The power of the coffee leaf

Dr. Claudine Campa, from the Institut de Recherche pour le Développement in France, has a bit of a leaf obsession. Campa specialises in looking at the phenolic composition of leaves – the natural compounds that build up in plants to help protect the plant from natural elements. Fortunately for the coffee industry, Campa recently turned her near obsession to this caffeinated plant. “Much of the focus of studies on coffee has been directed on its uses as a beverage. The research often starts with the cup in mind: the seeds, that is the coffee beans. Few people have thought about the leaves,” says Campa. “But when you think about it, everything is linked to the nutrition of a plant. From the roots, to the photosynthesis carried out by the leaves, it all comes together to define the health of the fruit and the beans inside.” The results of Campa’s coffee-leaf focus have resulted in a scientific paper she first-authors “A survey of mangiferin and hydroxycinnamic acid ester accumulation in coffee (Coffea) leaves: biological implications and uses” published in the Annals of Botany in April this year. The results could have profound implications for the coffee industry, offering new possibilities for breeding more resistant coffee varieties. Additionally, the potential health benefits discovered in the study open up new possibilities for using coffee leaves in pharmaceuticals and natural medicines. As well as the commercial coffee species, Coffea arabica (Arabica) and C. canephora (Robusta), Campa opted to look at less studied wild species in Africa and Madagascar. This follows on from the work of one her co-authors Dr. Aaron Davis. Davis, of the Royal Botanic Gardens, Kew (United Kingdom) has focused much of his recent work on discovering and studying wild coffee species, which includes estimating the medium- to long-term potential for coffee production. While several biochemical studies have focused on wild species, Campa says these have generally focused on green (unroasted) and roasted beans, with little attention paid to the leaves. Other than Arabica and Robusta, only one wild species has been studied for its leaf phenolic content. Furthermore, Campa says that chemical analysis of wild species from Madagascar has been limited. The last published study was by Jean Jacques Rakotomalala in 1992. Rakotomalala continues to work in Madagascar, at the coffee research station in Kianjavato, where they hold a large living collection of wild coffee plants. “But most coffee research has been focused on the seeds,” says Campa. “But if you think about it, the leaves are also of critical importance. With climate change, for example, it makes sense to start paying attention to other parts of the coffee plant, including the leaves.” In the study, led by Campa, the team looked at 23 coffee species, observing – as the title of her study suggests – the levels of accumulation of hydroxycinnamic acid esters (HCEs) as well as mangiferin. Mangiferin was first isolated from mangos, and provides plants with antioxidants, antimicrobial protection, and also helps shield against the sun’s UV rays. Study of these phenolic compounds helps scientists understand how plants evolve and adapt to environmental change. Prior to this study, mangiferin  had only been detected in Coffea pseudozanguebariae. A key result was the discovery that seven of the species studied, including the cultivated species Arabica (but not Robusta), stored mangiferin in their leaves, and also in the outer layer of their fruit. Campa says this could be one of the ways coffee species have evolved mechanisms to combat the damaging influence of harsh UV rays in environments (for instance at high altitude). “It’s really interesting to look at the composition of these wild species, especially from a commercial perspective,” she says. “Crossing these plants with cultivated species provide a way to help protect those species from climate change  while not affecting the quality of coffee.” Campa points out that focusing on protecting agents in coffee leaves provides a way to improve the quality altogether, because better healthier plants will be tasted in the cup. COFFEE LEAVES AS TEA?
