Herbal medicines are the oldest remedies known to mankind. Herbs had been used by all cultures throughout history. But India has one of the oldest, richest and most diverse cultural living traditions associated with the use of medicinal plants. In the present scenario, the demand for herbal products is growing exponentially through out the world and major pharmaceutical companies are currently conducting extensive research on plant materials for their potential medicine value. In many journals, national and international, we find an increasing number of research publications based on herbal drugs and their formulations.
These research works are carried out world wide by people from various departments like chemistry, veterinary science, agriculture, zoology, biochemistry, defence, biotechnology, marine, sidda, ayurveda, unani, botany, cosmetic, forest, homeopathy, pharmacy and medicine. Extensive literature survey reveals that works carried out by pharmacy persons in this area are on any one of the following categories:
● Pharmacognosy
● Pharmacology
● Phytochemistry
● Ethanomedicine
● Biotechnology
● Analytical study
● Pharmaceutical study
● Ethanomedicine
Indigenous knowledge is vital information. At present it is diminishing at an alarming rate. There is an urgent need to collect it before it is irretrievably lost. So, the ethano botanical surveys are carried out among tribals or people of particular community or rural areas of a particular district. The researchers collected information regarding their medical practices for the treatment of human ailments. Some times survey is conducted specifically such as practice for the treatment of hemorrhoids or vertinary purpose or increasing secretion of milk or women health disorders etc. The data were accrued through discussions and interviews with tribals, besides other rural people. It was confirmed by repeated enquiries and cross-questions in different seasons and in various villages/hamlets. The data is carefully recorded in audiotape as well as field notebooks. Some times patients are contacted to confirm the diagnosis of the diseases. Help of translator was sought for conversation. The collected medicinal plants were identified by local people of that area and authenticated by person working in any one of the following departments such as botany, pharmacognosy, taxonomy, horticulture, botanical survey of India, sidda, ayurveda, forest and agriculture or by comparing the characteristics of the parts with herbarium specimen. A voucher specimen of plant is also preserved for further reference.
From this study, vernacular names (vary from place to place and tribal to tribal), botanical name, family, morphology of useful parts, uses of medicinal plants, preparation of medicine, mode of administration and therapeutic combinations were enumerated.
Standardization of ayurvedic drugs and plant materials are the need of the day. Many of them do not have standard identification tests or analytical procedures to maintain their consistent quality. Several pharmacopoeias containing monographs on plant materials describe only the physico-chemical parameters and are lacking in identification and quantification of phytoconstituents of therapeutic importance present in the plant. So research works are going on to estimate either single or simultaneously two constituents of same herb by using techniques such as HPLC (piperine in p.nigrum, p.longum), HPTLC (colchicines in different parts of gloriosa superba), UV-VISIBLE spectrophotometry (embeline in embelia ribes) and TLC-densitometer methods (18 - glycyrrhetinic acid of yastimadu). This study may be useful for proper standardization of herb and its estimation in raw material or poly herbal formulations or its extracts or tissue culture of the plant.
Pharmacognostical study
For this study, the plants selected may be of particular family or containing same active constitutes or used in the particular system of medicine or particular part of the plant or having same property or used in the treatment of particular diseases or used by tribals of a particular area.
In this study, its macro/micro morphological (veil islet, vein termination number, stomatal number, stomatal index, palisade ratio), anatomical cnaracters, physico chemical standards such as, ash values, extractive values, loss on drying, crude fiber content, colour, consistency, solubility, pH & specific gravity of each extract, fluorescence characters of various extracts and leaf powder after treatment with different chemical reagents under U.V light ( short and long wavelength ) and day light, micro chemical test, histochemical analysis, powder microscopy, size of cells/tissues are studied. Thin layer chromatography, UV, IR, HPTLC finger printings also taken to fix pharmacognostical parameters to the plant.
The above mentioned parameters are helpful for the future identification and decide authentification of the plant in herbal industry / factories. The physico-chemical standards such as ash values, extractives values, crude fibre contents and fluorescence analysis will be useful to identify the authenticity of the drug even from the crushed or powdered plant materials. It will serve as a standard data for the quality control of the preparations containing this plant in future. It can be included as microscopical standards in Indian herbal pharmacopoeia. The information obtained from the ash values and extractive values are useful during the time of collection and also during extraction process. Using these standards, especially histological and chemical studies, the plant can be differentiated from the other related species.
Pharmacological study
A particular activity examined in a plant is based on its family or species used or active principle present (steroid- anti-inflammatory, saponin - wound healing and anti-fertility, terpenoids - CNS depressant, glycosides-purgative, flavonoid - antiulcer, hepatoprotective activity, essential oil-anti microbial) or its uses in indigenous system of medicine, like ayurveda, sidda, unani and homeopathy or its knowledge in folklore medicine/ traditional medicine/ ethano medicine.
The biological activities on plants can be studied either by using raw material or polyherbal formulation or herbomineral formulations or extracts or cell culture extract. Even juice of the fresh leaves is also used for this study. The extracts may be prepared by methods such as decoction, maceration (cold percolation), infusion and hot percolation (soxhlet extraction). The extract are formulated into jells (in evaluation of anti-inflammatory activity) and ointment (in evaluation of wound healing activity) to study the activity. The menstrum generally used are petroleum ether, chloroform, acetone, methanol, ethanol, benzene, n-butanol hexane, ethyl acetate, water, dichloromethane: methanol (1:1) sodium bicarbonate solution etc. The plant parts leaves, barks, whole plant, aerial parts, roots, seeds of the herb mostly undertaken to study the activity. Flowers, leaf stalk, fruits, heat wood, pericarp, fruit pulp are rarely utilized.
Mostly hepato protective, analgesic, anti-inflammatory, antidiabetic, antimicrobial, antiulcer, wound healing, CNS depressant activities are examined in herbs. Anti tumor, anti HIV, anti anxiety, purgative, antifeedant, cardio protective activities are rarely verified in plants. Various models are used to check one specific activity. For example, the hepatoprotective activity can be studied against paracetamol or rifampicin or Ccl4 or BHC induced liver damage models. Like wise, carrageenin or histamine or dextran induced paw edema in rat models are used to study the anti-inflammatory activity. Acetic acid induced writhing model / eddy's hot plate method / tail immersion method are used to investigate analgesic activity. So, even one research group studied the above activity in specific plant, can be taken by another group for same activity by changing inducing agent and experimental models. Further, if the activity verified by pharmacological method, can be supplemented through biochemical method by other group (the hepatoprotective activity can be studied via histopathological & by measuring marker enzymes like SGPT, SGOT, ALP). Sometimes the mechanism of action (anti oxidant mechanism via free radical scavenging activity or lipid peroxidation effect) was investigated for the already established activity. Normally, the activity is compared with synthetic drugs or standardised herbal extract or isolated compound (silymarin is used in hepato protective activity) having similar activity. Herbal extracts are combined with allopathic drugs also to find out the effect of drug interaction leads to synergistic or antagonistic, in different or additive effects. Further attempts are made to investigate the effect of extracts of plants on bioavailability of xenobiotics.
(The author is assistant professor with Adhiparasakthi College of Pharmacy, Melmaruvathur, TN)