In 130 BC, a ship fashioned from the wood of walnut trees and bulging with medicines and Syrian glassware sank off the coast of Tuscany, Italy.
Archaeologists found its precious load 20 years ago and now, for the first time, archaeobotanists have been able to examine and analyse pills that were prepared by the physicians of ancient Greece.
DNA analyses show that each millennia-old tablet is a mixture of more than 10 different plant extracts, from hibiscus to celery.
"For the first time, we have physical evidence of what we have in writing from the ancient Greek physicians Dioscorides and Galen," says Alain Touwaide of the Smithsonian Institution's National Museum of Natural History in Washington DC.
The box of pills was discovered on the wreck in 1989, with much of the medicine still completely dry, according to Robert Fleischer of the Smithsonian's National Zoological Park, also in Washington DC.
Fleischer analysed DNA fragments in two of the pills and compared the sequences to the GenBank genetic database maintained by the US National Institutes of Health. He was able to identify carrot, radish, celery, wild onion, oak, cabbage, alfalfa and yarrow. He also found hibiscus extract, probably imported from east Asia or the lands of present-day India or Ethiopia.
"Most of these plants are known to have been used by the ancients to treat sick people," says Fleischer.
Yarrow staunched the flow of blood from wounds, and Pedanius Dioscorides, a physician and pharmacologist in Rome in the first century AD, described the carrot as a panacea for a number of problems.
"They say that reptiles do not harm people who have taken it in advance; it also aids conception," he wrote around 60 AD.