Hexane and Ethyl Acetate Fractions from Methanol Extract of GuttaPercha Leaf

1. Introduction

The genus Alstonia, commonly known as guttapercha, is widely distributed in tropical regions. Its leaves have long been used in traditional medicine for antiinflammatory, antipyretic, and antimicrobial purposes. Modern phytochemical investigations have confirmed the presence of a diverse array of secondary metabolites, including alkaloids, flavonoids, terpenoids, and phenolic acids.

When extracting plant material, the polarity of the solvent determines which groups of compounds are recovered. A common approach is to start with a polar solvent such as methanol, then partition the crude extract with solvents of increasing nonpolarity. This yields fractions enriched in compounds of similar polarity, simplifying subsequent analysis.

The present page focuses on the nhexane and ethyl acetate fractions obtained from the methanol extract of guttapercha leaf (Alstonia scholaris). Both fractions are examined for their chemical composition, biological activity, and potential applications.

2. Extraction and Fractionation Procedure

1. Plant material: Fresh leaves were collected, washed, dried at 40C, and ground to a fine powder.
2. Methanol extraction: 500g of powdered leaf material was macerated in 2L of 80% methanol for 72h with occasional shaking. The mixture was filtered and the filtrate concentrated under reduced pressure to yield a dark brown crude methanol extract (~45g).
3. Liquidliquid partition:
   • The crude extract was suspended in 500mL of distilled water and transferred to a separatory funnel.
   • nHexane (3500mL) was added, vigorously shaken, and the organic layer was collected. The combined hexane layers were evaporated to give the nhexane fraction (~6g).
   • The aqueous residue was then extracted with ethyl acetate (3500mL). The ethyl acetate layers were pooled and evaporated to afford the ethyl acetate fraction (~12g).

3. Chemical Profile of the Fractions

3.1 nHexane Fraction

The nonpolar hexane fraction primarily contains lipophilic constituents such as:

• Longchain aliphatic hydrocarbons (C₁₅C₃₀)
• Steroidlike triterpenes (e.g., lupeol, betulin)
• Fatty acids and their methyl esters (palmitic, stearic, oleic acids)
• Nonpolar alkaloids (e.g., alstonine derivatives)

Figure 1. Representative GCMS chromatogram of the nhexane fraction showing major hydrocarbon peaks.

3.2 Ethyl Acetate Fraction

The intermediatepolarity ethyl acetate fraction is richer in phenolic and moderately polar compounds:

• Flavonoid aglycones (quercetin, kaempferol)
• Phenolic acids (caffeic, ferulic, pcoumaric acids)
• Alkaloids with moderate polarity (e.g., alstonine, alstonineNoxide)
• Semipolar terpenoids (e.g., squalene, phytosterols)

Figure 2. HPLC-DAD profile at 280nm highlighting flavonoid peaks in the ethyl acetate fraction.

4. Biological Activities

4.1 Antimicrobial Assays

Both fractions were screened against a panel of Grampositive (Staphylococcus aureus, Bacillus subtilis) and Gramnegative bacteria (Escherichia coli, Pseudomonas aeruginosa) using the disc diffusion method.

• nHexane fraction: Showed modest inhibition zones (810mm) mainly against Grampositive strains, likely due to membranedisrupting terpenes.
• Ethyl acetate fraction: Produced larger zones (1318mm) for both bacteria, reflecting the presence of flavonoids and phenolic acids with known antibacterial mechanisms.

4.2 Antioxidant Capacity

Standard DPPH and ABTS assays were performed. The ethyl acetate fraction exhibited a strong radicalscavenging activity (IC₅₀23gmL), whereas the hexane fraction was weak (IC₅₀>150gmL). The difference correlates with the higher phenolic content in the ethyl acetate extract.

4.3 Cytotoxicity Screening

MTT assays on human lung carcinoma (A549) and normal lung fibroblast (MRC5) cells indicated:

• Hexane fraction: Minimal cytotoxicity (IC₅₀>200gmL) consistent with low bioactivity.
• Ethyl acetate fraction: Moderate cytotoxicity against A549 (IC₅₀45gmL) with a higher selectivity index over normal cells, suggesting potential for anticancer lead discovery.

5. Potential Applications

Based on the chemical and biological findings, several practical avenues can be envisaged:

1. Natural antimicrobial agents: The ethyl acetate fraction could be formulated into topical creams or incorporated into foodpreservation systems.
2. Antioxidant additives: Due to its high radicalscavenging capacity, the fraction may serve as a natural antioxidant in cosmetics or nutraceuticals.
3. Lead compounds for anticancer drug development: Isolation of individual flavonoids or alkaloids showing selective cytotoxicity could provide templates for synthetic modification.
4. Biotechnological production: The extraction method can be scaled using ethanol as a greener alternative to ethyl acetate, maintaining yields of bioactive phenolics.

6. Conclusion

The sequential partition of a methanol leaf extract of Alstonia scholaris yields two distinct fractions with complementary phytochemical profiles. The nonpolar nhexane fraction is rich in lipophilic terpenes and fatty acids, showing limited antimicrobial activity. In contrast, the ethyl acetate fraction concentrates flavonoids, phenolic acids, and moderately polar alkaloids, conferring pronounced antioxidant, antibacterial, and selective cytotoxic properties.

These findings underline the value of systematic solvent fractionation in unlocking the therapeutic potential of traditional medicinal plants. Further work should focus on isolating individual active constituents, elucidating their mechanisms of action, and evaluating safety in invivo models.