October 31, 2014

The importance of plant identification - Part 3

Hubert Marceau - Popularization

Figure 1: S. lycopersicum (Source)
Have you ever heard of Tomtatoes? It is tomato plant, Solanum lycopersicum (Figure 1), graft on a potato plant, Solanum tuberosum. This gives a plant that bear edible roots (tubers to be more precise) and fruits. Why not them start using all the rest and make a salad with the leaves? Some of you may have already spotted the bad idea in this last sentence, for the other, know that the tomato plant, just like tobacco (Nicotiana tabacum), the pepper (Capsicum annuum), the datura (Datura stramonium), the deadly nighshade (Atropa belladona)... are part of the Solanaceae family and produce toxics alkaloids. Generally, potatoes contains a negligible amount of solanine (and others toxic glycoalkaloids) [Edit: /u/thalassa made me notice that tomato leaves don't containt solanine but tomatine, a non toxic analog.] , but can sometime produce more when they are in bad storage condition. There are known potatoe poisoning case, but they are very uncommon. Basically, you must not eat the tuber when they are green.

This post is not directly related to botanical identification, but I wanted to give you examples of some preconception that we may have on the security of plants. I will be using the toxicity of some of them considered edible. In the case of common foodstuff, the toxic effect often appears after over-consumption, a nutritional imbalance, or a predisposed condition.

Our first case is carambolas, Averrhoa carambola (Figure 2). The star fruit is known to be toxic to people with kidneys troubles since the 80's. Scientist have long though that the toxic compound was oxalic acid. It is only in 2013 that the real culprit was identified: caramboxin. This compound cause hiccups, neurologic and gastric problems, and confusion. People with renal problems are particularly sensitive because the kidney can't filter the product, but there have been reported cases of intoxication in healthy peoples after large consumption of the fruit. In these case, oxalic acid also had a toxic effect since it is dangerous in large quantity.

Figure 2: A. carambola (Source)
Since we are on the subject of oxalic acid, I would like to point out that rhubarb, Rheum rhabarbarum, also contains a lot of this compound.

Let's continue with a case a little bit more known: nutmeg (Myristica fragrans). This spice contains myristicin and elemicin who are both considered to be psychotropic. While it has never been proven, we suppose that the two are turn by the body into MMDA and TMA, two close derivative of MDMA (also know as Ecstasy). Due to their hallucinogenic properties, nutmeg intoxication are usually voluntary but there are known involuntary case. Involuntary case are pretty rare since they require a large quantity: 5 to 10 g, which correspond to a complete nut.

Figure 3: H. alpinum (Source)
Finally, lets talk about Christopher McCandless, the late protagoniste of the movie Into the Wild. Christopher was a young american who, at the age of 24, decided to live the complete summer of 1992 in the Alaska wilderness to live by himself off the land. He was found dead 4 months later. It was believe for a long time that the cause of his death was a confusion between two wild plants that he was using for food: Hedysarum alpinum (edible, figure 3) and Hedysarum boreale spp. mackenziei (toxic, figure 4). However, a more complete analysis of the case tend to demonstrate that he died of lathyrism. The seed of H. alpinum contains oxalyldiaminopropionic acid (ODAP). This amino acid is generally non-toxic, but when consumed in large quantity and the body is stressed, undernourished or starving, it create a degeneration of motors neurons and paralysis. This would have effectively stopped Christopher from being able to forage, eventually starving him to death. The presence of this compound in the seed of H. alpinum was confirmed in 2014. Christopher had no way of knowing the toxicity of the plant.
Figure 3H. boreale (Source)

In most case, the toxic compounds are unknown or only suspected. In others, uncommon interactions cause dangerous effects. Sometimes, a compounds that we think to be the cause of a biological activity is in fact hiding another (we call this internally the "Vakhtang effect"). All these situation demonstrate that the toxicity of plants is often not well understood. For most case the only security that we have is still the same that our ancestors had: if you didn't die when you ate it that mean that I can eat it.

October 24, 2014

The importance of plant identification - Part 2

Hubert Marceau - Popularization

Figure 1: A. ursinum (source)
In 2004, in the canton of Neufchâtel, Switzerland, clients from a restaurant who ordered fish with a bear's garlic sauce, Allium ursinum (Figure 1), went on a painful adventure. Shortly after eating they started to have severe gastrointestinal troubles. After analysis, it was found that the sauce contained colchicine, a toxic alkaloid. This compound is produced by the meadow saffron, Colchicum autumnale (Figure 2), a plant that looks pretty much like bear's garlic and often grows in the same environment. Furthermore, to be edilble, bear's garlic needs to be harvested in the early spring when the first leaves appear and before bolting. As we already saw in the last post, the use of only the leaves for botanical identification can sometimes be tricky. In this particular case the best way to be sure of the identity of the garlic and the saffron, and to a lesser extent the lily-of-the-valley, Convallaria majalis (seen on Figure 3), is to use our nose. Garlic smells like garlic, the others ones don't smell anything. Unfortunately, the smell has a tendency to stick to the finger and interfere with the identification, even more so when we harvest a big batch. This leads to an easy mix-up. This situation is not necessarily common, but can be fatal.

