The Triumph of Seeds (26 page)

To the public, Markov’s murder made the fantasy world of James Bond a sudden reality—in the same year,
The Spy Who Loved Me
became one of the highest-grossing British films of all time. To investigators, the case left two glaring questions unresolved: Who was the man with the umbrella, and—something British Intelligence and the CIA were keen to find out—what kind of poison could kill someone with such a tiny dose? The first question remains
unanswered. Soviet defectors later confirmed that the KGB provided the umbrella and pellets to the Bulgarian government, but critical details remain hazy, and no one has ever been
arrested for the crime. Resolving the poison puzzle, however, drew a unanimous opinion from an international team of pathologists and intelligence experts. They arrived at their conclusion after weeks of careful forensic analysis, with contributions from pharmacologists, organic chemists, and one 200-pound (90 kilogram) pig.

The first challenge lay in determining exactly how much poison had entered Markov’s body. Measuring less than a twentieth of an inch (1.5 millimeters) in diameter, the pellet removed from his thigh contained two carefully drilled holes with a total capacity estimated at sixteen millionths of an ounce (450 micrograms). (To put that into perspective, press a ballpoint pen lightly onto a piece of paper. The tiny ink-speck it leaves behind is the size of the pellet—seeing the holes would require a microscope.) Simply knowing that dosage narrowed the possibilities to a handful of the world’s deadliest compounds. The team immediately ruled out bacterial agents like botulin, diphtheria, or tetanus, all of which would have triggered telltale symptoms or immune reactions. Radioactive isotopes of plutonium and polonium didn’t fit the bill, either—they can be fatal, but their victims take a much longer time to die. Arsenic, thallium, and the nerve gas sarin weren’t nearly powerful enough, and while cobra venom might have produced a similar reaction, it would have required at least twice the dose. Only one group of poisons could have caused Markov’s deadly combination of symptoms so quickly: the poisons found in seeds.

For thousands of years, executioners and assassins have turned to seeds in search of ways to do in their victims. The plant kingdom in general offers a vast selection of toxins, but seeds offer the advantages of easy storage and high potency. They’re the most poisonous part of the hemlock plant that killed Socrates, as well as the white hellebore suspected of knocking off Alexander the Great. Strychnine trees bear seeds nasty enough to earn the nickname “vomit
buttons,” and their poison has figured in the murders of everyone from a Turkish president to the young women targeted by Victorian serial killer Dr. Thomas Cream. In Madagascar and Southeast Asia, hundreds of deaths every year are attributed to the nuts of a salt-marsh species known simply as the “suicide tree.” The murderous potential of seeds was not lost on William Shakespeare when he needed a convincing concoction to pour into the ear of Hamlet’s father. Most scholars agree that his “leperous distilment” must have been an extract of henbane seeds, just as mystery fans know that Arthur Conan Doyle modeled the “devil’s foot” that nearly killed Holmes and Watson on the deadly calabar bean of West Africa. These plants all rely on alkaloids to provide their poisons, but investigators in the Markov case quickly narrowed in on a toxin more unusual, more deadly, and more difficult to trace. It’s something the Castrol Motor Oil Corporation inadvertently hit on the head with their company motto: “It’s More Than Just Oil.”

Castrol got its start, and its name, by formulating engine oils from the seeds of the castor bean plant, a shrubby African perennial related to spurges. Castor beans store most of their energy as a thick oil that boasts a rare ability to maintain viscosity at extreme temperatures. (Although Castrol now makes a range of petroleum-based products, bean oil remains the lubricant of choice for high-performance racecars.) But the beans contain something more—a peculiar storage protein called
ricin
. Chemists know ricin for the odd, double-chain structure of its molecules. In a germinating seed, those molecules break down like any other storage protein, providing nitrogen, carbon, and sulfur to fuel rapid growth. But inside an animal—or a Bulgarian dissident—their odd structure gives them the ability to penetrate and destroy living cells. One chain pierces the surface while the other detaches inside and wreaks havoc on the ribosomes—small particles essential for translating the
cell’s genetic code into action. (In biochemistry, this puts ricin into a group called “ribosome inactivating proteins,” known by the fitting abbreviation RIPs.) Dispersed through the bloodstream, ricin sets off a wave of cell death so unstoppable that even scientific journals describe it with something like awe: “one of the most lethal substances known,” “one of the most fascinating poisons,” or simply, “exquisitely toxic.” As if to add insult to injury, castor beans also contain a potent allergen, so that, while dying, one can reasonably expect the further indignities of violent sneezing, a runny nose, and a painful rash.

