The plant
The plant is a perennial herb, erect and 1-3 m tall. It belongs to the family Asteraceae. The corolla is dark violet-purple and tubular. It flowers and fruits from July to October. It grows on rocky slopes and is widely cultivated. It is found at elevations from 2100 to 4500 m. The name Dolomiaea costus dates from 2020, and the plant was formerly known as Saussurea costus. Other names that have been used for the same plant are Aucklandia costus, Aucklandia lappa, Saussurea lappa, Aplotaxis lappa and Theodorea costus. It is a thistle native to South Asia and China. Records place it in India and Pakistan, and in China as a cultivated plant. Herbarium specimens come from Himachal Pradesh, Kashmir and Uttarakhand. The stem is simple, hairy above, and 0.8-2 cm across. The basal leaves are membranous, 10-12 × 7-9 cm and irregularly toothed, on winged stalks 4-30 cm long. The flower heads are 2.5-3.5 cm long, solitary or in clusters of 3-5, and usually terminal, with purple bracts. The corolla is 1.5-1.8 cm long. The fruit is a curved brown cypsela 0.6-1 cm long, topped by a brown feathery pappus.
The root and its uses
The root is also called by its Latin name radix aucklandiae. The roots are found as an essential oil, a ground powder or a dried stick. Incense sticks can be made by grinding the roots into a powder and then forming the stick. Dried sticks are commonly cut into thin slices, used as lightings for shrines or as tonics for hot baths. Rishi (Hindu) mystics of Kashmir especially ate this plant. The root is the part of the plant used for medicinal or homeopathic purposes. Cultivation is aimed mainly at the roots, and most of them are exported to China and Japan. High altitude favours seed germination and survival, which helps the plant thrive in the mountainous Himalayan region.
The essential oil
The essential oil from the roots is light yellow to brownish and resembles orris oil to some extent. The dry roots and the oil have become an important drug in the international market. In one analysis, the essential oil of the roots held about 80% sesquiterpenoids and 14% monoterpenoids. Its primary components were dehydrocostus lactone (46%) and costunolide (10%). A root extract examined in another study gave 22.5% dehydrocostus lactone and a costunolide peak area of 5.38%.
Chemistry
The main components of the plant are volatile constituents such as costunolide, dehydrocostus lactone, and cynaropicrin. Costunolide has the formula C₁₅H₂₀O₂, dehydrocostus lactone C₁₅H₁₈O₂ and cynaropicrin C₁₉H₂₂O₆. Costunolide is a naturally occurring sesquiterpene lactone, first isolated in Saussurea costus roots in 1960. Its CAS number is 553-21-9. Its molar mass is 232.323 g/mol. The plant has also been identified as a source of inulin. Saussure aldehyde, reynosin, santamarine and (+)-germacrene A are among the other compounds reported from the plant. The plant also contains sesquiterpene lactones that act against trypanosomes. Costunolide, dehydrocostus lactone and cynaropicrin are credited with antioxidant, antimicrobial, anti-inflammatory, antidiabetic, anti-ulcer, anti-cancer and hepatoprotective properties. Costunolide is also found in lettuce and chicory.
Sesquiterpene lactones
Sesquiterpene lactones are a class of sesquiterpenoids that contain a lactone ring. They are most often found in plants of the family Asteraceae. They can be allergenic and toxic in grazing livestock. They are colorless, lipophilic solids. The main classes are germacranolides, heliangolides, guaianolides, pseudoguaianolides, hypocretenolides and eudesmanolides.
Cultivation and medicine
The genus Saussurea grows wild at 2000-3500 m in the sub-alpine areas of the north-western Himalayas. In Indian medicine the roots are used against asthma, cough, cholera, chronic skin illnesses and rheumatism. Farmers in the Lahaul valley began growing the plant on a large scale in the early 1900s, but later replaced it with pea and potato because of its long cultivation cycle and lower yield. A field trial there found that 90 kg of nitrogen, 40 kg of phosphorus and 20 kg of potassium per hectare was the most suitable fertilizer combination.
Conservation and trade
The plant has been greatly over-collected. It is assessed as Critically Endangered in the IUCN Red List of Threatened Taxa. It is one of the most threatened medicinal plants of Kashmir Himalaya. It is threatened due to unregulated collection, over-exploitation, illegal trade, and loss of habitat. A workshop held in Lucknow assessed the plant as Critically Endangered nationally in India, with a population decline of 70% in the last 10 years. Uncontrolled grazing of yak is another influence heavily affecting its survival rate. According to CITES trade data, China and India are the main exporters of the product, with Hong Kong a noted re-exporter. The extract has been used in traditional medicine to treat a range of conditions. Habitat loss continues because of road construction and military establishments in many cultivation areas. Recreational activities and urbanization also limit cultivation. A second workshop, for northern India, assessed the plant as Critically Endangered in Jammu and Kashmir. The main customers for the root are large and small pharmaceutical companies, and very large quantities can be bought on demand in Indian markets. The species is in high demand because of bioactive compounds such as costunolide and cynaropicrin. It is overharvested for its aromatic roots. In one field survey only a single wild population was found, near Lahaul-Spiti in Himachal Pradesh, while the species was found in cultivation at various locations.
