HOGWEED AND UV RADIATION
There are some groups of compounds that are vital to life but cannot be produced (synthesized) by the human body. They are, however, produced in abundance by plants, and our bodies get these compounds from the food we eat. This group includes certain vitamins and other important protective compounds. Vitamin C and various antioxidants are known as essential elements of a healthy diet. The production of some of the compounds beneficial to people is facilitated by the exposure of plants to ultraviolet (UV) rays. These compounds are secondary metabolites in plants, phenols that have the ability to absorb UV rays. Plants use phenols as protection against excessive amounts of UV rays (that reach the Earth’s surface through solar radiation). In plants, the compounds also carry out numerous other useful functions (which we will probably write more about on our Website during the International Year of Light).
So, plants that grow in environments with intense solar radiation are particularly beneficial to people because of the many secondary, UV-radiation induced, metabolites that they possess. It is important to know that rich sources of phenolic compounds are, for examples, various types of medicinal plants, as well as fruits and vegetables, certain types of grain, tea plants, coffee plants, different varieties of beans, many varieties of red grapes (and fine red wine) and many other types of plants.
The hogweed (Heracleum sphondylium, Apiaceae) is an example of a herbaceous plant that reacts to UV radiation by increasing its production of phenolic compounds. The hogweed is both a wild edible plant and a medicinal plant. But alongside our mini „photo-story“, we also need to give a warning about touching and using the hogweed (because of the possibility of phototoxic dermatitis!), and about the side-effects that may occur in such cases due to exposure to the sun’s rays in people with photosensitivity. It should be noted, however, that the chemical compounds furanocoumarins are responsible for photosensitivity reactions to hogweed, rather than anthocyanins (visible as the purple colouring on the leaf stems in the below photo). This could be an interesting topic for our column „Interesting Features of Plant Life“.
Category: interesting features of plant life, phytochemistry, phytobiology, International Year of Light
Key words: hogweed (Heracleum sphondylium), UV radiation, phenolic compounds, photosensitivity reaction, furanocoumarins
Posted in September 2015