F
IGURE
11.1.  Castor bean (
Ricinus communis
). Beautiful enough to be sought after by jewelry makers, the mottled seeds of the castor plant contain a valuable oil as well as ricin, one of the world’s deadliest poisons. The spiny, protective capsule bursts upon drying, hurling individual beans as far as thirty-five feet (eleven meters) from the mother plant. I
LLUSTRATION
© 2014
BY
S
UZANNE
O
LIVE
.

Theoretically, the pellet from Markov’s leg could have held enough ricin to kill every cell in his body many times over. But investigators had precious little evidence to go on. He died too quickly for any recognizable antibodies to develop, and even though ricin
was known to be deadly, documented poisonings were extremely rare, and there was no clinical
description of the symptoms. So the pathologists decided to stage a test. They obtained their own batch of castor beans, refined a dose of ricin, and injected it into an unsuspecting pig. Within twenty-six hours the pig died in the same horrible manner as Markov. “The . . . animal defense people would be horrified,” a doctor on the case observed, but it emerged later that Bulgarian scientists had been even more brutal. They had fine-tuned the dose destined for Markov after testing a smaller amount on a prison inmate, who survived. When they worked out a quantity that would reliably kill a full-grown horse, they
put the plan into action.

Georgi Markov’s murder shone a bright media spotlight on the homicidal potential of seeds. Criminal elements took note, and ricin continues to surface as a bioterror weapon of choice. Anonymous letters tainted with it have been sent to the White House, the US Congress, the mayor of New York, and various other government offices in recent years, sometimes closing down mail-processing facilities for weeks. When London police raided a suspected Al Qaeda cell in 2003, they confiscated twenty-two castor beans, a coffee grinder, and enough chemistry equipment to perform a simple extraction. (Their haul also included quantities of apple seeds and ground cherry pits, both of which contain traces of cyanide.) Seed poisons retain their appeal because they are not only potent, but also readily available. When I wanted some castor beans of my own, searching the Internet quickly revealed dozens of varieties openly and legally for sale. People still grow them for their oil and as an ornamental, and the plant has become a common roadside weed throughout the tropics. With a few clicks and a credit card, I had a batch delivered to my door—beautiful, glossy things the size of a thumbnail, their smooth coats mottled with burgundy swirls. They come in shades from umber to pink and often show up in beaded necklaces, earrings, and bracelets. In fact, bright “warning” colors make a number of toxic seeds fashionable in the bead industry, from rosary pea to coral bean, horse-eyes, and various cycads. But castor
beans and other poisonous seeds remain common for another reason. It’s a principle that underlies the modern pharmaceutical industry, but it was also expressed perfectly in the nineteenth century by philosopher Friedrich Nietzsche and by children’s author Lewis Carroll.

People remember Nietzsche primarily for his views on religion and morality, but he also coined the maxim, “What does not kill me, makes me stronger.” He meant it as a general comment on life, but this phrase also describes a truth about seed poisons. Lewis Carroll made the same point when his most famous character, Alice, cautioned against “drinking much” from a bottle marked “poison.” By including the word “much,” Carroll implied that drinking “a little” from such a bottle wouldn’t be disagreeable at all, and might even do a person some good. Time and again, that is exactly the case with poisonous seeds. In doses short of deadly, many of those same toxins can be used medicinally—vital treatments for some of the world’s most serious diseases. For Alice, the bottle in question contained not poison but a shrinking potion, preparation for the next escapade in her continuing adventures in Wonderland. Nietzsche’s case seems more significant. He wrote his famed dictum shortly before suffering a mental collapse that scholars now interpret as the onset of brain cancer, one of the illnesses now being treated with seed extracts.

