Urtica

Nettles.

Nettles have long been known for their medicinal properties.

Nettles are used to make soup, to heal, and to eat.

History of nettles:

Description

Urtica species grow as annuals or perennial herbaceous plants, rarely shrubs. They can reach, depending on the type, location and nutrient status, a height of 10–300 centimetres (3.9–118.1 in). The perennial species have underground rhizomes. The green parts have stinging hairs. Their often quadrangular stems are unbranched or branched, erect, ascending or spreading.

Most leaves and stalks are arranged across opposite sides of the stem. The leaf blades are elliptic, lanceolate, ovate or circular. The leaf blades usually have three to five, rarely up to seven veins. The leaf margin is usually serrate to more or less coarsely toothed. The often-lasting bracts are free or fused to each other. The cystoliths are extended to more or less rounded.

In 1874, while in Collioure (south of France), French botanist Charles Naudin discovered that strong winds during 24 hours made the stinging hairs of Urtica harmless for a whole week.

Species

Detail of a male flowering stinging nettle.

Detail of female flowering stinging nettle.

A large number of species included within the genus in the older literature are now recognized as synonyms of Urtica dioica. Some of these taxa are still recognized as subspecies.

Species in the genus Urtica, and their primary natural ranges, include:[citation needed]

Urtica andicola Webb

Urtica angustifolia Fisch. ex Hornem. China, Japan, Korea

Urtica ardens China

Urtica aspera Petrie South Island, New Zealand

Urtica atrichocaulis Himalaya, southwestern China

Urtica atrovirens western Mediterranean region

Urtica australis Hook.f. South Island, New Zealand and surrounding subantarctic islands

Urtica cannabina L., Western Asia from Siberia to Iran

Urtica chamaedryoides (heartleaf nettle), southeastern North America

Urtica dioica L. (stinging nettle or bull nettle), Europe, Asia, North America

Urtica dioica subsp. galeopsifolia Wierzb. ex Opiz (fen nettle or stingless nettle), Europe. (Sometimes treated as a separate species Urtica galeopsifolia.)

Urtica dubia – illegitimate synonym of U. membranacea

Urtica ferox G.Forst. (ongaonga or tree nettle), New Zealand

Urtica fissa China

Urtica gracilenta (mountain nettle), Arizona, New Mexico, west Texas, northern Mexico

Urtica hyperborea Himalaya from Pakistan to Bhutan, Mongolia and Tibet, high altitudes

Urtica incisa Poir (scrub nettle), Australia, New Zealand

Urtica kioviensis Rogow. eastern Europe

Urtica laetivirens Maxim. Japan, Northeast China

Urtica lalibertadensis

Urtica linearifolia (Hook.f.) Cockayne (creeping or swamp nettle), or Urtica perconfusa, an at risk endemic climber, New Zealand[5]

Urtica mairei Himalaya, southwestern China, northeastern India, Myanmar

Urtica massaica Africa

Urtica membranacea Poir. ex Savigny Mediterranean region, Azores and Madeira

Urtica morifolia Poir. Macaronesia

Urtica minutifolia Griseb. Bolivia

Urtica parviflora Himalaya (lower altitudes)

Urtica peruviana D.Getltman Perú

Urtica pseudomagellanica D.Geltman Bolivia

Urtica pilulifera (Roman nettle), southern Europe

Urtica platyphylla Wedd. Kamchatka, Sakhalin, Japan

Urtica procera Mühlenberg (tall nettle), North America

Urtica pubescens Ledeb. Southwestern Russia east to central Asia

Urtica rupestris Sicily (endemic)

Urtica sondenii (Simmons) Avrorin ex Geltman northeastern Europe, northern Asia

Urtica taiwaniana Taiwan

Urtica thunbergiana Japan, Taiwan

Urtica triangularis

Urtica urens L. (small nettle or annual nettle), Europe, North America

Urtica urentivelutina

Ecology

Due to the stinging hairs, Urtica species are rarely eaten by herbivores, but rather provide shelter for insects, such as aphids, butterfly larvae, and moths.

Uses

Fabric woven of nettle fiber was found in burial sites in Denmark dating to the Bronze Age, and in clothing fabric, sailcloth, fishing nets, and paper via the process called retting (microbial enzymatic degradation, similar to linen processing). Other processing methods include mechanical and chemical.

In New Zealand, U. ferox is classified among poisonous plants, most commonly upon skin contact.

