Most people with even a basic knowledge of herbal medicine will tell you that the activity of an herb can not (or should not) be reduced to the activity of just one substance. However, the research on curcumin – considered the “primary bioactive component” of the famous spice turmeric – is so seductive that many people in the natural health crowd have started associating turmeric root mainly with that one particular compound.
[Note: The highlighted numbers below link to abstracts in PubMed.]
However, as one group of researchers pointed out, curcumin-free turmeric still possesses remarkable bioactivity (23847105). According to them, this bioactivity can further be traced to other chemical compounds in turmeric, such as turmerin, turmerone, elemene, furanodiene, curdione, bisacurone, cyclocurcumin, calebin A, and germacrone. In another study, a total of 19 antitumor constituents of turmeric were identified (24079186). Other researchers also mentioned β-elemene, δ-elemene, furanodienone, and curcumol (22820242). Many of these are constituents of turmeric’s volatile oil, i.e., they are associated with the aroma of turmeric, and their content is severely reduced in dry turmeric, which is the most familiar form of this herb to most people. Nevertheless, some studies are available on these individual compounds, which may enlighten us to the action of the whole herb, rather than just the highly concentrated fraction of curcuminoids.
[Update: A new study reports that curcuminoid- and oil-free turmeric extract possesses significant antiinflammatory activity (24454348).]
While some of these compounds are fairly well studied – for example, β-elemene has been linked to anticancer activity in no less than 65 studies – others have just recently came into focus of researchers. Of the less known ones, turmerin, a peptide with antioxidant and antimutagenic activity, has been characterized as an antidote for cobra venom (18177267). It has also been demonstrated to have antihyperglycemic effects (21972920).
Calebin A, a phenolic compound with the structure reminiscent of curcumin (note the addition of the oxygen atom in the middle, between the two ketone groups), has shown anticarcinogenic properties (18619958) and was found to protect cells from amyloid-beta toxicity (12350137).
The rest of the compounds mentioned in the second paragraph above belong to the volatile group, i.e., their content is lower in dry turmeric (see 20096323 for the comparison of essential oil constituents obtained from fresh vs. dry, non-powdered, turmeric):
Turmerone is the primary constituent of turmeric rhizome essential oil and oleoresin (20096323). It has shown significant antitumorigenic (15254774, 19250610), immunostimulating (23229920), anti-inflammatory (22766494), and antiplatelet (16112857) activities, and, similarly to curcumin, binds to peroxisome proliferator-activated receptor-gamma (PPARγ) (15713005) and, hence, is also hypoglycemic. Interestingly, turmerone in combination with curcumin, but not either of these agents alone, completely abolished colon cancer formation in mice (23233214).
Curdione, while being present in the more common Curcuma longa, is the primary constituent in the essential oil of C. aromatica, a species widely used in Japan (21785639). It has shown anti-inflammatory (18038902), anti-platelet (22560337), and hepatoprotective (12033504) activities.
Furanodiene and furanodienone are anti-inflammatory sesquiterpenoids common to myrrh. Furanodiene is also the primary constituent in the essential oil of C. wenyujin. It has been shown to inhibit the growth of multiple types of cancer cells (19606517), including breast cancer (22854281), lung cancer (22927878); and possess anti-angiogenic activity (21911050). Furthermore, its action was found to be synergistic with chemotherapy drugs paclitaxel (23554049) and tamoxifen (22422660). Anticancer properties have also been demonstrated for furanodienone (21461888, 21069738).
Bisacurone has shown antiadhesive properties (18602074).
[Update: Germacrone was also found to inhibit the H1N1 and H3N2 influenza A viruses and the influenza B virus at both the attachment/entry step and the early stages of the viral replication cycle (24095670).]
Finally, an unidentified diterpenoid from turmeric root inhibited pro-inflammatory response in human gastric cells infected with H. pylori (23964142).
Of course, multiple other constituents are present in turmeric root, as well as in any other plant. Although this is just a glimpse of the potential bioactivity hiding in the plant, we hope that the information in this post will provide you with some insights into potential benefit of whole turmeric preparations.
- The Alchemy of Curcumin (herbanaut.wordpress.com)