Alkanna, commonly known as alkanet, is a genus of the family Boraginaceae that includes 50 species of biennial and perennial herbaceous plants. These plants can be found in the wild and in cultivation around the Mediterranean and throughout much of Europe. The plants have many uses, from medicinal purposes to traditional and modern cosmetics. While the majority of species within this genus are quite common, several are critically endangered in some countries.
Considered weak and hairy herbs, Alkanna plants measure about 1 foot (0.3 m) in height once they reach full maturity. The leaves are bicuspid, oblong, and alternate. Usually in pairs, the flowers of these plants are small and disposed in terminal racemes that unroll when the flower expands. The color of the trumpet-shaped blooms range from blue to purple, arranged on the one-sided, scorpioid stalks. Contracted at the base, the fruits are made of four distinct nutlets.
The roots of Alkanna plants are the only parts that have significant uses. Externally, these roots appear dark purple, spongy, and pliable. The bark has dried, fissured, and cylindrical rhizomes that are brittle and exfoliating. Near the crown area, stem pieces and the remains of bristly leaves can be found.
Alkanna plants are astringents and used in cosmetics because of the red pigment produced by their roots. Cultivated species are not as rich in red pigment as the wild varieties. They are used for coloring purposes by manufacturers of ointments, hair oils, and pomades. The red coloring also serves as dye for cloth. Other uses include treatment for minor burns, though severe burns are reportedly unresponsive.
All organs of Alkanna plants contain pyrrolizidine alkaloid, but this alkaloid is more concentrated in the roots. Due to this harmful compound, pregnant and lactating women should not use Alkanna roots to avoid unfavorable effects. The other known adverse reactions to humans include liver failure, pulmonary hypertension, and heart failure. This alkaloid, though posing harmful effects to humans, serves as the plant’s defense against herbivores like insects.
To obtain the red pigment from the roots of Alkanna plants, exhausting with water is required so that the gum and foreign coloring matters are removed. The exhausted roots are then dried, minced, and percolated with alcohol. Hydrochloric acid is mixed with the alcoholic tincture, which is later distilled and evaporated to attain the consistency of a soft extract. The lower liquid is separated from the mixture by adding ether and water.