Xanthophyll and other Natural Colours Quiz

Answer: Yellow

Xanthophyll is composed of two Greek words: xanthos, meaning yellow, and phyllon, meaning leaf. So xanthophyll gives leaves a pale-yellowish appearance, typically present in plants that grow in less well lit spots.

Chemically, chlorophyll and xanthophyll are quite different, as chlorophyll contains nitrogen and magnesium, which are absent in xanthophyll. There are multiple molecules for both types, with one of the most occurring C55 H72 O5 N4 Mg for chlorophyll and C40 H56 O2 for xanthophyll.

Chlorophyll appears green because it absorbs red and blue light, and reflects green light. Xanthophyll has a yellow appearance as it absorbs only blue light, while reflecting green and red light.

Answer: Beetroot

Beetroot is one of the main sources of betanin, and it has contributed to the name of this molecule. Betanin has the general formula C24 H26 N2 O13. It is used as a food additive especially for frozen foods, as it degrades rapidly under the influence of light, heat or oxygen. But a high sugar content can maintain the betanin for prolonged periods.

The European authorities have made extensive studies into the safety of betanin as a food additive. Their conclusion was that betanin does not augment the risk of development of cancer, and that the low amounts of betanin used as a food additive do not exceed the daily intake via natural products.

Answer: Henna

Juglone and lawsone share the chemical formula C10 H6 O3, but they act as isomers. Juglone creates a brownish dye, while lawsone gives a vivid red colour. Lawsone comes from the henna plant, and has been used since ancient times for (temporary) colouring.

To prepare the dye, one has to dry and grind the henna leaves. Next one sifts the powder and adds liquids such as lemon juice or lavender oil, and lets it rest for about two days. Finally one applies it, and it will give the desired result after several hours.

Willow is a source of acetylsalicylic acid (in drugstores available under the name aspirin), while yew can be used to obtain the highly toxic taxine.

Answer: Fabaceae (bean family)

There are about 750 species in the genus Indigofera, which in turn belongs to the family of the Fabaceae (also known as Leguminoseae). Indigofera plants are usually shrubs with small flowers (mostly pink to red or purple) and grow fruits in a pod, like a bean. They are native to tropical and subtropical regions all over the world.

Most common natural sources of indigo include the Indigofera tinctoria native to Indonesia, the Indigofera arrecta native to India, the Indigofera suffruticosa native to the Caribbean, the not directly related species Strobilanthes cusia native to Japan and Isatis tinctoria (woad) native to southern Europe. These latter two don't belong to the Fabaceae family, but respectively to the Acanthaceae (acanthus family) and the Brassicaceae (cabbage family).

The indigo dye (chemical formula C16 H10 N2 O2) was traditionally obtained by oxidizing the plant, but it was an activity with relatively low output. That's why, since the end of the nineteenth century, almost all indigo is synthesized.

The best known application for the indigo dye is blue jeans.

Answer: Yellow

Curcumin (chemical formula C21 H20 O6) is derived from the turmeric plant (which is called curcuma in French and Italian, and Kurkuma in German and Dutch). The root of the turmeric is typically ground to make a yellowish-orangey powder used as spice in (mostly) Asian cuisine.

Use of curcumin as a fabric dye is quite limited, as it withers under influence of sunlight.

Traditional Asian medicines, such as the Ayurveda or Chinese herbology, use curcumin to treat various symptoms. Recent scientific research does not corroborate the medicinal effects of curcumin, although curcumin tea has resulted significantly to reducing stomach problems such as flatulence.

Answer: Carmine

Carmine red (chemical formula C44 H43 Al Ca2 O30) is the red colouring agent we were looking for. It is obtained by crushing Dactylocopius coccus (cochineal) insects and boiling the powder in ammonia (NH3), finally stabilizing the colour by adding alum (aluminium salt).

Carmine finds its origin in Central America. Spanish navigators imported carmine to Europe, and sold it for exorbitant prices. Later on carmine would also be synthetically prepared.

Carmine is mostly used for cosmetics, although the colour is rather unstable and degrades under the influence of light and humidity. Other uses for carmine are in painting, medicine and food - but the intake of carmine might provoke allergies (especially for those prone to insect allergies).

Answer: Citrus

Rutin has the chemical formula C27 H30 O16, which seems quite simple compared to the official name given by the IUPAC (International Union of Pure and Applied Chemistry): 3?,4?,5,7-Tetrahydroxy-3-[?-L-rhamnopyranosyl-(1?6)-?-D-glucopyranosyloxy]flavone.

Even worse to remember is the systematic IUPAC name: (42S,43R,44S,45S,46R,72R,73R,74R,75R,76S)-13,14,25,27,43,44,45,73,74,75-Decahydroxy-76-methyl-24H-3,6-dioxa-2(2,3)-[1]benzopyrana-4(2,6),7(2)-bis(oxana)-1(1)-benzenaheptaphane-24-one.

Popular alternative names for rutin are (among others) phytomelin, sophorin and birutan. Various studies have examined whether rutin could have medicinal properties. The hypothesis that a safe amount of rutin would reduce the chance of thrombosis and related diseases, has not been definitely proven.

Citrus fruits contain high doses of rutin in the peel, but also relatively high doses in the leaves. The fact that rutin is mostly yellow may have guided you to pick the correct answer as the best known citrus fruit is the lemon.

Fragaria is the genus of the strawberry, quercus is the genus of the oak and prunus is the genus of stone fruits such as the cherry or the plum.

Answer: Red

Alizarin has the chemical formula C14 H8 O4. The natural source is the madder plant Rubia tinctorum (common madder), Rubia peregrina (wild madder) or Rubia cordifolia (Indian madder). The madder plant belongs to a genus in the family Rubiaceae, which also contains the coffee plant (Coffea genus) and the quinine tree (Cinchona).

Alizarin was the first of the natural colourings to be synthesized, so that the economic importance of the madder plant has diminished. Besides its use as a fabric dye, alizarin has also been used as a biomarker for developing bone structures and as a dye for Easter eggs in countries such as Armenia and Georgia.

Answer: Snail

Murexide has the chemical formula N H4 C8 H4 N5 O6. In Greco-Roman times, Phoenicians created murexide with tons of predatory sea snails and related rock snails. The preferred species were the different species belonging to the Muricidae family as well as some others, Bolinus brandaris, Hexaplex trunculus and Stamonita haemastoma, to name a few.

As the industry creating dye from these snails was originally based in the (now Lebanese) city of Tyre, the dye was soon called Tyrian purple. It was so expensive only the wealthiest Romans could afford some - a full toga in Tyrian purple would cost about as much as a large villa.

Since about 1850 synthetic murexide has been available, and much more affordable. Murexide was used not only to dye fabric, but also as an indicator for certain metals in analytical chemistry. This last use has, however, faded because of the cheaper calcium-ion selective electrodes.

Answer: Black

Haematoxylin (chemical formula: C16 H14 O6), the extract of heartwood, has in itself, no colouring, but it oxidises readily with salts, for instance iron or aluminium salts, thus resulting in black colourants.

A typical use for haematoxylin dye is as a histologic stain, combined with the (red) colourant eosin. This combination of two different stains (among others) is used in the Pap test to detect cervical cancer.

Haematoxylin was also used to create writing ink or to dye fabric (mostly cotton), but since the start of the twentieth century cheaper alternatives for black dye have been invented.