Preliminary Phytochemical Characterization of Eucalyptus Oil with Implications for Respiratory Therapeutics

Rahul Choudhary, Sharuti, Prikshit Kumar, Inder Kumar*

Minerva College of Pharmacy, Indora, Kangra, Himachal Pradesh, India.

*Corresponding Author E-mail: inder.93kumar@gmail.com

ABSTRACT:

Eucalyptus oil is a well-known natural product widely used for its therapeutic properties, particularly in the treatment of respiratory disorders. The present study aims to perform a preliminary phytochemical characterization of Eucalyptus oil obtained through hydrodistillation and to evaluate its potential implications in respiratory therapeutics. The extracted oil was subjected to standard qualitative phytochemical screening to identify major bioactive constituents. The results indicated the strong presence of terpenoids, along with significant amounts of flavonoids, tannins, and phenolic compounds. Glycosides were found to be moderately present, while alkaloids were detected only in trace amounts, and saponins were absent. The predominance of terpenoids, especially eucalyptol (1,8-cineole), plays a crucial role in the pharmacological activity of Eucalyptus oil. These compounds exhibit potent expectorant, bronchodilator, anti-inflammatory, and antimicrobial properties, making the oil highly effective in managing respiratory conditions such as cough, cold, bronchitis, and sinusitis. Furthermore, the presence of phenolic compounds and flavonoids enhances antioxidant activity, which helps in reducing oxidative stress and protecting respiratory tissues. Overall, the findings support the traditional use of Eucalyptus oil in respiratory care and highlight its potential as a natural therapeutic agent. Further studies involving detailed quantitative analysis, formulation development, and clinical evaluation are recommended to validate its efficacy and safety for broader medical applications.

KEYWORDS: Eucalyptus oil, Hydrodistillation, Phytochemical screening, Terpenoids; Eucalyptol, Flavonoids, Respiratory therapeutics.

INTRODUCTION:

Essential oils (EOs) are extracted from various plant parts, such as wood, leaves, roots, flowers, and fruits, using steam or hydro-distillation techniques. These oils are complex combinations of terpenic chemicals, mainly monoterpenes and sesquiterpenes, along with alcohols, aldehydes, ethers, esters, ketones, and phenols, which contribute to their distinctive scents.¹ The Eucalyptus species comprises over 900 species and subspecies, is native to Australia and has been successfully cultivated in various regions with subtropical and Mediterranean climates. Eucalyptus, a member of the Myrtaceae family, is a fast-growing tree that reaches a height of up to 25-50 meters. This tree can grow in wide climatic conditions, and thrives best in tropical to temperate conditions.  This tree can tolerate drought stress, hence can be cultivated in drought areas and wastelands with a temperature range from 0-47°C. The leaves of this plant are used to extract Oleum Eucalypti (Eucalyptus oil) worldwide.²

One of the most widely used species for medicinal purposes is Eucalyptus globulus (commonly called Blue Gum). The leaves of eucalyptus contain volatile oil, mainly Eucalyptol (1,8‑cineole), which is responsible for its characteristic aroma and therapeutic effects. This compound exhibits antimicrobial, anti-inflammatory, and expectorant properties, making eucalyptus oil useful in the treatment of respiratory disorders such as cough, cold, bronchitis, and asthma.³ With regard to the cure of these highly treatable respiratory diseases, the World Health Organization (WHO) is promoting herbal medicine and pharmacological research to make better use of herbal remedies. The use of herbal remedies for the treatment of respiratory disorders is a common practice in many parts of the world.⁴

Traditional medicine has been an important source of products for developing countries in treating common infections. Medicinal plants are very vital in their uses for medication, besides providing ecological, economic, and cultural services. The world’s primary means of treating diseases and fighting infections has been based on the use of medicinal plants. From ancient times, plants have been a rich source of effective and safe medicines. In the world, 64% of the population relies on medicinal plants to treat health problems.⁵ Medicinal plants are widely used for the treatment of various diseases. Eucalyptus globulus is a medicinal plant widely used in traditional and modern medicine for the treatment of respiratory disorders. The essential oil obtained from its leaves is rich in bioactive compounds, particularly monoterpenes such as 1,8-cineole, which exhibit bronchodilatory, anti-inflammatory, and antimicrobial properties.⁶ Due to these therapeutic benefits, eucalyptus oil is commonly used for cough, cold, asthma, and sinusitis. Preliminary phytochemical characterisation is important to identify the major chemical constituents responsible for its pharmacological activity and to ensure quality and efficacy in respiratory therapeutics.⁷

