Classification (APG IV)
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Genus: Stevia 
Species: Sugar leaf - Stevia rebaudiana  Cav.

Botanical Description
Paraguay sugar leaf, or stevia (Stevia rebaudiana), is an evergreen herbaceous plant from the Asteraceae family and the Stevia genus, growing up to 0.9 meters tall. The leaves are lance-shaped or elliptical, serrated, alternate, simple, glossy, dark green, and rough-textured, sometimes slightly hairy. They measure up to 5 cm in length and 2 cm in width. The plant’s underground system consists mainly of a shallow root system with a thicker taproot extending deeper. The roots are fibrous and thread-like and are the only part of the plant without steviol glycosides.

Stevia is a dioecious plant that blooms in early spring in its natural habitat. The inflorescence is a corymb-like compound cluster, with 2–6 flower heads. The flowers are small, star-shaped, tubular florets with a two-layered, five-part perianth. The flowers are odorless. The fruit is a ~3 mm long achene with a feathery pappus at the tip. The plant is insect-pollinated, primarily by bees. [1]

Distribution
Stevia is a perennial plant native to South America, particularly Brazil and Paraguay. Major stevia-producing countries include Mexico, the United States, Thailand, Russia, the United Kingdom, Japan, Canada, and China. The plant has a high moisture requirement. [2,3] In temperate climates, it is grown as an annual plant.

Effects and Uses
Stevia is a source of high-quality, calorie-free sweeteners. Its sweetness comes from steviol glycosides, which are 100–300 times sweeter than sucrose. Additionally, stevia reduces oxidative stress and lowers diabetes risk. Its leaves have been used to control and treat diabetes and other metabolic disorders. [4] The main sweetening compounds are stevioside and rebaudioside A. These compounds are thermally stable up to 200°C, making stevia suitable for thermally processed foods. The plant is also believed to have antioxidant, antimicrobial, and antifungal properties. Stevia contains folic acid, vitamin C, and amino acids. [4]

References
1. Missouri Botanical Garden. (n.d.). Stevia rebaudiana. Retrieved November 17, 2023, from Missouri Botanical Garden
2. Petruzzello, M. (2017, December 12). "Stevia | Description, Plant, & Sweetener." Encyclopedia Britannica. Retrieved November 17, 2023.
3. Ramesh, K., Singh, V., & Megeji, N. W. (2006). Cultivation of Stevia [Stevia rebaudiana (Bert.) Bertoni]: A Comprehensive Review. In Advances in Agronomy (Vol. 89, pp. 137–177). Academic Press. DOI:10.1016/s0065-2113(05)89003-0
4. Patel, S., & Navale, A. (2023). The Natural Sweetener Stevia: An Updated Review on its Phytochemistry, Health Benefits, and Anti-diabetic Study. Current Diabetes Reviews. Advance online publication. DOI:10.2174/1573399819666230501210803
5. Lemus-Mondaca, R., Vega-Gálvez, A., Zura-Bravo, L., & Ah-Hen, K. (2012). Stevia rebaudiana Bertoni, Source of a High-Potency Natural Sweetener: A Comprehensive Review on the Biochemical, Nutritional, and Functional Aspects. Food Chemistry, 132(3), 1121–1132. DOI:10.1016/j.foodchem.2011.11.140

Süstemaatiline kuuluvus (APG IV)
Riik: Taimed (Plantae)
Klaad: Soontaimed (Tracheophyta)
Klaad: Katteseemnetaimed (Angiospermae)
Klaad: Päriskaheidulehelised (Eudicotyledonae)
Selts: Astrilaadsed (Asterales)
Sugukond: Korvõielised (Asteridae)
Perekond: Suhkruleht (Stevia)
Liik: Paraguai suhkruleht - Stevia rebaudiana  Cav.

Botaaniline kirjeldus
Paraguai suhkruleht ehk stevia on igihaljas kuni 0,9 meetri kõrguseks kasvav rohttaim korvõieliste sugukonnast, perekonnast suhkruleht. Lehed on lantsetikujulised või elliptilised, hambulised, vahelduvad, lihtsad, läikivad ja tumerohelised, pinnalt karedad, mõnikord veidi karvased, kuni 5 cm pikad ja 2 cm laiad. Taime maaaluse osa moodustab peamiselt pinnapealne juurestik, mille paksem peajuur ulatub sügavamale; juured on kiulised, lõimelised ning ainus osa taimest, kus stevioolglükosiide ei leidu.

Stevia on kahekojaline taim, kes õitseb oma looduslikus levilas varakevadel. 2-6 korvõisikut paiknevad kännasjas liitõisikus. Õied on kaheli õiekattega, viietised, väikesed, tähtjad putkõied. Õitel tajutav lõhn puudub. Viljaks on umbes 3 mm pikkune seemnis, mis on tipust sulgja pappusega varustatud. Taim on putuktolmleja, tolmeldajateks on peamiselt mesilased. [1] 

Levila
Stevia on mitmeaastane taim, mis looduslikult kasvab Lõuna-Ameerikas, eriti Brasiilias ja Paraguai. Paraguai suhkrulehe suurimad kasvatajariigid on Mehhiko, Ameerika Ühendriigid, Tai, Venemaa, Suurbritannia, Jaapan, Kanada ja Hiina. Taim on niiskuse suhtes nõudlik. [2,3] Parasvöötme tingimustes kasvatatakse üheaastase taimena.

Toime ja kasutamine
Stevia taimest saadakse kõrgekvaliteedilist, kalorivaba suhkruasendajat.  Magusus tuleneb stevioolglükosiididest, mis on 100-300 korda magusamad kui sahharoos. Lisaks vähendab stevia oksüdatiivset stressi, alandades diabeediriski. Selle lehti on kasutatud diabeedi ja mitmesuguste teiste ainevahetushaiguste kontrollimiseks ja raviks. [4] Peamised magusained on steviosiid ja rebaudiosiid A. Need ühendid on termiliselt stabiilsed isegi kuni 200°C temperatuuril, mistõttu sobi suhkruleht kasutamiseks toitudes, mis vajavad termilist töötlemist. Arvatakse, et taimel on antioksüdantne, antimikroobne ja seenevastane toime. Stevia sisaldab ka foolhapet, C-vitamiini ning aminohappeid. [4]

Kasutatud allikad
1. Missouri Botanical Garden. (n.d.). Stevia rebaudiana. Retrieved November 17, 2023, from https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=e489
2. Petruzzello, Melissa (12 December 2017). "stevia | Description, Plant, & Sweetener". Encyclopedia Britannica. Encyclopædia Britannica, inc. Retrieved 17 November 2023.
3. Ramesh, K., Singh, V., & Megeji, N. W. (2006). Cultivation of Stevia [Stevia rebaudiana (Bert.) Bertoni]: A Comprehensive Review. In Advances in Agronomy (Vol. 89, pp. 137–177). Academic Press. https://doi.org/10.1016/s0065-2113(05)89003-0
4. Patel, S., & Navale, A. (2023). The Natural Sweetener Stevia: An Updated Review on its Phytochemistry, Health Benefits, and Anti-diabetic study. Current diabetes reviews, 10.2174/1573399819666230501210803. Advance online publication. https://doi.org/10.2174/1573399819666230501210803
5. Lemus-Mondaca, R., Vega-Gálvez, A., Zura-Bravo, L., & Ah-Hen, K. (2012). Stevia rebaudiana Bertoni, source of a high-potency natural sweetener: A comprehensive review on the biochemical, nutritional and functional aspects. Food chemistry, 132(3), 1121–1132. https://doi.org/10.1016/j.foodchem.2011.11.140