Phytochemicals: A Treasure Trove in Citrus medica
Phytochemicals are naturally occurring, non-nutritive bioactive compounds synthesized by plants, and Citrus medica (citron) is exceptionally rich in them. These compounds are responsible for the plant's characteristic aroma, flavor, and its extensive use in traditional and modern medicine. The phytochemical profile varies significantly across different parts of the citron tree, including its peel, pulp, leaves, and seeds. This diversity accounts for the wide range of health benefits attributed to the plant, from its powerful antioxidant and anti-inflammatory effects to its antimicrobial and analgesic properties.
Key Flavonoids and Phenolic Compounds
Flavonoids, a major class of phenolic compounds, are abundant in Citrus medica, particularly in the peel and pulp. These compounds are potent antioxidants, protecting cells from damage caused by free radicals. The flavonoid profile is influenced by factors like fruit maturity and extraction methods. Phenolic acids, another group of antioxidant compounds, are also present. Common flavonoids found in citron include hesperidin, a dominant compound with anti-inflammatory and cardioprotective effects; naringin, which contributes to antioxidant capacity; quercetin, known for its strong antioxidant and anti-inflammatory properties; and eriocitrin, a flavanone significant for the fruit's antioxidant activity. Important phenolic acids like p-coumaric acid, trans-ferulic acid, and gallic acid also contribute to citron's biological activities.
Terpenoids and Their Volatile Nature
The characteristic aroma of Citrus medica comes from its essential oil, which is exceptionally rich in terpenoids. These volatile compounds are synthesized in the flavedo of the fruit and their composition can change as the fruit matures. Limonene is the most abundant terpenoid in citron's essential oil, known for its anti-inflammatory and antioxidant effects. Other major components include γ-terpinene and citral, which has antimicrobial properties. Limonoids such as nomilin and limonin contribute to the bitter taste and are being studied for potential anti-cancer activity.
Other Bioactive Compounds
Citrus medica also contains coumarins, polyphenolic compounds found in flowers, peel, and roots, with examples like citropten and scoparone, exhibiting anti-cancer effects. Alkaloids, saponins, and tannins have also been identified. The fruit and peel are also rich in pectin and heteropolysaccharides, which function as dietary fibers.
Bioactivity of Citrus medica's Key Phytochemicals
The phytochemicals in Citrus medica are biologically active and contribute to its medicinal applications. Flavonoids and phenolic acids are powerful antioxidants protecting against oxidative stress. Limonene and flavonoids possess anti-inflammatory properties. Essential oils show broad-spectrum antibacterial and antifungal activities. Extracts from peel and seeds may have antidiabetic potential, while limonoids and other phytochemicals are being investigated for potential anticancer activity.
A Comparison of Phytochemical Profiles in Citrus medica Parts
The concentration and type of phytochemicals can differ significantly depending on which part of the Citrus medica plant is analyzed. The following table provides a general overview based on current research.
| Phytochemical Class | Peel (Flavedo & Albedo) | Pulp | Seeds | Leaves | Essential Oil (from peel) |
|---|---|---|---|---|---|
| Flavonoids | Highest Concentration; especially hesperidin, naringin, quercetin, and rutin. | High concentration, particularly eriocitrin and hesperidin. | Lower concentration of flavonoids compared to peel and pulp. | Contains flavonoids, contributing to overall plant profile. | Not primarily composed of flavonoids, but extraction methods can influence their presence. |
| Terpenoids | Very High Concentration, especially in the essential oil, with limonene and γ-terpinene being predominant. | Lower concentration, primarily limonoids. | Contain limonoids like nomilin and limonin. | Contains terpenoids in its essential oil. | Highest Concentration of volatile terpenes, defining its aromatic profile. |
| Phenolic Acids | High concentration, with o-coumaric acid, p-coumaric acid, and ferulic acid present. | Present in moderate concentrations. | Present, though at lower concentrations than other parts. | Present. | Not the main component. |
| Coumarins | Present in varying amounts. | Present. | Present. | Present, with specific types found in extracts. | Present in some extracts, depends on technique. |
Extraction and Factors Influencing Composition
The extraction of phytochemicals from Citrus medica involves various techniques such as Soxhlet extraction, hydrodistillation, and solvent extraction. The choice of solvent and method influences the types of compounds isolated. Factors influencing the phytochemical composition include genotype, cultivar, maturity stage, and geographical location.
Conclusion
Citrus medica is a plant rich in diverse phytochemicals, including flavonoids, terpenoids, phenolic acids, coumarins, and limonoids, with concentrations varying across different plant parts. These compounds provide antioxidant, anti-inflammatory, antimicrobial, and potential anticancer effects, making citron a valuable source for nutraceutical and pharmaceutical research. Further research is needed to fully understand their potential.
One extensive review of citron's chemical and biological properties is available from the journal Molecules at An Insight into Citrus medica Linn.: A Systematic Review on Phytochemical Composition and Biological Properties.