MATERIAL AND METHODS:

The Eucalyptus officinalis plant leaves were collected from the Indora region of Himachal Pradesh. The plant was confirmed by CSK Himachal Pradesh Agriculture University, Palampur, India. All other chemicals and solvents were purchased from CDH (P) Ltd and were of analytical grade.

METHODOLOGY:

Fresh eucalyptus leaves were collected, washed, shade-dried, and powdered. Eucalyptus oil was extracted using hydrodistillation with a Clevenger apparatus. The obtained oil was dried and stored in airtight containers.⁸ Preliminary phytochemical tests were performed to identify major constituents such as terpenoids, flavonoids, and phenolic compounds. The phytochemical profile was analyzed to understand the potential role of eucalyptus oil in respiratory disorders like cough, cold, and bronchitis.⁹

Preparation of Plant Material:

Preparation of plant material is an important step before the extraction of eucalyptus oil. Proper preparation ensures the quality, purity, and maximum yield of essential oil during the hydrodistillation process.¹⁰

1. Collection of Plant Material:

Fresh and healthy leaves of Eucalyptus globulus are collected from mature eucalyptus trees. The leaves should be free from disease, dust, and insect damage.¹¹

2. Cleaning:

The collected leaves are washed thoroughly with distilled water to remove dust, soil, and other impurities. After washing, the leaves are allowed to dry at room temperature.¹²

3. Drying:

The leaves are dried in shade at room temperature for several days to remove excess moisture. Shade drying helps in preserving the volatile compounds present in the plant.¹³

4. Size Reduction:

The dried leaves are cut or crushed into small pieces using a clean knife or grinder. This increases the surface area, which helps in the efficient extraction of essential oil.¹⁴

5. Storage:

The prepared plant material is stored in clean, dry, airtight containers until it is used for the extraction process.¹⁵

6. Weighing:

A required amount of the prepared leaves (for example, 100–200 g) is weighed using a digital balance before starting the hydrodistillation process.¹⁶

7. Hydrodistillation:

Hydrodistillation is a method used to extract essential oils from plant materials by boiling them in water. The volatile components evaporate with steam and are then condensed back into liquid form, allowing separation of the essential oil from the water.¹⁷

Phytochemical Screening:

In phytochemical screening, the diluted product was synchronized with different reagents to identify the nature of the plant. The plant’s substitute was tested for the presence of flavonoids, tannins, and vitamin A by various methods. 2-3ml of the product sample was taken in different test tubes and for different chemical testing; the sample was treated with different solvents to check the presence or absence of specified chemical strains in the plant, using Standard methods as described in the table 1.¹⁸

