**1. Introduction**

With the increasing demand for herbal medicinal products, nutraceuticals, and natural products for primary healthcare worldwide, medicinal plant extract manufacturers and essential oil producers have started using the most appropriate extraction techniques. Different methods are used to produce extracts and essential oil of defined quality with the least variations.

Herbs and medicinal plants have been used for centuries as source of a wide variety of biologically active compounds. The plant crude material or its pure compounds are extensively used to treat diverse ailments by generations of indigenous practitioners [1, 2]. They are currently the subject of much research interest, but their extraction as part of phytochemical and biological investigations presents specific challenges that must be addressed throughout the solvent extraction [3]. Natural products provide unlimited opportunities for new drug discovery because of the unmatched availability of chemical diversity [4]. Thanks to two drugs

**Figure 1.**

*Chemical structures of a few important bioactive compounds isolated from plants.*

#### *Extraction of Bioactive Compounds from Medicinal Plants and Herbs DOI: http://dx.doi.org/10.5772/intechopen.98602*

derived from alkaloids of Madagascar's rosy periwinkle (*Catharanthus roseus*), the likelihood of remission for a child who has leukemia increased by 85 percent between 1960 and 1997 [5, 6]. New compounds, such as one recently discovered in a plant in Madagascar, are likely to provide novel antibiotics and help to curb the epidemic of antibiotic-resistant diseases [7].

Natural products are currently of considerable significance due to their unique attributes as a significant source of therapeutic phytochemicals and their efficacy, safety, and minimal side effects [2, 8]. Bioactive compounds in plants include alkaloids, terpenoids, coumarins, flavonoids, nitrogen-containing compounds, organosulfur compounds, phenolics, etc. A wide spectrum of bioactivities is exhibited by these compounds such as anti-inflammatory, immunostimulatory, anticancer, antioxidant, antimicrobial, etc.

Research on medicinal plants is particularly important as that on conventional drugs due to the beneficial phytochemicals from plants and the shift towards natural products in pharmaceutical and cosmeceutical industries. Chemical structures of a few essential bioactive compounds isolated from plants are presented in **Figure 1** [9–14].

Extraction of the bioactive constituents from plants has always been challenging for researchers [15]. As the target compounds may be non-polar to polar and thermally labile, the suitability of the extraction methods must be considered. The study on medicinal plants starts with extraction procedures that play a critical role in the extraction outcomes and the consequent assays.

Hence, this chapter aims to provide an overview of the process of plant extraction, describe, and compare extraction methods based on their principle, the effect of solvent on extraction procedures, strength, limitations, and economic feasibility, with their advantages and disadvantages. This chapter shall also emphasize the common problems encountered and methods for reducing or eliminating these problems. Since millions of natural products derived from plants are known, only selected groups and compounds are presented.
