The plant kingdom has experienced the creation and destruction of an incredible number of genera and species over the course of its millions of years of evolution. In the process, plants developed special abilities to biosynthesize numerous diverse molecules to ward off or kill their enemies and further their own survival. It is impossible to estimate how many species failed, but those adorning our world, whether big or small, are the successful ones. The chemicals synthesized by plants form the basis of phytotherapy, which uses so-called phytochemicals to bring about physiological changes in the body and can be useful in treating diseases.
Man has learned to instinctively identify the edible, poisonous, and therapeutic features of plants over the millennia by observing animals’ interactions with plants or through trial and error. This useful information was passed on from generation to generation. Today, we are sorting through this information, using science to either prove the efficacy of traditional medicines or discover new ones.
From a simple, practical viewpoint, a pharmaceutical tablet is no different to the leaf of an herb. Both affect the body because of the chemicals they contain. In a tablet, the active chemical is quantified, so its dosage can be easily calculated, but in a leaf, the chemicals may exist in minute quantities, so the dosage is different. The required dosage might only be possible by increasing the number of leaves or by extracting and concentrating the chemical ingredients. A substance can only be regarded as a medicine if it is made into an administrable form with an appropriate dosage. This is achieved through standardization.
A Short History of the Use of Medicinal Plants
The history of medicinal plants is as old as humanity’s. The earliest records of their use date back to 50,000 BC, where the pollens of medicinal plants were found around skeletons in Neanderthal graves in Shanidar cave in northern Iraq. In the last 5,000 years, all the records of all civilizations indicate the use of medicinal plants to treat diseases. This includes the Assyrians, Sumerians, Hittites, and Ancient Egyptians, as well as more recently the Romans, Ancient Greeks, Byzantines, and Ottomans. Traditional Chinese medicine and other traditional systems of medicine—such as Ayurveda, Unani, and Siddha (Ayush) in the Indian subcontinent—have existed in Asia for millennia.
In Turkey, medicinal plants bring images of aktars (herbalism shops) and old wives’ tales. While medicinal plants are found useful in all walks of life, the medical profession regards them suspiciously and with mistrust, and there are reasons for this. In the mid-1950s, the course Materia Medica was removed from the curricula of medical schools, and since then, doctors graduate without being educated about medicinal plants. In the USA and Europe, at least, alternative and complementary medicines are taught in medical schools, but in Turkey, there is neither an initiative nor a will to do the same. On the other hand, doctors—whether knowingly or not—prescribe numerous plant-based chemicals such as morphine, codeine, papaverine, quinine, quinidine, atropine, hyoscine, digitoxin, digoxin, sennoside, taxol, reserpine, rutin, vincristine, vinblastine, menthol, thymol, eucalyptol, ginkgo extract, ginseng extract, and so on. With a few exceptions, microorganisms produce all the antibiotics and antifungals.
The Rule of Five for Medicinal Plants
It is estimated that around 70,000 plant species from around the world are used for medicinal purposes. In Turkey, around 1,000 species are used for medicinal purposes. According to the World Health Organization, 80% of the world’s population use medicinal plants as the primary means of health care, since many people in developing countries have no access to modern health care. In populous countries, such as India and China, traditional systems of medicine are prevalent and respected both by the people and by the state.
The use of medicinal plants and herbal medicines requires some care and attention. To benefit from phytotherapy, the following rules must be followed:
- The correct plant material, collected at the right time, must be used.
- Fresh material must be used before it goes bad. If not, it should be dried or another appropriate postharvest treatment should be applied.
- The correct plant material, containing the correct amount of active ingredients, must be used.
- Herbal medicine must be prepared correctly, using appropriate ingredients in correct amounts and given in accurate dosages.
- Scientific literature on related herbal ingredients must be read and interpreted correctly by experts, and correct advice must be provided to users.
The above “rule of five” ensures the efficacy of an herbal medicine. It must be remembered that harmless home remedies—such as linden, mint, oregano, thyme, sage, fennel, dill, anis, chamomile, salep, ginger, clove, cinnamon, cardamom, turmeric, and so on—must be only used to treat light symptoms. For more serious symptoms, people should consult a physician. It is also not advisable to use plant materials with no established use or scientific information on their chemistry, pharmacology, and clinical use, or disappointment may be inevitable. Plants exert their medicinal activities through the chemicals they contain, as is the case with all medicines. Just as the inappropriate use of medicine can cause complications and undesired consequences, the inappropriate use of plants can have the same effect.
About Clinical Usage
One reason for the reluctance of the pharmaceutical industry to invest in developing new drugs based on medicinal plants is the fact that plants cannot be patented. A patent application can be made for their specific uses, but the industry sees this as a risk. Another risk for them is the obligation to distribute equal shares of the intellectual property rights to the community whose traditional knowledge was used to develop a modern medicine. Often, to whom the payment should be made is a cause of dispute between the government and the company. Successful plant-based medicines have been globally marketed after thorough investigations of their safety and efficacy through R&D and clinical trials.
According to a preliminary survey, around 100 plant materials have been subjected to over 800 clinical trials. Clinically speaking, the most studied plant-based drugs include licorice, St. John’s wort, and garlic. Ideally, all plants should undergo clinical trials, but these are costly and arduous, and they are only affordable by big, multinational pharmaceutical companies. Therefore, clinical trials are only conducted on those plant materials that exhibit extraordinary activities in animal studies. This is why the number of prescribed herbal medicines is so limited. Still, the potential of nature, particularly the plant kingdom, for the discovery of novel medicines is well recognized and respected by the pharmaceutical sector. In our world, microorganisms have existed for 3.8 billion years. Algae have been evolving for 1.8 billion years, and terrestrial plants for the last 450 million years. The chemical diversity that these organisms possess is far beyond what scientists can even dream of.
When we consider that only about 10% of the plant kingdom’s chemical diversity has been tapped to some extent, we need to work hard to employ this vast potential in improving our quality of life.
K. Hüsnü Can Başer