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Scientists look to Day of the Dead symbol to treat one of Mexico’s deadliest cancers

Known as the flower of the sun, the marigold is used to guide the souls of the deceased to the altars arranged by their loved ones on the Day of the Dead, but Mexican scientists have found that the flower has life-giving properties for those of us on this side of the grave.

MEXICO CITY (CN) — The marigold’s deep color and earthy aroma define Mexico’s Day of the Dead tradition, when the deceased return to their worldly homes to visit their loved ones who are still among the living. Pathways of vivid orange petals light the way from the front door to a family’s altar, where photos and favorite foods await the hungry souls of the dead. 

The symbols and rituals of Day of the Dead serve to blur the line between this life and whatever lies beyond, and to remind participants that said line is thinner than they may think. 

But modern science is starting to discover that the marigold has properties that could keep the living here a little longer before finally moving on. Researchers at Mexico’s National Polytechnic Institute (IPN) are looking into the flower’s ability to treat colon cancer, one of the country’s deadliest. 

“We have seen in the research that these plants have significant effects on gastrointestinal problems,” said Karen Magaly Soto, a postdoctoral research fellow at the the IPN’s Center for Research and Advanced Studies, or Cinvestav. Her research also examines the cancer-fighting properties of the castor oil plant, great mullein and a species of hibiscus known as roselle. 

“These plants have antioxidant compounds that help combat free radicals in the body that can cause harm,” Soto said.

Ground up marigold petals in an Erlenmeyer flask await testing at the Cinvestav laboratory in Querétaro, Mexico. (Cinvestav Querétaro)

The orange and yellow pigments in marigolds known as carotenoids are generous electron donors, which is the foundation of their antioxidant properties. But this ability also aids in another part of the process. 

When mixed into a metallic salt solution containing gold in a state of oxidation, the carotenoids promote the biosynthesis of gold nanoparticles. The antioxidants then adhere to the surface of the nanoparticles, which act as a medium for delivery to the affected cells. 

“In this way we get two different uses out of the compounds in these plants,” Soto said, adding this is not the only twofold application of materials in the process. “We have also observed that the gold nanoparticles themselves have anticarcinogenic properties that aid in fighting cancer cells.”

Colorectal cancer is one of the deadliest in Mexico and the world, due to the difficulty of early detection. It is the number one cause of cancer deaths among men aged 30 to 59 in the country, and the fourth most fatal for women of that age group, according to Mexico’s national statistics agency Inegi. It is also in the top five for men and women aged 60 and older. 

“People often confuse symptoms of colon cancer with other ailments, such as stress-induced colitis, and thus many don’t go to see a doctor, preferring to take a pill for it, and by the time the cancer is detected, it is already far advanced,” Soto said. 

Marigolds and other ornamental flowers adorn the cemetery for Day of the Dead celebrations in San Antonino Castillo Velasco, Oaxaca. (Cody Copeland/Courthouse News)

While science is only now starting to pinpoint the salubrious effects of flowers like marigolds, practitioners of traditional medicine in Mexico have long used the bright orange blooms to treat stomach conditions. 

“One of the main uses for marigolds, the flower of the sun, is for digestive issues, for everything from regular stomach aches to parasites,” said María Dolores Domínguez Romero, a folk healer who has practiced traditional medicine in Mexico City for more than 35 years. 

The most common way to prepare the flowers is in a tea, but it is also made into a tincture or applied topically as a poultice, depending on a patient’s needs. As a poultice, marigold extract is often combined with a plant called black physicnut — in Mexico, soldahuesos, "bone welder" — to treat broken bones. Domínguez has also used marigold petals to treat vaginal infections. 

The idea that science is starting to identify these qualities in the flower comes as no surprise to Domínguez, who has witnessed the curative effects of marigolds in her own practice. 

“No, it doesn’t surprise me at all, because we have used this flower for a long time,” she said. “The more we look into the qualities of these plants, the more medicinal uses we find they have.”

Soto’s research has yielded promising results so far. In the past year, her experiments have proven the cancer fighting qualities of the carotenoid-laden gold nanoparticles on both early and late-stage colon cancer cells. 

“We have seen a reduction in the viability of cancer cells when we add the treatment of the nanoparticles,” said Soto. The viability of early-stage cancer cells dropped by 80% in the studies they have conducted. 

The research is still in its early stages, however, with several years and rounds of testing to go before producing a medicine for colon cancer. They have only tested the treatment on isolated cancer cells, so details such as potential side effects, for example, will come in later experiments on live organisms. 

Marigolds for sale at Mexico City's Cuemanco flower and plant market. (Cody Copeland/Courthouse News)

For Alejandro Manzano Ramírez, head of Energy and Environmental Applications at Cinvestav, the benefit lies in finding more value-added applications for endemic plants that do not currently have many uses. While marigolds have been used in traditional medicine, such treatments are not widely used in Mexico. And the castor oil plant — the second most promising after marigolds in their study — is generally considered a weed that flourishes around creeks and irrigation ditches in the country. 

“Finding this added value in this largely ornamental plant is what is really valuable in this research,” said Manzano, highlighting the marigold’s potential for treating such a prolific killer as colon cancer. “This is one of the best examples of applied science finding a beneficial use for something from the natural world for the improvement of human health.”

Which is to say that the science, in its meticulously empirical way, is figuring out what Domínguez has intuited through her traditional use of the flower of the sun: “It is about cleaning and healing all that doesn’t belong to us.”

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