February 26, 2015

Plants vs. the World - Don't Feed on Me

Alexis St-Gelais, M. Sc., chimiste - Discoveries

Who's affraid of goats, sheeps, horses and cows? Most Humans are not, since these animals are rather pacific and useful to us. But herbaceous plants and shrubs have plenty of reasons to hold great resentment toward these species, who consistently eat them. So what is a plant to do when lunchtime rings? Poisoning is in fact a great way to go! Plants that are toxic to herbivories are plenty. Today, I'll review three examples of sophisticated chemical defenses produced by plants to deter hungry stomachs.

Blossoming sheep laurel. Source:
Wikimedia Commons
Sheep laurel (Kalmia angustifolia), also known as lambkill, certainly has a charming name. Sheeps are particularly vulnerable to the grayanotoxins biosynthetized by sheep laurel [1]. These molecules, belonging to the diterpenoid family, disrupt the normal functions of smooth muscles. The latter are responsible for the proper operation of the digestive tube, and as such grayanotoxins cause severe gastrointestinal troubles, accompanied by coordination disabilities and severe pain, and can be lethal [2]. Since sheep laurel retains its leaves throughout winter, even in the coldest aeras, it is an extremely efficient protection against herbivories in those months were food is rare, and when the kalmia becomes a tempting snack despite a rather unpleasant texture [1].

Structure of grayanotoxin I, one of the
compounds found in Kalmia angustifolia.
Grayanotoxins and their sophisticated chemical structures are also found in other plants of the Ericaceae family, including rhododendrons [2]. They in fact were likely the first chemical weapons used by mankind - an unusual purpose for natural products. Since grayanotoxins are present in the pollen of rhododendron, honey can become contaminated by the toxins, inducing what is known as "mad honey disease". Knowing that, the Ancient Greeks of the Pontus region, near the Black Sea, in their fight against Pompey in 67 BC, made sure that fouled honey was made available to their ennemies. The Romans ate the honey, and experimented nausea, vomiting and paralysis, which of course gave plenty of time for the Greeks to wipe them out [3].


Salicortin, a characteristic salicylic
derivative found in Salicaceae.
Poisoning is not the only way to go, though. Taste itself can be an effective deterrent for herbivories. Plants from the Salicaceae family, including the balsam poplar (Populus balsamifera) are well known for their production of polyphenolic glycosides compounds related to salicylic and gentistic acids [4]. If you ever chewed on an aspirin pill, you know from experience how bitter this class of molecule is. Salicylates and gentisates come along with a few specific volatile constituents which I have briefly talked about in my post about the volatile constituents of quaking aspen (Populus tremuloides) [5]. Together, these compounds are thought to create a unpleasant taste for poplar twigs, which appears to be an efficient protection against hares and other herbivories [4, 6].

Chemistry does not come for free - plants have to spend energy and carbon to biosynthetize defense molecules. As such, poplars show some seasonal variation in their phenolic constituents. In fact, the first sharp frost of the winter triggers heavy salicylates biosynthesis in the twigs, especially young [5] and thus more useful ones. Winter is a particularly sensitive period, because herbivories are more eagerly looking for food. The polyphenols are thus prepared especially for this time of the year, and their concentration slowly decreases back to low levels as spring comes around [6]. That is an impressive timing.
Cow parsnip (Heracleum maximum).
Source: Wikimedia commons
Bergapten, one of the furanocoumarins
found in Apiaceae.
Sometimes, we are the herbivories... And it may be more complicated to get rid of us! Many plants of the Apiaceae family, such as carrot and celery, have a dietary use for mankind, but the family also counts several toxic members. One of the hallmarks of several of the Apiaceae are furanocoumarins. These molecules, when present in large quantities, can penetrate the skin, where they interact with light to induce severe burns [7]. Cow parsnip (Heracleum maximum) is also called Indian celery, because several members of the First Nations in North America ate the stalks as a vegetable [8]. Yet, the plant is not devoid of furanocoumarins: they have been often reported in this species [7, 8]. This could have been an efficient protection, if only the wise First Nations did not peel off the first layer of the stalks before eating them. Since furocoumarins often cover the outer membrane of the plant, this proved to be an efficient way to avoid discomfortable "itches in the mouth" and burns around the lips [9].

