in
primrose produce bright red, yellow and orange shades. All plants produce
chemical compounds as part of their normal
metabolic activities. These
phytochemicals are divided into (1)
primary metabolites such as
sugars and
fats, which are found in all plants; and (2)
secondary metabolites—compounds which are found in a smaller range of plants, serving more specific functions. For example, some secondary metabolites are
toxins used by plants to
deter predation and others are
pheromones used to attract insects for
pollination. It is these secondary metabolites and pigments that can have therapeutic actions in humans and which can be refined to produce drugs—examples are
inulin from the roots of
dahlias,
quinine from the
cinchona,
THC and
CBD from the flowers of
cannabis,
morphine and
codeine from the
poppy, and
digoxin from the
foxglove. •
Alkaloids are a class of chemical compounds containing a nitrogen ring. Alkaloids are produced by a large variety of organisms, including bacteria, fungi, plants, and animals, and are part of the group of natural products (also called secondary metabolites). Many alkaloids can be purified from crude extracts by acid-base extraction. Many alkaloids are toxic to other organisms. •
Polyphenols ( phenolics) are compounds that contain
phenol rings. The
anthocyanins that give grapes their purple color, the
isoflavones, the
phytoestrogens from
soy and the
tannins that give tea its astringency are phenolics. •
Glycosides are molecules in which a sugar is bound to a non-carbohydrate moiety, usually a small organic molecule. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. These can be activated by enzyme hydrolysis, which causes the sugar part to be broken off, making the chemical available for use. •
Terpenes are a large and diverse class of
organic compounds, produced by a variety of plants, particularly
conifers, which are often strong smelling and thus may have a protective function. They are the major components of
resins, and of
turpentine produced from resins. When terpenes are modified chemically, such as by oxidation or rearrangement of the carbon skeleton, the resulting compounds are generally referred to as
terpenoids. Terpenes and terpenoids are the primary constituents of the essential oils of many types of plants and flowers. Essential oils are used widely as natural flavor additives for food, as fragrances in perfumery, and in traditional and alternative medicines such as aromatherapy. Synthetic variations and derivatives of natural terpenes and terpenoids also greatly expand the variety of aromas used in perfumery and flavors used in food additives. The fragrance of
rose and
lavender is due to
monoterpenes. The
carotenoids produce shades of red, yellow and orange in
pumpkin,
maize, and
tomatoes.
Natural products chemistry is a purified
cardiac glycoside that is extracted from the
foxglove plant,
Digitalis lanata. Digoxin is widely used in the treatment of various heart conditions. A typical protocol to isolate a pure chemical agent from natural origin is
bioassay-guided fractionation, meaning step-by-step separation of extracted components based on differences in their physicochemical properties, and assessing the
biological activity, followed by next round of separation and assaying. Typically, such work is initiated after a given crude drug formulation (typically prepared by solvent extraction of the natural material) is deemed "active" in a particular
in vitro assay. If the end-goal of the work at hand is to identify which one(s) of the scores or hundreds of compounds are responsible for the observed
in vitro activity, the path to that end is fairly straightforward: • fractionate the crude extract, e.g. by solvent partitioning or chromatography. • test the fractions thereby generated with
in vitro assays. • repeat steps 1) and 2) until pure, active compounds are obtained. • determine structure(s) of active compound(s), typically by using spectroscopic methods.
In vitro activity does not necessarily translate to biological activity in humans or other living systems.
Herbal In the past, in some countries in
Asia and Africa, up to 80% of the population may rely on
traditional medicine (including
herbal medicine) for primary health care. Native American cultures have also relied on traditional medicine such as ceremonial smoking of tobacco, potlatch ceremonies, and
herbalism, to name a few, prior to European colonization. Knowledge of traditional medicinal practices is disappearing in indigenous communities, particularly in the Amazon. With worldwide research into
pharmacology as well as
medicine, traditional medicines or ancient herbal medicines are often translated into modern remedies, such as the anti-malarial group of drugs called
artemisinin isolated from
Artemisia annua herb, a herb that was known in Chinese medicine to treat fever. However, it was found that its plant extracts had
antimalarial activity, leading to the Nobel Prize winning discovery of artemisinin. == Microscopical evaluation ==