The word pharmacognosy has been derived from two Greek words, i.e., “pharmakon” meaning drug, and “gnosis” meaning knowledge. Pharmacognosy can be described as the science of drugs of natural origins. This science discipline deals with the study of the physical, chemical, biochemical, and biological properties of a drug candidate of natural origin. According to the World Health Organization, around 80% of the world’s population still uses natural products for primary healthcare needs.
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A Brief History of Pharmacognosy
Most of the regions of South-East Asia have inherited a traditional system of medicine that includes the use of natural sources, especially medicinal plants, to treat many diseases. Secondary metabolites used for medicinal benefits are often derived from plants, microbes, and animal sources. Several forms of classical medicinal systems, for example, Siddha, Ayurveda, and Unani, are practiced in India.
Historians have traced the use of herbal medicines back to 3000BC by Pharaohs, followed by the Greeks and the Romans. They found that plants were predominantly used for therapy in the Middle Ages. This form of the medicinal system is mentioned even in the ancient Vedas.
Between 1950 and 1990, hundreds of new plant-based drugs were introduced. Common drugs include derbipidine, octoposide, ricinin, artemisinin nebulon, phenplastin, reserbine, and phenicristine. All these compounds are derived from higher plants.
Evolution of Pharmacognosy
The term “pharmacognosy” was coined by Anotheus Seydler, a German botanist. Pharmacognosy is a multidisciplinary science, and three of the most important members of this field are phytochemistry, phytomedicine, and phytochemical analysis. In phytochemical analysis, advancements in analytical tools and techniques such as mass spectroscopy, chromatographic techniques, microscopy, and metabolite extraction procedure have helped evolve pharmacognosy significantly.
Molecular biology also has made an essential contribution to pharmacognosy. It has played a significant role in the medicinal plant drug discovery analysis by identifying drug targets and analyzing the mode of action of a particular drug. Pharmacognosy has been closely associated with medicinal chemistry and pharmaceutical chemistry.
Recently, metabolomics and genomic pharmacognosy have been introduced, which have helped in the identification of novel drug targets. Computer-based methods that include chemical docking and cataloging, and classifying natural raw materials have immensely helped pharmacognosy research.
Both reverse pharmacognosy and reverse pharmacology, which are based on target-based drug discovery, have contributed to modern pharmacognosy. They identify drug targets for natural substances via virtual (e.g., high throughput screening) or experimental screening.
Reverse pharmacognosy also screens active ingredients present in natural resources. The main difference between classical pharmacognosy and reverse pharmacognosy is that the former discovers novel bioactive ingredients from plants. At the same time, the latter approach includes using bioactive compounds to find a novel therapeutic application of the natural compound. Scientists believe that reverse pharmacognosy is an effective tool for the rapid discovery of new drugs.
Pharmacognosy and Modern Medicine
The role of natural products in modern medicine is quite prominent as these products are the backbones for discovering new drugs. Plant-based drugs have incredible contributions to modern medicine. These metabolites are obtained from different parts of the plant, such as leaves, bark, roots, stigma, bulb, flower, stem, etc. Many of the drugs are regularly used for the treatment of serious diseases.
For instance, vinblastine extracted from the Catharanthus rosesus is used to treat leukemia in children, Hodgkin’s choriocarcinoma, testicular, neck cancer, etc. Vincristine is also used to treat acute lymphocytic leukemia in children and breast cancer. Podophyllotoxin is obtained from Phodophyllum emodi and is used to treat lymphomas (testicular cancer).
In Japan, Nothapodytes nimmoniana has been traditionally used to treat women with cervical cancer. Scientists revealed that this plant contains a metabolite known as camptothecin, which is a monoterpene indole alkaloid that plays an active role in the treatment of the disease. Taxol is a bioactive compound that is extracted from a plant named Taxus brevifolius, and is used for the treatment of lung and ovarian cancer. Plant-based drugs are used to treat many other diseases related to skin, lung, cardiac, hypertension, etc.
As stated above, besides plants, other living sources are used to obtain active metabolites that have medical value; for example, the precursor of acyclovir, which is a popular antiviral drug, is obtained from a marine sponge. Also, apicidin, a metabolite effective against malaria factor Plasmodium berghei, is extracted from a fungus called Fusarium pallidoroseum.
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Challenges Faced by Pharmacognosy
One of the challenges of pharmacognosy includes the assessment of medicinal drugs, which follow cultural tradition, and are not based on receptor theory. Popular traditional medicines are reported from China (Yin-Yang), Japan (Kampo), India (Ayurveda), and Mongolia (Dom). Another challenge is the evaluation of the role of pharmacognosy in biogenic material. For instance, the formulation of dietary supplements or nutraceuticals has an important therapeutic role, but its preparation lacks the legally binding characteristics of a drug.
Often nutraceuticals are used in controlled therapy. The use of marine organisms in pharmacognosy also poses a challenge, as the extraction methods are tricky and require an expert to isolate macromolecular substances containing unusual properties. However, the major part of pharmacognosy deals with small-molecule products that are relatively easier to handle.
Sources:
- Cahlikova, L. et al. (2020) Pharmacognosy and Its Role in the System of Profile Disciplines in Pharmacy. Natural Product Communications. https://doi.org/10.1177/1934578X20945450
- Perveen, S. and Al-Taweel, M. A. (2019). Introductory Chapter: Pharmacognosy, Pharmacognosy - Medicinal Plants. IntechOpen. DOI: 10.5772/intechopen.86019.
- Orhan I. E. (2014) Pharmacognosy: Science of natural products in drug discovery. BioImpacts : BI. 4(3). pp. 109–110.
Further Reading