Introduction

Abstract

Phytochemistry or plant chemistry, a borderline discipline between natural product organic chemistry and plant biochemistry, studies different chemicals including drug principles, food additives, and cosmetics of plant origin. It also deals with the structures, synthesis, regulation, and biological properties of secondary metabolites of plants and other bioactive principles as well as their biological functions in plants, human being, and other organisms. Phytochemistry plays significant role in the identification of therapeutically important plant substances and, in association with herbalism, ethnobotany, ethnopharmacology, metabolomics, and bioinformatics, computational biology, plays important role in discovery of new drugs. Phytochemistry initiated to play a significant role in pharmacognosy in the remote past as medicinal phytochemistry (but not until nineteenth century) when people began to isolate different active principles of medicinal plants such as quinine from Cinchona bark (1820), morphine, and codeine from the latex of the Cannabis, digoxin from Digitalis leaves, atropine from Hyoscyamine, etc. Thus, medicinal phytochemistry emerged, which includes the study of phytochemicals from medicinal plants including the bioactive phytochemicals, phytonutrients, food additives, cosmeceuticals, etc. These chemicals are of secondary metabolic origin of plants, and they protect plants from damages due to biotic and abiotic stresses. Such metabolites also contribute to the plant’s color, aroma, and flavor to assist insect pollination, repel herbivore, or elicit pharmacological or toxicological effects in man and animals. Metabolome and metabolomics include the systematic large-scale study of the small molecules or metabolic products (metabolome) of a biological system. Phytochemicals are non-nutritive but have health curative and disease preventive properties when their dietary intake is significant. They provide health benefits for humans beyond macronutrients and micronutrients. Phytochemicals as antioxidant activity, antimicrobial effect, modulation of detoxification enzymes, stimulation of the immune system, decrease of platelet aggregation, and modulation of hormone metabolism and anticancer property. A large diverse group of phytonutrients are found in vegetables, fruit, whole grain products, legumes and sprouts, nuts and seeds, onion, garlic, cumin, anise, basil, bay leaf, sparsely, cilantro, allspice, condiments, tea, coffee, chocolate, algae, etc. They include allyl sulfides, anthocyanins, β-carotene, β-sitosterol, caffeic acid, capsaicin, carnosol, catechins, chlorogenic acid, coumarins, cryptoxanthin, dietary fiber, 3,3′-diindolylmethane, ellagic acid, epicatechin, essential and fixed oils, ferulic acid, flavonoids (2-phenylchromans), folate, folic acid, hydrolysable tannins punicalagins, indoles, indole-3-carbinol, isoflavones (3-phenylchromans), isothiocyanates, lactones, lignans, limonene, lutein, lycopene, monoterpenes, monounsaturated fat, nasunin, niacin, organosulfures, omega (omega-3, omega-6 fatty acids), oxalic acid, perillyl alcohol, phenols and polyphenols, phytic acid, phytosterols, protease inhibitors, saponins, sesquiterpene, soluble fiber, sulforaphane, quercitin, resins, oleoresins, resveratrol, sulforaphane, tannic acid, thiosulfinates, saponins, silymarin, tartaric acid, vitamins B1, B6, E, K, vitamin C, xanthones, zeaxanthin, etc., as well as elements potassium, copper, manganese, selenium, magnesium, zinc, iodine, iron, chromium, etc. Crude drugs, over-the-counter remedies, ethical phytomedicines (standardized toxicologically and clinically defined crude drugs), etc., are promising low-cost alternative medicines used in primary health care of rural people of developing countries. The field herbal medicine also has benefited greatly in recent years from the interaction of the study of traditional ethnobotanical knowledge and the application of modem phytochemical analysis and biological activity studies to medicinal plants. Phytonutrients, vitamins, and minerals contained in plants had been hinted at for millennia. The field herbal medicine also has benefited greatly in recent years with the use of high-throughput robotic screening technique developed by industry, bioassay-guided fractionation of crude extracts aided by chromatographic separation techniques (LC, GC, TLC, MPLC, HPLC), chemical structure elucidation by spectroscopic (HPLC/MS, NMR, DIMS, FTMS), immunoassay, etc. Medicinal phytochemistry is receiving ever greater attention in research, pharmaceutical industry as well as in trade and economy. The estimated value of plant-based crude drugs in world trade is nearly US$45,000 million per year.