December 21, 2017



Citrus fruits (genus Citrus, family of the Rutaceae) are very juicy fruits, often with a sour taste, which are harvested from October to April. They are usually consumed fresh or squeezed to obtain juices (both for domestic and industrial purposes), but they are also used for the production of essential oils.

Numerous research has discovered their properties including antioxidant, antimicrobial, anti-inflammatory and antitumor, due to the presence of polyphenols, vitamins, minerals, fibers, essential oils and carotenoids.

The most recent experiments have focused their attention on the main wasted part of these fruit, the peel, in which citrus fruits is composed of a colored outer layer (skin) and a white inner layer (pith).

Inside, in addition to fibers and essential oil, there are components with antioxidant properties including an abundance of a particular group of flavonoids called Polymethoxyflavones.

Polymethoxyflavones are present exclusively in plants of the genus Citrus and they possess antioxidant, antitumor, anti-inflammatory, but above all neuroprotective properties.

This class of compounds acts on some enzymes that, if are not working correctly anymore, cause the onset of Alzheimer’s disease, a disease of the central nervous system that leads to a progressive death of neurons, resulting in loss of memory, difficulty in speaking and moving.


According to some experiments, Polymethoxyflavones could prevent the formation of senile plaques (extracellular formations composed of residues of amyloid protein and neuronal deposits) and neurofibrillary tangles (bundles of filaments formed around the nucleus of the neuron), by inhibiting two specific enzymes:

  • the enzyme BACE-1 (responsible for cutting the precursor protein of the beta-amyloid that repairs the neurons) that, when it becomes hyperactive, causes the formation of a tangle of cut parts that blocks the transmission of the nervous impulse;
  • the enzyme Acetylcholinesterase (responsible for demolishing the neurotransmitter Acetylcholine after it has transmitted the signal from the nerve cells to the muscle cells) which, when it no longer acts properly, lowers the Acetylcholine values.

The inhibition of Acetylcholinesterase is helped by the essential oils of citrus fruit, in particular those extracted from the peel and from lemon’s leaves (Citrus limon) and sweet orange (Citrus sinensis), thanks to the presence of coumarins and monoterpenes, which have also shown to increase memory capacity.


Citrus fruits are affordable and are easily found in all markets therefore, it may not be worth waiting for the research to give us further confirmation.  By finding an efficient way to extract the precious Polymethoxyflavones from the peel, we should try to consume these fruit daily, preferring fresh ones, with juice, maybe without completely removing the white part that covers the pulp (pith).

And the outer peel? It is difficult to eat because of the excessively bitter taste, but we can try to consume it dried and reduced to powder or grated fresh, added to the dishes … the important thing is making sure it is of organic!




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