Tomato fruit received a boost recently by the discovery that it can be a source of valuable nutraceutical substance extracted and purified from the outer gel like coating of the seed. Now comes the news that Lectin from Banana can be used to counteract spread of HIV infection and minimize incidence of Acquired Immunity Deficiency Syndrome (AIDS) in humans. If sufficient supporting evidence is forth coming from this discovery, many food materials, especially fruits, vegetables and spices are going to be of relevance to the pharmaceutical industry in coming years.
The story of Tomato is very interesting as consuming whole tomato as part of a regular diet does not confer any special health benefit though it is a good source of Vitamin C and antioxidants. Tomato as a part of the vegetable intake compliments the virtues of other vegetables collectively in ensuring normal health without any deficiency disorders. But the purified fraction of Tomato seed extract, with aspirin-like activity, keeps blood thin just like aspirin which is taken regularly in small doses by millions of people to prevent platelet aggregation and consequent myocardial infarction. Where Tomato extract excels aspirin is in preventing gastro intestinal injury and consequent intestinal bleeding commonly encountered amongst aspirin consumers. Added to this is its claimed effectiveness against Deep Vein Thrombosis and Triglyceride deposits in arteries. Most interestingly the claimed benefit from the fractionated preparation of tomato seed is not available by consuming fresh tomatoes in regular diets. Probably the rationale is that the gel like seed coating is not digestible in human GI system.
All plant materials contain Lectins which are proteins or glycoproteins with specific biological function assigned to them by nature. They have active sites that can bind sugars and sugar derivatives through which they identify foreign invaders like a virus and attach themselves to such pathogens to prevent access to human cells. Lectins are present in food grains including legumes, dairy products in significant concentrations. One of the most renowned (for wrong reason) examples of a Lectin is Ricin, extracted from Castor seed and reported to have been used during the last world war as a part of the biological warfare. Ricin at concentrations as low as 500 ug in the air can cause breathing problem with lethal consequences. Though food grains like wheat and soybean contain toxic lectins, they are destroyed mostly during processing and thermal treatment.
That toxicity of Lectins can be gainfully exploited for beneficial purpose has been proved by the studies on banana Lectin which has two characteristic primary sites that can bind the sugar moiety in viral particles disabling it from entering into the host cells in human beings. Lectins, being proteins, can be isolated through many biotechnological methods like chromatography of different types and such pure preparations are considered effective against the much dreaded AIDS. Present anti-viral drugs like T-20 and Maraviroc are often ineffective against this virus when continuous mutation occurs. Banana Lectin was found to have virocidal effect and its regular use can prevent this sexually transmitted disease with high degree of success. According to the claims by the discoverers even at 20% coverage of vulnerable population and with 60% efficiency, Banana Lectin can prevent up to 2.5 million new cases of AIDS in the world every year.