Phytochemistry

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 phytochemicals are described below, with examples of medicinal plants that contain them. Human settlements are often surrounded by weeds containing phytochemicals, such as nettle, 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. File:Koeh-018.jpg|Deadly nightshade, Atropa belladonna, yields tropane alkaloids including atropine, scopolamine and hyoscyamine. File:DMT.svg|N,N-Dimethyltryptamine (DMT) a powerful psychedelic compound which is present in several plant species found across the globe, commonly found in Mimosa and Acacia species but has also been discovered in grasses such as Philaris Aquatica.

Glycosides

Anthraquinone glycosides are found in senna, rhubarb, and Aloe.

The cardiac glycosides are phytochemicals from plants including foxglove and lily of the valley. They include digoxin and digitoxin which act as diuretics.

File:Senna alexandrina Mill.-Cassia angustifolia L. (Senna Plant).jpg|Senna alexandrina, containing anthraquinone 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. File:Digoxin.svg|Digoxin is used to treat atrial fibrillation, atrial flutter and sometimes heart failure.

Polyphenols

Polyphenols of several classes are widespread in plants, including anthocyanins, phytoestrogens, and tannins. Polyphenols are secondary metabolites produced by almost every part of plants, including fruits, flowers, leaves and bark.

File:Angelica sylvestris 3.jpg|Angelica, containing phytoestrogens File:Phytoestrogens2.png|Polyphenols include phytoestrogens (top and middle) File:Figure 1 Chemical structures of the three main types of anthocyanins.jpg|Anthocyanins are a class of polyphenol that contributes to the color of many plants. File:Tannic acid.svg|Tannic acids are one example of many complex polyphenolic structures produced by plants.

Terpenes

Terpenes and terpenoids of many kinds are found in resinous plants such as the conifers. They are aromatic and serve to repel herbivores. Their scent makes them useful in essential oils, whether for perfumes such as rose and lavender, or for aromatherapy. Some have had medicinal uses: thymol is an antiseptic and was once used as a vermifuge (anti-worm medicine).

File:Thymian.jpg|The essential oil of common thyme (Thymus vulgaris), contains the monoterpene thymol, an antiseptic and antifungal. File:Thymol2.svg|Thymol is one of many terpenes found in plants. 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, polyketides in Pooideae, benzoxazinoids in Zea mays, triterpenes in Avena sativa, Cucurbitaceae, Arabidopsis, and momilactone diterpenes in Oryza sativa.

References

References

1. (1993). "Angiosperms: Division Magnoliophyta: General Features".
2. Meskin, Mark S.. (2002). "Phytochemicals in Nutrition and Health". CRC Press.
3. (2009). "Plant-Derived Natural Products: Synthesis, Function, and Application". Springer.
4. (24 September 2014). "Chemistry: Chemical con artists foil drug discovery". Nature.
5. (July 2014). "The essential roles of chemistry in high-throughput screening triage". [[Future Medicinal Chemistry]].
6. (1998). "Atropa Belladonna". The European Agency for the Evaluation of Medicinal Products.
7. (2003). "The interaction of phosphorus and potassium with seed alkaloid concentrations, yield and mineral content in narrow-leafed lupin (Lupinus angustifolius L.)". Springer.
8. "Nicotinic acetylcholine receptors: Introduction". International Union of Basic and Clinical Pharmacology.
9. (August 1987). "Laxative potency and acute toxicity of some anthraquinone derivatives, senna extracts and fractions of senna extracts". Pharmacology & Toxicology.
10. (2013-11-11). "Phytochemistry of Medicinal Plants". Springer Science & Business Media.
11. "Active Plant Ingredients Used for Medicinal Purposes". United States Department of Agriculture.
12. "Digitalis purpurea. Cardiac Glycoside". Texas A&M University.
13. (1 February 2016). "Flavonoids". Micronutrient Information Center, Linus Pauling Institute, Oregon State University.
14. (1965). "Reviewed Work: ''The Biosynthesis of Steroids, Terpenes & Acetogenins''". Sigma Xi, The Scientific Research Society.
15. (2000). "Terpenes and the Thermotolerance of Photosynthesis". Wiley.
16. Roy, Kuhu. (2015-09-01). "Tinospora cordifolia stem supplementation in diabetic dyslipidemia: an open labelled randomized controlled trial". Functional Foods in Health and Disease.
17. "Thymol (CID=6989)". NIH.
18. (2020-10-06). "Combinatorial Control of Plant Specialized Metabolism: Mechanisms, Functions, and Consequences". [[Annual Reviews (publisher).