**1. Introduction**

Medicinal plants are a rich source of producing bioactive natural products in most precise and selective way. Since the mid-nineteenth century, many natural products have been purified from plants, and most of them exist to be used as active elements of the modern medication. The search of excellence, real, inexpensive, and simply accessible natural compound enzyme inhibitor is one of the drug finding and strategy investigation works in the study organizations through the world [1].

Medicinal plants, extracts, and its fractions are used by 80% of the world population for their simple health necessities. The association among human, medicinal plants, and derived drugs from medicinal plants defines the past of men. Medicinal plants are the significant basis of natural drug molecules. The medicinal plants are expected to comprise secondary metabolites which have properties to use in modern medication for the cure of

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

various diseases which are not treatable. Throughout the historical period, old-style systems of medicine have developed a topic of global significance. Present approximations recommended that in numerous emerging republics a huge population trusts seriously on traditional specialist and medicinal plants to chance the main health care wants, though modern drug may be obtainable in these countries. Herbal medicines must frequently preserved approval for important and national reasons. Presently, several people in the advanced countries have initiated to go to another or complementary treatments, containing therapeutic herbs [2]. Ayurvedic medication for drug adjustment switches to medicinal plants. Ayurvedic medicine is a combination of numerous elements which is ready from medicinal plants, but the active compounds when purified from that medicinal natural plant source fail to provide the wanted activity. In the nonappearance of pharmacological data on several medicinal plants and isolated compounds which is not likely to regulate the vigorous compounds consuming wanted biological potency. Earlier trainings presented the poisonous properties of chemotherapy and radiation in handling of cancer by decrees by Ayurvedic medication, and wound curing might be complete by using Ayurvedic medicine. Modern discipline production is an important part in this procedure, to grow natively establishing materials for wanted quality [3].

Enzyme inhibitors are mainly bioactive secondary metabolites that bind with an enzyme and decrease its bioactivity. Subsequently, blocking enzyme activity can kill a pathogen or correct a metabolic imbalance; many drug molecules are enzyme inhibitors, and mainly enzyme activators connect to various enzymes, increase their enzymatic actions, and subtract link and subsequently distort to products in the catalytic cycle of the enzymes. The linking of inhibitors can finish a substrate from the enzyme-active site and stays the enzyme in catalyzing in chemical reaction. Enzyme inhibition is both an irreversible and reversible process. The irreversible inhibitors react with enzyme and adjust it chemically by a covalent likening formation. Then, these inhibitors adjust important amino acid remnants wanted from an enzymatic reversible inhibitors which are non-covalently bonded; different types of inhibition are shaped depending on whether inhibitors link non-covalently, and dissimilar types of inhibition are shaped depending on whether these inhibitors bind to the enzyme and produced enzyme substrate complex or both [4].

Many natural products are enzyme inhibitors; the finding and development are dynamic areas of pharmacology and biochemistry. Medicinal enzyme inhibitors are frequently mediated by its specificity and its effectiveness that designated the absorption desirable to inhibit the enzyme. Great specificity and potency confirm that a medicinal drug will have few side effects and possess low toxicity. Natural enzyme inhibitors are involved in the guideline of much metabolic procedure. Actually, enzyme is a metabolic pathway which can be inhibited by many downstream yields. These types of bad response slow the manufacture line when product activates to shape up and a significant way to reservation homeostasis in cell. An additional cellular enzyme inhibitor is protein which specially binds and inhibits an enzyme objective. These help regulator enzymes which may be harmful to cell alike proteases. The well-categorized example of this is the ribonuclease inhibitor that link ribonucleases in the tightest recognized protein contact. Many natural enzyme inhibitors may also be poisonous and are used as defenses besides predators as habits of killing several preys [4].