Figure 2: C. automnale (source)
This situation is a good representation of the hazards that can cause a misidentification. As I already have demonstrated, many plants can look the same and be confused with one another. In North America there is also a wild garlic, ramp, Allium tricoccum (Figure 4), that can also be confused with other plants in their juvenile form: Clintonia borealis (edible, young leaves only), Convallaria majalis (toxic), Cypripedium acaule (dubious edibility) and many more.

Figure 3: Comparaison of the leaves (source)
Figure 4: A. tricoccum (source)


Figure 5: H. maximum (source)
Figure 6: H. mantegazzianum (source)
Another interesting case, albeit less common, is the Cow Parsnip, Heracleum maximum (Figure 5). America's First Nations ate the stems of this plant like a legume, and today it is still considered edible (its consumption is marginal though). This is an interesting case due to its great ressemblance to its cousin: the Giant Hogweed, Heracleum mantegazzianum (Figure 6). The later has the disagreable properties of causing serious burns when we enter in contact with any part of the plant. If you enter in contact with the plant, hide the affected part from the sun or any strong light during at least 1 to 2 months. By experience, even with this precaution, it is possible that the affected skin turn a bit darker, but, at least, it won't cause blisters. A misidentification can therefore have serious consequences. It is important to note that Cow Parsnip can have the same effect on sensitive people, but the latter is generally considered safe if peeled. Sensitive people can also have the same problems when touching limes or other plants: it is called phytophotodermatitis.

Finally, here is a very special case. To keep with the tradition of the last post, I will ask you to check the two following pictures and to keep an eye out for what could differentiate those two plants.
Figure 7: Plant A

Figure 8: Plant B
It is two varieties of the same plant, Acorus calamus (A, source) and Acorus calamus var. americanus (B, source). The difference between these two plants are the number of chromosomes, and their concentration in β-asarone, a carcinogenic compound that also cause vomiting. The American variety is diploid (2n) and contains no or almost no β-asarone. The European and Asian version are tri- or tetraploid (3n and 4n) and contain a lot of β-asarone. I will give you more information on these kind of chemical and environmental variation in a later post.

There is still a lot of plant that can be confused, which we will see later. In the next post, we will explore the toxicity of edible plants (!).

Edit: My thanks to /u/Thallassa on reddit for the revision and input.

October 20, 2014

The importance of plant identification - Part 1

Hubert Marceau - Popularization

Figure 1C. sativa (source)
October 1st 2014 will surely be a memorable day for a retired man from Georgia, USA. To his suprise, a heavily armed police force assisted by a K9 unit and a helicopter dropped in his garden. The local police department were suspecting the presence of Cannabis sp. (Figure 1), also known as marijuana. To their surprise they only found Abelmoschus esculentus (Figure 2), or okra, a comestible fruit.

Figure 2 : A. esculentus (source)



Plant identification is a crucial process in the field of naturals products. In the case presented here, it is hard to confuse the two plants when we look at them closely. But in some case even a close inspection may not be enough for an untrained eyes. Would you be able to easily tell the difference between cannabis and kenaf, Hibiscus cannabinus (Figure 3)? Better, would you be able to describe the difference? Sometimes it is not an easy task.

Figure 3 : H. cannabinus (source)

Here is another example of similar plants that can be sometime hard to distinguish for an untrained eyes: Kalmia polifolia, Kalmia angustifolia and Rhododendron groenlandicum. The first two are toxics plants that contains grayanotxins; the last one is used to make tea. In this case, an error could be dangerous. The figure 4 show the leaves (which are often a very important identification criterion) of each of these plants and others from the same family which are often confused.

You can see that the difference can sometimes be subtles (from left to right: Rhododendron groenlandicum, Kalmia angustifolia, Kalmia polifolia, Chamaedaphne calyculata and Andromeda polifolia). It is very important to specify that an good identification must be based on many morphological characteristics and be done on a complete plant, ideally with a fruit or a flower available.

Figure 4 : Multiple Ericaceae leaves (source, used with author permission)

In this last example, I would like to bring your attention to the characteristics of hair or a fold on the side being present, or not, and the general shape of the leaves. Even by looking at the parameters, some leaves are still hard to differentiate. In these cases we couldn't tell with certainty without having the complete plant.

Lastly, I would like to show you the two following plants pictures. Pay particular attention to the leaves: the shape, the stems, the color, how they attach on the branch, etc. What do you see?

Figure 5: Plant A

Figure 6: Plant B

These two pictures are in fact of the same species! Eucalyptus globulus (source figure 5 and source figure 6). This kind of dimorphism is called heteroblasty. It is a variation in the shape of the leaves and the plant in general in function of the age. The first image is a young specimen and the second is a mature one. This situation seems to be specially common in New-Zealand. Sometimes the dimorphism is strong enough to confuse even professional botanist. Closer to us (in North America), young balsam poplars have leaves that are much larger than their mature counterpart.

Plant identification is a very important aspect that can't be taken lightly in the field of natural products. Next time we will see examples where a misidentification can bring potentially serious consequences.

Edit: My thank to /u/Thallassa on reddit for the correction.