The flowers are superficially similar to those of Woody Nightshade and some other nightshades including potato and tomato in that they have 5 petals and a central column of stamens sticking rudely out.
Uniquely identifiable characteristics : No other plant looks like this.
The hairs on Borage can cause skin irritation on contact in certain individuals. White flowered plants are also fairly commonly found, but the blue variation is genetically dominant over that of the white. Because all the flowers of any one plant flower almost simultaneously, it is suspected that the flowers have a high degree of probability of pollinating those on the same plant, a property called Geitnogamy.
Thesinine, a pyrrolizidine, is one of the few non-toxic pyrrolizidine alkaloids produced by plants, and is responsible for the deep blue colour of the flowers of Borage. It tastes sweet, honey-like and is one of the few blue but edible compounds. The flowers or petals are edible and often used as a garnish on salads and soups and in Poland used to flavour pickled gherkins.
Borage also produces small amounts of the poisonous pyrrolizidine alkaloids Intermedine and its enantiomorph Lycopsamine, and their 7-acetyl derivatives. Lycopsamine is also present in
Comfrey and Lungwort. Pyrrolizidine alkaloids are metabolically activated within the liver and there will alkylate both proteins and DNA molecules; they are therefore hepatotoxic causing liver damage, as well as mutagenic and carcinogenic. Substantial ingestion results in inhibition of neurons and paralysis.
Amabiline and Supinine are other pyrrolizidine alkaloids (PA) manufactured within Borage. Both are structurally similar to Indicine, another natural PA found in the plant world. Amabiline is hepatotoxic as are many PAs. Supinine has a low concentration in Borage.
Caterpillar moths of species Hyalurga syma sequester all these poisonous pyrrolizidine alkaloids from the borage that they consume when in this larval stage, and escape un-harmed if caught by orb-weaving spiders Nephila clavipeswho would normally eat them. This averse reaction by the spiders is though to be due to the PAs within the moths which are poisonous to the spiders.
The oil from the seeds seems to be free from PA's, but the seeds themselves and the leaves contain only only extremely low levels (10ppm by dry weight), and most of that is due to the non-poisonous deep-blue Thesinine which out-weighs the other PAs by 10:1.
Borage seed oil can be extracted from the seeds, which contains a high proportion of
γ-Linolenic Acid (GLA), a vegetable oil commonly known as an omega-6 fatty acid because the first double-bonded carbon atom is the sixth from the methyl group at the end (leftmost in the diagram). Luckily, there is very little of the pyrrollydizine alkaloids in Borage seed oil.
Alpha-Linolenic Acid (ALA,
α-Linolenic Acid) [not shown], on the other hand, has the same number of carbon atoms and the same number of un-saturated carbon atoms, but the double bonds are in different positions, starting from the third carbon atom from the methyl end, and is thus known as an omega-3 fatty acid. The plant
Linseed naturally produces alpha-linolenic acid].
Linolenic Acids should not be confused with Linoleic Acid, which has the same number of carbon atoms (18) but only two double bonds. γ-linolenic Acid, found in the seeds of Borage as well as in the seeds of a few other plants (
Hemp), is not poisonous but rather a healthy dietary supplement; an omega-6 fatty acid. Linolenic Acid was first discovered in the seeds of
Evening Primrose and sold as Evening Primrose Oil. Borage oil is safe to take internally for it has virtually none of the toxic pyrrolizidine alkaloids found in the leaves and other parts of the plant.