vitamin C and chirality

26.I.1430

A couple of notes relating to nutrition and a pattern in life.

The daily recommended intake of vitamin C for adults between 20 and 60 is about 110 mg. For those such as smokers with higher exposure to oxidants, the dose should be at least 200 mg.

While an orange will have about 60 mg of vitamin C per 100 g(which is L-asorbic acid, and we'll come to the L- later), a lemon 65. Honey has the lowest amount only 0.5 mg.

It turns out that guyava has a much higher store of vitamin C, about 245 mg per 100 g.

Great economizing (unless oranges are much cheaper than guyava). Instead of having to take four oranges per day, or chewing on 2/10th of a kilo of dill leaves, a single guyava would cover more than my need of vitamin C. Joy.

Now concering the L-part, there is something very peculiar about life.

Many molecules are chiral (better yet see wp:Chirality_(chemistry)).

So is vitamine C which can be left-handed or right-handed. Other biomolecules that are chiral include amino-acids such as alanine (shown from wp) and sugars such as glucide.

The interesting thing is that living organisms select only one of the chiral orientation (L or left-handed) and not the other (D or right-handed). This is true for amino-acids sugars and other alimentary acids like vitamin C.

That is, the (D-Ascorbic acid) if administered to our body will not be assimilated into the body. Only L-Ascorbic acid enantiomer of vitamin C is accepted by the body.

Moreover there is an asymmetry in the quantity of L- vs. D- biological molecules, which some ascribe to meteor impacts that predate the appearance of life.

Whereas when made synthetically in laboratory conditions (read symmetric) the L- to D- ratio is 50/50, called a racemic mixture.