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Pharmacognosy And Phytochemistry > Natural product chemistry I > Flashcards

Natural product chemistry I Flashcards

1
Q

What is the historical significance of natural products in medicine, and what are drug leads?

A

Historical Role: Core of medicines and a significant source of drug leads.

Drug Leads Definition: Compounds with potential for development into medicines well

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2
Q

Where was Paclitaxel initially isolated, and what is its market name

A

Initially isolated from the bark of the Pacific yew tree, Taxus brevifolia.

Market Name: Paclitaxel marketed as Taxol.

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3
Q

How are natural products produced in an eco-friendly manner, and what are the methods mentioned?

A

Production of natural products is eco-friendly and can be achieved by growing plants or fermenting micro-organisms.

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4
Q

Natural products

A

Definition: Bulk substances from nature, including crude plant material, foodstuffs, and plant extracts like myrrh and frankincense.

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5
Q

What are the initial steps in the drug discovery process, and what is the purpose of biomass collection?

A

Biomass (plant, microbe, marine organism) collected, dried, and extracted using organic solvent.

Extract screened in a bioassay to assess biological activity

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6
Q

How is the assessment of biological activity divided, and what are the two formats mentioned?

A

Low throughput screening.
High throughput screening.

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7
Q

Describe the process of bioassay guided isolation and its purpose.

A

Active extracts fractionated using chromatographic techniques.
Biological activity checked during each stage until a pure active compound is obtained

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8
Q

What steps are involved in evaluating a lead compound, and why is structure elucidation important?

A

Ongoing biological evaluation.
Structure elucidation for three-dimensional structure determination.
Establish novelty, chemical class, and prior reports of biological activity.

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9
Q

What is the next step after lead compound evaluation, and what aspects are assessed during this step?

A

Extensive in vivo studies to establish activity, toxicity, and efficacy.

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10
Q

Classes of natural products

A

The polyketides
Shikimic-acid-derived natural products
The terpenes
The glycosides
The alkaloids

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11
Q

What are polyketides mainly derived from?

A

Polyketides are mainly acetate (C2)-derived metabolites

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12
Q

Which filamentous bacteria is known for producing structurally diverse polyketides?

A

Streptomyces

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13
Q

Name some examples of polyketide groups.

A

Fatty acids, glycerides, tetracyclines, griseofulvin, erythromycin A, statins.

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14
Q

How does the biosynthesis of polyketides occur?

A

The biosynthesis involves the condensation of malonyl-CoA with acetyl-CoA, to produce long-chain fatty acids.

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15
Q

What is the mechanism involved in forming these compounds (polyketides)?

A

Claisen reaction mechanism

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16
Q

What are glycerides?

A

Glycerides are fatty acid esters of propane-1,2,3-triol (glycerol).

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17
Q

How can glycerides be converted into soaps?

A

Glycerides can be converted into soaps by a strong base (NaOH), as they are saponifiable natural products

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18
Q

Why are fatty acids important in pharmacy?

A

Fatty acids are crucial as formulation agents and vehicles in pharmacy.

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19
Q

Give an example of a fatty acid found in olive oil.

A

Oleic acid, which is widespread in plants, is a major component of olive oil from the olive tree Olea europaea.

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20
Q

What is the main purgative ingredient of castor oil?

A

Ricinoleic acid is the main purgative ingredient of castor oil from the seeds of Ricinus communis.

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21
Q

Which acid is a constituent of linseed oil?

A

α-Linolenic acid is a constituent of linseed oil from Linum usitatissimum.

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22
Q

What is the origin of tetracycline?

A

Tetracycline comes from mutants of Streptomyces aureofaciens.

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23
Q

What is the spectrum of activity for tetracycline antibiotics?

A

Tetracycline antibiotics have a very broad spectrum of activity against Gram-positive and Gram-negative bacteria, spirochetes, mycoplasmae, rickettsiae, and chlamydiae.

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24
Q

How are minocycline and doxycycline produced?

A

Minocycline and doxycycline are produced semi-synthetically from natural tetracyclines

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25
Q

What is the source of erythromycin A?

A

Erythromycin A is a complex polyketide from Saccharopolyspora erythrea, a filamentous bacterium originally classified in the genus Streptomyces.

26
Q

What is the composition of the therapeutic antibiotic marketed as erythromycin?

A

The therapeutic antibiotic erythromycin is marketed as a mixture containing predominantly erythromycin A, with small amounts of erythromycins B and C.

27
Q

What medical conditions is erythromycin commonly used to treat?

A

Erythromycin is used to treat Legionnaire’s disease and respiratory tract infections in patients allergic to penicillin.

28
Q

What is the source of griseofulvin?

A

Griseofulvin, also known as Grisovin, is a polyketide antibiotic derived from the fungus (mould) Penicillium griseofulvum

29
Q

What type of infections is griseofulvin recommended for?

A

Griseofulvin is recommended for the systemic treatment of fungal infections of the skin, hair, nails, and feet caused by fungi belonging to the genera Trichophyton, Epidermophyton, and Microsporum.

30
Q

What is the primary function of statins?

