Süstemaatiline kuuluvus (APG IV)
Riik: Taimed (Plantae)
Klaad: Soontaimed (Tracheophyta)
Klaad: Katteseemnetaimed (Angiospermae)
Klaad: Päriskaheidulehelised (Eudicotyledonae)
Selts: Astrilaadsed (Asterales)
Sugukond: Korvõielised (Asteraceae)
Perekond: Käokuld (Helichrysum)
Liik: Harilik käkuld - Helichrysum arenarium (L.) Moench

Botaaniline kirjeldus
Harilik käokuld on mitmeaastane korvõieliste sugukonda, perekonda käokuld kuuluv taim. Taim kasvab 10-30 (50) cm kõrguseks ning selle juurestik ulatub sügavalt maa sisse. Varred on lehistunud ja tipu osas harunenud. Leheseis vastak. Varre lehed 2-5 cm pikkused, lihtsad, lineaalsed, roodudeta ja terve servaga. Juurmised lehed on äraspidimunajad ja moodustavad roseti. Nii lehed kui ka vars on halli-hõbeda villkarvane.

10-30 (-100) kerajat 3-6 mm läbimõõduga korvõisikut paiknevad ebasarikas. Korvõisiku üldkatise moodustavad 3-7 reas paiknevad rohked (umbes 50) pisut lõdvalt kattuvad lehekesed. Need on erksalt sidrunikollased, heledamalt kollased, roosakad või oranžid; välised katise lehekesed on elliptilised, ümara tipuga, alt tihedalt karvased; sisemised katise lehekesed on peaaegu lineaalsed. Õisikus 25-50 putkõit. Pappus koosneb umbes 30 kollakasvalgest karvast, mis on sama pikad kui õiekroon. Vili on viiekandiline, piklik, pruun pappusega seemnis, 0,7–1,2 mm pikk. [1,2]

Levila
Harilik käokuld kasvab kuival liivasel pinnal, sageli tühjal alal või rohu sees, liivaluidetel, põlluservadel, nõlvadel, teeäärtel ja õhukestes männimetsades. Mullastik peab olema kuivanud ning taim ei saa kasvada varju all. Liigi nimetuses olev sõna arenarium on tulnud ladinakeelsest sõnast „arena“, mis tähendab liiva. [1, 2]

Viimasel ajal on käokulda nähtud kasvamas ka liivastel kesamaadel Lõuna Rootsis, ent taimed tihti kaovad aastate möödudes. Looduslikult kasvab taim Kesk- ja Ida-Euroopas ning Kaukasusel, samuti Taani ida-aladel, Leedu kaguosas ja Lätis, kuid on siiski haruldane sealpool. Eestis kasvab ta paiguti, peamiselt kagu- ja lõunaosas, harva ilutaimena aedades. Islandil, Norras ja Soomes pole leitud. [1, 2].

Toime ja kasutamine
Suuremalt jaolt sisaldab taim flavanoide. Leidub ka kampferooli, apigeniini, naringeniini, kvertsetiini ja nende glükosiide, isosalipurosiidi, mis omakorda annab lehtedele tsitruselise värvitooni, ning antibiootilisi komponente koos fenoolhapetega. [2]

Rahvameditsiinis on harilik käokuld olnud kasutusel Euroopas, Põhja- ja Lõuna-Aafrikas, Põhja-Ameerikas, Hiinas ja Austraalias juba antiikajast saadik ning on registreeritud mitme riigi farmakopöades. Kuigi taime farmakodünaamilisi ja -kineetilisi omadusi ei ole veel täies mahus uuritud, on täheldatud, et õiedroogid avaldavad kerget kolereetilist ja spasmolüütilist toimet, mistõttu kasutatakse neid abiainena kroonilise sapipõiepõletiku ja krambitaoliste sapipõiehaiguste ravimites. Nii in vitro kui in vivo uuringud on tõestanud taime maksakaitsvaid, antimikroobseid ja antioksüdantseid omadusi. Samas on taim tuntud ka kui kergemate reumaatilise lihasvalude ja põiepõletiku sümptomite leevendaja ning tänu spasmolüütilisele omadusele aitab kergendada akuutseid kõhuvalusid. [2,3]

Tänu kliiniliselt tõestatud antioksüdantsetele omadustele on hariliku käokulla õli leidnud kasutamist ka nahateraapias, kuna avaldab antiallergilist, põletikuvastast ja rakkude taastavat funktsiooni välispidiselt määrides. Lõuna-Aafrikas, kus taim on võõrliik, on käokulla perekonda kuuluvad taimed kasutatud nii-öelda külmetushaiguste raviks ning putukatõrjevahendina. [3].

