**3. Pharmocognosy of medicinal plants**

The term pharmocognosy was first time coined by the Austrian physician Schmidt in 1811. A "crude drug" means a dried unprepared natural material of plant, animal or mineral origin, which is used for medicine. The word pharmacognosy is derived from the Greek word *pharmakon*-drug and *gnosis*- knowledge. Pharmacognosy is the study of medicines derived from natural sources, mainly from plants which may further lead to development of new drug. Phytochemicals ('Phyto' means plant) are biologically active natural chemical constituent of plants such as sugar, amino acids, protein, chlorophyll, alkaloids, flavonoids, steroids, tannins etc. Phytochemicals are active ingredients which possess therapeutic properties and are considered as a medicine or drug. More than 4000 phytochemicals have been obtained cataloged and are classified by protective function, physical and chemical characteristics of which 150 phytochemicals have been studied in details [11]. Latest outcome suggest that majority of phytochemicals have beneficial activities like anti- microbial, anti-malarial, anti- diabetic, anti-arthritic and anti-cancerous etc. The medicinal, biological and pharmaceutical value of phytoconstituents helps in the utilization and exploration of plant resources in recent years. The chemical information of plant coupled with medicinal properties and supported by other biological activities will add additional value for development of valuable herbal drugs [12].

During pharmacognostic investigations, physico-chemical analysis also considered as important parameter in evaluation and identification of crude drug. Macroscopic and microscopic analysis is necessary for the detection of adulterants, contaminants of herbal drug and for assessing quality before going for further study. The extractive value and solubility value is useful to evaluate specific chemical constituent dry yield in different solvents. Ash value analysis is useful in determination of unrelated matter (sand and soil) adhering to the surface of plant [13]. Moisture content is essential for evaluation of stability of crude drug. Fluorescence analysis is a reliable tool for standardization of crude drug. The different chemical constituent present in the plant extract showed characteristic fluorescence when illuminated suitably. Certain chemical substances that are not naturally fluorescence themselves are treated with different reagent to attain fluorescence [14].

## **4. Phytochemicals of medicinal plants**

The curative properties of medicinal plants are due to presence of major group of active components which are mainly alkaloids, triterpenoids, essential oils and phenolic compounds etc. Alkaloids are the secondary metabolites of plants having noticeable pharmacological activity. Roots, leaves, bark and seeds are common parts of plants which contain alkaliods. In general the alkaloids occur as salts of citric acid, oxalic acid, acetic acid and tartaric acid. These are mostly colorless, water

insoluble and non-polar solvents soluble in nature. Pharmacologically, alkaloids act as cardiac depressants, antihypertensive, anti-leukemic, analgesic, nerve stimulants and local anesthetic. Triterpenoids are made up of six isoprene units. Saponins, sterols and cardiac glycosides are chief triterpenes. The medicinal plants which have saponins are roots of *Glycyrrhiza glabra*, tuberous roots of *Asparagus racemosus* and roots of *Smilax glabra*. Typically sterols are animal substances but recently detected from plants also. Ergosterol, stigmasterol, campesterol and β- sitosterol are chief sterols derived from plants. In several plants characteristic odor is due to presence of essential oils or volatile oils which occur in lysigenous or schizogenous cavities, in glandular hairs or in specialized tubes. A variety of plant parts such as leaves of lemongrass, bark of cinnamon, flower buds of clove, nutmeg seeds and camphorwood contains volatile oils. The phenolic compound are soluble in water and includes phenols, phenolic acids, phenyl propanoids, coumarins, phenyl propenes, flavonoid pigments, anthocyanins, flavonols, flavones and tannins [15].
