There is a growing trend to use “natural” products in several fields e.g., natural cosmetics, natural home and personal care products, natural supplements, etc. Well, there might be many reasons for the success of these kind of products and some of them might be good, but there is a thing that always puzzles and, to be honest, bothers me: many of them are labelled as “chemical-free” …and that’s simply the biggest misleading advertisement ever! We can actually just go ahead and call it a lie.
First of all, usually these products are water based and water of course is a chemical and, to cut is short, also all of the other ingredients are chemicals. Now, without being so fussy about this, let’s give it for granted that we understand them to be chemical-free in the meaning that they do not contain any chemical synthesized in the laboratory. Hence, all the chemicals used in these products (are claimed to) derive from natural sources. Are we really sure that this is good for us or for the environment? This question does not have a universal answer, and we should rather analyse case by case. However, what I would like to address with you today is that usually what is natural is perceived as safe and, well, that’s another wrong assumption.
Let’s focus now on organic molecules i.e., those chemicals based on a carbon backbone. In these molecules, carbons (and atoms of a few other elements) are bound together in certain ways. The possible combinations are countless and therefore we have so many different molecules. The way atoms are bound together and the way bonds are arranged in space determine how the compounds interact with other molecules and ultimately influence how they affect cells and organisms. Are the effects dependent on whether a molecule with a specific structure is synthesized in a lab or by a plant (or any other organism)? The answer is simply no. Actually, to be precise, chemicals synthetized in the lab are usually far more controlled and subject to stricter regulations than those obtained from natural sources. Once again, one cannot make generalization, but it is important to understand that often there is an unfounded prejudice against what is perceived as “chemical” (check out “chemophobia”) and an equally unjustified blind faith towards everything that is perceived as “natural”.
If you are still convinced that natural does equal safe, well here there is another point: many of the deadliest substances are of natural origin and many natural products are toxic to humans.
Strychnine is a chemical found in the seeds of the plant Strychnos nux-vomica and in other plants of the same genus. This compound is highly toxic if injected, inhaled, ingested, or absorbed through mucous membranes . It acts on the central nervous system. Symptoms usually begin 15-30 minutes after ingestion and include violent convulsions and spasms of the body’s muscles starting with the head and neck. The convulsions progress and increase in intensity and frequency until the backbone arches continually (this can happen without loss of consciousness) and until death occurs from asphyxiation, within 2-3 hours after exposure . The toxic effects of strychnine have been well-known since ancient times in China and India . Historic records indicate that it has been used to kill dogs, cats, rats and birds in Europe as far back as 1640 and there are numerous records of the use of this compound or of the plant extract for criminal purposes [1–2]. Perhaps the latter is the reason why many crime novel writers, like for example Agatha Christie, make their killers use this poison sometimes .
When the Greek philosopher Socrates was sentenced to death, he had to dye by drinking a dose of poison (pharmakon) that contained, among other plants, poison hemlock. This plant, Conium maculatum, belonging to the Apiaceae family (to which also carrots, celery, and parsley belong) contains the toxic alkaloid coniine. Coniine acts on the central nervous system (although the mechanisms are different from those of strychnine) and leads to death by respiratory paralysis . Symptoms of intoxication are once again quite gruesome, and often do not include unconsciousness [5–6].
Plants are not the only organisms that produce toxic chemicals. Batrachotoxin is an extremely poisonous cardio- and neurotoxic steroidal alkaloid found in certain species of beetles, birds, and frogs (as the name would suggest, since bátrachos is the ancient Greek for frog). There are, actually, several structurally related alkaloids collectively called batrachotoxins. Some species of brightly-coloured frogs indigenous to Central and South America have copious amount of this compound on the skin and are therefore among those used for poisoning darts . It appears that batrachotoxins of frog skin are probably derived unchanged from dietary insects . The latter do not make them from scratch, but instead very likely use phytosterols from plants as a scaffold that they or their symbiont microorganisms modify .
Strychnine, coniine and batrachotoxin are only a few examples of natural chemicals that are not exactly safe. The list of toxic natural molecules is long and, as you could already see, does not include only plant-derived chemicals, and also does not include only small molecules (I am pretty sure, for example, that you heard about the botulinum toxin, which is a protein).
Please, never assume that natural equals safe!