Anti-bacterial, Anti-fungal, Anti-oxidant and Anti-inflammatory Activities of Two Sri Lankan Cultivars of Mango (Mangifera Indica L.) Extracts

In the humid orchards of Sri Lanka, mango trees are more than just sources of fruit; they are battlegrounds where plants fight invisible invaders. Like all living things, mangoes are constantly under siege by microscopic organisms, including bacteria and fungi, that cause spots, rot, and blight. For decades, farmers have relied on synthetic chemicals to stop these infections, but these solutions come with heavy costs: they can harm the environment, pose risks to human health, and often lead to the microbes becoming resistant to the very drugs meant to kill them. Nature, however, has its own arsenal. Plants produce a complex mix of chemical compounds to defend themselves against disease, and scientists have long suspected that these natural defenses could be harvested to protect crops without the downsides of industrial chemicals. The question is not just whether plants can fight back, but whether specific parts of a specific tree can be turned into a reliable shield for the farmer.

A team of researchers at the University of Kelaniya set out to test this idea using two of Sri Lanka's most beloved mango varieties: Karthakolomban and Villard. They were not looking at the fruit people eat, but rather at the parts of the tree that are usually discarded or overlooked: the leaves, the peels, the seeds, and the pulp. The researchers collected samples of diseased leaves from various gardens across the country to identify the specific bacteria and fungi attacking the trees. Once they knew their enemies, they turned their attention to the mangoes themselves. They gathered healthy leaves, peels, seeds, and pulp from the two varieties and soaked them in ethanol, a type of alcohol, to draw out the active chemical compounds hidden inside the plant tissues. This process created a series of liquid extracts, each representing a different part of a different mango variety, ready to be tested against the pathogens.

The first step in the investigation was to see if these extracts could stop the growth of the microbes in a controlled setting. The researchers placed the extracts on plates where the bacteria and fungi were growing and watched to see if a clear zone formed around the liquid, indicating that the microbes could not survive there. The results were striking. The extracts from the seeds and peels showed the strongest ability to halt the growth of bacteria. In particular, the extract from the seeds of the Villard variety proved to be the most powerful antibacterial agent tested overall. While the seed extract was the top performer, the researchers also found that the Villard leaf extract was highly effective against a specific type of bacteria called Bacillus pumilus, stopping its growth at a very low concentration of 6.25 micrograms per milliliter. When the researchers measured exactly how much extract was needed to stop the microbes, they found that a very small amount was sufficient for these specific successes. While the extracts were also effective against fungi, they generally needed higher concentrations to do the job, suggesting that fungal cells are tougher to penetrate than bacterial ones.

Beyond simply killing the microbes, the researchers wanted to know if the extracts could stop them from forming biofilms. Biofilms are slimy communities that bacteria build to protect themselves, making them much harder to treat. The study found that the peel extract from the Karthakolomban variety was remarkably good at preventing this. It stopped the formation of biofilms by a specific bacterium, Pantoea wallisii, by nearly 60 percent. This is a significant finding because it suggests that these natural extracts don't just kill existing bacteria; they can also disrupt the way bacteria organize and defend themselves. The researchers also tested what happened when they mixed extracts from different parts of the tree. They discovered that combining extracts, such as mixing Villard seed extract with Karthakolomban leaf extract, often worked better than using either one alone. This suggests that the different chemicals in the various parts of the mango might work together to create a stronger defense, a concept known as synergy.

To ensure these findings were not just laboratory tricks, the team took the research to the field. They applied the extracts directly to diseased leaves on living mango trees in a home garden. Over a period of two weeks, they observed the treated leaves alongside untreated ones. The results mirrored the lab tests: the leaves treated with the mango extracts showed a clear reduction in the spread of disease. The lesions did not grow as large, and the blight did not advance as it did on the untreated leaves. This practical demonstration confirmed that the extracts could effectively manage disease under real-world conditions, offering a viable alternative to harsh chemical sprays.

The study concludes that the waste parts of the mango tree—seeds, peels, and leaves—are rich sources of natural antibiotics that can protect the crop itself. By using these extracts, farmers could potentially manage diseases like black spot and leaf blight in a way that is safer for the environment and sustainable for the future. The research does not claim to have solved every problem in mango farming, but it provides strong evidence that nature has already provided the tools needed to fight back. The seeds and peels of the Villard and Karthakolomban mangoes, often discarded after the fruit is eaten, hold the power to protect the next generation of trees, turning agricultural waste into a vital resource for crop health.