A

Statins are used to lower the production of cholesterol.

31
Q

Provide examples of statins and their original sources.

A

Mevastatin, initially isolated from cultures of the fungi Penicillium citrinum and Penicillium brevicompactum,

Lovastatin, isolated from Monascus ruber and Aspergillus terreus.

32
Q

What is another name for shikimic acid?

A

Shikimic acid is sometimes referred to as shikimate.

33
Q

What role does shikimic acid play in biosynthesis?

A

Shikimic acid serves as a simple acid precursor for various natural products and aromatic amino acids, including phenylalanine, tyrosine, and tryptophan.

34
Q

Name some classes of compounds derived from shikimic acid.

A

Phenylpropenes, lignans, coumarins, flavonoids, and tannins

35
Q

Biosynthesis of propylene

A

Propylene is biosynthesized into cinnamic acid through the oxidation of phenylalanine, catalyzed by the enzyme phenylalanine ammonia lyase.

36
Q

How is cinnamaldehyde, a major component of cinnamon oil, derived?

A

is obtained by reducing cinnamic acid.

37
Q

What is the hallucinogenic component in nutmeg?

A

Myristicin, a component of nutmeg (Myristica fragrans), is known for its hallucinogenic properties.

38
Q

Name the major components of star anise, aniseed, and fennel.

A

Safrole and trans-anethole are the major components of star anise (Illicium verum), aniseed (Pimpinella anisum), and fennel (Foeniculum vulgare). They are commonly used as essential oils

39
Q

What enzyme is involved in the biosynthesis of cinnamic acid?

A

the enzyme phenylalanine ammonia lyase.

40
Q

What are lignans, and how are they formed?

A

Lignans are low molecular weight polymers formed by the coupling of two phenylpropene units. A common precursor of lignans is cinnamyl alcohol.

41
Q

Name some compounds derived from Podophyllum peltatum and Podophyllum hexandrum used in treating warts.

A

Podophyllotoxin, 40-demethylpodophyllotoxin, α-peltatin, and β-peltatin, used in the treatment of warts by North American Indians

42
Q

Why is podophyllotoxin not used clinically despite its therapeutic properties?

A

Podophyllotoxin is highly toxic

43
Q

How are coumarins derived, and what is their origin?

A

Coumarins are shikimate-derived metabolites formed when phenylalanine is deaminated and hydroxylated to trans-hydroxycinnamic acid, which readily converts to the cis form and undergoes a lactonization reaction to form coumarin itself

44
Q

What are phytoalexins?

A

Phytoalexins are coumarins synthesized de novo by plants.

45
Q

When are phytoalexins produced by plants?

A

Phytoalexins are produced by plants following infection by a bacterium or fungus.

46
Q

Provide an example of a phytoalexin.

A

Aesculetin is an example of a phytoalexin, occurring in horse chestnut (Aesculus hippocastanum).

47
Q

How is aesculetin used in phytotherapeutic preparations?

A

used in phytotherapeutic preparations to treat capillary fragility.

48
Q

What are psoralens?

A

Psoralens are coumarins with a furan ring.

49
Q

Where are psoralens typically found?

A

Psoralens are typical of the citrus (Rutaceae) and celery (Apiaceae) families.

50
Q

What protective role do psoralens play in plants?

A

Psoralens may be produced by plants as a protection mechanism against high doses of sunlight.

51
Q

How are some coumarins, including psoralens, utilized?

A

Some coumarins, including psoralens, are formulated into sunscreens and cosmetics for their protective properties against sunlight

52
Q

How have preparations with psoralens been used in the context of the disease vitiligo?

A

Preparations using apiaceous and rutaceous plants containing psoralens have been used to promote skin pigmentation in the disease vitiligo

53
Q

How are flavonoids produced?

A

Flavonoids are products of mixed biosynthesis, consisting of units derived from both shikimic acid and polyketide pathways

54
Q

What ecological role do flavonoids play in nature?

A

Flavonoids have high ecological importance in nature, serving as color attractants to insects and birds to aid in plant pollination.

55
Q

Why are flavonoids considered to have dietary significance?

A

Flavonoids, such as quercetin, are strongly antioxidant, contributing to their dietary significance. They are used to reduce the effects of poisoning by fungi of the genus Amanita.

56
Q

What is the composition of tannins?

A

Tannins comprise water-soluble polyphenolic acids

57
Q

How are hydrolysable tannins formed?

A

Hydrolysable tannins are formed by the esterification of sugars (e.g., glucose) with simple phenolic acids that are shikimate-derived, such as gallic acid.

58
Q

What is another name for non-hydrolysable tannins?

A

Non-hydrolysable tannins are sometimes referred to as condensed tannins.

59
Q

What key feature of tannins makes them useful in various applications?

A

A key feature of tannins is their ability to bind to proteins, making them useful for tanning leather, clarifying beer, and as astringent preparations in pharmacy.

60
Q

Provide an example of a tannin used in a topical preparation for cold sores.

A

Tannic acid is used as a topical preparation for cold sores.

Pharmacognosy And Phytochemistry (4 decks)

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