Easily confused with :
Greater Periwinkle (Vinca major) but that has slightly wider (and slightly hairy - with hairs on the edge of the leaf, which Lesser Periwinkle lacks) leaves and has teeth on the sepals. There is also an
Intermediate Periwinkle (Vinca difformis) to further obfuscate identification (but luckily that is not extant where these photographs were taken).
Periwinkles have uniquely identifiable characteristics
Distinguishing Feature : The five propeller-like, large, blue-violet petals.
INDOLE ALKALOIDS FOUND WITHIN VINCA MINOR
These are just a small variety of the differing indole alkaloids found within Vinca minor, some much more abundant than others.
Eburnamine (aka Vincamone, Vinburnine or Eburnal) and Vincamine are structurally similar. Eburnamenine is found within Hunteria eburnea, from where it derives its name.
Vincamine is used pharmaceutically as a drug to dilate the veins in the brain, thereby increasing the blood flow to the brain. It also acts as a nootropic (a cognitive enhancer), improving memory. Found in the leaves, it comprises between 25% and 65% by weight of the indole alkaloids found within the plant. A man-made derivative of Vincamine with just one extra carbon atom after the -O- group called Vinpocetine is used similarly to Eburnamenine.
Strictamine (aka Vincamidin(e), and Picrinin(e) are structurally similar, having some resemblance to another indole alkaloid, Strychnine. Picrinine is Strictamine with an additional epoxy bridge. Ingestion of Strictamine depresses the CNS; the LD50 for a mouse is 160mg/kg body weight.
Picrinine is also found in other members of the Periwinkle Family (Apocynaceae).
In the Dita Bark tree (Alstonia scholaris) (which is non-native to the UK) an astonishing cage-monoterpene indole alkaloid, Scholarisine A, has been found, which is alas not present in the Vinca Genera, and drawn just for interest.
The only difference between these two is the extra methyl group on the nitrogen atom of
Minovine. Both are indole alkaloids with aspidospemane structure. They both differ from all the previous compounds in that the extra rings are attached to the top-side the indole group, rather than tagged on below it.
Vincadifformine exhibits anti-spasmodial properties, in that it inhibits smooth muscle contractions, particularly in the gastrointestinal tract.
'PSEUDO-DIMERS' of VINCADIFFORMINE & MINOVINE
This set of alkaloids are based on dimers and near-dimers of the
Vincadifformine and Minovine types, shown above. They are founded on the two multi-ring compounds catharanthine with a nine-membered ring (upper left half) and vindoline (lower right half) which are connected by a single bridge.
Vincristine was first found in
Rosy Periwinkle (Vinca rosea), a plant not native to the UK but which is grown commercially to extract these and similar vinca alkaloids. It is a pharmaceutical and one of the most commonly administered anti-cancer drugs used in 'chemotherapy'. It is active against Hogkin's Lymphoma disease, Kaposi's sarcoma, breast and testicular cancer and various other cancers and lymphomas. Vincristine also possesses some immuno-suppressant effects. Vincristine inhibits cell division by binding to tubulin dimers, which disrupts mitosis, or cell division. Naturally, this affects all cell division within the body, and not just those cells that are cancerous, so side effects are inevitable. One of the first side effects to develop is neuropathy, which can cause a condition referred to as 'foot-drop' because they also inhibit the axonal microtubules in neurons. Hair-loss is another characteristic of these, and most other, anti-cancer drugs. It is almost always fatal if accidentally (or otherwise) injected into the spinal cord; paralysis and death the inevitable result. These dimericindole alkaloids (and their semi-synthetic derivatives vindesine and vinorelbine) are 10 times more potent at blocking mitotic cell division than is Colchicine.
Vinblastine is a chemical analogue of Vincristine with very similar pharmacological properties and uses.
Vindesine is used pharmacologically in a similar manner to the above two chemotherapy agents. Melanoma and Lung cancer may be additional conditions for witch it is a useful treatment.
Vinorelbine (not shown) is the forth Vinca-type alkaloid that is used pharmaceutically against various cancers; it is not a natural product, but a semi-synthesized derivative.
The striking property of all these various secondary metabolites found in Lesser Periwinkle is that almost all contain two Nitrogen atoms separated by 3 carbon atoms, as shown: N-C-C-C-N (apart from those with a broken ring where the two nitrogen atoms are separated by 4 carbon atoms, as shown: N-C-C-C-C-N. Another exception is
Scholarisine A [but that is not found in Periwinkles] where there are only 2 carbon atoms separating the 2 nitrogen atons, as shown: N-C-C-N).
SUB-UNITS of the 'PSEUDO-DIMERS'
Vindolene (not a German window cleaning product) are the two basic sub-units upon which Vincristine, Vincadifformine and Vindesine are based. [Your author can find no evidence that Lesser Periwinkle actually contains Catharanthine, and almost certainly doesn't]. [Most articles draw catharanthine from a totally differing topological perspective (to avoid drawing a long bold line connecting bottom to top); however, for the purposes of illustration and comparison, your author has drawn it in the same perspective as Vincristine. Both ways are chemically correct; there is no wrong way or a right way to draw it schematically, as long as the topology is identical]. Catharinthine is found in rosy-pink
Madagascar Periwinkle (Catharanthus roseus) which is not found growing in the wild in the UK, but numerous cultivars exist which may be found in gardens.
Vascicine (aka Peganine) also occurs in Vinca Minor and in Goat's-Rue and is used pharmaceutically as a cerebral stimulant.