In the language of poisons, ricin is known as a
cytotoxin
—a cell killer. Along with similar compounds from the seeds of mistletoe, soapwort, and rosary pea, it shows great promise for assassinations at a much smaller scale: the targeted killing of cancer cells. By attaching these “RIP” proteins to the antibodies fighting a tumor, researchers have successfully attacked cancer in laboratory tests, clinical trials, and, in the case of mistletoe extracts, tens of thousands of patients. The challenge, of course, is twofold: finding the right dosage, and making sure the poisons don’t diffuse to other parts of the body.

Whether or not ricin will become a widespread cancer treatment remains to be seen. If it does, it will join a long list of other seed and plant-based curatives dating back to the origins of medicine itself.
Wild primates from chimpanzees to capuchin monkeys regularly treat themselves with botanicals, choosing specific seeds, leaves, and bark known to have healing properties. When researchers in the Central African Republic observed a gorilla plucking junglesop seeds from the dung of elephants, no one was surprised to learn those seeds contained potent alkaloids, and that local healers prescribed them (as well as the plant’s leaves and bark) as a treatment for everything from sore feet to stomach problems. This pattern repeats itself throughout the tropics: primates shopping around the apothecary of the rainforest to help rid themselves of parasites, or relieve the pain of injury and disease. Few anthropologists doubt that our own ancestors did the same thing, and in fact a study in the Amazon found that hunter-gatherers used a list of plants that closely mirrored those preferred by monkeys. These ancient habits not only lie at the heart of traditional medicines, they continue to spur the development of new drugs.
*

To gauge the importance of seeds in modern medicine, I contacted David Newman, an expert on drug development at the National Institutes of Health. He told me that until the mid-twentieth century, a huge proportion of medications came from plants, many of them from compounds found in seeds. Even today, in an era of synthetics, antibiotics, and gene therapy, nearly 5 percent of all new drugs approved for use in the United States come directly from botanical extractions. In Europe, the number is higher. A recent attempt to summarize medicinal research on seeds quickly ran to more than 1,200 pages, with contributions from 300 scientists
working in labs around the world. Seed extracts play a role in treatments for everything from Parkinson’s disease (vetch and velvet bean) to HIV (blackbean, pokeweed), Alzheimer’s disease (calabar bean), hepatitis (milk thistle), varicose veins (horse chestnut), psoriasis (bishop’s flower), and cardiac arrest (climbing oleander). Like ricin, many of these compounds serve double duty as both poison and cure, and it turns out that another well-known example happens to come from the seeds of the
almendro
tree.

F
resh from their shells,
almendro
seeds look quite a bit like the almonds that give them their Spanish name, but stretched thin and polished to a dark sheen. The first time I roasted a batch, I immediately noticed the sweet, spicy smell that had brought them to the attention of perfumers in the nineteenth century. Known by the trade name “tonka beans,” the fragrant seeds also became popular as a vanilla substitute and as a flavoring for pipe tobacco and spiced rum. Commercial varieties came from an Amazonian
almendro
closely related to the ones I studied in Central America. They spawned an industry that was briefly lucrative enough to warrant huge tonka bean plantations in Nigeria and the West Indies. A French chemist isolated the active ingredient and called it
coumarin
in honor of an Indian name for the tree,
cumarú
. Things went along cheerfully for tonka bean farmers until the 1940s, when researchers discovered that coumarin was toxic to liver cells. Regulators warned that even small amounts could be harmful, and soon banned it altogether as a food additive. Needless to say, consumption of tonka beans has since plummeted, though daring chefs continue to add a few shavings to specialty chocolates, ice creams, and other desserts.