**1. Introduction**

Herbs and spices from leaves, seeds, bark, roots, rhizomes, or buds of aromatic plants have long been used for ages in food and medicine. Although herbs and spices are used to enhance flavor, taste, and color of foods, they also supply basic nutrients, promote health, and prevent from the risk of development of chronic diseases [1–5]. There are numerous groups of bioactive compounds present in herbs and spices due to which they are gaining continuous interest over time from scientific and health perspectives [3–7]. Several phytochemicals comprising carotenoids, phenolic compounds (flavonoids, flavonol, flavanols, anthocyanins, proanthocynains, and phenolic acids), phytosterols, phytostanols, tocotrienols,

organosulfur compounds, alkaloids, dietary fibers, prebiotics, protein, amino acids, and minerals contribute to the potential health benefits [3, 4, 7]. In general, the spices phytochemicals are safe to humans and recognized as GRAS (Generally Recognized As Safe) by USFDA (United State Food and Drug Administration) except some cases with age, and medical conditions. The spices are consumed as fresh, processed, or cooked where it could undergo physical and chemical transformation from the original sources and could affect their levels of content and efficacy [4–7]. Numerous research reports supported the potential role of spices phytochemicals in reducing and curing form diseases such as coronary heart disease, hypercholesterolemia, high blood pressure, diabetes, inflammation, cancers, arthritis, microbial, viral, and parasitic infections [4–10]. Extensive *in vitro* and *in vivo* studies and clinical trial investigations confirmed the correlations of molecular structures of these phytochemicals and their biochemical activities [4–10]. However, most of their mechanisms of actions are still not completely understood to underscore their corresponding health benefits. One of the major pathways of these protective roles of phytochemicals are associated with their antioxidant activities by reducing activities of reactive oxidants which cause oxidative stress related chronic diseases like cancer, diabetes, cardiovascular diseases and other pathogenic conditions [8, 9]. In order to exert the biological benefits of spices chemical compounds it needs to bioavailable which depends various factors like nature and composition of food matrices and health status of human being [11, 12]. However, one of the major challenges of most of the spice phytochemicals is poor oral bioavailability. Several strategies such as nanoparticles, polymers, and liposomes inclusion have been adopted to improve the bioavailabilities of phytochemicals. Moreover, in most of the cases the health benefits of spices are attributed to the isolated and/or synergistic biological activities of phytochemicals present in the spices [13, 14]. Novel formulations and supplements have been developed using the extracts of spice phytochemicals for multiple health benefits following synergistic effect. This chapter gives and overview of bioactive compounds and their potential health benefits such as antioxidant activities, antiinflammatory activities, antidiabetic, and anticancer activities by some selective spices such as turmeric, garlic, ginger, onion, chili, cinnamon, and black peppers.
