Methylparaben (Nipagin M)

Methylparaben (Nipagin M)

Chemical Name: p-Hydroxybenzoic Acid Methyl Ester
Chemical Formula: C₈H₈O₃
Appearance: White crystalline powder or colorless crystals
Boiling Point: 270–280°C
Solubility: Soluble in alcohol, ether, and acetone; slightly soluble in water; sparingly soluble in benzene and carbon tetrachloride

Functions & Mechanism of Action:

Methylparaben is widely used as an antimicrobial preservative in organic synthesis, cosmetics, food, pharmaceuticals, and animal feed. Due to its phenolic hydroxyl group, it has stronger antibacterial properties than benzoic acid and sorbic acid.

Mechanism:
It works by disrupting microbial cell membranes, leading to protein denaturation, and inhibiting the activity of respiratory enzymes and electron transport systems within microbial cells.

Physical & Chemical Properties:

1. Appearance: Colorless crystals or white crystalline powder, odorless or with a slight irritating odor

2. Relative Density (20°C/4°C): 1.1208

3. Relative Density (25°C/4°C): 1.1097

4. Melting Point: 131°C

5. Boiling Point (at normal pressure): 275°C (decomposes)

6. Solubility:

   • Slightly soluble in water

   • Soluble in ethanol, ether, acetone

   • Slightly soluble in benzene and carbon tetrachloride

7. Freezing Point: 131°C

Applications:

• Cosmetic Preservative:
  A phenolic preservative effective against molds, yeasts, and bacteria. Due to its relatively weak individual antimicrobial strength, it is usually combined with ethylparaben to enhance performance through additive and synergistic effects.

  • Typical Dosage: 0.1%–1.0%

  • pH Sensitivity:

    • At pH 7, activity is reduced to about 2/3 of its maximum

    • At pH 8.5, activity drops to about 1/2

  • Note: Activity may be bound and neutralized by certain polymers such as methylcellulose, gelatin, or proteins.

• Pharmaceutical Use:
  As a preservative in medicinal preparations.

• Other Uses:
  Used in organic synthesis, food preservation, fragrance protection, and photographic film additives.

Safety Note:

Methylparaben may cause skin irritation upon direct contact.