Phytochemical Pharmacy: The Healing Potential of Plants | Scientific American
Plants are often seen as the static background components of the landscape. They grow and get bigger, maybe change color in the fall, but to the casual observer they are no livelier than the surrounding rocks. It is a shame that so many people hold this common model, because plants can be every bit as vibrant and dynamic as animal life.
Fascinatingly, plants have developed a variety of biochemical defences to cope with the constraint of their sessile existence. When an animal is attacked, it can fight or run away, and when a plant is attacked it fights back too, just on a whole new level.
The types of molecules most often employed by plants in their defences are called secondary metabolites, because they are made using supplementary reactions, which are usually the continuation of a pathway. During metabolism, the photosynthesis reactions allow the plant to retrieve energy stored chemically in the form of glucose. The glucose is then broken down during respiration, when the plant requires energy for cell growth, development, and repair.
The chemical compounds generated from the complex metabolism reactions can also be further modified into adapted variations, often unique to a species. For example, the substance aconitine, a potent neurotoxin produced by the monkshood plant Aconitum napellus, is derived from terpene, a metabolic product that functions as a precursor for many other compounds (Stewart 2009).
Of course many of the compounds, secondary or otherwise, produced by plants can remain quite beneficial when they are taken out of their plant system context. We are always reminded to eat plenty of fruits and vegetables because they are rich in essential vitamins. Well, the plants don’t care at all that these molecules happen to keep us healthy. For them, the vitamin K group is produced as a crucial component of the photosynthetic machinery. The vitamin C group works in the chloroplasts as a powerful reducing agent to help repair the oxidative strain caused by photosynthesis. This oxidative capacity is usurped by animals that consume the plant, and it is used in similar repair situations (citation).
Another familiar molecule, beta carotene, is a major light harvesting compound which helps the plant capture solar energy, and yet prevents too much energy from harming the cells. Once eaten, this plant molecule can be split apart and used to help synthesize Vitamin A, which is required for proper sight (Cazzonelli 2011).
Like basic photosynthetic machinery, other metabolites that have become ubiquitous in our culture may have a completely different role for a plant. Both caffeine and nicotine are produced because they are lethal to insects and parasites, as I’m sure a plant would have no reason to stay up all night.
Of course this report would not be complete without paying due tribute to the poster child of medicinal plant success: aspirin, or salicylic acid. Produced by members of theSalix genus, the group that includes willow trees, salicylic acid is actually a hormone employed by the tree to induce a systemic resistance against pathogens. This means that the whole tree becomes resistant even if it’s only attacked in one specific area (Taiz and Zeiger 2010).
So plants can create many substances that go way beyond their objective to produce sugar/take care of photosynthetic machinery, and these compounds could yield an array of possibilities for manipulating the human body’s biochemistry. This means that there is a potential gold mine of chemical therapies just waiting to be harvested from nature. A compound isolated from plants could be subsequently modified to increase its effectiveness, as was the case with aspirin.
When compared to other methods of drug development, there are several reasons why naturally produced compounds could make better therapeutic candidates. The first has to do with the developmental process. One way to go about manufacturing a new drug is to modify an existing compound that is already in the market, say to improve its ability to target specific tissues, or lessen current side effects. Although easier than starting from scratch, this method is still inherently limiting.
However, with no previous knowledge of where to begin, a trial and error approach may be discouraging and expensive. This is where plants come in, because human civilizations have been using herbal remedies for centuries; we have already discovered, perhaps by accident, the physiological effects that different botanical species create. A simple look into our history could inspire drug developers into the next step of cancer research.
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