[2.4] CARBOHYDRATES (PRODUCTS OF SUGAR METABOLISM)

ALDEHYDES

Most important sugar

OXIDATION

Gives rise to Sugar Acids

OXIDATION

Primary ROH → [Oxidation] → RCOH → [Oxidation] → RCOOH (Sugar Acid)

How many carboxyl groups do plant acids usually have?

2-3 carboxyl groups

REDUCTION

Gives rise to Sugar Alcohols

REDUCTION

RCOH → [Hydrogenation] → ROH (Sugar Alcohol)

Plant/Sugar acids

are products of oxidation of an aldose sugar

Carbohydrates that cannot undergo oxidation are referred to as

REDUCING SUGAR or AGENT

Reducing sugars

have free aldehyde/ketone groups.

Non-reducing sugars

do not have free aldehyde/ketone

Plant Acids

Chemical Nature

Organic acids derived from plants containing:

-2-6 C atoms

-At least 2-3 carboxyl groups

Plant Acids are Organic acids derived from plants except

formic acid, a volatile poison, because it is derived from ant bites.

Plant Acids

Uses

-Acidulants in effervescent formulations

-component of buffers (regulate pH)

Plant Acids include

citric acid

lactic acid

tartaric acid

malic acid

oxalic acid

formic acid

ascorbic acid

protocatechuic acid

shikimic acid

Citric Acid

(6C)

C₆H₈O₇

Citric Acid

Isolated by Scheele from lemon juice (acidic & antioxidant) in 1784

Citric Acid

related acids

Isocitric acid: Isomer

Aconitic acid: Dehydrated form

Citric Acid

uses

antioxidant

Citric Acid

-Common to all plants as they all undergo cellular respiration

-Product of Krebs / Citric acid / Tricarboxylic acid cycle

Lactic Acid

(3C)

C₃H₆O₃

Lactic Acid

use

Acidulant in infant feeding formula

Lactic Acid

Product of Lactic Acid Fermentation done by Lactic acid-forming bacteria

Tartaric acid

(4C)

C₄H₆O₆

Tartaric acid

By-product of wine industry

Tartaric acid

uses

anticoagulant

Ingredient in many food products

Tamarind (Sampalok

-Tamarindus indica

-Fabaceae family

-Plant rich in tartaric acid (sour taste used in sinigang)

Malic acid

(4C)

C₄H₆O₅

Malic acid

-Present in pomace of apple

apple

Malus domestica or Malus malus

Rosaceae family (Rose Family)

Malic acid

uses

Antioxidant, stabilizer, effervescent

Oxalic acid

(2C)

C₂H₂O₄

Oxalic acid

From Family Oxalidaceae Family

-Members are rich in oxalic acid

Oxalic acid is present in

kamias

balimbing

gabi

Oxalic acid

-Oxidation product of Ethylene Glycol Poisoning

-Naturally safe but toxic in high amounts

Kamias:

Averrhoa bilimbi

Kamias:

Causes itchiness in tongue (due to oxalate crystals)

More sour than balimbing

Puckering taste

Balimbing:

Averrhoa carambola

Gabi:

Colocasia esculenta

Gabi:

-Source of Raphides, which are made of Calcium Oxalate (nagform ng calcium oxalate dahil marami siyang oxalic acid)

-We eat the STEM

P-uckering taste

Formic acid

(1C)

CH₂O₂

Formic acid

-From ant bites (only one not from plants)

-Volatile Poison

-Oxidation Product of Methanol Poisoning

Formic acid: lambanog

If not produced properly, produces methanol, which then gives rise to formic acid

Protocatechuic acid

(7C)

C₇H₆O₄

Protocatechuic acid

-Present in onion varieties

-Make it resistant to attacks of a particular fungus

native onion (reddish)

have longer storage period

Shikimic acid

(7C)

C₇H₁₀O₅

Shikimic acid

-Precursor of aromatic compounds / amino acids

-One of the most important acids for secondary metabolite formation

Vanillin (from orchid)

A derivative of shikimic acid

Amino acids: alkaloids, nitrogenous compounds, some are from

shikimic acid pathway

Ascorbic acid

(6C)

