Sawi langit or also known as sirangak in West Sumatra Indonesia is scientifically called Cyanthillium cinereum in Latin. Previously, this species was classified under the scientific name Vernonia cinerea. Internationally this plant is popular with the name little ironweed or vernonia.
In China, little ironweed is known as ye xiang niu. Machadita, rabo de buey or yerba morada in Spanish-speaking countries and ayapana sauvage in France. In India, this plant is known as ankari, ankta or sandri, mura-saki-mukashi-yomogi in Japan, agas-moro or bulak-manok in the Philippines and rumput taki babi in Malaysia.
Little ironweed is believed to originate from the tropical region of Asia which includes Indonesia, India, Sri Lanka, Bangladesh, Bhutan, Thailand, Vietnam, Malaysia, Myanmar, Japan and China as well as the tropical region of Africa which includes Yemen, Uganda, Tanzania, Senegal, Mali, Somalia and South Africa and Australia. This plant later became naturalized in the tropical regions of America and the Pacific islands.
The species was introduced into various countries accidentally as a contaminant or as a weed in seedling material (Rojas‐Sandoval & Acevedo‐Rodríguez, 2022).
Little ironweed is an annual herbaceous plant that can grow to a height of 80 to 150 cm. The stem only has branches or sometimes even no branches. The leaves are oval or elliptical with a sharp or blunt apex with a leaf stalk up to 1.5 cm long.
The flowers are composed of flower heads with flat tops. Each of the flowers has a pink or purplish disc floret. However, this plant does not have flower buds.
This species is similar and can be confused with the species Emilia sonchifolia. The difference lies in the flower leaves of the Emilia sonchifolia species which are much longer and vase-shaped.
Little Ironweed as Weed
This species is easily spread by wind and has the potential to grow as a weed in agricultural fields and pastures. Now, little ironweed has been declared a weed in 27 crops in 47 countries in Asia, East and West Africa, and the Caribbean (Rojas‐Sandoval & Acevedo‐Rodríguez, 2022). In Indonesia, little ironweed as a weed has attacked many rice farms, cocoa, rubber, and tea plantations.
Benefits of Little Ironweed for Health
The local people of the Minangkabau tribe in West Sumatra use little ironweed or better known as singarak in the area in traditional medicine to heal wounds. Clinical trials on its use have also been carried out through an observation process with research results showing that sirangak oil is able to accelerate wound healing significantly by 85.6% compared to controls with wound healing of 71.6%. Hematological analysis conducted by Muhammad Rahmanda Fadillah & Santoso (2019) also showed that sirangak oil can significantly increase the number of erythrocytes, hemoglobin concentration, hematocrit, mean cell volume (MCV) and mean blood cell hemoglobin concentration (MCHC), especially in the early days of treatment.
Not only in Indonesia, this plant has also been widely used traditionally and is recorded in Ayurvedic records. The leaves of the species Cyanthillium cinereum or little ironweed are said to have analgesic, antipyretic, and anti-inflammatory effects. A paste from the stem or bark is used to heal wounds, while the flowers are traditionally used to treat conjunctivitis, arthritis and rheumatism. An infusion of the roots is used as an antidote for scorpion stings and snake venom (Guha et al., 2011).
In the Philippines, this species is used as an infusion to treat coughs and skin diseases. A poultice made from the leaves is believed to reduce headaches, while a decoction of the roots can relieve stomach aches and diarrhea. In Thailand, the leaves are used in the treatment of asthma and bronchitis. Meanwhile, the young shoots are eaten as a cooked vegetable in Java (Rojas‐Sandoval & Acevedo‐Rodríguez, 2022).
Although generally used traditionally to help treat illnesses and wounds, little ironweed is also used as an aid to stop smoking in Thailand. Until now, its use has become quite popular, resulting in acts of product counterfeiting using the Emilia sonchifolia (L.) DC species. which are often found in herbal markets (Kannika Thongkhao et al., 2020).