Some similarities to both : Russian Lettuce and : Common Blue-Sowthistle, the flowers are much the same colour and form.
Slight resemblance to : Agrimony, in that the flowers are held close to a tall single stem, although of a totally different shape and colour.
Confusion: There is also a vegetable called Chicory, or Endive, (Cichorium Endivia, whose leaves are in a compact club-shape much like an elongated lettuce. The leaves are eaten as a salad. This vegetable is from the same genus as the above (Common) Chicory, Cichorium Intybus, but of differing species.
Uniquely identifying characteristics: Chicory has pale blue flowers in ones, or threes, on the upper part of the tall, but zig-zag stem. The flowers are very close to the stem, pointing away from the stem and are dandelion-like, but have only ray florets, no disc florets in the centre. The colour of the flowers is at its best in the morning, and fades in the afternoon.
Chicory has many uses: the roots of Chicory are used, roasted and ground, as a caffeine-free coffee substitute sold as Chicory Coffee; the flowers are used to garnish salads; the buds are pickled and the leaves applied as a poultice for inflammation of the skin.
The flowers open in the morning and are heliotropic, following the sun, but close at midday when the sun is over-bright.
The leaves yield a blue dye, the flowers, paradoxically, a yellow dye.
Chicory contains within the milky fluid exuded by broken stems the allergenic Guanolide Sesquiterpene Lactones, Lactucin, Lactucopicrin and DeOxyLacucin, which all taste bitter. Lactucin acts as a sedative and analgesic. These Guanolides (the 'olide' referring to the lactone moiety) are also present in
Lettuce and are responsible for the bitter taste of that also.
The DeOxy form of Lactucin, called
DeOxyLactucin, is also present.
It also contain the toxic Sesquiterpene Lactone Lactucopicrin otherwise known as Intybin. Both of these compounds can result in growers, handlers, pickers or grocers developing an allergic skin reaction to the vegetable Endives, better known as contact allergenic dermatitis (ACD). The same toxic principles are responsible for ACD in handlers of
Artichokes (Cynara Scolymus),
Lettuce (Lactuca Sativa) and of course Chicory. Lactucopicrin is the second bitterest substance within Chicory with a detection threshold of 0.5ppm (w/w) and has both a sedative and analgesic effect, acting upon the CNS. The bitterest substance within Chicory is the derivative 11,13-DiHydroLactucopicrin (not shown) at 0.2ppm (w/w). [Note: On the internet there appear to be two differing representations of Lactucopicrin with about equal prevalence; one with the Picric Acid moiety (shown in red) attached as shown here on the 5-carbon ring, and one with it attached instead replacing the -OH group on the 7-membered ring. Your Author does not know which portrayal (if any) is correct, but the one shown here is the form as shown by Wikipaedia (as of 10th Nov 2014)].
Sesquiterpene lactones like these serve as defensive mechanisms against infection by bacteria and fungi within Chicory. Chicoralexin is a related Guanolide present in smaller amounts that the three main ones above and behaves as a phytoalexin within Chicory, being present in Chicory only when it has been invaded by the bacterium Pseudomonas cichorii. Chicoralexin also completely inhibits the germination of the fungus Bipolaris leersiae. Phytoalexins are anti-microbial and often anti-oxidant substances that are rapidly generated at the site of infection in response to the plant being under attack from invading organisms.
Eudesmanolides are also sesquiterpene lactones and are also present in Chicory. One such is Cichoriolide A, but
Sonchoside C is also present, where the -OH group is replaced by the glucoside as depicted by -OGlc and the =CH2 is replaced by -CH3. Sonchoside C is also present in the milky latex of Sonchus species (Sow-thistles), such as Smooth Sow-Thistle. These are only minor constituents of Chicory.
Germacranolides are also sesquiterpene lactones, this time based upon
Germacrene. Shown is Cichorioside C, but
Sonchuside A where the -OH group is replaced by -H is also present in Chicory. Sonchuside A is also present in the milky latex of Sonchus species. These are only minor constituents of Chicory.
Chicory contains the glycosidic coumarin variously called
Cichoriin or, more rarely,
Chicoriin, which is a 6-hydroxy-7-glucoside of coumarin chemically not dis-similar to
Chicory also contains the Coumarin Aesculetin which helps to prevent liver damage caused by an over-dose of Paracetamol. Aesculetin is thus anti-hapatotoxic, which may explain the folklore use of Chicory for liver damage. An alternative name for Aesculetin is Cichorigenin, named after the scientific name for Chicory.
Chicoric Acid (aka Cichoric Acid) (or di-caffeoyl-tartaric acid, a phenyl-propanoid) was first discovered in Chicory, hence the name, but its concentration is higher in
Purple Coneflower (Echinacea purpurea), a garden plant. It also occurs in the leaves of Dandelion,
Basil, Lemon Balm and in
Sea Grasses. It is dimeric and symmetrical, consisting of two units of Caffeic Acid joined by a single
Tartaric Acid (which is itself a dimer of Acetic Acid). Chicoric Acid energises the immune system making it attack pathogens more efficiently. It stimulates T-cell production, and increases the production of interferon and immunoglobin thereby helping wounds to heal. It also inhibits the penetration of virii into cells. It also stimulates phagocytosis; the engulfing of foreign particles by the membrane of cells, thus isolating a potential problem.
Shown above are Caffeic Acid and
Tartaric Acid (the di-hydroxy derivative of
Succinic Acid) to show their relation to Chicoric Acid. Tartaric Acid occurs in many edible fruits but particularly in
Tamarind. They are not necessarily present in Chicory.