Abstract purple drapery cloth, Dark violet fabric background 1500 x 844
Photo credit: Adobe Stock Photos

So there we were, standing around a squatting Quechua Indian woman in Chinchero, high in the Andes of Peru. The women were weavers of Andean llama, alpaca and vicuña textiles, famous for their rich colors and wonderful designs.

As I watched them work their magic, I wondered, where did these vibrant pigments come from? I very quickly found out. The women created a small heap of grayscale-insects called cochineal (pronounced co-chee-kneel) that they had collected by hand from some of the local species of cactus.

One of the women crushed the pile of insects with a pestle. Another poured some lemon juice on the crushed bodies of these dead insects. We collectively gasped – the crushed powder turned red, then red-purple, and finally a beautiful blue-purple.

I felt the same sense of wonder as I felt in elementary school when the teacher demonstrated the litmus test. But beyond that, all of us watching felt a sense that we just witnessed a very complicated experiment carried out not by medical students but rather by people who are one with their environment – living its most intimate secrets even if they didn’t understand the chemistry.

How on earth did they figure this out?

As members of generation X or Y would say: AWESOME! How did the Quechua stumble on the idea of crushing gray cochineal insects in order to produce carminic acid and adding the calcium citrate in lemon juice would render the powder into a living purple pigment (also called carmine blue)?

Of course there was no use asking the women. For them chemistry is not a laboratory exercise; it is as obvious as knowing that the sun comes up in the morning and sets in the evening. It is simply part of their day-ti-day life.

The surprising role of purple in history

As early as 3000 years ago, the ancient Phoenicians made three major discoveries:

  • They gave us the alphabet we are using today.
  • They discovered that by heating silicon oxide, found in unlimited quantities in the sands of the Mediterranean beaches, they could make glass.
  • And, by extracting the secretions of the seashell Bolinus brandaris (also called Murex brandaris) found on the beaches of the eastern Mediterranean they could make a highly-prized purple dye that did not fade with time but rather increased in brilliance with exposure to air and sunlight.

The dye was called Tyrian Purple, after the Phoenician port city of Tyre. They also extracted another dye, Royal Blue, from a closely related species.

Being seafarers and famous traders, (or infamous, as the Greeks and Romans loved to point out), they sold these pigments and cloth and silk dyed with them all around the known ancient world from Egypt to Mesopotamia and to Greece and Rome.

The process of extraction was tedious and inefficient: thousands of Murex shells were required for dying one Roman toga. They Phoenicians demanded a very high price for these goods. The fabulous profits led to a resentment against them. The Phoenicians were considered as gougers and thieves. Now we know better, of course, the traders were simply reacting to the reality of supply and demand: they had, after all, cornered the market.

Of Kings and Emperors

The Emperor Justinian in all of his purple glory

Because the purple stuff was so expensive, only kings and emperors could afford it. They allowed senators to have togas with a stripe of purple, but that was it.

Commoners could wear white, or earth tones like brown or green. In fact, sumptuary laws were passed that regulated who could wear what. These laws were ostensibly designed to avoid conspicuous consumption; in reality, they fixed the demarcation between the aristocracy and the rest of us (assuming, dear reader, that you are not an aristocrat). As a consequence (not completely unintended), they also limited the demand for these sumptuous dresses–keeping the price more affordable for them.

After the sack of Constantinople in 1204 by the crusaders who were supposed to liberate Jerusalem (and not plunder the capital of the Christian Byzantine Empire), the impoverished Byzantine emperors could not afford the glorious purple dye anymore.

Later, medieval kings and fabulously rich Popes (who weren’t sworn to poverty at the start of their ecclesiastical careers) adorned themselves with Tyrian purple dresses. The Church also controlled the message by paying its favorite artists de jour quite handsomely to tell the stories of the Bible through art. So only the artists close to the trough could afford the brilliant purple dye. And the message? Only the VIPs, such as Jesus, Mary, and some favorite kings merited Tyrian Purple.

