Flavonoids are chemically 2-phenyl-gamma-benzopyrones (2-phenyl-chromones) or tructurally related, mostly phenolic compounds. They either are associated with sugars (glycosides) or without sugars (aglycones).
Flavonoids can be subdivided into: flavones, flavonols, and flavanonols.
FLAVONES include: apigenin and luteolin.
FLAVONOLS include:
- aglycones
quercetin, kaempferol, myricetin, and isorhamnetin
- glycosides
hyperoside, isoquercitrin, quercitrin, rutin, astragalin, and narcissin.
FLAVANONOLS include:
- aglycones
naringenin, eriodictyol, homoeridictyol, hesperetin, taxifolin;
- glycosides
naringin, eriocitrin, hesperidin.
Phenols, which are also called polyphenols or phenolic compounds, are plant substances which have an aromatic ring containing one or more hydroxyl groups.
The flavonoids constitute about one-half of the eight-thousand or so recognized phenols.
Flavonoids are molecules responsible for the color of fruit and flowers. They are beneficial to man as antioxidants, antiallergic agents, antiviral agents. Some can stimulate protein synthesis; some are antiinflammatory; others are antithrombotic; some are diuretic; antifungal, and antibacterial.
Some flavonoids may be classified as flavonoid glycosides but ALL ARE PHENOLS. Hence, flavonoids, flavonals, flavanones, isoflavones, and xanthones, can all be considered as phenol derivatives.
Glycosides, or sugar ethers, are a complex grouping of ACETALS (aldehydes and alcohols), which can be broken down to yield one or more sugars (GLYCONES), PLUS A NON-SUGAR COMPONENT (AGLYCONE).
The glycosides are not a major classification of phytochemicals, such as terpenoids, phenols, alkalioids, etc.
HOWEVER, IT IS THE GLYCOSIDIC FORM THAT IS MOST OFTEN THE ACTIVE FORM OF THE COMPOUND. Hence, isolation of the active compound must also include identification of the sugar(s) that are attached to it. It is just as important to note where the sugar and how the sugar is attached to the parent molecule.
It is interesting to note that most of the terpenes and terpenoids are simply multiples of the 5-carbon unit referred to as an "isoprene unit".
This geometric potential in the terpenoid synthesis areas of living forms allows for their diverse requirements of chemical communication systems that are observed in insects, plants, and mammals.
Many phylogenists have attempted to classify plants on the basis of terpene or terpenoid composition. In some cases, this has proven fruitful. In most, however, it has provided more frustration than success.
A number of steroid compounds can be built from the basic squalene structure in all species that require hormone synthesis for function.
The significance of one such steroid is best illustrated by the digitalis glycosides obtained from several plant species. It is unknown exactly why these compounds are found in plants but we know they are invaluable in strengthening the failing mammalian heart. In man, they increase the stroke volume by producing a positive inotropic action (increase force of muscle tissue. However, we do not know how they exert their cardio-active actions in the heart.
Many biologists pass over these compounds as being too complicated to study because of their chemistry and apparent presence in so many living forms.
Plant biology was the basis for the development of the fields of TOXICOLOLGY and PHARMACOLOGY. Many pharmaceutical companies have begun to reinvestigate "herbals" for new drug development.
This lack of complete scientific information may account for the resurgence of the use of "herbals" in human ailments. There is no question that active chemicals exist, but we need more information than is currently available.
Consumers need protection from these "herbal" producing companies. They need more information about: the concentration of the active ingredients in the product they are buying; the fate of these chemicals once consumed; and the the overall safety of these chemicals and the others included in the concoctions being sold.
The field of nutrition must also take into account the many stimulant and depressant chemicals that we regularly consume when we eat plant derived foods.
However, many are also adding "herbals" and vitamins (as antioxidants) to their daily routines. Daily, it seems - new supplements are being recommended. Who is monitoring the safety of the combinations - drugs, vitamins, herbals?
