Comparative Phytochemical Characterization and Evaluation of Free Radical Scavenging and Biocidal Activities of Leaf, Fruit and Flower of Cucumis melo var. flexuosus from Mahasamund District, Chhattisgarh

Medicinal plants have been utilized since ancient times as important sources of therapeutic agents and bioactive compounds for the prevention and treatment of various human diseases (Harborne, 1998). Plant-based medicines are widely recognized due to the presence of naturally occurring phytochemicals possessing significant biological and pharmacological activities (Sofowora, 2008). Secondary metabolites such as flavonoids, alkaloids, tannins, phenolics, glycosides, and terpenoids are known to contribute to antioxidant, antimicrobial, anti-inflammatory, antidiabetic, and anticancer properties in medicinal plants (Trease & Evans, 2009). Due to their lower toxicity and eco-friendly nature, medicinal plants are increasingly explored as alternatives to synthetic drugs and preservatives (Cowan, 1999).

The extensive use of synthetic therapeutic agents has raised concerns regarding adverse side effects and microbial resistance (WHO, 2020). Increasing antibiotic resistance among pathogenic microorganisms has become a major global health challenge (Cowan, 1999). As a result, scientific research has shifted toward the identification of safer and naturally derived bioactive compounds from medicinal plants (Sofowora, 2008). Plant-derived compounds are considered promising candidates for pharmaceutical and nutraceutical development because of their therapeutic efficacy and biological compatibility (Harborne, 1998).

The family Cucurbitaceae includes several medicinally and economically important species cultivated worldwide for nutritional and therapeutic purposes (Robinson & Decker-Walters, 1997). Species belonging to this family are known to contain diverse phytochemicals with important biological activities (Dhillon et al., 2013). Cucumis melo var. flexuosus, commonly known as snake melon or Armenian cucumber, is an edible cucurbit valued for both nutritional and medicinal applications (Robinson & Decker-Walters, 1997). Traditionally, the plant has been used for digestive disorders, hydration, body cooling, and general health improvement (Sofowora, 2008). Previous studies on the genus Cucumis have demonstrated the presence of flavonoids, carotenoids, phenolics, and antioxidant compounds associated with free radical scavenging and antimicrobial properties (Dhillon et al., 2013).

Figure 1.1 Leaf ,flower and Fruit of  Cucumis melo var. flexuosus

Different plant parts such as leaves, fruits, flowers, and seeds often vary in their phytochemical composition due to differences in metabolic and physiological functions (Harborne, 1998). Such variations significantly influence the biological and medicinal properties of plant extracts (Trease & Evans, 2009). Comparative evaluation of different plant parts is therefore essential to identify the most biologically active component of the plant (Sofowora, 2008).

Free radicals and reactive oxygen species (ROS) are highly reactive molecules produced during normal cellular metabolism and environmental stress (Brand-Williams et al., 1995). Excessive accumulation of ROS may result in oxidative stress, causing lipid peroxidation, protein degradation, DNA damage, cellular aging, and chronic disorders such as cancer, diabetes, cardiovascular diseases, and neurodegenerative disorders (Brand-Williams et al., 1995). Antioxidants neutralize free radicals by donating electrons or hydrogen atoms and thereby reduce oxidative damage in biological systems (Harborne, 1998). Natural antioxidants obtained from medicinal plants are considered safer and more beneficial compared to synthetic antioxidants because of their reduced side effects and biological compatibility (Trease & Evans, 2009).

Among the available methods for antioxidant analysis, the DPPH free radical scavenging assay is widely used because of its simplicity, reproducibility, and accuracy in determining antioxidant potential (Brand-Williams et al., 1995). The assay provides important information regarding the hydrogen-donating capacity of plant extracts and their ability to neutralize free radicals (Brand-Williams et al., 1995).

Medicinal plants are also extensively investigated for their antimicrobial or biocidal activities against pathogenic microorganisms (Cowan, 1999). Phytochemicals such as tannins, flavonoids, alkaloids, and terpenoids can inhibit microbial growth by disrupting cell membranes, interfering with enzyme systems, and affecting nucleic acid synthesis (Cowan, 1999). Therefore, medicinal plants serve as important reservoirs of natural antimicrobial agents with potential pharmaceutical applications (WHO, 2020).

Although several studies have reported the medicinal importance of cucurbit plants, limited comparative investigations are available on the phytochemical characterization and biological activities of leaf, fruit, and flower extracts of Cucumis melo var. flexuosus (Dhillon et al., 2013). Comparative analysis of different plant parts may provide valuable information regarding the distribution of bioactive compounds and their therapeutic significance (Harborne, 1998). Therefore, the present study was undertaken to comparatively evaluate the phytochemical constituents, free radical scavenging activity, and biocidal potential of leaf, fruit, and flower extracts of Cucumis melo var. flexuosus (Trease & Evans, 2009). The findings of this investigation may contribute to the identification of potential natural antioxidant and antimicrobial agents for future pharmaceutical and nutraceutical applications (Sofowora, 2008).

