Page 52 - PG 504-theoretical notes-phyto-1-2024-2025..

Clinical pharmacy PharmD program Third level Phytochemistry-1 (PG-504)

C) Action of Oxidizing Cations:

Mono-, di- and some polysaccharides which contain free anomeric carbon

(i.e., a sugar group), undergo oxidation in the presence of oxidizing cations such

++
as Cu in alkaline solution (e. g., Fehling’s reagent, Benedict’s reagent).

D) Action of Acids on Monosaccharide:

• The effect of acids on monosaccharide depends on:

a) Concentration b) Temperature

i. Dilute non-oxidizing acid at room temperature:

In this case the monosaccharide is stable.

ii. Hot concentrated acids:

▪ Hot concentrated hydrochloric acid eliminates water from the sugar

molecule with the formation of non-carbohydrate (i.e., furan derivatives):

o Pentose gives furfural, which is steam volatile.
o Methyl pentose gives 5-methyl furfural, which is steam volatile.

o Hexoses give at first 5-hydroxymethyl-furfural which is then
decomposed by heating to laevulinic acid and formic acid (non-

volatile.

Aldo- or keto- Methyl-pentose Aldo- or keto- COOH
pentose (6-Desoxyhexose) hexose
CH 2
CH
O CHO H C O CHO HOH C O CHO 2
3
2
C=O
CH 3
Hydroxmethyl- Laevulinic
Furfural Methyl-furfural furfural acid

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