C₆H₈O₆

Ascorbic Acid

Cofactor of collagen hydroxylases

Ascorbic acid

(Vitamin C)

Scurvy:

Ascorbic acid deficiency

Scurvy symptoms

Impaired collagen synthesis

Hematoma

Bruise

Gum bleeding

ALPHA HYDROXY ACIDS (AHA)

Lactic, Tartaric, Citric, Malic acids

ALPHA HYDROXY ACIDS (AHA)

Function: skin exfoliation

All are acidulants with tart taste

most water soluble aha

tartaric acid

Sugar alcohols

are products of reduction of an aldose sugar.

Sugar alcohols include

ethanol

mannitol

sorbitol

Ethanol

Sources: For wine production

Fermentation of yeast (anaerobic respiration)

yeast

Saccharomyces cerevisiae

Ethanol

sources: For solvent/disinfectant purpose

Catalytic hydration of ethylene

Ethanol

USP Definition

94.9% w/v (92.3% w/w) at 15.56 o C

15.56 o C

temperature used for standardization of physical constants

Ethanol

uses

CNS stimulant:

CNS depressant

ethanol as cns stimulant

In low concentration

Mostly releases dopamine

ethanol as cns depressant

In higher concentration

Sedative effect (attacks GABA receptor)

Ethanol

dilute alcohol

48.4 - 49.5% w/v ethanol at 15.56o C

Brandy

40% ABV

Brandy

From distillation of WINE (grapes)

Whiskey

40% ABV

Whiskey

From distillation of MALTED GRAIN

Rum

40% ABV

Rum

From distillation of FERMENTED MOLASSES

molasses

By-product of processing refined sugar from the official source: Sugarcane (Saccharum officinarum)

molasses

-is a thick, brown syrup, made by crushing the sugar cane to extract its juice, boiling the juice to form sugar crystals, and then removing the crystals

-remaining liquid

Beer

3-13 ABV

Beer

From fermentation of starches from cereal grain

Wine

8-14 ABV

Wine

From fermentation of grape juice

Higher alcohol content than beer

Mannitol

Sources

Manna (Fraxinus ornus)

Mannitol

Sources

-Commonly produced today by catalytic hydrogenation of fructose at C2 due to the presence of ketone group

-Extracted from a variety of plants

Mannitol

uses

osmotic diuretic (iv)

osmotic laxative (oral)

mannitol as Osmotic diuretic (IV) can be utilized for

Kidney failure

Glaucoma

Increased intracranial pressures

Sorbitol

synonyms

glucitol

Mountain-ash

(Sorbus aucuparia)

Sorbitol

Sources

Mountain-ash (Sorbus aucuparia)

Nowadays, it is produced by bacterial biotechnology

Sorbitol

use

Sweetener (tastes half as sweet as sucrose)

Sorbitol

-It is not absorbed on oral ingestion so it is used in the manufacture of toothpastes and chewing gums; used as humectant

Sorbitol is a byproduct of

glucose metabolism whenever a person has hyperglycemia (high blood sugar levels) (via the polyol pathway)

DM complications: dryness and kidney failure

= attributed to excessive formation of sorbitol

POLYOL PATHWAY

Glucose accumulation can lead to sorbitol excess, which depletes NADPH levels → lower antioxidant activity → possible oxidative damage to cells & microvasculature (especially in diabetics)

Glucose accumulation

can lead to sorbitol excess, which depletes NADPH levels → lower antioxidant activity → possible oxidative damage to cells & microvasculature (especially in diabetics)

Glucose → Sorbitol

(NADPH → NADP+)

by aldose reductase

Sorbitol → Fructose

(NAD+ → NADH)

by sorbitol dehydrogenase

POLYOL PATHWAY

Normal process in the human system; to maintain homeostasis and REDOX balance

Hyperglycemia

is a complication wherein high glucose levels also implicates high sorbitol levels.

Higher sorbitol levels leads to

depletion of NADPH

Why do we need NADPH?

used to convert glucose to sorbitol, is important in the liver for the formation of GSH (antioxidant).

GSH (Glutathione)

is necessary for a good antioxidant / defense mechanism.