natural products as sources of drugs

Question 1

what are some sources of lead compounds?

Answer 1

plant life / microorganisms / animal life, chemical synthesis
computer aided drugs

Question 2

do synthetic drugs occur naturally?

Answer 2

no they are produced by the pharmaceutical industry

Question 3

what are natural products / secondary metabolites?

Answer 3

organic compounds isolated from natural sources (cultures of microorganisms or plants)

Question 4

proteins in the body, are they built from L or D amino acids?

Answer 4

L, d-amino acids are not natural

Question 5

do natural products contain many chiral centres?

Answer 5

yeah

Question 6

what are some characteristics of natural products?

Answer 6

chirality, stereoselectivity, and stereospecific production of chemicals

Question 7

give some examples of plant extract drugs

Answer 7

from opium - morphine
from yew tree - taxol
from willow tree - salicylic acid
from coca bush - cocaine

Question 8

give some examples of antibiotics produced by microorganisms

Answer 8

penicillin, cephalosporins, tetracyclines, streptomycin, chloramphenicol

Question 9

are secondary metabolites required for growth and maintenance?

Answer 9

no they are not involved in essential life processes, they do not appear to provide a function that is required for growth and life maintenance

Question 10

name some primary metabolites and give their function

Answer 10

sugars, peptides, proteins, fatty acids, and sterols, they are essential for growth and survival of the producing organiism

Question 11

describe the appearance of secondary metabolites

Answer 11

rather large, complicated, organic molecules and may require as many as 30 separate enzymatic steps to synthesise.

Therefore, microorganisms devote significant energy and resources to the biogenesis of secondary metabolites that are not involved in essential life processes

This leads one to the conclusion that these molecules are important, if not essential, to the survival of these organisms

Question 12

why do microorganisms produce secondary metabolites

Answer 12

not completely understood but one suggestion is that drugs give plants and microbes survival nutritional advantage by antagonism against the competition.
also, the toxicity of secondary metabolites to competing organisms is sufficient to make secondary metabolism valuable

Question 13

what is the classification of secondary metabolites based on?

Answer 13

their structural properties

Question 14

what what are the main classes of classification of secondary metabolites?

Answer 14

specialised amino acids and peptides, polyketides, terpenoids and steroids, alkaloids, specialised carbohydrates

Question 15

which class do b-lactam antibiotics antibiotics fall in?

Answer 15

specialised amino acids and peptides

Question 16

what is the mechanism of action of b-lactam antibiotics?

Answer 16

Penicillin inhibits a bacterial enzyme - transpeptidase which is involved in the synthesis of the bacterial wall.
penicillin becomes covalently linked to the enzyme’s active site leading to irreversible inhibition.

penicillin is an irreversible inhibitor of transpeptidase.
penicillin inhibits the final cross linking stage of cell wall synthesis, it reacts with transpeptidase to form an irreversible covalent bond which leads to a weakened cell wall. the cell swells due to water entering the cell, then bursts (lysis)

Question 17

what does transpeptidase catalyse?

Answer 17

the final cross linking reaction of the bacterial cell walll biosynthesis

Question 18

name some beta lactam antibiotics?

Answer 18

penicllin G, cephalosporin C, Tetracycline

Question 19

what is erythromyocin

Answer 19

a non aromatic polyketide known as a macrlide

Question 20

how does macrolide inhibit protein synthesis

Answer 20

inhibits bacterial protein synthesis by binding to the 50S ribosome subunit. these drugs are active against the majority of aerobic and anaerobic gram positive cocci and against gram negative anaerobes

Question 21

where are alkanoids most commenly encounterd?

Answer 21

in the plant kingdom

Question 22

the nitrogen containing part of an alkaloid, what is it a derivative of?

Answer 22

of amino acids

Question 23

how do aminoglycosides inhibit protein synthesis & give an example of one

Answer 23

they bind to the 30S ribosome and inhibit bacterial protein synthesis by preventing the formation of an initiation complex with mRNA. They are active only against aerobic gram-negative bacilli and staphylococci

An example is Gentamicin.