Objectives of the Study

1. To perform comparative phytochemical screening of leaf, fruit, and flower extracts of Cucumis melo var. flexuosus.
2. To evaluate the free radical scavenging activity of different plant parts.
3. To assess the biocidal activity of the extracts against selected microbial strains.
4. To identify the plant part with maximum biological activity.

MATERIALS AND METHODS

Collection of Plant Material

Fresh leaf, fruit, and flower samples of Cucumis melo var. flexuosus were collected from selected agricultural fields of Mahasamund district, Chhattisgarh, India. The collected samples were washed thoroughly with distilled water to remove dust and impurities and then shade dried at room temperature.

Preparation of Plant Extracts

The dried plant materials were powdered separately using a mechanical grinder. About 20 g of powdered sample from each plant part was extracted using methanol/ethanol through Soxhlet extraction or maceration technique. The extracts were filtered and concentrated using a rotary evaporator and stored at 4°C until further analysis.

Preliminary Phytochemical Screening

The prepared extracts of leaf, fruit, and flower of Cucumis melo var. flexuosus were subjected to preliminary phytochemical screening using standard qualitative analytical procedures to identify the presence of various biologically active secondary metabolites. The analysis was carried out for the detection of major phytoconstituents including alkaloids, flavonoids, phenolic compounds, tannins, saponins, glycosides, terpenoids, and steroids.

These phytochemicals are known to possess significant pharmacological and therapeutic properties such as antioxidant, antimicrobial, anti-inflammatory, and free radical scavenging activities.

The presence or absence of these compounds was determined based on characteristic color changes or precipitate formation during specific chemical tests. Comparative evaluation of the phytochemical profile among different plant parts was performed to identify the extract containing higher concentrations of bioactive constituents.

Table 1.1 Preliminary Phytochemical Screening

(+ = Present, ++ = Moderate, +++ = High)

Determination of Antioxidant

Determination of Antioxidant Activity

The antioxidant activity of the extracts was determined using DPPH free radical scavenging assay. Different concentrations of extracts were prepared and mixed with DPPH solution. The absorbance was measured using a UV-Visible spectrophotometer at 517 nm.

The percentage inhibition was calculated using the formula:

Scavenging activity(%)=A0-A1A0

Where:

A0? = Absorbance of control

A1? = Absorbance of sample

Biocidal Activity

The antimicrobial activity of the extracts was evaluated using agar well diffusion method against selected bacterial strains such as:

Escherichia coli and Staphylococcus aureus

The zone of inhibition was measured after incubation and compared among different extracts.

RESULTS AND DISCUSSION

The comparative phytochemical investigation of leaf, fruit, and flower extracts of Cucumis melo var. flexuosus confirmed the presence of several biologically active secondary metabolites. Qualitative analysis revealed that flavonoids, phenolic compounds, tannins, alkaloids, and terpenoids were present in varying concentrations among the tested plant parts.

The leaf extract exhibited a comparatively richer phytochemical profile, particularly in terms of phenolics and flavonoids, which are well known for their antioxidant potential.

The antioxidant activity of the extracts was evaluated using DPPH free radical scavenging assay. All extracts showed concentration-dependent antioxidant activity; however, significant variation was observed among different plant parts.

The leaf extract demonstrated the strongest free radical scavenging ability with the lowest IC50 value, indicating higher antioxidant efficiency.

The flower extract also exhibited considerable antioxidant activity, whereas the fruit extract showed comparatively moderate activity.

Table 1.2 Comparative Antioxidant Activity of Different Plant Extracts

Figure 1.2  Comparative antioxidant assay of plant extracts

Figure 1.3 DPPH assay for Fruit,leaf and flower parts

The lower IC50 value observed in the leaf extract suggests the presence of higher concentrations of antioxidant phytoconstituents capable of neutralizing free radicals more effectively. Similar findings have been reported in medicinal plants rich in phenolic and flavonoid compounds.

The antimicrobial assay revealed that all extracts possessed measurable inhibitory activity against the selected bacterial strains. Among the tested samples, the leaf extract showed the maximum zone of inhibition against Escherichia coli and Staphylococcus aureus, indicating comparatively stronger biocidal efficacy. The flower extract also demonstrated noticeable antibacterial activity, while the fruit extract produced relatively smaller inhibition zones.

Table 1.3 Comparative Biocidal Activity of Plant Extracts

Figure 1.4 Comparative biocidal activity of plant extracts