05. The chemistry of manna

The term "manna" indicates a sugary exudate consisting mainly of mannite, organic acids, water, glucose and, to a lesser extent, levulose, mucilage, resins and nitrogen compounds. The qualitative and quantitative composition of the manna is very complex and the percentage incidence of the its constituents depends on various factors (the area of origin, the age of the ash, the chemical-physical constitution of the soil and its exposure, the seasonal trend, etc., type of manna used) table 1.

 
Tab. 1 - Percentage value of the constituents of manna and manna in cannoli.

Some principles, even present in a homeopathic percentage, are positively felt by the fine biological reactivity of the human organism.
But manna generally contains 40-60% (with peaks over 70%) of mannite or D-mannitol (C6H14O6), which is a hexavalent alcohol of mannose, commonly called manna sugar.
Here is the chemical structure of D-mannitol:

CH2OH
|
HO-C-H HO-C-H
|
H-C-OH
|
H-C-OH
|
CH2OH

D-mannitol comes in the form of polverand crystalline, or of transparent rhombic prisms (crystallization from water), or of bright needles gathered in groups or arranged in rays (crystallization from hot alcohol).
It is odorless, colorless and non-hygroscopic.
It tastes sweet, but the sweetening power is lower than that of sugar.
Melts at 165-166º C.
Above melting point it decomposes and emits a burnt sugar smell.
It has a specific weight of 1,485-1,489.
AND well soluble in hot water, less so in cold water.
AND, at the same temperature, the more soluble in alcohol the lower the alcohol content.
AND insoluble in the ether.
It can be oxidized into d-fructose (i.e. in the corresponding monoketone) by Bacterium xylinum or Bacterium aceti.
It can be fermented in the presence of mineral salts by schizomycetes giving alcohol, butyric acid and lactic acid, and can also undergo lactic and butyric fermentation.

The photosynthesis of mannitol
Mannite can be considered as one of the final products of chlorophyll photosynthesis, a complex photochemical process that allows the transformation of light energy into chemical energy, thus making it possible to synthesize complex organic substances such as sugars, starting from simple inorganic substances such as carbon dioxide and water, according to the reaction:

nH2O + nCO2 --- & gt; (CH2O) n + nO2

Photosynthesis occurs in cytoplasmic organelles surrounded by double membranes called chloroplasts, whose outer membrane is freely permeable to low molecular weight substances, while the inner one is permeable only to a few substances including carbon dioxide.
The region of the chloroplast enclosed by the inner membrane is called the stroma; suspended in the stroma there is a continuous membrane, the thylakoid membrane, which is considerably folded to form a network of flattened vesicles called thylakoids.
The photosynthetic process consists of two sets of reactions, those to light and those to dark.
The first (reactions of the light phase) take place at the level of the thylakoid membranes, where the light energy captured by the chlorophyll molecules is, through the splitting of water, converted into chemical energy (ATP, NADPH).
The second (dark phase reactions) take place in the stroma of the chloroplast and transform carbon dioxide into phosphorylated sugars (3-phosphoglyceraldehyde) and water through the cycle of photosynthetic reduction of carbon called the Calvin-Benson cycle. A part of the 3-phosphoglyceraldehyde molecules produced remains in the chloroplast and guarantees the maintenance of the Calvin-Benson cycle; others are transported into the cytoplasm and following condensation with a second molecule with three carbon atoms, they determine the formation of a fructose molecule which is transformed into D-mannose which is subsequently reduced to mannitol. Organic compounds deriving from photosynthesis are distributed throughout the plant by translocation that takes place in the phloem, a vascular tissue containing thin interconnected tubes formed by living cell walls. The incision of the ash tree trunk, a phloemic level, causes the escape of the circulating elaborate lymph which, solidifying in contact with the air, gives rise to the formation of manna.