|LETTER TO EDITOR
|Year : 2010 | Volume
| Issue : 1 | Page : 27-28
Do medicinal plants possess significant activities?
Sanjib Bhattacharya1, KK Mueen Ahmed2, Vipra Kundoor3
1 Bengal School of Technology (A College of Pharmacy), Delhi Road, Sugnadha, Hooghly 712102, West Bengal, India
2 Department of Pharmaceutical Sciences, College of Clinical Pharmacy, King Faisal University, Al-Hassa, Saudi Arabia
3 U. S. Food and Drug Administration, Rockville, Maryland, USA
|Date of Web Publication||20-Sep-2010|
Bengal School of Technology (A College of Pharmacy), Delhi Road, Sugandha, Hooghly 712102, West Bengal
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Bhattacharya S, Mueen Ahmed K K, Kundoor V. Do medicinal plants possess significant activities?. J Pharm Negative Results 2010;1:27-8
The use of medicinal plants and their preparations for the treatment of diseases is as old as mankind, and even today majority of the world population depends on herbal health care practices. Exploring medicinal plants in the context of modern science is the need for optimum and proper utilization of medicinal plants. Research on medicinal plants for biological activities is an area of interest worldwide. Lots of scientific research has been carried out on a large number of medicinal plants, as evident from increase in the number of research articles on biological activity of plants. In spite of increased research on medicinal plants, there is no considerable development in the number of marketable drugs as plant derived chemical entities or herbal formulations with modern standards of safety and efficacy. In this situation, the medicinal properties of medicinal plants become questionable, raising the title question.
Even now, patients favor herbal medications for their perceived efficacy and good safety profile. Although opportunities for developing plant-based drugs with international acceptance are vast, at present it appears that there is lack of integrated research focusing on the development of commercially viable and useful phytomedicines. Majority of the research publications on medicinal plants show significant pharmacological activities of crude or partially purified/fractionated plant extracts in experimental animal models, mentioning the almost common refrain in conclusion: further studies are required to isolate the bioactive compounds and/or further studies are required to clarify the mechanism of examined activity. Unfortunately, publications on such further studies are very much rare on those plants, despite claiming so-called significant activities. In this way, majority of the medicinal plant research starts and ends at this preliminary level of observations. Most of these studies are repetitive, using similar models. Further, in some cases in terms of further study, a medicinal plant is credited with innumerable pharmacological activities without focusing practical therapeutically beneficiary effects. Sometimes, repetition of these studies elsewhere does not show the claimed activity. Hence, the reproducibility of the effects is questionable, especially in case of humans.
If a medicinal plant really possessed certain significant activity, then why there is not any concerted effort toward further definitive chemical pharmacological and clinical studies leading to possible drug development?
Many reasons can be found for this and the challenges in phytopharmacology have been elaborately discussed by the researchers elsewhere. Various problems inherently associated with herbal medicine include: identification of plants, cultivation, collection and processing, extraction, standardization, toxicological data and poor methodological quality of animal studies. Among them, the last point appears to be important while significant activity of medicinal plants is concerned. Reports show that animal studies are poor predictors of effects in humans.  There are several methodological problems associated with phytopharmacological studies in animal models.  Some of these include the following.
Most of the research publications on medicinal plants are animal studies and majority of these studies suffer at least one of the problems mentioned above.
- Differences in animal species and strains
- None or less availability of suitable higher mammals like cat, dog, and monkey
- Different means for inducing disease or injury with varying similarity to the human conditions
- Variation in dose selection and dosing regimen that is of uncertain relevance to the human conditions
- Lack of proper screening of experimental animals to avoid false positive results
- Choice of comparison treatment (none/vehicle/positive control)
- Small experimental group with inadequate sample size
- Simple statistical treatment of experimental data
There are certain complications associated with crude or partially purified plant extracts while detecting their pharmacological properties. These include:
Use of isolated compounds can circumvent the above said difficulties. However, purification of extracts or isolation of compounds often leads to decrease or complete loss of pharmacological activities. Expensive and time consuming isolation of constituents frequently leads to re-isolation and re-identification of known or less important compounds like phenolics, sugars, etc.
- differences in solvents used for extraction,
- differences in extraction methods,
- presence of tannins and related polyphenols which frequently give false positive pharmacological response both in vitro and in vivo,
- presence of residual solvents in extracts and
- disparity in standardization methods.
It is also discouraging to observe that among numerous research articles on medicinal plants, very few are clinical studies. Clinical trials with herbal medicines are very less globally. Evidence to justify the potential use of herbal medicine in mainstream medicine is therefore lacking. The issues, difficulties and possible alternative strategies of clinical trials of herbal medicine have been discussed by several researchers in pursuit of a better outcome. 
The cause of raising questions toward activities of medicinal plants may be that most of the work in this field has remained within clinics of traditional practitioners or confined to academic research laboratories and not taken by industries which are strong and dynamic in research and development. There are several international patents granted for different pharmacological activities of medicinal plants and yet these have not been commercially exploited. The earlier successes have been achieved distinctly when the industry effort was intensive. Majority of the drugs (whether natural or synthetic) would not have been developed or their development would have been delayed significantly in the absence of scientific or technical contribution from pharmaceutical companies.
In spite of several doubts and questions regarding the activities of medicinal plants in contemporary therapeutics, the prospect of medicinal plants for health care system should not be considered so bleak in view of the development of some herbal drugs of promising therapeutic utility. Although at present development of pure phytochemicals as drugs is very few, there are several standardized or purified extracts from known medicinal plants (silymarin comes to mind first) showing good safety and efficacy in humans. Standardized plant extracts in formulations are increasingly being accepted in European and American countries.
For several compelling reasons, researchers involved in modern drug discovery processes have started revisiting medicinal plants to reduce the typical innovation deficit faced today. There is no denying that medicinal plants are endowed with significant medicinal properties since time immemorial and have furnished several important drugs. Nowadays there are some publications and patents describing interesting and novel leads form medicinal plants acting at the molecular level mechanisms. Many promising leads like curcumins and withanolides are available; only industry-based integrative research and development is required to yield many more successes like reserpine and artemisinin. Best of public and private sectors comprising academia and industry experts should come together to explore the seemingly low-valued but highly gifted wealth of medicinal plants for the benefit of mankind.
| References|| |
|1.||Knight A. Systematic reviews of animal experiments demonstrate poor human clinical and toxicological utility. ALTEX 2007;14:125-30. |
|2.||Pandora P. Where is the evidence that animal research benefits humans? BMJ 2004;328:514-17. |
|3.||Guo R, Canter PH, Ernst E. A systematic review of randomized clinical trials of individualized herbal medicine in any indication. Postgrad Med J 2007;83:633-37. [PUBMED] [FULLTEXT] |