Powerful Periwinkles

Madagascar Periwinkle (Catharanthus, not Vinca)

I’m not certain who needed to poison dogs in ancient times, or when particular Mediterranean plants might have been brought into play for animal control, but the several European Periwinkles (Vinca) are part of a large family of plants, the Apocynaceae, a group that inherited the nickname Dogbane from their early association (apo = away, cyan = dog) with poisons. It is, indeed, a powerful group. In addition to Dogbane, the membership includes Rauwolfia serpentina (Indian snakeroot, an ancient medicinal plant from which chemists extracted the tranquilizing drug reserpine in 1952), Nerium oleander (a toxic South African shrub, common in Southern California landscapes), and Asclepias (the butterfly weeds that confer toxic protection to Monarch butterfly larvae.)

Vinca minor, the European twining vine called Periwinckle by Blackwell in her Curious Herbal (1737), citing text by Miller (1722) (image from Missouri BG copy, on line)

Periwinkles are not so-named because they have an eye, or wink at you; and the nomen has no reference to poisons. Joseph Miller (Botanicum Officinale, 1722) called two blue-flowered, European native plants by many names, most commonly Vinca, Pervinca, and Perriwinkle, names that come to us from the Latin pervincire, which is “twining” – referencing their somewhat twining, or binding habit. As to its virtues, he tells us: “This is a good vulnerary Plant, and of frequent Use in Wound-drinks, for Bruises, Contusions, inward Bleeding, and Wasting, Spitting of Blood, the Excess of the Catamenia (vaginal discharge), and the Fluor albus (the whites).” Periwinkles are commonly encountered garden plants, even classified as invasive in many areas around the world. One of the Periwinkles, Vinca minor, produces flowers of such a clear and predictable blue as to have given name to the color, periwinkle. They are well-known to Western gardeners.

Garden plant of Catharanthus roseus, Madagascar’s Periwinkle

The Madagascar Periwinkle (which doesn’t twine at all) was first brought to the attention of Europeans by Étienne de Flacourt, who mentioned the plant (which he called Tongue) in his Histoire de la grande isle de Madagascar (1658) and sent specimens to Paris. A pressed sample from 1715 is found in the herbarium of the notable botanist, Sébastien Vaillant, which makes it one of the earliest tropical plant specimens pressed and mounted for study. Flacourt’s plant was similar enough to Vincas (the European Periwinkles) he knew as to be given the scientific name Vinca rosea by botanists, which was codified by Linnaeus (1759). But the plants are not so similar; Scottish botanist George Don, recognizing significant differences between the European and African plants, established the separate genus Catharanthus in 1838. Recent studies confirm that Vinca and Catharanthus should be considered clearly separate genera.

A small planting of Catharanthus roseus in the Huntington Herb Garden

We imagine the Madagascan plant was adopted by sailors who claimed it suppressed appetites, but the Catharanthus was also later considered useful in treating diabetes as well as other issues (in fact, an extract trade-named Vin-qu-Lin was marketed in Great Britain for diabetes treatment). Though studies as early as 1926 demonstrated the plant has no effect on blood sugar levels, it was during testing (in the 1950s) for antidiabetic activity that a surprising toxicity brought the plant’s particular form of poisoning to the attention of Canadian scientist Robert Noble (brother to Clark Noble, who shared the Nobel Price for discovery of insulin with Charles Best and James Collip.) Test rats that died when given Catharanthus extract showed a significant drop in white blood cells and damage to bone marrow – a chance discovery that led to isolation of the alkaloid vincaleukoblastine. (search: R. L. Noble, C. T. Beer, and J. H. Cutts, 1958. “Role of Chance Observations in Chemotherapy: Vinca rosea,” Annals of the New York Academy of Sciences 76(3): 882-894; Jacalyn Duffin, 2000. “Poising the spindle: serendipity and discovery of the anti-tumour properties of the Vinca alkaloids.” Canadian Journal of Medical History 17: 287-308.)

From those beginnings, the initial important chemicals (vinblastine and vincristine) were discovered. Though easily extracted, chemical purification from plant tissue showed very low yield. At one point in the early 1960s, Ely Lilly scientists were only able to produce 28 grams of vinblastine from 15 tons of dry leaves (about two parts in a million – see Muriel LeRoux and Françoise Guéritte, 2017. Navelbene and Taxotere, History of Sciences, Elsevier).

Researchers did not give up. Indeed, the early Catharanthus alkaloids, so successfully employed in treating childhood leukemia, now constitute a host of compounds that are used in cancer treatment, all of which are synthesized through a range of processes developed specifically around the important work that first yielded results in 1958.

Tales of toxins from the Dogbane family that have become powerful medicines remind us cancers result from cells that multiply and grow in abnormal ways. The current state of science and treatment often involves targeted, controlled use of poisons to selectively kill out-of-control cells. Plant families known for their toxic properties have been an especially rich source for those medically-useful complex molecular poisons.

And, the Madagascar Periwinkle has taken on new life as a garden plant. In the last couple of decades, hybridizers have bred and selected a bold race of sturdy border and pot plants from available stock, sporting shiny foliage and large, bright-colored flowers. It is one of many remarkable plants from the otherworldly island flora of Madagascar.

Check Taxon for an article on evolution in the Vinca tribe: https://www.researchgate.net/profile/Ingrid_Koch/publication/301554193_Systematics_and_character_evolution_of_Vinceae_Apocynaceae/links/59b3ec75aca2728472d88b8c/Systematics-and-character-evolution-of-Vinceae-Apocynaceae.pdf

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