DNA extracted from 2,000-year-old plants recovered from an Italian shipwreck could offer scientists the key to new medicines.
Carrots, parsley and wild onions were among the samples preserved in clay pills on board the merchant trading vessel that sank around 120 BC. It's believed the plants were used by doctors to treat intestinal disorders among the ship's crew.
Such remedies are described in ancient Greek texts, but this is the first time the medicines themselves have been discovered.
"Medicinal plants have been identified before, but not a compound medicine, so this is really something new," says Alain Touwaide, director of the Institute for the Preservation of Medical Traditions, which has the world's largest digital database of medical manuscripts.
Prof Touwaide is working with scientists at the Smithsonian's Natural History Museum, who carried out the DNA analysis. They discovered traces of carrot, parsley, alfalfa, celery, wild onion, radish, yarrow and hibiscus contained in the ancient pills.
The pills, which researchers believe were diluted with vinegar or water to make them easier to ingest, were preserved inside tin boxes and were the size of coins.
"I was always wondering if the texts were only theoretical notions without practical application," he says. "Now we know they were applied."
In May, Prof Touwaide's conclusions, based on the DNA findings and his own study of medicinal texts, will be formally presented to an international gathering of archaeologists, historians of medicines and other experts in Rome.
"What is remarkable is that we have written evidence [from the ancient Greeks] of what plants were used for which disorders," says Alisa Machalek, a science writer for the National Institutes of Health, one of the world's leading research centres.
"This research is interesting, especially for medical historians, because it confirms that what we eat affects our bodies."
Prof Touwaide hopes his research will help to develop modern treatments.
"We extract the information from these texts so that scientists can see if they can make shortcuts to pharmacological discoveries," he says.
"We re-purpose ancient medical information and jump from the past to the future."
For instance, the Roman statesman Cato recommended eating broccoli to stay healthy and Prof Touwaide has found references to the Greek physician Galen using it in the 2nd Century AD to treat intestinal cancer.
Prof Touwaide says modern research is now under way to isolate a compound found in broccoli that may be a source for the treatment of cancer today.
"This is a huge field in chemistry and pharmaceutical science," says Ms Machalek.
"Native Americans chewed on willow bark to relieve pain - now we pop open a bottle and chew on aspirin which contains similar compounds. Taxol, a cancer medicine, is derived from the bark of the Pacific Yew."
Early Greek writings
To understand the significance of the plants contained in the 2,000-year-old pills, Prof Touwaide studied a number of medical works, including the Hippocratic Collection.
The collection is one of the earliest sets of Greek writings still in existence and is attributed to Hippocrates, considered to be the founder of Western medicine.
He cross-referenced those findings with other works, such as the Encyclopaedia of Natural Substances, written in the 1st Century AD by Dioscorides.
Dioscorides noted that "the large onion is sharper than the round onion. All onions are pungent and apt to cause flatulence. They stimulate the appetite. They are thirst making. They cleanse the bowel."
"They are good for opening outlets for various secretions as well as haemorrhoids, and they are used as suppositories, pilled and dipped in olive oil," Dioscorides wrote.
A significant percentage of commercial medicines are derived from natural sources, but the active compound has been isolated, concentrated, standardised and packaged into measured doses.
The shift toward synthetic chemical medicines occurred in the 20th Century, but according to Mark Blumenthal, the founder and executive director of the American Botanical Council, there is renewed interest in the medicinal benefits of natural foods - including those found in the pills.
"A lot of ancient plants have modern functions," he says.
"There's a lot of marketing going on for so-called functional foods - foods with high levels of antioxidants, for improving the cardiovascular system or reducing the risk of cancer.
"Hibiscus tea is growing in popularity and research shows that it lowers blood pressure. Garlic and to some degree onions, continue to have cardiovascular benefits and reduce the build-up of plaque."
But Prof Touwaide says the traditional cures based on plants and minerals are in danger of being forgotten.
He says part of the problem is that too few people now study classical Greek, Latin or Arabic and there are not enough experts to interpret the original texts.
Prof Touwaide is proficient in 12 languages and has spent years collecting his library of 15,000 books on plants and their uses.
He believes such ancient knowledge should become protected by Unesco as part of the world's heritage.
O'Brien, Jane. 2011. "Plants found in ancient pills offer medicinal insight". BBC News. Posted: April 27, 2011. Available online: http://www.bbc.co.uk/news/world-us-canada-13190376