Table 1: Preliminary Phytochemical Screening for Plant Extracts^19,20

S. No.	Phytoconstituents	Tests	Observations
1	Flavonoids	Extract + Lead acetate solution	Yellow precipitate
		Extract + NaOH solution	Intense yellow color
		Extract + Mg ribbon + Conc. HCl (Shinoda test)	Pink/red color
		Extract + Ammonia solution	Yellow fluorescence
		Extract + AlCl₃ solution	Yellow fluorescence
		Extract + Zn + HCl (Reduction test)	Red coloration
		Extract + Ferric chloride	Greenish color
		Extract + Sulfuric acid	Orange color
2	Glycosides	Keller–Killiani test	Brown ring at the interface
		Fehling’s test (after hydrolysis)	Brick red precipitate
		Benedict’s test (after hydrolysis)	Orange-red precipitate
		Legal’s test	Pink/red color
		Borntrager’s test	Pink/red in the ammonia layer
		Modified Borntrager’s test	Rose pink color
		Baljet test	Orange colour
		Sodium nitroprusside test	Red color
3	Tannins	Extract + Ferric chloride (5%)	Blue-black/green color
		Extract + Gelatin solution	White precipitate
		Extract + Lead acetate	White precipitate
		Extract + Potassium dichromate	Red precipitate
		Extract + Vanillin + HCl	Red color
		Goldbeater’s skin test	Brown/black color
		Extract + Bromine water	Decolorization
		Extract + Dilute iodine	Faint red color
4	Phenolic Compounds	Extract + Ferric chloride	Deep blue/black color
		Extract + Lead acetate	White precipitate
		Extract + Potassium permanganate	Decolorization
		Folin–Ciocalteu reagent	Blue color
		Ellagic acid test	Muddy brown ppt
		Extract + Ammonia	Yellow color
		Extract + Nitric acid	Yellow nitration color
5	Terpenoids	Salkowski test (Chloroform + Conc. H₂SO₄)	Reddish-brown interface
		Liebermann–Burchard test	Blue-green color
		Copper acetate test	Emerald green color
		Noller’s test	Purple color
		Extract + Tin + Thionyl chloride	Pink color
		Extract + Acetic anhydride + H₂SO₄	Color change (blue/green)
6	Alkaloids	Dragendorff’s reagent	Orange/red precipitate
		Mayer’s reagent	Cream precipitate
		Wagner’s reagent	Brown/reddish precipitate
		Hager’s reagent	Yellow precipitate
		Tannic acid test	Buff precipitate
		Picric acid test	Yellow crystalline ppt
		Phosphomolybdic acid test	Yellow ppt
		Iodine test	Brown precipitate
7	Saponins	Froth test (shake with water)	Persistent foam
		Foam test	Stable froth
		Emulsion test (with oil)	Stable emulsion
		Hemolysis test	RBC lysis (clear zone)
		Sodium bicarbonate test	Honeycomb froth
		Olive oil test	Emulsion formation
		Blood agar test	Hemolytic zone
		Foam persistence test (15 min)	Stable foam

RESULT AND DISCUSSION:

The Phytochemical screening of the plant Eucalyptus in two different solvents, viz., methanol and petroleum ether, was done successfully.²¹ The results are presented in the following table 2.

Table 2: Phytochemical Screening of Eucalyptus Extract^{22, 23}

S. No.	Phytoconstituent	Test	Observation	Result
1	Flavonoids	Lead acetate	Yellow ppt	++
		NaOH test	Intense yellow	++
		Shinoda test	Pink/red	++
		Ammonia test	Yellow fluorescence	++
		AlCl₃ test	Yellow fluorescence	++
		Zn + HCl	Red color	+
		Ferric chloride	Greenish	+
		H₂SO₄	Orange	+
2	Glycosides	Keller–Killiani	Brown ring	+
		Fehling’s	Brick red ppt	+
		Benedict’s	Orange-red ppt	+
		Legal’s test	Pink/red	+
		Borntrager’s	Pink/red layer	+
		Modified Borntrager’s	Rose pink	+
		Baljet test	Orange	+
		Sodium nitroprusside	Red	±
3	Tannins	Ferric chloride	Blue-black/green	++
		Gelatin test	White ppt	++
		Lead acetate	White ppt	++
		K₂Cr₂O₇	Red ppt	+
		Vanillin + HCl	Red	+
		Goldbeater’s skin	Brown/black	++
		Bromine water	Decolorization	+
		Iodine test	Faint red	±
4	Phenolics	Ferric chloride	Deep blue/black	++
		Lead acetate	White ppt	++
		KMnO₄	Decolorization	++
		Folin–Ciocalteu	Blue	++
		Ellagic acid	Muddy brown ppt	+
		Ammonia	Yellow	+
		HNO₃	Yellow	+
5	Terpenoids	Salkowski	Reddish-brown ring	++
		Liebermann–Burchard	Blue-green	++
		Copper acetate	Emerald green	++
		Noller’s test	Purple	++
		Tin + SOCl₂	Pink	+
		Acetic anhydride + H₂SO₄	Blue/green	++
6	Alkaloids	Dragendorff’s	Faint ppt	±
		Mayer’s	Slight ppt	±
		Wagner’s	Weak brown ppt	±
		Hager’s	Yellow ppt (trace)	±
		Tannic acid	Buff ppt	±
		Picric acid	Yellow ppt	±
		Phosphomolybdic acid	Yellow ppt	±
		Iodine	Brown ppt	±
7	Saponins	Froth test	No foam	−
		Foam test	Unstable froth	−
		Emulsion test	No emulsion	−
		Hemolysis	No clearing	−
		NaHCO₃	No froth	−
		Olive oil	No emulsion	−
		Blood agar	No hemolysis	−
		Foam persistence	No stable foam	−

