For tens of thousands of years people have used plants to cure illness but many of their medical uses have yet to be identified.
A UAE study has now moved science a step closer to better realising the pharmaceutical potential of plants by highlighting possible uses in medicine of two mulberry species that grow in the country.
Morus nigra, the black mulberry, a species native to the Emirates, and Morus alba, the white mulberry, a non-native that grows wild in the country, are potential sources of antibiotics and other medicines, the research indicates.
Fujairah Research Centre and Umm Al Quwain University scientists tested whether extracts of the leaves, branches and roots inhibited the growth of laboratory cultures of bacteria or fungi.
Writing in Nature Communications, they said the inhibitory effects of bacterial or fungal extracts were “significantly stronger” than those in some previous studies with other plants. The Morus species have, they said, “exceptional antimicrobial potential”.
Antibiotics boost
“These findings underscore the medicinal and therapeutic potential of both species, particularly M. alba, in developing natural antimicrobial alternatives, as well as new antibiotics and antifungal drugs,” they wrote.
Both mulberry species offer “innovative natural solutions” to antimicrobial resistance, which is the process by which bacteria and other microbes becoming immune to medicines used to control them.
Antimicrobial resistance is described by the World Health Organisation as one of the biggest public health and development threats, with an estimated 1.3 million deaths each year caused directly by bacterial resistance to antibiotics evolving.
Ian Graham, a professor of biochemical genetics at the University of York in the UK, who researches medicinal crops, said many useful medicinal properties of plants have yet to be characterised.
“They are a treasure trove that’s still waiting to be discovered,” said Prof Graham, who was not connected to the UAE research.
Plants contain antimicrobial substances because in nature they are a vital line of defence against the likes of bacteria, fungi and viruses. Since plants started to evolve hundreds of millions of years ago, they have “been in an arms race” with pathogens, Prof Graham said.
“It’s a chemical arms race,” he said. “They have had to be very, very good at that because unlike animals, if they’re attacked they cannot get up and run away. Quite often the rich complexity of chemicals inside plants is because they have been evolving to defend themselves.”
Prof Graham said the latest technology was making it easier for researchers to identify novel and potentially useful substances in plants. “Using things like DNA sequencing you can then also discover the genes responsible for the production of some of these compounds,” he said.
Sometimes the compounds are present in “very, very small amounts in plants”, but if the gene to produce them is identified, it offers the potential that it could be inserted into a host organism, often a bacterium, which could then produce the substance in large quantities.
“It’s a really exciting time in the world of biology,” Prof Graham said. “We’re better able to discover the compounds and produce them commercially and then treat people.”
Countering stubborn bacteria
Prof Michael Heinrich, of the School of Pharmacy at University College London, said plant extracts could have “broad spectrum activity” against micro-organisms. As a result, resistance among micro-organisms may be less likely to develop.
More careful use of antibiotics can also cut the likelihood of resistance to them developing among bacteria.
Prof Heinrich said the use of antibiotics, most of which were originally discovered in fungi rather than plants, must be reserved for situations “where they are essential”.
“We must reduce our use of antibiotics,” Prof Heinrich said. “This requires complex responses, including a reduction in prescriptions, since most uses of antibiotics are not necessary if they are for minor self-limiting conditions or driven by patients’ expectations for a ‘quick fix’ which does not work.”
He described the preventive use of antibiotics in animals, which campaigners have said is often done to prevent the spread of disease in intensive farming systems, as a “major concern”.
Although researchers are interested in analysing plants to discover whether they could be sources of new antibiotics, plants have long been a source of many other types of pharmaceutical substances.
For example, Artemisia annuaor – sweet wormwood – has been used against malaria in traditional Chinese medicine for millennia, and in recent decades a substance from the plant, artemisinin, has been used in modern medicine to treat the condition, which is caused by the Plasmodium parasite.
“Somebody suffering from malaria will take that medicine entirely derived from plants that can kill the parasite and cure malaria. It’s used to cure millions of people,” Prof Graham said.
Another example concerns the opium poppy, which is a source of codeine and morphine, two of the most widely used painkillers. Poppies grown, for example, on the Australian island of Tasmania are used in codeine production.
The researchers who carried out the study on the two Morus species analysed in the UAE said further analysis was needed to fully assess what biologically active substances were present.
It may not just be medicines that could be extracted from them, as the latest research suggests they also contain a wealth of nutrients.
“In addition to their medicinal and pharmaceutical applications, their rich mineral and nutrient profiles highlight their significant potential for industrial use in food supplements and healthcare sectors,” the researchers wrote.
