Magnolia Compound Is a Potent Anti-Cancer Agent

Cancer researchers have shown that honokiol, a compound isolated from magnolia suppresses tumor growth by inhibiting the activity of the enzyme phospholipase D (PLD).

Honokiol is a biphenolic molecule present in the cones, bark, and leaves of Magnolia grandiflora that has been used in traditional Japanese medicine as an anxiolytic, anti-thrombotic, anti-depressant, anti-emetic, and anti-bacterial. While early research on the effective compounds in traditional remedies simply used whole magnolia bark extracts, known as houpu magnolia, more recent work has identified honokiol and its structural isomer magnolol as the active compounds in magnolia bark.

Elevated phospholipase D (PLD) activity provides a survival signal in several human cancer cell lines and suppresses apoptosis when cells are subjected to the stress of serum withdrawal. The tumor promoting effects of PLD are lined to the activity of RAS, which drives molecular pumps that remove chemotherapy drugs from cancer cells.

Investigators at the Emory University School of Medicine (Atlanta, GA, USA) used human cell lines growing in culture to evaluate the dependence of PLD survival signals on Ras and the effect of honokiol on Ras activation.

Results published in the July 2008 issue of the journal Clinical Cancer Research revealed that PLD activity was commonly elevated in response to the stress of serum withdrawal, and that the stress-induced increase in PLD activity was selectively suppressed by honokiol. The stress-induced increase in PLD activity was accompanied by increased Ras activation, and the stress-induced increase in PLD activity in MDA-MB-231 breast cancer cells was dependent on a Ras. These results allowed the authors to conclude that honokiol may be a valuable therapeutic reagent for targeting a large number of human cancers that depend on Ras and PLD for their survival.

"Knowing more about how honokiol works will tell us what kinds of cancer to go after,” said senior author Dr. Jack Arbiser, associate professor of dermatology at Emory University School of Medicine. "We found that it is particularly potent against tumors with activated Ras. Honokiol could be effective as a way to make tumors more sensitive to traditional chemotherapy.”


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Emory University School of Medicine