Page 137 - Pharmd general phytochemistry I-Final2024_LEUCTERS

 Several triterpenes have been isolated from Colocynth. The two main triterpenes are

cucurbitacin E and cucurbitacin I.

HO O

HO O 24
HH 25
2
23 OR

OH

O3

Cucurbitacin E, R= -COCH3
Cucurbitacin I, R= H

Uses of Colocynth:
 Colocynth has been used as a cathartic because of the increasing problems of

synthetic laxatives habituation and also because of their toxicity.
 Being a powerful cathartic, it is not used now in standard medicine. Nevertheless,

there is a considerable interest in its constituents (cucurbitacins) due to their
cytotoxic activities.

Substituent Effects on the Cytotoxicity of Cucurbitacins:
1. Introduction of a double bond at C-23 increases cytotoxic activity.
2. Reduction of the 3-keto group reduces the cytotoxic activity.
3. Introduction of an acetyl group at C-25 increases the cytotoxic activity.
4. Introduction of 1,2-double bond may increase the activity.
5. Introduction of a hydroxyl group at C-24 decreases the activity.
 A compound containing a 1,2-double bond, a 23, 24-double bond, a' 3-keto group and

an acetyl group at C-25 is expected to be highly cytotoxic. The compound cucurbitacin
E contains all of these features and has an ED50 of 4.5 x 10-7 μg/ml.

Podophyllotoxins

Source: Podophyllum and podophyllum resin.
 Podophyllum consists of the dried rhizomes and roots of Podophyllum peltatum

(American Podophyllum) and P. hexandruin (Indian Podophyllum), Family
Berberidaceae.

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