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BFI: Chemistry > Azoles > Flashcards

Azoles Flashcards

1
Q

First generation azoles

A

Fluconazole + Ketoconazole

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2
Q

Mechanism of action of azoles

A

Inhibit fungal Lanosterol 14-alpha demethylase; causing accumulation of lanosterol; inhibiting fungal growth

This is by an azole (ketoconazole) hetrocyclic N atom binding to the haem Fe(III) in the binding site of sterol 14-alpha demthylase (substrate binding + catalysis affected)

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3
Q

Second generation azoles

A

Itraconazole, Posaconazole + Voriconazole

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4
Q

Function of ergosterol

A

Membrane component
Provides membrane fluidity, asymmetry + integrity
Plays hormone-like role in stimulating fungal growth

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5
Q

Precursor of ergosterol

A

Lanosterol

- sterol 14-alpha demethylase transforms lanosterol

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6
Q

Other known name for sterol 14-alpha demethylase

A

Cytochrome P450 subclass 51A1

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7
Q

Function of sterol 14-alpha demethylase

A

Catalyses removal of the sterol 14-alpha methyl group to ergosterol by 3 oxidative steps

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8
Q

3 oxidative steps to remove sterol 14-alpha methyl group

A

methyl > hydroxymethyl > carboxaldehyde

followed by oxidative elimination

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9
Q

Cofactor of CYP450

A

Haem

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10
Q

An nitrogen atom for x in the azole core structure makes…

A

Triazole

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11
Q

An carbon atom for x in the azole core structure makes…

A

Imidazole

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12
Q

Adverse effect of azole antifungal therapy

A

cross-over inhibition of human
CYP51A1 (sterol 14α-demethylase) and other CYP450s.
- drug metabolism inhibited, elevated levels of drug

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13
Q

3 classes of antifungals

A

Azole, Polyenes + Nucleosides

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14
Q

Polyene drugs

A

Nystatin, Amphotericin B

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15
Q

Nystatin

A

Isolated from the fermentation broth of streptomycins noursei

  • can’t be given parentally + not absorbed orally
  • limited clinical use
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16
Q

Amphotericin B

A

Isolated from streptomyces nodosum

  • similar structurally to Nystatin but broad-spectrum anti-fungal activity
  • excellent activity against Candida spp.
  • effective treatment of systemic + CNS infections
17
Q

Nucleoside drugs

A

Flucytosine

18
Q

Flucytosine

A

developed as anticancer drug

  • interferes with pyrimidine metabolism, RNA + DNA metabolism + protein biosynthesis
  • In the cell, flucytosine is converted to 5-fluorouracil
  • 5-fluorouracil is converted to 5-fluorodeoxydeoxyyuridine monophosphate disrupting DNA synthesis
  • ineffective when used alone so used with Amphotericin B
  • Limited use due to bone marrow toxicity
19
Q

Mechanism of action of flucytosine

A

In the cell,

  • flucytosine is converted to 5-fluorouracil
  • 5-fluorouracil converted to 5-fluorodeoxyuridine monophosphate disrupting DNA synthesis

BFI: Chemistry (3 decks)

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