 and 2015: 1) flavanols in cocoa solids at doses exceeding 200 mg per day may contribute to maintenance of vascular elasticity and normal blood flow; 2) olive oil polyphenols (5 mg of hydroxytyrosol and its derivatives (e.g. oleuropein complex and tyrosol ) may "contribute to
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#1732780277206648-648: A role in epicuticle hardening ( sclerotization ). The hardening of the cuticle is due to the presence of a polyphenol oxidase . In crustaceans, there is a second oxidase activity leading to cuticle pigmentation . There is apparently no polyphenol tanning occurring in arachnids cuticle. Polyphenols are thought to play diverse roles in the ecology of plants. These functions include: Flax and Myriophyllum spicatum (a submerged aquatic plant) secrete polyphenols that are involved in allelopathic interactions. Polyphenols incorporate smaller parts and building blocks from simpler natural phenols , which originate from
702-576: A solvent like water, hot water , methanol, methanol/formic acid, methanol/water/acetic or formic acid. Liquid–liquid extraction can be also performed or countercurrent chromatography . Solid phase extraction can also be made on C18 sorbent cartridges. Other techniques are ultrasonic extraction, heat reflux extraction, microwave-assisted extraction, critical carbon dioxide , high-pressure liquid extraction or use of ethanol in an immersion extractor. The extraction conditions (temperature, extraction time, ratio of solvent to raw material, particle size of
756-604: A source of food for many cultures around the world. For instance, the Ancient Greek lower classes and the Japanese (during the Jōmon period) would eat acorns, especially in times of famine. In ancient Iberia they were a staple food, according to Strabo . Despite this history, acorns rarely form a large part of modern diets and are not currently cultivated on scales approaching that of many other nuts. However, if properly prepared (by selecting high-quality specimens and leaching out
810-475: Is a lack of commercially available standards for all polyphenolic molecules. Some polyphenols are traditionally used as dyes in leather tanning . For instance, in the Indian subcontinent , pomegranate peel , high in tannins and other polyphenols, or its juice, is employed in the dyeing of non-synthetic fabrics. Of some interest in the era of silver-based photography, pyrogallol and pyrocatechin are among
864-434: Is made from acorns, and dotori guksu are Korean noodles made from acorn flour or starch. In the 17th century, a juice extracted from acorns was administered to habitual drunkards to cure them of their condition or else to give them the strength to resist another bout of drinking. Roasted acorn flour is a main ingredient in sweet cakes special to Kurdish areas of Iran and Iraq . Acorns have frequently been used as
918-457: Is particularly true of the acorns of American red oaks and English oaks . The acorns of white oaks , being much lower in tannins, are nutty in flavor; this characteristic is enhanced if the acorns are given a light roast before grinding. Tannins can be removed by soaking chopped acorns in several changes of water, until the water no longer turns brown. Cold water leaching can take several days, but three to four changes of boiling water can leach
972-628: Is related to the Gothic name akran , which had the sense of "fruit of the unenclosed land". The word was applied to the most important forest produce, that of the oak. Chaucer spoke of "achornes of okes" in the 14th century. By degrees, popular etymology connected the word both with "corn" and "oak-horn", and the spelling changed accordingly. The current spelling (emerged c. 15th–16th century) derives from association with ac (Old English: "oak") + corn . Acorns play an important role in forest ecology when oaks are plentiful or dominant in
1026-1053: Is the rapid polymerisation of o-quinones to produce black, brown or red polyphenolic pigments that causes fruit browning . In insects, PPO is involved in cuticle hardening. Polyphenols comprise up to 0.2–0.3% fresh weight for many fruits. Consuming common servings of wine, chocolate, legumes or tea may also contribute to about one gram of intake per day. According to a 2005 review on polyphenols: The most important food sources are commodities widely consumed in large quantities such as fruit and vegetables, green tea, black tea, red wine, coffee, chocolate, olives, and extra virgin olive oil. Herbs and spices, nuts and algae are also potentially significant for supplying certain polyphenols. Some polyphenols are specific to particular food (flavanones in citrus fruit, isoflavones in soya, phloridzin in apples); whereas others, such as quercetin, are found in all plant products such as fruit, vegetables, cereals, leguminous plants, tea, and wine. Some polyphenols are considered antinutrients – compounds that interfere with
1080-515: Is used as a reagent for staining phenolics in thin layer chromatography . Polyphenols can be studied by spectroscopy , especially in the ultraviolet domain, by fractionation or paper chromatography . They can also be analysed by chemical characterisation. Instrumental chemistry analyses include separation by high performance liquid chromatography (HPLC), and especially by reversed-phase liquid chromatography (RPLC), can be coupled to mass spectrometry . Purified compounds can be identified by
