Citral

Source and Occurrence of Citral:

• Citral is a key component of lemongrass (Cymbopogon citratus) and lemon myrtle (Backhousia citriodora) essential oils.
• It exists in two isomeric forms: geranial (trans-citral) and neral (cis-citral).

Isolation

1. Extraction:

   • Steam Distillation: Similar to menthol, citral is extracted via steam distillation of lemongrass leaves.
   • Solvent Extraction: Alternatively, organic solvents like hexane or ethanol can be used to extract essential oils containing citrals.

2. Separation:

   • Post-distillation, the essential oil is separated from water.
   • Fractional Distillation: To isolate citrals from other components based on boiling points.

3. Purification:

   • Chromatography: Utilizing techniques like column chromatography on silica gel to separate citrals from other terpenoids.
   • Recrystallization: Not typically applicable for citrals as it is a liquid at room temperature, but distillation under reduced pressure can enhance purity.

Identification

1. Physical Properties:

   • Appearance: Colorless liquid.
   • Boiling Point: ~230°C.
   • Odor: Strong lemon-like aroma.

2. Spectroscopic Techniques:

   • IR Spectroscopy: Detects functional groups such as aldehyde (~1720 cm⁻¹) and C=C stretching (~1650 cm⁻¹).
   • ¹H and ¹³C NMR Spectroscopy: Elucidate the molecular structure, confirming the presence of aldehyde and double bonds.
   • Mass Spectrometry: Molecular ion peak at m/z 152.

3. Chromatographic Techniques:

   • GC: Essential for separating citral isomers and confirming purity via retention times.
   • HPLC: Used for quantitative analysis.

Analysis

1. Quantitative Analysis:

   • GC-FID: Measures citrals concentration in essential oils.
   • HPLC: Provides precise quantification in purified samples.

2. Quality Control:

   • Assessing purity through spectral data and chromatographic profiles.
   • Ensuring absence of impurities or other isomers beyond acceptable limits.

Applications and Significance of Citral:

• Citral is widely used in the flavor and fragrance industry for its lemon scent.
• It also possesses antimicrobial and anti-inflammatory properties, making it valuable in cosmetics and medicinal formulations.

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