Ajuga reptans (Bugle)

2016

Ajuga reptans () is a member of the Lamiaceae (Labiatae), subfamily Lamioideae (). It is a small perennial plant, 10 to 40 cm high and common in Europe, West Asia, North America, Algeria, and Tunisia (synonym: Bugula reptans; French name: bugle; German name: Giinsel). It is cultivated as an ornamental plant and several varieties have been described: var. viridissima (dark-colored leaves), var. atropurperea (deep blue-purple-colored leaves), var. variegata (leaf borders are white and aquamarine), var. alpina G.B., var. stolonifera, var. alba G.B. (white flowering). Most plants have blue flowers; plants with white, rose or lilac-colored flowers are seldom. Ajuga reptans grows on all kind of soils, especially under trees and in grasslands. It produces stolons, from which the floral shoots stand up. Normal leaves have a peduncle; leaves from flower shoots have no peduncle.

Hybrids between Ajuga reptans and Ajuga genevensis and between A. reptans and A. pyramidalis are also known.

Ajuga reptans has been used in treating lung diseases, for gargling, as an astringent, and has bile-stimulating activity. Together with mint leaves, it has been used as an anti-dispepticum (). In some regions, the young plants and sprouts are eaten in salads. Mixed with ferrous sulfate, the plants were also used for coloring cotton. A. reptans has no special odor and essential oils are present only in small amounts.

Other Ajuga species have been used for wound healing, against arthritis and strokes, and for their antipyretic and diuretic characteristics. They are also used in tonics and aperitifs. Other applications are mentioned in Bonnier and Douin ().

Visually selected callus cultures of Ajuga reptans produced a mixture of anthocyanins, mainly based on cyanin with a minor fraction based on delphinidin. Light increased the anthocyanin accumulation in callus cells (2.5-3% on dry weight), but the pigments were produced also in the dark (1%). Suspension cultures produced anthocyanins in a shake flask or in a classically agitated fermentor, yielding 1-2% pigments or 18 mg cyanin equivalents per liter per day.

2,4-D and kinetin stimulated growth and color production; high sucrose concentrations decreased biomass production and hence total anthocyanin production.

Although there was some variation in growth and anthocyanin accumulation within one cell line, the cultures were stable. The majority of the anthocyanins were acylated with aromatic and/or aliphatic carboxylic acids. Acylation makes anthocyanins more stable, which is advantageous for their use as food colorings. In preliminary experiments, bugle extracts indeed proved to be more stable towards light and pasteurization than an industrially used grape extract. Combined with the good cell growth and anthocyanin production in fermentors, this technology offers good prospects for producing natural food colorings.

Biochemical research revealed that PAL activities in anthocyanin-producing callus cultures were higher than in cultures which did not produce these pigments. Uncolored calli accumulated more of an unknown UV-absorbing product, which was also present in anthocyanin-producing suspension cultures, composed of a mixture of colored and uncolored cells (data not shown). From identification of this product, more could be learned about the anthocyanin biosynthesis enzymes in bugle cells, which might result in methods for increasing anthocyanin yields.

The anthocyanin pattern of the cell cultures reflected more the pattern observed in blue colored leaves of flower shoots than the anthocyanin flower pattern.

 

Selections from the book: “Medicinal and Aromatic Plants V”, 1993.