1134-478: The diphenylpicrylhydrazyl (DPPH), oxygen radical absorbance capacity (ORAC), ferric reducing ability of plasma (FRAP) assays or inhibition of copper-catalyzed in vitro human low-density lipoprotein oxidation. New methods including the use of biosensors can help monitor the content of polyphenols in food. Quantitation results produced by the mean of diode array detector –coupled HPLC are generally given as relative rather than absolute values as there
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#17327802772061188-406: The phenylpropanoid pathway for the phenolic acids or the shikimic acid pathway for gallotannins and analogs. Flavonoids and caffeic acid derivatives are biosynthesized from phenylalanine and malonyl-CoA . Complex gallotannins develop through the in vitro oxidation of 1,2,3,4,6-pentagalloylglucose or dimerization processes resulting in hydrolyzable tannins. For anthocyanidins, precursors of
1242-516: The 21st century of a possible effect on cardiovascular diseases. For most polyphenols, there is no evidence for an effect on cardiovascular regulation, although there are some reviews showing a minor effect of consuming polyphenols, such as chlorogenic acid or flavan-3-ols , on blood pressure. Higher intakes of soy isoflavones may be associated with reduced risks of breast cancer in postmenopausal women and prostate cancer in men. A 2019 systematic review found that intake of soy and soy isoflavones
1296-616: The Porter's assay). Total phenols (or antioxidant effect) can be measured using the Folin–Ciocalteu reaction . Results are typically expressed as gallic acid equivalents. Polyphenols are seldom evaluated by antibody technologies. Other tests measure the antioxidant capacity of a fraction. Some make use of the ABTS radical cation which is reactive towards most antioxidants including phenolics, thiols and vitamin C . During this reaction,
1350-535: The WBSSH and Quideau definitions include the black tea theaflavin-3-gallate shown below, and the hydrolyzable tannin, tannic acid . Polyphenols are reactive species toward oxidation , hence their description as antioxidants in vitro . Polyphenols, such as lignin, are larger molecules ( macromolecules ). Their upper molecular weight limit is about 800 daltons , which allows for the possibility to rapidly diffuse across cell membranes so that they can reach intracellular sites of action or remain as pigments once
1404-454: The absorption of essential nutrients – especially iron and other metal ions, which may bind to digestive enzymes and other proteins, particularly in ruminants . In a comparison of cooking methods, phenolic and carotenoid levels in vegetables were retained better by steaming compared to frying . Polyphenols in wine, beer and various nonalcoholic juice beverages can be removed using finings , substances that are usually added at or near
1458-494: The acorn symbol is used as an ornament on cutlery , furniture, and jewelry; it also appears on finials at Westminster Abbey . In the Artemis Fowl book series, "The Ritual" describes the method used by faeries to regenerate their magical powers. The acorn was used frequently by both Union and Confederate forces during the American Civil War . Modern US Army Cavalry Scout campaign hats still retain traces of
1512-527: The acorn today. The acorn is the symbol for the National Trails of England and Wales , and is used for the waymarks on these paths. The acorn, specifically that of the white oak, is also present in the symbol for the University of Connecticut . Acorns are also used as charges in heraldry . Polyphenol Polyphenols ( / ˌ p ɒ l i ˈ f iː n oʊ l , - n ɒ l / ) are
1566-609: The autumn, to fill and fatten themselves on acorns. Heavy consumption of acorns can, on the other hand, be toxic to other animals that cannot detoxify their tannins , such as horses and cattle, especially if eaten in excess. The larvae of some moths and weevils also live in young acorns, consuming the kernels as they develop. Acorns are attractive to animals because they are large and thus efficiently consumed or cached. Acorns are also rich in nutrients. Percentages vary from species to species, but all acorns contain large amounts of protein , carbohydrates and fats , as well as
1620-482: The bitter tannins in water), acorn meal can be used in some recipes calling for grain flours. In antiquity, Pliny the Elder noted that acorn flour could be used to make bread. Varieties of oak differ in the amount of tannin in their acorns. Varieties preferred by Native Americans, such as Quercus kelloggii (California black oak), may be easier to prepare or more palatable. In Korea, an edible jelly named dotorimuk
1674-467: The blue ABTS radical cation is converted back to its colorless neutral form. The reaction may be monitored spectrophotometrically. This assay is often referred to as the Trolox equivalent antioxidant capacity (TEAC) assay. The reactivity of the various antioxidants tested are compared to that of Trolox , which is a vitamin E analog. Other antioxidant capacity assays which use Trolox as a standard include
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1728-925: The cell senesces . Hence, many larger polyphenols are biosynthesized in situ from smaller polyphenols to non-hydrolyzable tannins and remain undiscovered in the plant matrix. Most polyphenols contain repeating phenolic moieties of pyrocatechol, resorcinol, pyrogallol, and phloroglucinol connected by esters (hydrolyzable tannins) or more stable C-C bonds (nonhydrolyzable condensed tannins ). Proanthocyanidins are mostly polymeric units of catechin and epicatechin . Polyphenols often have functional groups beyond hydroxyl groups . Ether ester linkages are common, as are carboxylic acids . The analysis techniques are those of phytochemistry : extraction , isolation, structural elucidation , then quantification . Polyphenols readily react with metal ions to form coordination complexes , some of which form Metal-phenolic Networks . Extraction of polyphenols can be performed using
