Honokiol is a bi-phenolic compound with the formula C18H18O2 and a relatively small molecular weight of 266 grams/mole. This molecule is found in several species of the genus magnolia including M. officinalis, obovata, and grandifolia. It is an isomer of another compound also found in magnolia materials called magnolol, which has 1000 times the antioxidant potential of vitamin E. The dried bark of M. officinalis usually has about 1-5% hanokiol and 2-10% magnolol.
Magnolia Species and Traditional Use
While magnolia species have been incorporated in traditional healing systems throughout the world, the barks of Chinese M. officinalis and Japanese M. obuvata have become quite popular due to their verified levels of phytochemicals like honokiol. The bark of M. officinale (houpa) is often sought for incorporation in traditional Chinese formulas addressing “chi stagnation”, asthma, anxiety, cancer, and digestive disorders.
China produces well over 200 tons of magnolia bark a year. With its popularity comes the concern of over-harvesting since the tree is killed during bark procurement. A positive side to this is that the honokiol molecule is not very complex and is easily synthesized through organic chemistry methods.
Pharmokinetics
Honokiol appears to be non toxic, easily absorbed, and systematically available. This is important since many promising materials like Epigallocatechin Gallate (EGCG) are not absorbed well in the digestive tract. Honokiol also avoids immediate clearing by the liver (first pass effect) and crosses blood barriers that often exclude other compounds.
Recent studies have explored honokiol and found validation for it as a treatment option for anxiety, cancer, peridontal disease, stroke, inflammation, and even weight loss.
Cancer Management
Honokiol has been effective in vitro and in vivo against several types of cancers. It appears to turn off the division of some cancer cells while inducing others to kill themselves (apoptosis). It has antiangiogenesis properties (eliminating the blood supply to tumors) and some studies are recommending it as adjunct treatment with other types of chemotherapy.
Fighting Anxiety
Honokiol has an anti-anxiety (anxiolytic) effect comparable to benzodiazepines like clonazepam (klonopin) and diazepam (valium) while avoiding their sedative and addictive nature. Research indicates that honokiol selectively modulates GABA receptors. GABA (gamma Aminobutyric acid) is the major inhibitory neurotransmitter for nervous tissue. Many sedatives work by targeting and attaching to its receptors in the brain.
2000 Years of Clinical Study
While magnolia bark has been used in traditional Chinese medicine for over 2000 years, only recently have researchers explored its components. Recent human, animal, and in vitro studies are confirming what traditional herbalists have already known about its safety and efficacy. A challenge with further exploration of simple molecules like honokiol is that it is easy to manufacture and exists in nature. There is little incentive for the pharmaceutical industry to invest in research on a simple compound such as this. Presently there are several patents in process regarding modified honokiol molecules in the treatment of cancer and other conditions.
Supplemental Resource:
Pharmacognasy, 15 edition, Trease and Evans, Bailliere Tindall; Dec 2001
Clincancerres.aacrjournals.org/cgi/content/abstract/14/4/1248; Apoptosis
www.jbc.org/cgi/content/abstract/278/37/35501;Antiangiogenesis
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