From the courtesy of Limmi
The yellow colour of lemons depend on bioflavonoids, which belong to the group of flavonoids.
Well, actually, it’s not so easy to explain, but etymology can help us.
Let’s ensue step by step.
Flavonoids and bioflavonoids are compounds that contain the Flavone.
The Flavone, from latin Flavo (flāvu, see Indo-European roots bhel-) an adjective which means “ golden yellow, blonde”, is a natural organic pigment which give colour to plants, flowers and fruits.
Colourful vegetal world
The typical brilliant yellow-orange colour of many citrus fruits, fruits and vegetables chiefly derives from the anthocyan (pigment from the group of flovonoids, which changes colour as the pH goes up or down) and from the carotenoids, pigments named for the carotene, the well-known yellow-orange pigment, that was first identified in carrot’s root in 1831(Daucus carota).
The most common yellow-orange vegetable are: apricot, orange, carrot, clementine, kaki, lemon, mandarin, melon, medlar, nectarinia, pepper, peach, grapefruit, pumpkin.
Thus, if flavonoids determine the yellow of lemons, the anthocyans provide the colour of blackberries, blueberries, grapes, oranges, raspberries, strawberries, cherries and of the red cabbage.
On the other hand, carotenoids, other very common pigments, are responsible for many of the red, orange, and yellow hues of vegetables: the red of tomato, the orange of carrot and maize, the yellow of saffron, calendulas and of the autumnal leaves.
Carotenoids are also into the unripe fruits, the leaves and the stems, even though they are hidden by chlorophyll.
Carotenoids are antioxidants, they prevent cells aging, contrast cancer and cardiovascular pathologies and have protective effects against degenerative eye disease.
But nature is full of yellowish. Do you know what quercitron is?
From the Italian quercitone or Quercus tinctoria, the name is a shortened form of quercicitron, from Latin quercus, oak, and citron, lemon.
Quercitron is a glycoside obtained from the bark of the Horse-chestnut and of the Quercus tinctoria.
It’s a crystalline powder of a brilliant citron yellow colour, soluble in alcohol, that supports blood vessel and capillary integrity.
In the past it was used to dye cloths.
After all, it’s not a sheer chance that nature is so colourful: in fact, keep in mind that all this vegetal colours assist our health!