1782-418: The chemical structure allowing antioxidant activity in vivo; they may exert biological activity as signaling molecules . Some polyphenols are considered to be bioactive compounds for which development of dietary recommendations was under consideration in 2017. In the 1930s , polyphenols (then called vitamin P ) were considered as a factor in capillary permeability , followed by various studies through
1836-516: The completion of the processing of brewing. With respect to food and beverages, the cause of astringency is not fully understood, but it is measured chemically as the ability of a substance to precipitate proteins. Astringency increases and bitterness decrease with the mean degree of polymerization . For water-soluble polyphenols, molecular weights between 500 and 3000 were reported to be required for protein precipitation. However, smaller molecules might still have astringent qualities likely due to
1890-457: The condensed tannin biosynthesis, dihydroflavonol reductase and leucoanthocyanidin reductase (LAR) are crucial enzymes with subsequent addition of catechin and epicatechin moieties for larger, non-hydrolyzable tannins. The glycosylated form develops from glucosyltransferase activity and increases the solubility of polyphenols. Polyphenol oxidase (PPO) is an enzyme that catalyses the oxidation of o-diphenols to produce o-quinones . It
1944-534: The epidermis, bark layers, flowers and fruits but also play important roles in the decomposition of forest litter, and nutrient cycles in forest ecology. Absolute concentrations of total phenols in plant tissues differ widely depending on the literature source, type of polyphenols and assay; they are in the range of 1–25% total natural phenols and polyphenols, calculated with reference to the dry green leaf mass. Polyphenols are also found in animals. In arthropods , such as insects, and crustaceans polyphenols play
1998-537: The fluorescence signal. Polyphenolic content in vitro can be quantified by volumetric titration . An oxidizing agent, permanganate , is used to oxidize known concentrations of a standard tannin solution, producing a standard curve . The tannin content of the unknown is then expressed as equivalents of the appropriate hydrolyzable or condensed tannin. Some methods for quantification of total polyphenol content in vitro are based on colorimetric measurements. Some tests are relatively specific to polyphenols (for instance
2052-436: The formation of unprecipitated complexes with proteins or cross-linking of proteins with simple phenols that have 1,2-dihydroxy or 1,2,3-trihydroxy groups. Flavonoid configurations can also cause significant differences in sensory properties, e.g. epicatechin is more bitter and astringent than its chiral isomer catechin . In contrast, hydroxycinnamic acids do not have astringent qualities, but are bitter. Polyphenols are
2106-565: The landscape. The volume of the acorn crop may vary widely, creating great abundance or great stress on the many animals dependent on acorns and the predators of those animals. Acorns, along with other nuts, are termed mast . Wildlife that consume acorns as an important part of their diets include birds, such as jays , pigeons , some ducks , and several species of woodpeckers . Small mammals that feed on acorns include mice , squirrels and several other rodents . One beetle species, Thorectes lusitanicus , also feeds on acorns. Acorns have
2160-511: The landscapes. Oaks produce more acorns when they are not too close to other oaks and thus competing with them for sunlight, water and soil nutrients. The fires tended to eliminate the more vulnerable young oaks and leave old oaks which created open oak savannas with trees ideally spaced to maximize acorn production. A motif in Roman architecture , also popular in Celtic and Scandinavian art,
2214-509: The means of nuclear magnetic resonance . The DMACA reagent is an histological dye specific to polyphenols used in microscopy analyses. The autofluorescence of polyphenols can also be used, especially for localisation of lignin and suberin . Where fluorescence of the molecules themselves is insufficient for visualization by light microscopy, DPBA (diphenylboric acid 2-aminoethyl ester, also referred to as Naturstoff reagent A) has traditionally been used, at least in plant science , to enhance
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2268-431: The minerals calcium , phosphorus and potassium , and the vitamin niacin . Total food energy in an acorn also varies by species, but all compare well with other wild foods and with other nuts. Acorns also contain bitter tannins , the amount varying with the species. Since tannins, which are plant polyphenols , interfere with an animal's ability to metabolize protein, creatures must adapt in different ways to use
2322-424: The nutrients bound in dead leaves and other plant debris into the soil, thus fertilizing oak trees while clearing the ground to make acorn collection easier. Most North American oaks tolerate light fires, especially when consistent burning has eliminated woody fuel accumulation around their trunks. Consistent burning encouraged oak growth at the expense of other trees less tolerant of fire, thus keeping oaks dominant in