And so it went until the 18th century and the age of enlightenment, when liberal and democratic ideals swept away the symbols of Church and State hierarchy, and chemistry began producing brilliant pigments affordable by the new middle class. But that isn’t the end of the story.

Pigments in medicine

With the democratizing effect of chemistry-for-the-masses came another revolution: the Biology Revolution. The microscope allowed scientists to view cells for the first time. The electron microscope allowed them to see the innards of the cell. Pathologists are able to stain tissues, depending on their surface charge, with either a blue dye (hematoxylin) or a red one (eosin). And to increase the staining specificity beyond just surface charges, researchers developed antibodies to specific cell types, like lymphocytes or muscle cells or neurons, and bound them chemically to various dyes. Now they could visualize exactly how the heart muscle is organized, or how one lymphocyte type differs from another, or how neurons are organized in the brain.

But as important as this pigment revolution was, it still had a major shortcoming: it showed the cells as static objects. And, in biology, nothing is static. Cells move within tissues and all around the body. Inside the cells, there is a constant flow of proteins and organelles busily performing their duties.

For many years, researchers could only speculate on what’s happening inside the cell, using clues and speculation. But then a quantum jump occurred in the development of pigments that made tracking of cell components inside the cell possible.

The first one was a green fluorescent protein (GFP) obtained from a jellyfish. This discovery spawned such a revolution in cell biology and medicine that its discoverers, Martin Chalfie, Osamu Shimomura and Roger Y. Tsien were awarded the Nobel Prize in Physiology and Medicine in 2008.

Here are some short quotes from the Nobel committee:

“To obtain such knowledge (of the dynamic behavior of cells), new experimental and conceptual tools were required. Now, at the beginning of the 21st century, we are witnessing the rapid development of such tools based on the green fluorescent protein (GFP) from the jellyfish Aequorea victoria, its siblings from other organisms and engineered variants of members of the “GFP family” of proteins.

Indeed, no other recent discovery has had such a large impact on how experiments are carried out and interpreted in the biological sciences, as witnessed by the appearance of more than 20,000 publications involving GFP since 1992”.

To close the loop, a paper published in the May 2008 issue of Genetics announced the discovery of a new Purple Fluorescent Protein. Now we can track simultaneously many proteins and organelles as they course through the cell; some staining green, some blue, some red, and yes –some staining brilliant, majestic purple; a veritable ballet in dazzling colors.

Purple: metaphor for the struggle between the haves and have-nots

The history of the color purple goes beyond amazing; it is a metaphor for the eternal struggle between the haves and have-nots. Originally the pigment was so expensive so as to be afforded by kings, emperors, and the church hierarchy. These powerful people passed laws ostensibly to prevent conspicuous consumption, but in reality, such sumptuary laws were designed to restrict competition for the pigment, ensuring lower prices for themselves.

The dawn of the enlightenment and the empirical science of chemistry that it gave birth to made the pigment purple affordable to the masses. These dual triumphs of democratization and technology resulted in the totally unforeseen explosion of knowledge applied to the understanding of our biology and development of modern medicine. This was quite a journey for the color purple–from the service of emperors and Popes to the service of all humanity. An exhilarating journey indeed.

Is there a lesson here for our times?

This post was originally published on 5/5/11. It has been reviewed and updated by the author.

Dov Michaeli, MD, PhD
Dov Michaeli, MD, PhD loves to write about the brain and human behavior as well as translate complicated basic science concepts into entertainment for the rest of us. He was a professor at the University of California San Francisco before leaving to enter the world of biotech. He served as the Chief Medical Officer of biotech companies, including Aphton Corporation. He also founded and served as the CEO of Madah Medica, an early stage biotech company developing products to improve post-surgical pain control. He is now retired and enjoys working out, following the stock market, travelling the world, and, of course, writing for TDWI.

Comments are closed.