This renewed focus on coffee leaves opens up new possibilities for the potential future usage of the plant beyond the cherry. To this end, Davis says there are varied interests in coffee leaves as a beverage and a health remedy. “Chlorogenic acids are powerful antioxidants. In the green beans of Robusta their content is very high typically 6 to 7 per cent and a bit less in Arabica.” he says. “Coffee-leaf tea might be another way to consume high levels of antioxidants via a beverage that’s not coffee.” Chlorogenic acids, derived from green coffee beans, have received recent publicity as a means of reducing body fat, leading to weight loss. Davis says, however, that further study would be needed to confirm coffee-leaf tea as a metabolism-boosting agent, or indeed for consumption in general. Shortly after the 2012 study was released, Davis travelled to South Sudan with World Coffee Research’s Executive Director Tim Schilling and visited a small village on the Boma Plateau. They met a woman who had been gathering wild Arabica in the forests for years. “It was clear she wasn’t interested in coffee beans but only the leaves,” Davis recalls. “This woman would trek into the forest on a weekly basis to collect coffee leaves to make tea. She used it as a beverage and as a very concentrated tea-like infusion as a purgative when she was ill.” Coffee-leaf teas and other drinks made from the outer part of the coffee cherry are also widely used in Ethiopia, and other parts of Africa. There is also a long history of coffee-leaf tea drinking. Davis has found numerous records of its use, dating back to the 1800s, in countries including Jamaica, India, Java and Sumatra. In the Economic Botany collection in Kew, there are numerous examples of coffee-leaf tea, processed either like green tea or a fragmented black tea (see photo on page 44). Dr Gardner of Ceylon took out a patent for preparing coffee-leaf tea in the 1850s. The infusion of the coffee-leaf had long been an article of universal consumption among the natives of parts of Sumatra, according to P.L Simmonds in The Commercial Products of the Vegetable Kingdom. Wherever coffee was grown, the leaf had become one of the “necessaries of life”, which the natives regarded as “indispensable”.  Looking back on its fascinating history, Davis says it’s fair to say the first consumers of coffee-leaf would have had a degree of knowledge about its health benefits, based on personal experience. “At one stage it was considered more popular than drinking water,” he says. For Davis, who was involved in Campa’s study as the expert on wild coffee species, some of the most compelling questions are the origins and history of coffee leaf usage. “Why was it once so popular in certain parts of the world, particularly Asia and Africa, and is no longer?” he asks. “It may be that the market was just saturated with normal tea and there was no interest in it. Maybe there wasn’t enough for production, we just don’t know.” Arabica was widely grown in South East Asia up until the end of the 18th Century, until it started to attract diseases. Robusta was then taken from West and Central Africa to South East Asia in the 1900s and Davis wonders whether this switch prevented the practice of coffee-leaf drinking to carry on through the 19th and 20th centuries in parts of Asia. “There is no concrete evidence to confirm this idea, but there does seem to be some historical correspondence,” he says. So far it appears that only Arabica leaves are used to make tea, but this also requires confirmation. With a possible regeneration in interest in coffee-leaf tea, Davis says there might be potential for growing a crop of coffee leaves in areas that are not suitable for coffee production. “I wonder if there is the potential for using defunct coffee plantations that may not be good for growing beans, but are good for growing coffee leaf tea?” he asks. Davis is not the first to have this thought. On 14 April 1977 The Brisbane Courier reported that coffee-leaf tea had the same potential to advance at the rate of Chinese tea. “If found superior it would lead to a change in the cultivation of the coffee tree in plantations abroad,” the article stated. “It would be more profitable to cultivate the coffee tree for its leaf than its berry or it might enable the plantar to secure first the berry, and hence a crop of leaves with greater yield would enable him to sell both as cheap as the crop of berry alone.” Davis points out that production is one thing, but taste and quality are another. In 1876 The British Medical Journal stated that various travellers, both in the West and in the East of the Eastern Archipelago spoke very favourably of the flavour. “The taste of coffee-leaf tea was considered ‘fresh’ and ‘most delicious’… So it might just have value as a niche beverage and perhaps be popular once again,” Davis says. SAVE THE LEAF, SAVE THE TREE
Campa is hoping that her study will help demonstrate some of the many qualities of plants, and as such the dangers of cutting them down. She notes that deforestation, in Madagascar in particular, has been devastating. Other than protected areas (such as national parks), she says the country’s forests are being destroyed at an alarming rate. “Perhaps if they know more about the amazing attributes these plants hold, they’ll be more careful,” she says. “These plants hold some amazing qualities, many of which we’re only just beginning to discover.” GCR

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