Urtica, called kopriva in Croatian, Serbian, Bulgarian and Slovenian, and urzica in Romanian, is an ingredient in soups, omelettes, banitsa, purée, and other dishes. In Mazandaran, northern Iran, a soup (Āsh) is made using this plant. Nettles were used in traditional practices to make nettle tea, juice, and ale, and to preserve cheeses, such as in Cornish Yarg.

In folklore

Nettles have many folklore traditions associated with them. The folklore mainly relates to the stinging nettle (Urtica dioica).[citation needed]

Literature

Asian

Milarepa, the great Tibetan ascetic and saint, was reputed to have survived his decades of solitary meditation by subsisting on nothing but nettles; his hair and skin turned green and he lived to the age of 83.

Caribbean

The Caribbean trickster figure Anansi appears in a story about nettles, in which he has to chop down a huge nettle patch in order to win the hand of the king's daughter.

European

An old Scots rhyme about the nettle:

"Gin ye be for lang kail coo the nettle, stoo the nettle

Gin ye be for lang kail coo the nettle early

Coo it laich, coo it sune, coo it in the month o' June

Stoo it ere it's in the bloom, coo the nettle early

Coo it by the auld wa's, coo it where the sun ne'er fa's

Stoo it when the day daws, coo the nettle early."

(Old Wives Lore for Gardeners, M & B Boland)

Coo, cow, and stoo are all Scottish for cut back or crop (although, curiously, another meaning of "stoo" is to throb or ache), while "laich" means short or low to the ground. Given the repetition of "early," presumably this is advice to harvest nettles first thing in the morning and to cut them back hard [which seems to contradict the advice of the Royal Horticultural Society].

A well-known English rhyme about the stinging nettle is:

Tender-handed, stroke a nettle,

And it stings you for your pains.

Grasp it like a man of mettle,

And it soft as silk remains.

In Hans Christian Andersen's fairy-tale "The Wild Swans," the princess had to weave coats of nettles to break the spell on her brothers.

More about nettles:

Nettle family are of considerable interest as preservatives in foods for both human and animal consumption. They have also been used for centuries in traditional medicine. This paper reviews the properties of nettles that make them suitable for wider applications in the food and pharmaceutical industries. Nettles contain a significant number of biologically-active compounds. For example, the leaves are rich sources of terpenoids, carotenoids and fatty acids, as well as of various essential amino acids, chlorophyll, vitamins, tannins, carbohydrates, sterols, polysaccharides, isolectins and minerals. Extracts from the aerial parts of nettles are rich sources of polyphenols, while the roots contain oleanol acid, sterols and steryl glycosides. Due to the variety of phytochemicals and their proportions they contain, nettles show noticeable activity against both Gram-positive and Gram-negative bacteria. These properties make nettles suitable for a range of possible applications, including functional food, dietary supplements and pharmacological formulations. Despite these benefits, the nettle is still an underestimated plant source. This paper provides a unique overview of the latest research on nettle plants focusing on the possibilities for transforming a common weed into a commercial plant with a wide range of applications. Special attention is paid to the antimicrobial activity of the active compounds in nettles and to possible uses of these valuable plants in food and feed formulations. Keywords: Urtica spp., bioactive compounds, antioxidant activity, antimicrobial activity, traditional medicine, food industry, animal breeding.

In a study of nettles by Rafajlovska et al., higher quantities of proteins were found in the leaves than in the stems and roots. The content of proteins in the leaves ranged from 16.08 ± 0.38–26.89 ± 0.39%, depending on the source of the sample. The highest protein contents in the stem and roots were 14.54 ± 0.27% and 10.89 ± 0.11%, respectively. Other studies of nettle composition have found that the plants contain a significant number of biologically-active compounds. The nettle leaves contain terpenoids , carotenoids including β-carotene, neoxanthin, violaxanthin, lutein and lycopene, fatty acids, especially palmitic, cis-9,12-linoleic and α-linolenic acids , different polyphenolic compounds, essential amino acids, chlorophyll, vitamins, tannins, carbohydrates, sterols, polysaccharides, isolectins [and minerals , the most important of which is iron.

