Moroidin has shown to have anti-mitotic properties, chiefly by inhibiting the polymerization of tubulin. Tubulin protein polymers are the major component of microtubules. During mitosis, microtubules form the organizing structure called the mitotic apparatus, which captures, aligns, and separates chromosomes. The proper alignment and separation of chromosomes is critical to ensure that cells divide their genetic material equally between daughter cells. Failure to attach chromosomes to the mitotic apparatus activates the mitotic checkpoint, preventing cells from entering anaphase to proceed with cell division. Agents that disrupt microtubules therefore inhibit mitosis through activation of this checkpoint.
Moroidin and its related compounds, the celogentins, inhibit tubulin polymerization. Of this family, celogentin C is the most potent (IC 0.8×10 M), and it is more potent than the anti-mitotic agent vinblastine (IC 3.0×10). Moroidin has the same potency as vinblastine. Because of this biological activity, compounds in this family have potential as anti-cancer agents.
The mechanism of tubulin disruption is not known, but the degree of biological activity has been linked to the structure of the right-hand ring containing the Trp-His linkage. Moroidin and the celogentins can be divided into three groups according to structural similarity of the right-hand ring. Celogentin C, the most potent compound, has a unique right-hand ring containing a proline residue. Moroidin and its analogous celogentins all have activity comparable to that of vinblastine, and a third group of celogentins all have reduced activity. In contrast, stephanotic acid, a cyclic compound analogous only to the left-hand ring and containing the same Leu-His linkage, has no anti-mitotic activity.
Other anti-tubulin agents used as chemotherapy agents have painful side effects known as neuropathy when the drugs are exposed to tissue. Although the exact mechanism for the cause of neuropathy is unknown, it is thought to be related to the degradation of microtubules, which are essential components of neurons.