Exploring the potential of Manilkara zapota leaves in corneal wound healing through phytochemical screening and in-vitro studies
Imagine a world where a simple scratch on the surface of your eye could lead to lasting vision problems, chronic pain, and limited treatment options.
This is the reality for millions worldwide who suffer from corneal wounds—one of the most common and challenging ocular conditions faced by ophthalmologists. The cornea, the eye's transparent front window, plays a critical role in focusing vision, and any damage to its delicate epithelial layer can compromise its clarity and function. Traditional treatments often focus on managing symptoms rather than actively promoting regeneration, leaving a significant gap in effective therapeutic options.
In the quest for innovative solutions, scientists are increasingly turning to nature's pharmacy, exploring medicinal plants that have been used for centuries in traditional healing systems. One such promising candidate is Manilkara zapota—commonly known as sapodilla—a tropical evergreen tree native to southern Mexico and Central America. While its sweet, malty fruit has delighted palates for generations, researchers are now uncovering remarkable healing properties in its leaves that could transform how we treat corneal injuries 8 . This article explores the exciting scientific journey to develop a novel herbal treatment from M. zapota leaves that may accelerate corneal healing and restore vision more effectively than current options.
The cornea is a marvel of biological engineering—a completely transparent tissue that lacks blood vessels yet remains exquisitely sensitive. Its exposed position makes it particularly vulnerable to injury from chemical, physical, and pathological insults. Corneal wound healing is an intricate dance of cellular processes that must occur in perfect sequence to restore vision without scarring.
Neighboring epithelial cells flatten and migrate to cover the defect within hours of injury.
Stem cells from the corneoscleral junction multiply to replenish lost cells.
The extracellular matrix reorganizes to restore normal architecture and transparency.
Nerve fibers regenerate to restore sensitivity and trophic support.
This process is regulated by a complex interplay of cytokines, growth factors, and signaling pathways 5 . When any aspect of this sequence is disrupted, complications can arise—including persistent epithelial defects, stromal scarring, and impaired nerve regeneration, all of which can permanently affect visual acuity.
Current treatments primarily aim to prevent infection and manage inflammation, but few options actively promote the regenerative processes. The development of treatments that can modulate multiple aspects of the healing response represents a significant unmet need in ophthalmology.
Manilkara zapota has a rich history of traditional use for various ailments. Different parts of the plant have been employed in traditional medicine to treat fever, hemorrhage, ulcers, and wounds 6 . The milky latex from its bark—known as chicle—was once the primary base for chewing gum, while its delicious fruit is enjoyed throughout the tropics 8 .
Neutralizes harmful free radicals that can damage tissues.
Modulates the body's immune response to reduce inflammation.
Effective against various pathogens that can infect wounds.
Modern scientific investigation has begun to validate and expand upon these traditional uses. Previous research on M. zapota has revealed a range of beneficial properties that suggested it might contain compounds with significant tissue-healing potential. However, until recently, its specific effects on corneal wound healing remained unexplored.
| Compound Class | Specific Compounds Identified | Known Biological Activities |
|---|---|---|
| Triterpenoids | Lupeol acetate, Oleanolic acid | Anti-inflammatory, Antioxidant, Wound healing |
| Flavonoids | Apigenin-7-O-α-L-rhamnoside, Myricetin-3-O-α-L-rhamnoside | Antioxidant, Anti-inflammatory, Collagen stabilization |
| Phenolic Acids | Caffeic acid | Antioxidant, Antimicrobial, Wound healing |
| Fatty Acids | Oleic acid, Linoleidic acid, Linoleic acid | Membrane repair, Anti-inflammatory |
The turning point came when researchers began to identify the specific phytochemicals responsible for these biological activities. The leaves of M. zapota have been found to contain a rich array of bioactive compounds, including flavonoids, triterpenes, and phenolic compounds . These natural products work in concert through multiple biological pathways, making them particularly interesting for complex processes like wound healing.
To systematically evaluate the corneal wound healing potential of M. zapota leaves, researchers designed a comprehensive study focusing on the PKM1 variety of the plant. This particular variety was selected for its uniform growth characteristics and consistent phytochemical profile, important considerations for reproducible herbal medicine development.
The leaves of Manilkara zapota (L.) Van Royen var. PKM1 were collected, authenticated, and shade-dried to preserve their bioactive components. The dried leaves were ground into a coarse powder using an electric grinder. Researchers then prepared extracts using a Soxhlet extraction system with 90% ethanol as the solvent—a method chosen for its efficiency in extracting a broad range of phytochemicals 6 . The resulting extract was concentrated using a rotary evaporator and stored in controlled conditions until use.
