Natural Products Flashcards
Phenolics Outline
Many OH substituents on an aromatic ring. Ubiquitous occurring free (OH not attched) or in glycosides (OH attached to NH). Can be simple or complex. 2 types complex: hydrolysable and non-hydrolysable
Complex phenolic compounds (Tannins) Outline
Contain 1-2 phenolic groups per 100 M.W., water soluble, interact with proteins. 2 types: hydrolysable and non-hydrolysable, Phenazone percipitates all tannins
Psuedotannins vs tannins
Psuedotannins have a lower molecular weight and don’t give positive tanning test
Hydrolysable Tannins Outline
Contain an ester. Can be broken down by enzymes or acids. Break down in water/acid/base. Hydrolysable tannins turn blue-black in presence of iron
Non-hydrolysable/condensed tannins
Mainly C-C bonds, no sugar groups. Not easily separated in water/acid/base. Need really intense conditions eg boiling acid. Turns green in presence of iron
Relationship between polymer complexity and hydrolysability
more complex = less easily hydrolysed
Proanthocyanidins Outline
Proanthocyanidins are oxidised in an acidic alcohol solution to produce red anthocyanidins. Tannin used in diarrhoea treatment, prevent bacteria adhering to urinary tract
Tannins Medicinal Properties
Used in the treatment of mouth ulcers (styptic, closes wounds) and diarrhoea (astringent, protein tightening slows motility)
1st line treatment of dehydration
Water and electrolytes
Rice suspensions in treatment of diarrhoea
Rice polysaccharides hydrolysed in GIT. Co-absorbed with Na+ creating stronger osmotic gradient, enhancing water absorption
Can crude extracts be used OTC
No. Not refined enough testing
Natural Bulk Laxatives
Outer seed layers rich in polysaccharides (arabinoxylan). When in contact with water produce a mucilaginous swelling in testa epidermis ( 1 soluble in warm and other in cold water). Need to be taken with water to prevent sticking. seeds (P. afra) = psyllium and husk (p.ovata) = ispaghulla
Negative effects of bulk laxatives
Drug interactions, may coat drugs preventing their absorption
Natural component of stimulant laxatives
Anthraquione glycosides. Increase Cl- secretion = increased water excretion = increased peristalsis = decreased transit rate
Anthraquinone Glycoside Outline
Similar to phenolics: are free and glycosidic. Exist alos in reduced forms and in dimers
Plants containing athraquinones
senna, frangula, cascara, rhubarb and aloes
Anthraquinone Structure
Aromatic rings on left and right of non-aromatic rings. to double bond Os in non-aromatic ring (2 ketone groups opposite eachother)
Sennosides Outline
Anthraquinone and dianthrone glycosides. Dianthrone glycosides hydrolise to aglycones sennidins A and B. aglycones increase Cl- secretion in colon
Frangula Outline
Bark contains glycosides (eg glucofrangulin A). Treats partucularly hypertonic and slow transit constipation (resistant to bulk)
Test for Anthraquinones
Borntragers. Macerate substance with organic solvent. Add NH3 + shake. Red/pink colour in aqeuos layer = positive. Hydrolyse glycosides in powdered drug
Consequences of stimulant laxative abuse
Psuedomelanosis coli result from use over a longer period of time. Cells of colon turn brown due to pigment build up (damaged). Can also reduce in dermatitis
Natural component of antispasmodics
Terpenes, specifically monoterpenes (10 C chains). Contained in compounds like thyosine and pepermint. Act as a Ca2+ antagonist
4 steps terpene biosynthesis
Acetyl Co A to IPP, prenyltransferase adds more Cs to chain, self condensation (different chains join together) and secondary transformations (eg redox, isomerization and conjugation). When chains are joined together a positive charge can be spread across 3 bonds and then in final product charge is neutralised
Monoterepenes Outline
Formed from acetyl Co A. From leaf glands, skin and peel of fruit. Alphiatic or aromatic. Generally volatile and lipophilic. Insect attractant and anti8microbrial
