Curcumin: The reason we love turmeric

In India, if you go to a spice shop and ask for turmeric, the attendant may give you a knowing smile, nod their head and say, “Ah, the golden spice.” 

It’s no secret that Indians love turmeric; they are the world's largest producers and consumers of the spice.  In Sanskrit, the language of Indian classics, turmeric has many names:

  • Haridra (dear to hari, Lord Krishna)
  • Bhadra (auspicious or lucky)
  • hemaragi (exhibits golden color)
  • survanavara (which exhibits golden color)

(turmeric flower) 

Most of these names reference turmeric’s golden color, it's the spice's most well-known feature. But do you know what gives turmeric its distinct hue? Turmeric’s golden color comes from an orange essential oil and curcumin, the latter of which is the focus of today’s article. 

What is curcumin?

Curcumin is a compound that is bright yellow and produced by the Curcuma longa plant. It belongs to a group of compounds known as curcuminoids and is the primary curcuminoid of the turmeric plant. It is also the plant's principal active compound. 

Its chemical formula is C21H20O6.

(Skeletal formula of curcumin) 

Biosynthesis of curcumin

Now that we know a little bit more about curcumin, let's look at hod w it's produced in the turmeric plant. 

At the moment, scientists are still unsure of curcumin’s biosynthesis route; however, they do have a couple of theories. The two most popular theories were proposed by Peter J. Roughley and Donald A. Whiting in 1973.  Although the two approaches are different, they have one thing in common; in both, cinnamic acid is the starting point. Cinnamic acid is an organic compound derived from phenylalanine, an amino acid. 

In the first theory of curcumin biosynthesis, chain extension reaction by cinnamic acid and five malonyl-CoA molecules eventually lead to the formation of a curcuminoid. In the second theory of curcumin biosynthesis, the process is guided by two cinnamate units coupled together by malonyl-CoA.

(Possible biosynthesis routes of curcumin) 

The history of curcumin

Although curcumin has existed as a compound in turmeric for as long as humans have been using the spice, it was first discovered in the early 19th century; 1815, to be exact.

Two German scientists, Pierre Joseph Pelletier and Vogel, isolated what they referred to as a “yellow coloring-matter” from the rhizomes of the turmeric plant. They named it curcumin, which was derived from the word Curcuma, the genus name of the turmeric plant. The substance that they isolated was later found to be a mixture of turmeric oil and resin. 

In 1842, Vogel Jr managed to obtain a pure sample of curcumin; however, he did not identify the compound's chemical structure. Vogel’s work in 1842 inspired other scientists to study curcumin, and several worked to determine its chemical formula.

In 1910, Lampe and Milobedzka became the first scientists to describe the chemical formula of curcumin correctly. The chemical formula they described was diferuloylmethane, or 1,7-bis(4-hydroxy-3-methoxyphenyl)hepta-1,6-diene-3,5-dione. In 1913, Lampe and Milobedzka were able to synthesize curcumin. 

Another scientist who contributed to our understanding of curcumin is K. R. Srinivasan, who conducted a chromatographic study of curcumin. During his study of curcumin, he was able to use chromatography to separate and quantify the components of curcumin. 

 

(turmeric powder, a major source of curcumin) 

Curcumin’s bioactivity

Although curcumin had been discovered in the early 19th century, researchers weren’t aware that it was bioactive until the mid-twentieth century. The researchers who identified its bioactivity were E. Schraufstätter and H. Bernt. 

In a paper published in 1949 in Nature, they found that curcumin is biologically active and has antibacterial properties. In particular, they found that curcumin is active against the following bacteria:

  • Taphylococcus aureus
  • Salmonella paratyphi 
  • Trichophyton gypseum 
  • Mycobacterium tuberculosis
  • Despite these findings, the scientific community was not excited about curcumin. From 1949 to 1969, researchers only published five papers on curcumin. However, in the 1970s, the scientific community renewed their interest in curcumin. 

    During this period, three independent groups discovered that curcumin has a diverse array of characteristics such as:

    • cholesterol-lowering  
    • anti-diabetic 
    • anti-inflammatory 
    • anti-oxidant

    These discoveries increased the scientific community’s interest in curcumin, and more scientists worked to identify other properties of curcumin. By June 2011, there were more than 400 articles on curcumin listed in the National Institutes of Health PubMed database. 

    The discoveries also increased government interest in turmeric, and according to Forbes, the US government spent $150 million in funding research into turmeric. 

    However, not all is golden where curcumin is concerned. 


    Research fraud

    The most significant blow to the credibility of a new wonder drug is the revelation of research fraud. It is a hundred times worse when the research fraud was perpetrated by one of the leading researchers in the field. 

    This is the position the curcumin community found itself in after it was revealed that Bharat Aggarwal had committed research fraud. 

    For a long time, Bharat Aggarwal had been a star in the curcumin community. He became famous because of his work in identifying whether curcumin could be used as a potential cancer treatment. He published multiple papers, founded his own company, Curry Pharmaceuticals, and was a professor at the University of Texas MD Anderson Cancer Center in Houston, Texas. 

    All this came crashing down in 2012 when academic whistleblowers notified the US Department of Health and Human Services' Office of Research Integrity of image manipulation in Aggarwal’s work. The Office of Research Integrity reached out to MD Anderson, prompting the officials at the school to review Aggarwal’s research. As a result of this review, 28 of Aggarwal’s papers were retracted, and he retired from MD Anderson. 

    Does this mean that all curcumin research is flawed?

    In light of Aggarwal’s actions, it’s tempting to view all curcumin research as flawed. 

    However, his actions do not delegitimize the work of other researchers who have made it their life’s goal to unravel the mysteries of curcumin. The work of these researchers can stand on their own. 

    What about the other issues with curcumin?

    One of the biggest stumbling blocks to widespread acceptance of curcumin is its low bioavailability. Bioavailability refers to the proportion of a substance that enters the circulation when it's introduced into the body and can have an effect on the body.

    Researchers believe that curcumin’s poor bioavailability is primarily caused by rapid metabolism, poor absorption, and rapid systemic elimination. Several measures have been proposed, and some implemented to improve the bioavailability of curcumin. 

    One of these methods is delivering curcumin as solid lipid nanoparticles (SLNs). This method has proven successful in increasing curcumin’s bioavailability. Studies have shown that curcumin was released from the nanoparticle preparate up to 12 hours after it was ingested. SLNs are also popular because they protect the curcumin from chemical degradation. 


    (using micelles can improve the bioavailability of curcumin) 


    Final thoughts on curcumin

    Curcumin is a compound with lots of potential and an ever-growing fanbase. We believe that we are only scratching the surface when it comes to fully understanding this compound. More research is needed to determine other potential benefits of curcumin. 


    This article is the first part of a series on curcumin. In the next part of the series, we’ll look at how curcumin interacts with the human body, particularly the immune system.