Chemistry of Seed Spices

Historically, India has been recognized as a land of spices. Spices have been known for ages as a culinary and effective therapeutic food. The power of spices to impart biological activity is now emerging as an area of interest for human health. The seed spices constitute an important group of agricultural commodities and play a significant role in our national economy. There are about 20 seed spices grown in India. The most prominent among them are cumin, coriander, fennel, fenugreek, ajwain, dill, nigella, celery, anise, and caraway. Seed spices produce numerous secondary metabolites or phytochemicals; these are naturally occurring, biologically active chemical compounds in plants, where they act as a natural defense system for host plants and that have historically been used as pharmaceuticals, fragrances, flavor compounds, dyes, and agrochemicals. Even today, these metabolites are a major source of new drugs. They are classified by functional groups, e.g., alcohols, aldehydes, amines, esters, ethers, ketones, terpenes, thiols, and other miscellaneous compounds. In spices, the volatile oils constitute these components. Plant secondary metabolites/phytochemicals are components that add value to a crop. Therefore, it has been a potential area of research for many years from the point of high-value compounds, their pharmaceutical/biological activities, and various industrial applications. In recent years, there has been an emphasis on secondary metabolites in relation to dietary components, which may have a considerable impact on human health. The majority of herbs, spices and medicinal plants produce bioactive secondary metabolites which possess versatile pharmacological and medicinal properties. The growing awareness of consumers about traditional medicines, their natural source, and increasing tendency of natural/self-care are the main driving force for the growth of global phytochemical industry. Today, these crops and metabolites therein are the major source of new drugs. Plant-derived substances have recently become of great interest owing to their versatile applications. According to recent estimates, about 25% of the drugs used presently come from higher plants. Hence, the present chapter is a compilation of identification of important high-value compounds in seed spices that can be explored as source of medicinally important biomolecules and preparation of some useful natural products of seed spices as major ingredient. Scientific documentation in the form of important metabolites, flavor constituents and antioxidant capacity of these crops will help in protecting the wealth of medicinally important spice crops. The present chapter deals with the phytochemical aspects of seed spices in general and the major seed spices (coriander, cumin, fenugreek, fennel, and nigella) in particular. The discussion is mainly centered on the essential oil components (being the flavor components of spices) and also lipids, steroids, and other components.