Crocus nudiflorus

Iris Family [Iridaceae]  

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5th October 2005, River Mersey, Didsbury, Manchester. Photo: © RWD

5th October 2005, River Mersey, Didsbury, Manchester. Photo: © RWD

5th October 2005, River Mersey, Didsbury, Manchester. Photo: © RWD

5th October 2005, River Mersey, Didsbury, Manchester. Photo: © RWD

5th October 2005, River Mersey, Didsbury, Manchester. Photo: © RWD

Easily confused with : Early Crocus except that one flowers in early spring and the other in late autumn!

Some similarities to : Veined Autumn Crocus (Crocus Speciosus) whose petals have darker purple veins.

No relation to : Meadow Saffron (colchinum autumnale) which is sometimes, confusingly, also known as Autumn Crocus, but Meadow Saffron belongs to the Lily Family, whereas the real Autumn Crocus (crocus nudiflorus) detailed on this page belongs to the Iris Family.

When flowering (in autumn) there are no leaves for they appear in spring and wither in the summer before the flowers appear. There are no native Crocuses in the UK, Autumn Crocus was naturalised in mediaeval times by Monks and occurs especially in Lancashire, Huddersfield and Halifax. It grows in grassy places. The Monks may have been using the stigmas for saffron because Saffron Crocus will not grow reliably in the UK, for the climate is too cold. Saffron is a deep yellow spice (being the stigmas [of which there are three per flower] from Saffron Crocus).


  Saffron was once used as a dye but its high price nowadays precludes that use. It finds favour as a spice in food colouring and flavouring.

The stigma of the Saffron Crocus are used to produce perhaps the most expensive spice, Saffron. The intense yellow coloration of saffron is due to various Carotenoids, amongst which is Zeathanthin an analogue of β-Carotene and which has two additional hydrozyl radicals at the number three positions, which β-carotene lacks. β-Zeaxanthin, (aka β-carotene-3,3'-diol) is one of only two carotenoids found within the retina of the human eye (the other is Lutein (β-ε-carotene-3,3'-diol). These and other carotenoids in saffron are also responsible for its anti-oxidant and anti-cancer properties. Zeaxanthin is found in corn maize (Zea Mays, in which it produces a yellow coloration. Zeaxanthin is a permitted yellow food colouring (E-161h). It can be seen that Zeaxanthin is a dimer, being made of two identical halves.

  Lutein is another Xanthophyll, one of over 600 naturally occurring carotenoids. It too is a yellow pigment, found not only in Autumn Crocus, but also in the yolks of eggs, and in the retina, but whereas Zeaxanthin above mostly resides in the macula, lutein occupies the remaining parts of the retina. It is also present in the leaves of green vegetables such as spinach and kale. Notice the only difference between zeaxanthin and lutein is the position of one of the double bonds on the two six-membered rings; it is not symmetric, and therefore not a dimer.


Picrocrocin is a monoterpene glycoside which has a bitter taste responsible for most of the taste of saffron (but not the aroma). Picrocrocin is the pre-cursor to Safranal which is primarily responsible for most of the aroma of saffron.

When the saffron is dried it liberates the enzyme β-glucosidase (not shown), which acts upon picrocrocin, releasing the sugar molecule and leaving the aglycone HTCC (4-hydroxy 2,6,6-trimethyl 1-cyclohexene 1-carboxaldehyde), and which is subsequently transformed into Safranal during the drying process. Note that zeaxanthin consists of two units of HTCC (less the oxygen atoms), joined by two conjugated hydrocarbon chain with side-branches.

HTCC, in losing a molecule of water, H2O, becomes the required product Safranal, an aldehyde. Safranal is responsible for much of the aroma of saffron. It is thought to be derived from the decomposition of the carotenoid Zeaxanthine via the intermediate product Picrocrocin. Safranal is also to be found within the seeds of Cumin (Cuminum cyminum), the leaves of Fig (Ficus carica), Common Stork's-bill (Erodium cicutarium), Elderberry (Sambucus nigra) and Lemons (Citrus limon) amongst several others found in foreign lands.

The production of Safranal is one of the aims of drying the stigmas, which must be carried out with due regard to temperature and humidity, both of which can adversely affect the quality of the end product: saffron.


  Crocin is another carotenoid occurring in Crocus flowers, as well as those of Gardenia. Crocetin (below) is a carotenoid with two carboxylic acid terminations. It too is dimeric, being made of two identical units. Crocin is the diester formed by the acid crocetin with the disaccharide Gentiobiose. As crystals, Crocin is a deep red colour but when dissolved in water becomes an orange solution. It is one of the dyes primarily responsible for the colour of saffron. Crocin too is dimeric as is Crocetin below.

