**Abstract**

Plants have been used as a source of medicine for the treatment of different diseases from thousands of years ago. There is numerous evidences are available for use of plants as a medicine in the treatment of diseases in Indian, Egyptian, Chinese, Greek and Roman system of medicine. Pharmacognosy is the study of medicines derived from natural sources, mainly from plants which may further lead to development of new drug. The exploration, extraction and screening of biological diversity such as herbs, spices, microbes and other natural resources is the worldwide activity in recent years. Phytochemicals are the naturally available bioactive compounds which are derived from different plant parts and are primarily responsible for biological activities. The most important chemical compounds which are present in the plants are alkaloids, phenols, saponins, carbohydrates, terpenoids, steroids, flavonoids and tannins etc.

**Keywords:** Medicinal plants, pharmacognosy, phytochemicals, biological activities

#### **1. Introduction**

Since from ancient period man depended on nature for their survival and lives strictly connected with nature. Man depends upon surrounding environment for their livelihood, healthcare, and sustenance and also for basic needs (food, fibers, shelter, clothing and gum). Besides providing basic necessities, plants also provided his requirement of medicine. Along with the plant man has been started using animal products and other bio-resources available in nature for preparation of medicine. As a result, different traditional medicine systems have evolved based on environmental condition, social and cultural background with respect to the ethnic group in different countries [1, 2].

Plants are served as major natural resources for traditional as well as modern medicinal system all over the world. The therapeutic potential of plants and plant products can be traced back to thousands of years ago. The information with respect to medicinal benefits of plants with other therapies has been preserved in several documentations in Babylonia, Egypt, China, Greece and Rome etc. Previous works of Theophrastus (370–287 B.C.), Aristotle (384–322 B.C.), Hippocrates (460–370 B.C.) and Dioscorides (50–100 A.D) are providing evidence that Greeks and Romans are familiar with many of today's plant drugs. The "Ebers Papyrus", the best known Egyptian pharmaceutical record documented over 700 drugs represents the history of Egyptian medicine (1500 BC). Erh-ya (300B.C), Svu-ching (1000B.C) and Ben-tsao (1250A.D) are the early herbal documentations available in China, describes more than 600 medicinal plants [3]. In Asia, the earliest records of

**Figure 1.** *Natural system of herbal medicine used in India.*

plants usage are found in the clay tablets in Mesapotamia (1700 BC). In India, herbal remedies and health care preparations are also described in ancient texts like 'Charka Samhita' (100–800 B.C), 'Sushruta Samhita' (800–700 B.C), 'Rigveda' (1400–1800 B.C) and 'Atharva-veda' (4500–2500 B.C). Ayurveda is the fundamental source of Vedic knowledge for understanding remedial properties of plants (1000 BC). Ayurveda is considered as ancient medicinal system and it is the compilation of 'Charka Samhita', 'Sushruta Samhita' and 'Ashtanga Hridaya Samhita' [4]. In addition to Ayurveda, Siddha and Unani are other conventional systems of medicine providing additional information of plant based drugs used in India. 'Unani' system of medicine originated in Greece and introduced to India by Arabs and Persians after the discovery of sea route to India. During 10th to 15th century, 'Sidda' system of medicine originated in southern parts of India and is parallel to Ayurvedic system of medicine (**Figure 1**) [5].

Now a day the herbal medicine has renewed attention and hopeful both practical and scientific view points. Herbal remedies are complex mixture different parts of single herb or many herbs which may sometime produce synergistic effect with each other ensuing in the increased therapeutic potential of drug. The identification of biologically active compound responsible for its medicinal property and there is a crucial requirement for quality control. So the correct identification and quality assessment is important to ensure quality of herbal medicine, which contributes to its safety and efficacy. Therapeutic action of herbal formulation depends on its photochemical constituents. The photochemical investigation of the medicinally important plants should be carried out, as this would be beneficial in standardization, quality assessment and efficacy of herbal drugs. Thus pharmacognosy is considered as important tool to study medicinal plants for their identification, validation and standardization [6, 7].