Kasutatud kirjandus
1. WFO (2024): Helichrysum arenarium (L.) Moench. Published on the Internet;http://www.worldfloraonline.org/taxon/wfo-0000090226. Accessed on: 06 Jan 2024
2. Pljevljakušić, D., Bigović, D., Janković, T., Jelačić, S., & Šavikin, K. (2018). Sandy Everlasting (Helichrysum arenarium (L.) Moench): Botanical, Chemical and Biological Properties. Frontiers in Plant Science, 9, 1123. https://doi.org/10.3389/fpls.2018.01123
3. Olsson, K., Pihlik, U., Radušienė, J., Bladh, K. W. (2005). Spice- and Medical Plants in the Nordic and Baltic Countries Conservation of Genetic Resources. Report from a project group at the Nordic Gene Bank, 55–65. https://pure.au.dk/ws/files/127457212/SPIMED_report_maj_2006.pdf#page=76 (04.10.2023).
4. Tammeorg, J., Kook, O., Vilbaste, G. (1984). Eesti NSV ravimtaimed. Tallinn: Valgus. 

Classification (APG IV)
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Genus: Helichrysum 
Species: Dwarf everlast - Helichrysum arenarium (L.) Moench

Botanical Description
Dwarf everlast is a perennial plant from the Asteraceae family, belonging to the Helichrysum genus. The plant grows 10–30 (up to 50) cm in height, with a root system that extends deep into the soil. The stems are leafy and branched at the top. The leaf arrangement is opposite. The stem leaves are 2–5 cm long, simple, linear, without veins, and with entire margins. The basal leaves are obovate and form a rosette. Both the leaves and stems are covered in gray-silvery woolly hairs.

The plant produces 10–30 (-100) globular flower heads, each 3–6 mm in diameter, arranged in a compound corymb. The involucre of the flower head consists of numerous bracts arranged in 3–7 rows, with about 50 overlapping bracts that are loosely packed. The bracts are bright lemon yellow, lighter yellow, pinkish, or orange. The outer bracts are elliptical, rounded at the tip, and densely hairy underneath, while the inner bracts are almost linear. The flower head contains 25–50 tubular florets. The pappus consists of about 30 yellowish-white hairs, equal in length to the corolla. The fruit is a five-angled, elongated, brown achene with a pappus, measuring 0.7–1.2 mm in length. [1,2]

Distribution
Dwarf everlast grows on dry, sandy soils, often in open areas, grasslands, sand dunes, field edges, slopes, roadsides, and sparse pine forests. The soil must be well-drained, and the plant cannot grow in the shade. The species name arenarium originates from the Latin word "arena," meaning sand. [1,2]

Recently, dwarf everlast has also been observed growing in sandy abandoned fields in southern Sweden, though populations often disappear over time. Naturally, the plant grows in Central and Eastern Europe and the Caucasus, as well as in eastern Denmark, southeastern Lithuania, and Latvia, though it remains rare in those regions. In Estonia, it occurs sporadically, mainly in the southeast and southern parts of the country, and is occasionally cultivated as an ornamental plant. It has not been found in Iceland, Norway, or Finland. [1,2]

Effects and Usage
The plant primarily contains flavonoids, including kaempferol, apigenin, naringenin, quercetin, and their glycosides. It also contains isosalipurposide, which gives the leaves a citrus-like color tone, along with antibiotic components and phenolic acids. [2]

Dwarf everlast has been used in traditional medicine in Europe, North and South Africa, North America, China, and Australia since ancient times, and it is registered in the pharmacopoeias of multiple countries. Although its pharmacodynamic and pharmacokinetic properties have not been fully studied, its flowering tops have been observed to have mild choleretic and spasmolytic effects, making them useful as adjuvants in the treatment of chronic cholecystitis and spasmodic gallbladder disorders. Both in vitro and in vivo studies have confirmed the plant’s hepatoprotective, antimicrobial, and antioxidant properties. It has also been known to alleviate mild rheumatic muscle pain and cystitis symptoms and, due to its spasmolytic effects, to help ease acute abdominal pain. [2,3]

Due to its clinically proven antioxidant properties, sandy everlasting oil has also been used in dermatological treatments, as it exhibits anti-allergic, anti-inflammatory, and cell-regenerating effects when applied externally. In South Africa, where the plant is an introduced species, related Helichrysum species have been used for cold remedies and insect repellents. [3]

References
1. WFO (2024): Helichrysum arenarium (L.) Moench. Published on the Internet; http://www.worldfloraonline.org/taxon/wfo-0000090226. Accessed on: 06 Jan 2024.
2. Pljevljakušić, D., Bigović, D., Janković, T., Jelačić, S., & Šavikin, K. (2018). Sandy Everlasting (Helichrysum arenarium (L.) Moench): Botanical, Chemical and Biological Properties. Frontiers in Plant Science, 9, 1123. https://doi.org/10.3389/fpls.2018.01123
3. Olsson, K., Pihlik, U., Radušienė, J., Bladh, K. W. (2005). Spice- and Medical Plants in the Nordic and Baltic Countries Conservation of Genetic Resources. Report from a project group at the Nordic Gene Bank, 55–65. https://pure.au.dk/ws/files/127457212/SPIMED_report_maj_2006.pdf#page=76 (04.10.2023).
4. Tammeorg, J., Kook, O., Vilbaste, G. (1984). Eesti NSV ravimtaimed. Tallinn: Valgus.