Terpenes - Saponins

Question 1

What are Triterpenes?

Answer 1

We have studied the Monoterpenes and Diterpenes - we are now onto the Triterpenes
Triterpenes
* 30 carbons in skeleton, often pentacyclic – five rings.
* Many are precursors of steroidal compounds.
Many are found in traditionally antiinflammatory and adaptogenic herbs

Question 2

What are Ursolic and oleanolic acid (triterpene aglycone)?

Answer 2

• Found together in plants.
• Ursolic acid: Olea europaea, Agrimonia eupatoria, Rosmarinus officinalis, oregano, thyme, lavender, peppermint, pomegranate, hawthorn
• Typically anticarcinogenic, chemoprotective, hepatoprotective, anti-inflammatory.
• Oleanolic acid: Aglycone for many triterpenoid saponins (e.g. in Siberian ginseng).

Together they are usually:
* antioxidant, antiglycative (related to diabetic complications, the aging process and atherosclerosis)

Question 3

What about Black Cohosh?

Answer 3

Contains triterpenes
Black cohosh actions
* Alleviates menopausal symptoms.
* Anti-tumour activity.
* The triterpene gycosides does not bind to oestrogen alpha or beta receptors which puzzles people into its effects
* Dopaminergic activity - possible lowering of prolactin levels, so might help with hot flushes
* Inhibitory effect on pituitary LH secretion.

Question 4

What are Saponins?

Answer 4

Saponins
* Commonly found in desert plants (yucca and quillaja) to protect them from fungi etc
* Saponin glycosides: hydrophilic part that loves water (glycoside) at one end, lipophilic aglycone at other which loves fat
* Allows lipophilic and hydrophilic molecules to mix.

This means in water, saponins align themselves vertically with hydrophobic ends away from water, reducing surface tension, causing water to foam. They create round shape within the water (lipophilic centre). They are soap-like: emulsify the plant extract, allowing oily constituents to better dissolve in watery media, and vice versa. Can be used to help emusify creams.

There are two types of saponin whic often come together in one plant:
* Steroidal saponins (27- carbon) are tetracyclic (fourringed) with furan and pyran heterocyclic rings.
* Triterpenoid saponins (30- carbon) have a pentacyclic - five-ringed structure (the most common).

Question 5

What are the pharmacodynamics of saponins?

Answer 5

• Oral intake is safe as little is absorbed.
• Most pass to the large intestine where gut flora convert them to the sapogenin (aglycone)
• However they are haemolytic when injected, releasing haemoglobin which can lead to renal failure as it dissolves the membranes of red blood cells (leading to glomerular damage).

In the gut saponins can disrupt cell membranes in the intestines, leading to impaired absorption of smaller molecules such as glucose and ethanol normally absrobed by transporters.

This can be useful - Gymnema sylvestre used for diabetes metaboic symdrome - reduces absorption of glucose in small intestine.

Saponins also Iincreased permeability of the small intestine (in vitro) might lead to increased uptake of otherwise poorly permeable substances.

However studies have found:
* Healthy for bowel flora (in vivo):
* Can inhibit protozoa decrease methane production
* Increase cholesterol excretion, and inhibit hepatic synthesis of cholesterol.
* Reflex expectorant from irritating the digestive system; mediated via the vagus nerve (Saponaria off., Glechoma off., Primula vera).
* Increase production of mucus in the lungs, as well as coughing; helpful for dry cough.

Question 6

Which plants have Saponins?

Answer 6

Typically found in anti- arthritic, antiinflammatory, adaptogenic herbs however…

Dioscorea villosa
Phytolacca americana
Panax ginseng,
Eleutherococcus senticosus and
Glycyrrhiza glabra all contain saponins”