The extract underwent comprehensive phytochemical analysis to identify its chemical constituents. Advanced techniques including IR, UV, MS, ¹H-NMR, and ¹³C-NMR spectroscopy were employed to characterize the isolated compounds . This detailed chemical profiling is essential for standardizing herbal preparations and ensuring consistent biological effects.
The core of the experiment utilized a well-established scratch wound assay on Statens Seruminstitut Rabbit Corneal (SIRC) epithelial cells 5 . This model system closely mimics the behavior of human corneal epithelial cells and provides a controlled environment to study wound healing mechanisms.
The experimental procedure followed these key steps:
This methodology allowed researchers to precisely measure the extract's effects on cell migration, proliferation, and protection against free radical damage—all critical processes in corneal wound healing.
The experimental findings demonstrated compelling evidence for the wound healing potential of M. zapota leaf extract. The in-vitro scratch assay revealed a significant acceleration of wound closure in cells treated with the extract compared to untreated controls.
| Time Point | Control Group (% Wound Closure) | M. zapota Treated (% Wound Closure) | Significance Level |
|---|---|---|---|
| 12 hours | 28.5% | 45.7% | p < 0.01 |
| 24 hours | 52.3% | 75.6% | p < 0.001 |
| 36 hours | 78.9% | 92.4% | p < 0.01 |
| 48 hours | 95.2% | 99.1% | p < 0.05 |
The data show that at every time point measured, the M. zapota treated cells demonstrated significantly faster wound closure. By 24 hours—a critical period in corneal healing—the extract had achieved nearly 50% greater wound closure compared to the control group.
When corneal epithelial cells were exposed to hydrogen peroxide (H₂O₂)—a potent inducer of oxidative damage—pretreatment with M. zapota extract significantly reduced reactive oxygen species (ROS) formation. This antioxidant effect is particularly relevant for corneal wound healing, as oxidative stress is known to impede repair processes and contribute to poor outcomes 5 .
The safety profile of the extract was also established during these experiments, with high LD₅₀ values (the dose at which a substance becomes lethal to 50% of test subjects) recorded for both alcoholic and aqueous extracts, suggesting a favorable safety profile for potential therapeutic use .
The combined results of accelerated wound closure, reduced oxidative stress, and low toxicity profile position M. zapota leaf extract as a promising candidate for further development as a corneal wound healing therapeutic.
Corneal wound healing research requires specialized materials and methods to obtain reliable, reproducible results. The following table details key reagents and their functions in studying herbal-based wound healing therapies:
| Research Reagent | Function in the Experiment |
|---|---|
| SIRC Cell Line | Immortalized rabbit corneal epithelial cells providing a consistent in-vitro model for corneal wound healing studies |
| Eagle's Minimum Essential Medium (EMEM) | Specialized nutrient medium optimized for maintaining SIRC cell growth and function |
| Soxhlet Extraction Apparatus | Laboratory equipment for continuous extraction of plant materials with solvent reflux |
| Ethanol (90%) | Extraction solvent effective for isolating a broad range of medium and high-polarity phytochemicals |
| Hydrogen Peroxide (H₂O₂) | Chemical inducer of oxidative stress to test the antioxidant capacity of the extract |
| DCFDA Assay Kit | Fluorescent method for detecting and quantifying intracellular reactive oxygen species |
| Gelatin Solution | Coating agent to promote cell adhesion to culture plates for consistent monolayer formation |
| Type IV Collagen | Natural extracellular matrix component used to coat culture surfaces to mimic the corneal basement membrane |
The compelling evidence for M. zapota's corneal wound healing activity opens exciting avenues for both natural product research and ophthalmic drug development. The multifactorial nature of corneal healing—requiring coordinated modulation of inflammation, oxidative stress, cell migration, and proliferation—makes a multi-targeted herbal approach particularly attractive.
The findings align with a growing recognition in pharmacology that complex herbal combinations often have advantages over single-compound drugs, especially for processes involving multiple interconnected biological pathways. This "network pharmacology" perspective helps explain how the diverse phytochemicals in M. zapota extract might work synergistically to promote healing more effectively than isolated compounds.
The integration of traditional botanical knowledge with modern pharmacological research continues to yield valuable therapeutic candidates. M. zapota represents an excellent example of how systematic scientific investigation can transform traditional remedies into evidence-based medicines.
As research progresses, we may soon see a new generation of herbal-based ophthalmic preparations that offer enhanced healing for corneal injuries—potentially reducing suffering and vision loss for millions. This research not only validates traditional wisdom but also demonstrates the continuing relevance of natural products in addressing contemporary medical challenges.
The journey from traditional remedy to modern medicine continues, with nature's pharmacy offering promising solutions to some of ophthalmology's most persistent challenges.