References

[1] Newfoundland and Labrador Deptarment of Natural Resources - Animal Health Division. Sheep Laurel Poisoning in Newfoundland and Labrador, [Online], (page consulted on 26/02/2015), URL: http://www.nr.gov.nl.ca/nr/agrifoods/animal/animal_health/pdf/vs_01_003_sheep_laurel.pdf

[2] Li, Y.; Liu, Y.; Yu, S. Grayanoids from the Ericaceae family: Structures, biological activites and mechanism of action, Phytochem. Rev., 2013, 12, 305-325.

[3] Ashcroft, F. Using Honey as the First Chemical Weapon, interview, [Online], (page consulted on 26/02/2015), URL: http://www.thenakedscientists.com/HTML/content/interviews/interview/1000404/

[4] Boeckler, G. A.; Gershenzon, J.; Unsicker, S. B. Phenolic glycosides of the Salicaceae and their role as anti-herbivore defenses, Phytochemistry, 2011, 72, 1497-1509.

[5] Reichardt, P. B.; Bryant, J. P.; Mattes, B. R.; Clausen, T. P.; Chapin III, F. S.; Meyer, M. Winter chemical defense of alaskan balsam poplar against snowshow hares, J. Chem. Ecol., 1990, 16(6), 1941-1959.

[6] Clausen, T. P.; Chen, J.; Bryant, J. P.; Provenza, F. D.; Villalba, J. Dynamics of the volatile defense of winter "dormant" balsam poplar (Populus balsamifera), J. Chem. Ecol., 2010, 36, 461-466.

[7] Camm, E. L.; Wat, C.-K.; Towers, G. H. N. Assessment of the roles of furanocoumarins in Heracleum lanatum, Can. J. Bot., 1976, 54, 2562-2566.

[8] Webster, D.; Taschereau, P.; Belland, R. J.; Sand, C; Rennie, R. P. Antifungal activity of medicinal plant extracts: preliminary screening studies, J. Ethnopharmacol., 2008, 115, 140-146.

[9] Kuhnlein, H.; Turner, N. Cow-parsnip (Heracleum lanatum Michx.): An indigenous vegetable of native people of northwestern North America, J. Ethnobiol., 1987, 6(2), 309-324.

February 18, 2015

Plants vs. the World

Alexis St-Gelais, M. Sc., chimiste - Discoveries

Climate can be rough around here, in Saguenay. With temperatures regularly dropping under -25ºC, February is way colder than the average, this year. Fingers get nimble very quickly, and the tip of your nose can freeze within minutes. Although this might not be comfortable every day for us, Humans, other living beings have it a lot harder than us these days: plants! Many die out every year, but dozens of species survive years and years of biting cold, only to bloom again next spring.

This is only one aspect of the perillous life of a plant. Indeed, when you think about it, being a plant is simply a pain. Of course, you can feed autonomously, but on the downside, you usually have no way to move from where you stand. This implies that you will be heavily challenged. Not only can you be preyed upon by any herbivory passing by without being able to anything: there is also no way to escape extreme temperatures, intense sunlight and its deleterious UV rays, or unusual variations in what you'd expect from your soil, like pollution. Throngs of fungi, bacteria and viruses want to rip you apart. You can be trampled by anytime by even the most pacific moving being coming around. And except in the most extreme environments, you are likely surrounded by a very diverse neighbourhood, among which you will find many other plants that would rather see you dead as to gain some space for their own growth or their seedlings'.

Plants can not move, and as such, they had to develop at times impressive adaptations to cope with their situation. Some are physical, such as a thick bark against fire or spikes to discourage herbivories. But chemistry is a wonderful tool to defend yourself, in such a situation. Plants thus produce a tremendous diversity of chemical compounds, far beyond what can usually be found among animals.

Photo of plant diversity  - Photo credit : Wikimedia.org


Animals and Plants share some building blocks: proteins, lipids, sugars and aminoacids (constitutive of DNA) are as such considered to be primary metabolites, which contribute to the very structure of life in general. But plants may also count on what has come to be known as secondary metabolites, which in fact encompass almost everything else that we encounter in vegetals: phenolic compounds, terpenoids, saponins, alkaloids, complex polymers... And although if science does not understand much of their functions in plants, it is thought that they serve as defense against herbivories, bacteria and fungi, contribute to wound healing, play a role in interactions with insects, and may even be implied in plant-to-plant communications. I will present some specific cases in upcoming posts.

