Natural Products in Cancer Chemotherapy

Vocabulary flashcards covering natural anticancer agents, cell cycle phases, taxanes (paclitaxel, docetaxel), podophyllotoxins (etoposide, teniposide), structure-activity relationships, and vinca alkaloids.

Metastases

The process by which cancer cells present in one part of the body proliferate rapidly and spread to other areas by means of blood or the lymphatic system.

Neoplasm

A life-threatening diseased form of tissue growth characterized by uncontrolled division of cells.

G1 Phase

The Gap-1 period of the cell cycle when a newly created cell is born and actively grows in size before moving to the synthesis phase.

S Phase

The synthesis phase of the cell cycle lasting $1\text{ to }3\,hrs$ during which DNA replicates and two copies of DNA are present in the cell.

G2 Phase

The phase of the cell cycle where cells prepare for final division through tubulin synthesis before entering the M phase.

M Phase

The cell division phase (mitosis) during which a parent cell divides to produce two daughter cells.

G0 Phase

A dormant or resting state that daughter cells may enter after mitosis instead of continuing in the active cell cycle.

Paclitaxel

A naturally occurring taxane diterpenoid alkaloid with molecular formula $C_{47}H_{51}NO_{14}$ and molecular weight $853.91\,g\,mol^{-1}$ that binds $\beta\text{-tubulin}$ to stabilize microtubules and arrest cells in the $G_2/M$ phase.

Taxus brevifolia

The Pacific yew tree, whose bark is the primary natural source from which paclitaxel was originally isolated in 1962 by Wall and Wani.

10-Deacetylbaccatin III

A natural biosynthetic precursor extracted from the renewable needles of Taxus baccata (European yew) used to produce paclitaxel and docetaxel semi-synthetically.

Docetaxel

A semi-synthetic taxane diterpenoid with molecular formula $C_{43}H_{53}NO_{14}$ and molecular weight $807.88\,g\,mol^{-1}$ derived from 10-deacetylbaccatin III, featuring higher potency and improved solubility compared to paclitaxel.

Oxetane Ring

A four-membered oxygen-containing heterocycle within the taxane diterpenoid skeleton that is essential for microtubule stabilization and antineoplastic activity.

Structure-Activity Relationship of Paclitaxel

The activity profile of paclitaxel requiring the taxane ring system, oxetane ring, C13 side chain, benzamide group, and 2'-hydroxyl group, where removal of the oxetane ring or C13 side chain leads to total loss of activity.

Mitosis Blocked by Paclitaxel

The antimitotic mechanism where paclitaxel promotes tubulin polymerization and prevents microtubule depolymerization, freezing the cell in metaphase and triggering apoptosis.

Podophyllotoxin

A non-alkaloid toxin lignan extracted from the roots and rhizomes of Podophyllum species (such as Podophyllum hexandrum and Podophyllum peltatum) containing five fused rings and an essential trans-lactone ring.

Structure-Activity Relationship of Podophyllotoxin

The structural requirements of podophyllotoxin where Ring A and Ring E are essential for antimitotic activity, Ring D is preferred as a trans-lactone, and aromatization of Ring C causes loss of activity.

Etoposide

A semisynthetic trans-configured beta-D-glucoside derivative of podophyllotoxin that acts as a Topoisomerase II poison by trapping TOP2-DNA cleavage complexes and blocking DNA religation.

Teniposide

A semisynthetic podophyllotoxin derivative topoisomerase II inhibitor structurally distinguished from etoposide by containing a thienyl ring in place of a methyl group.

Topoisomerase II Poison

An agent like etoposide that stabilizes the intermediate topoisomerase II-DNA cleavage complex, converting temporary strand breaks into permanent, cytotoxic double-strand DNA breaks.

Vinca Alkaloids

Antitumor plant alkaloids isolated from Catharanthus rosea (Vinca rosea) composed of vindoline and catharanthine units (e.g., Vincristine and Vinblastine) that block cell division by causing metaphase arrest.