Alkanna tinctoria (L.) Tausch - syn.Alkanna matthioli Tausch; Alkanna tuberculata (Forssk.) Meikle; Lithospermum lehmanii Tineo - Boraginaceae
alkanet, dyer's alkanet, dyer's bugloss, Schminkwurz, Alkanna, Färberkraut

Perennial herb, up to 30cm high, native to South Europe, West Asia and North Africa, also cultivated there; stem and leaves hairy; leaves simple, alternate, lanceolate; flowers bright blue.

„The root produces a fine red colouring material which has been used as a dye in the Mediterranean region since antiquity. The root as a dyestuff is soluble in alcohol, ether, and the oils, but is insoluble in water… In alkali environments the alkanet dye has a blue color, with the color changing again to crimson on addition of an acid.“ http://en.wikipedia.org/wiki/Alkanna_tinctoria

The dried root (Radix Alkannae, Radix Anchusae tinctoriae) contains a mixture of red pigments (5%) known as „alkanna red“, consisting mainly of esters of alkannin with β-acetoxy-isovaleric acid, β,β-dimethylacrylic acid, isovaleric acid, and angelic acid.
[Hagers Handbuch der pharmazeutischen Praxis, Springer-Verlag, Berlin, 2010]

„From the roots of Alkanna tinctoria Tausch, the alkannin esters of the following acids were isolated and identified: β,β-dimethylacrylic acid, β-acetoxy-isovaleric acid, isovaleric acid, and angelic acid. These esteric pigments showed excellent wound healing properties in a clinical study on 72 patients with ulcus cruris.“
[Wound healing properties of naphthaquinone pigments from Alkanna tinctoria., Papageorgiou, V. P., Experientia, 34(11), 1978, 1499-1501]

„From time immemorial the root of this herb is applied internally äs antidiarrheal agent and externally in cases of skin diseases. Due to its intensively purple-colored dyestuffs, called alkannins, the bark of the root is also used for staining cosmetics and foods. Three open-chain alkaloids, 7-angeloylretronecine, triangularine and dihydroxytriangularine, were isolated from the bark of the root in a total concentration of 0.25 to 0.3%. The drug should however no longer be administered internally. Prior to staining of foods, e.g. of lemonades, alkaloids should previously be eliminated.“
[Medicinal plants in Europe containing pyrrolizidine alkaloids., Roeder, E., Pharmazie, Vol.50(2), 1995, 83-98]