These are the "useful" molecules that we are often referring to when we think of natural products. Many of them have some interaction with our biological functions, which can be detrimental or beneficial. Thus, next time you sip a good coffee and feel the energizing effect of caffeine, enjoy the soothing scent of eucalyptus oil in case of cough or buy ginseng extracts to boost you up, have a thought for the harsh life of plants!

February 14, 2015

Quality Control 101, Part I. Third Party Testing is Good for You

Alexis St-Gelais, M. Sc., chimiste - Popularization

Any business in the field of natural substances production (encompassing health products, extracts, refined phytochemicals, herbs, essential oils, and anything comprising one of these ingredients) will eventually have to take a stand about the kind of quality control that should be performed on its products. In many cases, complex chemistry is at stake, which requires some specific testing. There are three possible views on this matter.

The first approach is laissez-faire: considering that quality control is costly or superfluous. This is a risky path. Quality control ensures that those products you put on the market are reliable and consistent. Your reputation is at stake - and in business, reputation means a lot. Providing certificates of analysis to your customers is a huge demonstration of seriousness. Without quality control, you also give up on opportunities to improve your methods on the basis of solid scientific data. Most of all, you put yourself at risk of being challenged by customers, only to be unable to answer their questions. Some cases even end up in court, with heavy associated costs. Quality control is an insurance policy, and should be considered just as you probably also consider insurances against fire or theft. As such, it is not surprising that batch to batch quality control is mandatory under several regulations, especially when health claims are at stake.

It should be noted that as far as batches are involved, performing a test once on one batch is not quality control at all. The results can under no circumstance be extrapolated to subsequent batches without incurring serious risks of being challenged. Variation is a normal component of production processes, and it should be monitored to make sure that it remains within reasonable boundaries.

Chemical quality control requires some
specific equipment, which are not always
worth the cost for your sole internal needs.
A second approach to quality control is to proceed with internal testing. This can be a very good habit. It lets you detect quickly any failure in your processes, and react before anything is released on the market. However, for most small businesses, anything beyond simple physicochemical testing such as pH will likely be much costlier when performed by your own team. Purchasing the equipment, taking care of it, and having access to properly trained employees can be quite a hassle. Internally performed tests also suffer a major drawback: you place yourself in an apparent conflict of interest when providing your customers with internal certificates of analysis. Whether consciously or not, you will be faced with a pressure to come up with analytical results that are in your favor. Even if you strive to stand by the results you get, some customers might (in due right) frown upon this practice and have their own testing done. If a discrepancy is found, it will be up to you to stand by your results, explain them, and eventually legally enforce them. In all this process, you will always start with a strike against you, since there is no objective distance between your company and the results you have.

The safest way to go is to proceed with third party testing of quality, for several if not all of your lots. My colleague Laurie has briefly covered this matter previously, in a post about alimentary fraud. Independant laboratories such as ours count on a highly trained staff, strictly dedicated to chemical analyses. They are also already equiped with what is required for your needs, and if you sum up the cost of your third party quality control plan, it is likely far less than what you would have paid for your own equipment and staff. Having someone outside your business test your products tremendously empowers the certificates you provide to your own customers: there is no way that you can interfere in the production of the scientific data, and as such your partners may have a high level of trust in your numbers. You will also be completely sure that anything unusual will honestly be reported to you - with proper scientific counseling to solve the problem. And last but not least, should you ever be challenged, the responsibility is not yours. It is up to the third party laboratory to deal with the situation and demonstrate the quality of their own results. This leaves you with your time, money and energy to keep up with your own business.

Even if you go with internal quality control, it is a great idea to send from time to time one of your batches to a third party laboratory for independent testing. This lets you check whether your methods are up to date, and if your results are reliable. Random batch retesting is an essential component of well-designed quality control.

All in all, third party testing is the best way to enforce your seriousness and reliability in your business. It is also an excellent way to keep your money and peace of mind, should trouble arise. As a trained chemist, I can only highly recommend to consider performing at least ponctual third party testing of your products, if it is not already the case in your organization. This is a strong commitment to high-quality and independant standards, which can in turn influence your relationship with your own customers.