  Crocetin, another red compound, is also an important constituent of saffron and shows significant potential use as an anti-tumour agent. It occurs in both petals and stigmas. Crocetin is an ApoCarotenoid DiCarboxylic Acid which is not only found in Crocus flowers but also in Gardenia jasminoides. Crocetin is an agent which can be used for both cancer therapy and prevention.


Colchicine alkaloids are extremely poisonous, and possess two fused 7-membered rings. They occur in the corm, flowers and seeds at 0.3% to 1.2% by dried weight.

Colchicine tastes bitter and has been used to treat acute gouty arthritis, but there are concerns about its toxicity. It is also used pharmaceutically as an anti-tumour agent and to treat Behcet's disease. But there is a fine line between a therapeutic dose and a toxic dose and must be used with caution. Indeed, it is not suitable for use by those suffering from liver or kidney problems, problems with heart or digestive system, if you are pregnant, or have a severe blood disorder such as low counts of white or red blood cells, low platelet count or problems with bone marrow function. Any of those alone is enough to put your Author off from using Colchicine for anything!

Colchicine is anti-mitotic, binding with tubulin and disrupting cell division; this property being linked to its ability to treat gout. In the axons of neurons it disrupts axoplasmic transport. By stimulating the synthesis of prostaglandins disturbances of the gastrointestinal tract will occur. It is also a capillary poison. Its off-label use for home remedies is to be highly discouraged; it is too toxic, especially to those pregnant or with kidney, liver or heart problems. The lethal dose is just 20mg, and not more than 8mg should ever be used to treat an acute attack of gout.

The symptoms of colchicine poisoning arrive following a latency period of 2 to 6 hours, after which a burning and prickling sensation in the mouth and throat may occur, together with a thirst and difficulties in swallowing, nausea, frequent and violent vomiting and wanting to pee. Cell division is blocked after 10 hours, and gastrointestinal problems such as bloody diarrhoea and stomach pain start after 15 hours or so. CNS problems then commence, such as breathlessness, cyanosis, hallucinations, spasms, hypothermia, rapid weak pulse, hypotension, heart arrhythmia, kidney failure and epileptic seizures. Paralysis and death after 2 days due to either cardiac arrest or respiratory failure. If the patient survives, hair loss will occur, sometimes permanently, and aplastic anaemia.

For humans, the toxic dose is 10mg; 40mg is always lethal.

Demecolcine is also used pharmaceutically as an anti-tumour agent used in chemotherapy. Like the drug Paracetamol, the difference between a useful dose and a lethal or dangerous dose of colchicine is quite close! Probably too close for comfort! As the reader can see, it is closely related to Colchicine but with the acetyl moiety (top right) replaced by a methyl group, which makes it less toxic than Colchicine.

Recently Professor Laurence Patterson has devised a method of using the toxicity of Colchicine to kill cancer cells (by using it as a VDA [vascular disruptive agent] which prevents the growth of the supporting blood vessels of the cancer cells) but without the whole-body toxicity that using neat colchicine would bring. By binding the colchicine molecule to another huge molecule, he has made the combined molecule, provisionally called ICT2588, non-toxic until activated by a specific trigger within the tumour membranes. It is thus entirely innocuous by itself, but when it finds a tumour, its latent toxicity is unleashed by the cancer cells themselves; a clever trick which he calls a 'smart bomb'. The colchicine molecule is detached from its encumbent extra molecule and sets about its business of being locally toxic to the cancer cells, since there is insufficient for it to be toxic to the rest of the body.

The Colchicine entity is shown in red. Note the sulfur atom, in yellow, and the spiro-1,3-dihydroxyxanthene molecule in green. There are a few polymerized amino acids (with nitrogen molecules in the main chain - which are then peptides) scattered along its length. The function of these units is not known to your Author save to enable the molecule to be recognised and altered by biochemical mechanisms within the cancer cells themselves. The cancer cells are thus the agents of their own destruction. The molecule is an engineered trap designed to mimic some other biochemical that the cancer cells are expecting to see, as far as the Author understands. When it finds it, it processes it, and in so doing un-leashes the colchicine moiety to go about its toxic business at the exact site where the cancer cells are located. Toxic effects will thus be localised and not global throughout the body as is the case with some other anti-cancer drugs.

Over 90% of the Worlds total production of saffron (190 tons) is produced in Iran. Crocuses exhibit Thermonasty, a means shared only by Tulips, of opening and closing the flower as the temperature changes.

  Crocus nudiflorus  ⇐ Global Aspect ⇒ Iridaceae  

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Crocus nudiflorus

Iris Family [Iridaceae]  

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