2376-689: The nutritional value acorns contain. Animals may preferentially select acorns that contain fewer tannins. When the tannins are metabolized in cattle, the tannic acid produced can cause ulceration and kidney failure. Animals that cache acorns, such as jays and squirrels, may wait to consume some of these acorns until sufficient groundwater has percolated through them to leach out the tannins. Other animals buffer their acorn diet with other foods. Many insects, birds, and mammals metabolize tannins with fewer ill effects than do humans. Species of acorn that contain large amounts of tannins are very bitter, astringent , and potentially irritating if eaten raw. This
2430-619: The oak family. Once acorns sprout, they are less nutritious, as the seed tissue converts to the indigestible lignins that form the root. In some cultures, acorns once constituted a dietary staple , though they have largely been replaced by grains and are now typically considered a relatively unimportant food, except in some Native American and Korean communities. Several cultures have devised traditional acorn-leaching methods, sometimes involving specialized tools, that were traditionally passed on to their children by word of mouth. Acorns served an important role in early human history and were
2484-542: The odd acorn may be lost, or a jay or squirrel may die before consuming all of its stores. A small number of acorns manage to germinate and survive, producing the next generation of oaks. Scatter-hoarding behavior depends on jays and squirrels associating with plants that provide good packets of food that are nutritionally valuable, but not too big for the dispersal agent to handle. The beak sizes of jays determine how large acorns may get before jays ignore them. Acorns germinate on different schedules, depending on their place in
2538-522: The oldest photographic developers . Natural polyphenols have long been proposed as renewable precursors to produce plastics or resins by polymerization with formaldehyde , as well as adhesives for particleboards. The aims are generally to make use of plant residues from grape, olive (called pomaces ), or pecan shells left after processing. The most abundant polyphenols are the condensed tannins , found in virtually all families of plants. Larger polyphenols are often concentrated in leaf tissue,
2592-498: The protection of blood lipids from oxidative damage", if consumed daily. As of 2022, clinical trials that assessed the effect of polyphenols on health biomarkers are limited, with results difficult to interpret due to the wide variation of intake values for both individual polyphenols and total polyphenols. Polyphenols were once considered as antioxidants , but this concept is obsolete. Most polyphenols are metabolized by catechol-O-methyltransferase , and therefore do not have
2646-455: The ranges of several species of oaks overlap, increasing the reliability of the resource. One ecology researcher of Yurok and Karuk heritage reports that "his traditional acorn preparation is a simple soup, cooked with hot stones directly in a basket," and says he enjoys acorns eaten with "grilled salmon , huckleberries or seaweed ." Unlike many other plant foods, acorns do not need to be eaten or processed right away, but may be stored for
2700-553: The sample, solvent type, and solvent concentrations) for different raw materials and extraction methods have to be optimized. Mainly found in the fruit skins and seeds, high levels of polyphenols may reflect only the measured extractable polyphenol (EPP) content of a fruit which may also contain non-extractable polyphenols. Black tea contains high amounts of polyphenol and makes up for 20% of its weight. Concentration can be made by ultrafiltration . Purification can be achieved by preparative chromatography . Phosphomolybdic acid
2754-421: The tannins in under an hour. Hot water leaching (boiling) cooks the starch of the acorn, which would otherwise act like gluten in flour, helping it bind to itself. For this reason, if the acorns will be used to make flour, then cold water leaching is preferred. Being rich in fat, acorn flour can spoil or molder easily and must be carefully stored. Acorns are also sometimes prepared as a massage oil. Acorns of
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#17327802772062808-439: The tannins). In terms of properties, the WBSSH describes the polyphenols as follows: In terms of structures, the WBSSH recognizes two structural family that have these properties: According to Stéphane Quideau, the term "polyphenol" refers to compounds derived from the shikimate / phenylpropanoid and/or the polyketide pathway, featuring more than one phenolic unit and deprived of nitrogen-based functions. Ellagic acid ,
2862-464: The white oak group, Leucobalanus , typically start rooting as soon as they are in contact with the soil (in the fall), then send up the leaf shoot in the spring. Acorns are too heavy for wind dispersal , so they require other ways to spread. Oaks therefore depend on biological seed dispersal agents to move the acorns beyond the mother tree and into a suitable area for germination (including access to adequate water, sunlight and soil nutrients), ideally
2916-479: The winter when other resources were scarce. Acorns that germinated in the fall were shelled and pulverized before those germinating in spring. Because of their high fat content, stored acorns can become rancid. Moulds may also grow on them. The lighting of ground fires killed the larvae of acorn moths and acorn weevils by burning them during their dormancy period in the soil. The pests can infest and consume more than 95% of an oak's acorns. Fires also released
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