Volatile Oils: Phytochemistry Module PCGc304

• Phytochemistry-2 Pharm-DC module (PCGc304) covers volatile oils

Lab Rules and Safety

• Only attend the lab in your assigned group.
• Only one permission per semester is allowed before the lab session.
• Lab attendance times are 9:10 am, 12:00 pm, or 2:00 pm maximum.
• Attendance is not permitted without a lab coat.
• Lab safety requires wearing a lab coat and mask before entry.
• Eye goggles are mandatory.
• Maintain cleanliness in the workspace.
• A positive attitude is expected.
• Eating or drinking and pipetteing by mouth are prohibited.
• Wear safety gear and report accidents.
• Never play mad scientist.
• Know emergency procedures.

Course Content

• The course covers volatile oils and alkaloids.

Essential Oils Overview

• Essential oils are also known as essences, volatile oils, or ethereal oils.
• They are generally products of complex composition comprising volatile principles found in plants.
• Essential oils are volatile in steam and evaporate when exposed to air or ordinary temperature.
• These oils represent the odorous principles found in various plant parts.
• Essential oils occur as hydrocarbons and oxygenated derivatives.

Uses of Essential Oils

• Used for flavoring food and drinks.
• Important in the perfume industry.
• Used in aromatherapy.

Analysis of Essential Oils

• Analysis can be Quantitative or Qualitative.
• Quantitative analysis determines the concentration of major compounds in volatile oils.
• Qualitative analysis identifies the chemical properties of an unknown substance, such as carbohydrates and alkaloids.

Quantitative Assay of Volatile Oils

• The assay of eugenol in clove oil depends on the phenolic compound forming a water-soluble phenate salt when shaken with alkali, such as KOH.
• The total volume of the oil decreases as a result of phenate salt formation.
• Clove oil (5 ml) has a Phenolic and Non-phenolic portion.
• Phenolic (eugenol)
• Non-phenolic
• Addition of alkali (50 ml)
• Phenate salt (water soluble) is formed.
• Non-phenolic portion remains (still water insoluble).
• The conclusion: the oil volume decreases.

Procedure for Eugenol Assay

• Mix 5 ml of clove oil with 50 ml of 5% aq. KOH in a Cassia flask.
• Stopper the flask with cotton.
• Heat the mixture in a water bath at 70°C for 15 minutes, then cool.
• Add 5% aq. KOH to raise the oily layer to the graduated neck.
• Determine the volume of the non-phenolic portion.
• % of eugenol = [5 - volume of nonphenolic portion] × 100 / 5

Important Remarks for Eugenol Assay

• Heating on a boiling water bath allows saponification of any eugenyl acetate present, so the reaction mixture is not heated to determine eugenol only.
• KOH is preferred over NaOH because potassium phenate salts have higher solubility in water.
• Alcoholic KOH is avoided due to the solubility of both phenolic and non-phenolic portions of the oil in alcohol.
• A 5% concentration of KOH is used because higher concentrations of aqueous alkali may dissolve all oil constituents.
• This method estimates high phenol concentrations in volatile oils; low concentrations are determined by colorimetric or chromatographic methods.