pharmacognsy Flashcards
what is pharmacognosy
the study of medicinal drugs derived from plants or other natural sources. it includes analysis of their biological , chemical , biochemical and physical properties
example of medicinal plants
atropine , ephedrine , taxol , salicylic acid and caffeine
botany
the identification , genetics and cultivation of plants
chemical characterisation
includes the isolation , identification and quantification of constituents in plant materials
pharmacology
the study of the biological effects that the chemicals in medicinal plants have on cell cultures , animals and humans
crude drugs
it is used for those natural products such as plants or part of plants , extracts and exudates which are not pure compounds
Phytochemicals
plants produce chemical compounds as part of their normal metabolic activities .
these phytochemicals are divided into
1) primary metabolites - examples include sugar and fats , these are found in all plants
2) secondary metabolites - compounds which are found In a smaller range of plants , serving a more specific function. examples of these are detergents used to get rid of predation . these secondary metabolites can have therapeutic actions in humans and can be refined to produce drugs. examples include quinine from the cinchona for malaria and morphine and codeine from the poppy
plants synthesise a bewildering variety of phytochemicals but more are derivatives of a few biochemical groups :
alkaloids
polyphenols
glycosides
terpenes
Alkaloids
contain a nitrogen ring
produced by a large variety of organisms including bacteria , fungi , plants and animals .
many alkaloids are toxic to other organisms
they often have pharmacological effects and are used in medications , recreational drugs and entheogenic rituals
they often invoke a bitter taste
drugs alkaloids produce
local anaesthetic and stimulant cocaine
psychedelic psilocin
stimulant caffeine
analgesic morphine
anticancer compound vincristine
vasodilator vincamine
anti-arrythmia compound quinidine
antimalarial drug quinine
polyphenols
the compounds that contain phenol rings
examples of polyphenols
anthocyanins that give grapes their purple colour
the isoflavones
the phytoestrogens from soy
tannins that give tea its astringency
glycosides
are molecules in which a sugar is bound to a non-carbohydrate moiety , usually a small organic molecule
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 .
example of a glycoside
Digoxin . it 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 , namely atrial fibrillation , atrial flutter and sometimes heart failure
terpenes
large and diverse class of organic compounds , produced by a variety of plants particularly conifers which are often strong smelling and have a protective function.
they are major components in resin and of turpentine produced from resin.
terpenes are major biosynthetic building blocks within nearly ever living creature.
examples of terpenes
steroids derived from triterpene squalene
essential oils - natural flavour additives for food
vitamin A
fragrance of rose and lavender is due to monoterpenes
carotenoids produce reds , yellow and oranges of pumpkins , corn and tomatoes
the microbial world
microorganisms such as bacteria and fungi are rich for leaf compounds eg antimicrobial drugs : penicillins , cephalosporins , tetracyclines, ahminoglycosides , chloramphenicol , rifamycins
the marine world
coral ,sponges , fish and marine microorganisms have biological potent chemicals , with interesting anti-inflammatory , antiviral and anticancer activity e.g. curacin A (anti-tumour )
animal sources
antibiotic peptides were extracted from the skin of African clawed frog .
the microbial world - anticancer - antibiotics - anthracyclines
daunorubicin was isolated from streptomycin coeruleorubidus and s.peucetius . this significant discovery was made independently in France and Italy in 1963. the most important member of the anthracycline , doxorubicin was isolated from s.peucetius var.caesius in 1969 in Italy
Doxorubicin hydrochloride- mechanism of action
anthracyclines inhibit DNA and RNA synthesis by intercalating between base pairs of the DNA/RNA strand , thus preventing the replication of rapidly-growing cancer cells. they also create iron-mediated free oxygen radicals that damage the DNA and cell membranes which also cause toxic side-effects
the marine world - the cone snail
cone snail has a toxin packed venom that shocks and paralyses prey. one of these poisons is a painkiller 1,000 times more powerful than morphine . the snail derived drug jams nerve transmission in the spinal cord and blocks certain pain signals from reaching the brain.
