Alkanna is a genus of about 66 species of herbaceous flowering plants belonging to the borage family Boraginaceae, placed in the order Boraginales. The genus is distributed across southern and east-central Europe, western Asia, and North Africa, with the greatest diversity centred in the eastern Mediterranean and Anatolian region.
Plants in the genus are typically bristly or hairy perennials with simple, alternate leaves. They bear small, tubular flowers, most commonly in shades of blue or yellow, characteristic of many Boraginaceae genera. The inflorescences are scorpioid cymes, a structural hallmark of the family.
The most economically significant member is Alkanna tinctoria, known as dyer's alkanet or alkanet. Its roots contain alkannin, a red naphthoquinone pigment that is insoluble in water but readily extracted by oils, waxes, and organic solvents. This dye has been used since antiquity across the Mediterranean to colour foods, cosmetics, and wood. Alkannin (also called anchusin) was historically used as a lipstick colourant and is still used in some regions; in Australia it is approved as a food colouring, while EU approval (formerly E103) has been withdrawn.
Other species in the genus, such as Alkanna strigosa, Alkanna orientalis, and Alkanna cordifolia, are known from arid and semi-arid habitats around the eastern Mediterranean and Middle East. The genus was described in the context of Mediterranean flora and remains predominantly a genus of the Old World dry zones.
Etymology
The genus name Alkanna derives from the Arabic al-ḥinnā (الحنة), meaning henna, referring to the dye-yielding properties of the roots, most prominently in Alkanna tinctoria. The common English name "alkanet" shares the same Arabic root and was historically applied specifically to A. tinctoria before being extended informally to related plants.
Distribution
The approximately 66 species of Alkanna are native to southern and east-central Europe, western Asia, and North Africa, with highest diversity in the eastern Mediterranean basin and Anatolia. Alkanna tinctoria ranges across the broader Mediterranean region, while other species such as Alkanna strigosa and Alkanna cordifolia are found in the Levant and surrounding arid zones.
Cultural Uses
Alkanna tinctoria has been exploited for its root dye since antiquity. The active compound, alkannin, imparts a red or crimson colour in oily or acidic environments and a blue colour in alkaline conditions. It has been used to colour cheeses, low-quality wines, and cosmetics such as lipstick. Mixed with oil and applied to wood, it produces a dark red-brown stain resembling rosewood. Alkannin is approved as a food colouring in Australia; in the European Union it was formerly listed as E103 but approval has been withdrawn.