The leaves of Urtica spp. contain around 4.8 mg/g DM of chlorophyll, depending on the climate and environmental conditions. Interestingly, more chlorophyll and carotenoids are usually found in plants that have been harvested from shady places. Kukrić and co-workers noted that there were differences in the content of chlorophyll and carotenoids in leaves of different ages . The concentration of chlorophyll increases in growing leaves and decreases during plant aging. The fresh leaves contain high concentrations of vitamins A, C, D, E, F, K and P, as well as of vitamin B-complexes . The leaves are also known to contain particularly large amounts of the metals selenium, zinc, iron and magnesium. Rafajlovska et al. noted that stinging nettle leaves, stems and roots contained larger amounts of calcium than magnesium. These two elements were present at quantities almost three-times higher in the leaves than in the stems and roots. The calcium content expressed in relation to the dry mass ranged from 2.63–5.09% in leaves, from 0.76–1.42% in stems and from 0.61–0.92% in roots. Zinc was found in the highest concentrations in the leaves (27.44 mg/kg of dry mass), followed by copper (17.47 mg/kg) and manganese (17.17 mg/kg). The mean values for cobalt content were significantly higher in leaves than in stems and roots. The contents of cobalt in the leaves, stems and roots, respectively, were in the ranges of 0.11–0.21 mg/kg, 0.10–0.18 mg/kg, and 0.08–0.16 mg/kg, relative to the corresponding dry mass. Urtica leaves in addition contain boron, sodium, iodine, chromium, copper and sulfur .

The total phenolic content of one gram of nettle powder has been reported as 129 mg GAE (Gaelic Acid Equivalent), which is two-times higher than the phenolic content in 100 mL of cranberry juice (66.61 mg GAE) . Stinging nettles have been shown to be richer in individual polyphenols than other wild plants . Ghaima and co-workers found that the content of phenolic compounds in stinging nettle leaves was significantly higher than in dandelion leaves . Vajić et al. reported that the predominant phenolic compound in stinging nettle leaves is rutin . Ðurović and co-workers studied the chemical composition of stinging nettle leaves using different analytical approaches. Soxhlet extraction was performed and qualitative analysis of Ultrasound-Assisted (UA) extracts using the UHPLC-DAD technique with MS/MS. Differences in the chemical profiles were found. For example, after Soxhlet extraction, syringic, cinnamic and protocatechuic acids were detected in the products, which was not the case with the UA extract. On the other hand, ferulic, caffeic, chlorogenic and sinapic acids were detected only after ultrasound-assisted extraction .

Orčić and co-workers quantified various plant phenolics in methanol extracts of U. dioica, for flowers, roots, stems and leaves separately, harvested from different locations in Serbia . The polyphenol profiles were dependent not only on the parts of the plants, but also on the location of their acquisition. The researchers found that inflorescence extracts were the richest in phenolics. The most abundant compound was 5-O-caffeoylquinic acid (chlorogenic acid), followed by quercetin 3-O-rhamnosylglucoside (rutin) and 3-O-glucoside (isoquercetin).

The quantitative and qualitative composition of the roots differs from that of the aerial parts of the plants . The content of the majority of the phenols in the root extracts is significantly lower, and the only prominent compound is secoisolariciresinol. Therefore, the roots of stinging nettles are considered to be the poorest part in terms of bioactive compounds. The root extracts contain only a few acids and derivatives in significant amounts . They contain starch, gum, albumen, sugars and resins, as well as neurotransmitters and receptors, such as histamine, acetylcholine, choline or serotonin. Methanolic extracts of nettle roots have an inhibitory effect on aromatase, a key enzyme in the biosynthesis of estrogens. The lipophilic fractions usually contain phytosterols, pentacyclic triterpenoids, coumarins, ceramides and hydroxyl fatty acids. In turn, isolectins and some polysaccharides have been isolated from the hydrophilic fractions . Krauss and Spitteler identified eighteen phenolic compounds (including homovanillyl alcohol, vanillin, vanillic acid and phenylpropanes) and nineteen ligands (including isolaric, iresinol, secoisolariciresinol and neoolivil) in root extracts . Scopoletin, a coumarin derivative, has also been identified in nettle roots . All these compounds are considered to be very important in medicine and pharmacology. For example, homovanillyl alcohol has been shown to protect against cardiovascular disease , while histamine influences the complex physiology of brain systems, affecting cognitive processes, including learning and memory , as well as neurotransmitters involved in neuromodulation processes . Phytosterols reduce the absorption of cholesterol in the gut and thereby lower blood cholesterol levels . Scopoletin is a stimulator of lipoprotein lipase activity and protects against cardiovascular diseases . Lignans improve immune responses