++ = Strongly present, + = Moderately present, ± = Trace / less present, − = Absent

These tests showed the presence of several bioactive secondary metabolites, which might be responsible for their medicinal attributes. The observations and implications made in the phytochemical tests are presented as follows:

Flavonoids:

Flavonoids present in Eucalyptus contribute to respiratory health through their strong antioxidant and anti-inflammatory properties. They help reduce inflammation in the airways, making them beneficial in conditions like asthma and bronchitis. They also protect lung tissues from oxidative stress.²⁴

Glycosides:

Glycosides found in Eucalyptus support respiratory function by exhibiting mild expectorant and antimicrobial effects. They help in loosening mucus and facilitating its removal from the respiratory tract, thereby improving breathing.²⁵

Tannins:

Tannins contribute to respiratory health due to their astringent and antimicrobial properties. They help reduce irritation in the throat and respiratory tract and may provide relief from cough and minor respiratory infections.²⁶

Phenolic Compounds:

Phenolic compounds play a major role in respiratory therapy by providing antioxidant and anti-inflammatory effects. They help protect lung tissues, reduce airway inflammation, and prevent damage caused by free radicals, especially in chronic respiratory diseases.²⁷

Terpenoids:

Terpenoids are the most important constituents for respiratory benefits in Eucalyptus. Compounds like cineole (eucalyptol) act as powerful expectorants, bronchodilators, and antiseptics. They help clear mucus, open airways, and provide relief in conditions such as cough, cold, sinusitis, and bronchitis.²⁸

Alkaloids:

Alkaloids are generally absent or present in trace amounts in Eucalyptus, so they do not play any significant role in respiratory activity.²⁹

Saponins:

Saponins are typically absent in Eucalyptus. Therefore, they do not contribute significantly to respiratory therapeutic effects in this plant.³⁰

CONCLUSION:

The present study investigated the preliminary phytochemical composition of eucalyptus oil extracted from the leaves of Eucalyptus globulus using hydrodistillation followed by qualitative phytochemical screening. The results confirmed the presence of several important secondary metabolites, including terpenoids, phenolic compounds, flavonoids, tannins, and alkaloids, which are known to contribute to the medicinal properties of eucalyptus oil. Among these constituents, terpenoids were found to be the predominant compounds, particularly Eucalyptol, which has been widely reported for its anti-inflammatory, antimicrobial, expectorant, and bronchodilator activities. These properties support the traditional use of eucalyptus oil in the management of respiratory disorders such as Bronchitis, Asthma, and the common cold. The presence of phenolic compounds and flavonoids indicates potential antioxidant and antimicrobial activities, while tannins and alkaloids may also contribute to the overall therapeutic effects. These phytochemicals collectively enhance the pharmacological value of eucalyptus oil and support its potential application in respiratory therapeutics.

CONFLICT OF INTEREST:

None.

ACKNOWLEDGEMENT:

The authors are sincerely grateful to Minerva College of Pharmacy for providing the necessary facilities and support to carry out this work.

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Received on 22.04.2026      Revised on 11.05.2026

Accepted on 26.05.2026   Published on 08.07.2026

Available online from July 13, 2026

Res. J. Pharmacognosy and Phytochem. 2026; 18(3):243-248.

DOI: 10.52711/0975-4385.2026.00035

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