Natural Products in GIT conditions

What are phenolic compounds

Phenolic compounds are ubiquitous in distribution in the planet kingdom, occurring free and as glucosides

May be simple polymers or complex polymers

What are the two main types of tannins

Hydrolysable tannins or non-hydrolysable tannins

How is hydrolysable tannins formed , name some examples, subtypes and what happens with iron salts

Formed by the esterification of sugars with simple phenolic acids e.g. gallic acid

Subtypes: Gallitannins, Ellagitannins

Solutions turn blue with iron salts

May be hydrolyzed by acids or enzymes

Outline non-hydrolysable tannins

Also called condensed tannins or Proanthocyanidins

Not readily hydrolysed

Do not contain sugars

Occurs with biosynthetic intermediates such as Catechins and Flacandiols

What is Proanthocyanidins

Term referred to the acid catalyzed oxidation reaction that produces red anthocyanidins upon heating PAs in acidic alcohol solutions

What are the properties of and tests for tannins

Properties

Tannin solutions precipitate heavy metals, alkaloids, glycosides and gelatin

Gallitannins & Ellagitannins- Blue- black ppts

Condensed tannins- Brown-green ppts

Tests

Goldbeaters skin test- Brown Black colour

What are the biological effects of tannins

Useful medicinal products

Traditional use predominantly on GIT and skin

Treatment for mouth ulcers and diarrhoea

Seeds of what and husk of what yield Psyllium and Ispaghula

Seeds of P.afra, P.indica yield Psyllium

Husk of P. ovata yield Ispahgula

Where are stimulant laxatives found in and what does it contain

Found in a range of medicinal plants for example: Senna, Cascara and Frangual

Contain active anthraquinone glycosides

which stimulate Cl- secretion, Increase water excretion, increases peristalsis, decreases GI transit time

What does Senna contain

Contains anthraquinone and dianthgrone glycosides

Dianthrone glycosides hydrolyze to yield aglycones, including Sennidins A and B

In vivo, the aglycones may work via affecting Cl- transport across cells of the colon

Explain the Borntragers Test for Anthraquinones

Hydrolyse glycosides in powdered drug

Macerate with organic solvent

Filter, add NH3, shake

A red/pink colour in aq. layer is positive

What is a terpene

a member of the largest class of secondary metabolite

Outline the 4 main phases of terpene biosynthesis

1. Acetl=yl CoA converted to IPP

2. Prenyltransferases generate higher building blocks

3. Self Condensation to C30 and C40

4. Secondary transformations: oxidation, reduction, isomerisation, conjugation, etc