Phytochemistry is the study of , which are chemicals derived from . Phytochemists strive to describe the structures of the large number of secondary metabolites found in plants, the functions of these compounds in human and plant biology, and the biosynthesis of these compounds. Plants synthesize phytochemicals for many reasons, including to protect themselves against insect attacks and . The compounds found in plants are of many kinds, but most can be grouped into four major biosynthetic classes: , , , and .
Phytochemistry can be considered a subfield of botany or chemistry. Activities can be led in or in the wild with the aid of ethnobotany. Phytochemical studies directed toward human (i.e. drug discovery) use may fall under the discipline of pharmacognosy, whereas phytochemical studies focused on the ecological functions and evolution of phytochemicals likely fall under the discipline of chemical ecology. Phytochemistry also has relevance to the field of plant physiology.
Techniques
Techniques commonly used in the field of phytochemistry are extraction, isolation, and structural elucidation (MS,1D and 2D NMR) of
natural products, as well as various
chromatography techniques (MPLC, HPLC, and LC-MS).
Phytochemicals
Many plants produce chemical compounds for defence against herbivores. The major classes of pharmacologically active
are described below, with examples of medicinal plants that contain them.
Human settlements are often surrounded by weeds containing phytochemicals, such as
Urtica dioica,
dandelion and
chickweed.
Many phytochemicals, including curcumin, epigallocatechin gallate, genistein, and resveratrol are pan-assay interference compounds and are not useful in drug discovery.
Alkaloids
Alkaloids are bitter-tasting chemicals, widespread in nature, and often toxic. There are several classes with different modes of action as drugs, both recreational and pharmaceutical. Medicines of different classes include
atropine,
scopolamine, and
hyoscyamine (all from
nightshade),
the traditional medicine
berberine (from plants such as
Berberis and
Mahonia),
caffeine (
Coffea),
cocaine (
Coca),
ephedrine (
Ephedra),
morphine (
opium poppy),
nicotine (
tobacco),
reserpine (
Rauvolfia serpentina),
quinidine and
quinine (
Cinchona),
vincamine (
Vinca minor), and
vincristine (
Catharanthus roseus).
File:Opium poppy.jpg|The opium poppy Papaver somniferum is the source of the alkaloids morphine and codeine.
File:Nicotine.svg|The alkaloid nicotine from tobacco binds directly to the body's Nicotinic acetylcholine receptors, accounting for its pharmacological effects.
Glycosides
Anthraquinone glycosides are found in senna,
, and
Aloe.
The cardiac glycosides are phytochemicals from plants including foxglove and lily of the valley. They include digoxin and digitoxin which act as .
File:Senna alexandrina Mill.-Cassia angustifolia L. (Senna Plant).jpg| Senna alexandrina, containing Senna glycosides, has been used as a laxative for millennia.[
Digitalis purpurea2.jpg|The foxglove, Digitalis purpurea, contains digoxin, a cardiac glycoside. The plant was used to treat heart conditions long before the glycoside was identified.][
]
Polyphenols
of several classes are widespread in plants, including
,
, and
.
Polyphenols are secondary metabolites produced by almost every part of plants, including fruits, flowers, leaves and bark.
[
]
File:Angelica sylvestris 3.jpg|Angelica, containing
File:Phytoestrogens2.png| include (top and middle)
File:Figure 1 Chemical structures of the three main types of anthocyanins.jpg|Anthocyanin are a class of polyphenol that contributes to the color of many plants.
File:Tannic acid.svg|Tannic acid are one example of many complex polyphenolic structures produced by plants.
Terpenes
Terpenes and terpenoids of many kinds are found in plants such as the conifers. They are aromatic and serve to repel herbivores. Their scent makes them useful in essential oils, whether for such as rose and lavender, or for aromatherapy.
File:Thymian.jpg|The essential oil of common thyme ( Thymus vulgaris), contains the monoterpene thymol, an antiseptic and antifungal.[
File:Isoprene Structural Formulae V.1.svg|Terpenes are polymer of isoprene
]
Genetics
Contrary to bacteria and fungi, most plant metabolic pathways are not grouped into biosynthetic gene clusters, but instead are scattered as individual genes. Some exceptions have been discovered: steroidal glycoalkaloids in Solanum, in Pooideae, benzoxazinoids in Zea mays, in Avena sativa, Cucurbitaceae, Arabidopsis, and momilactone diterpenes in Oryza sativa.
