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Answering the Call of the Wild: Polyphenols in Traditional Therapeutic Practice
Mary Ann Lila1 and Kriya Dunlap2
1 Plants for Human Health Institute, Department of Food Bioprocessing and Nutrition Sciences, North Carolina State University, Kannapolis, USA
2 Department of Biochemistry, University of Alaska Fairbanks, Fairbanks, USA
3.1 Introduction
Polyphenols, ubiquitous and exceptionally human health–relevant plant‐derived compounds, have had a central role in ethnomedicine (traditional herbal medicine) and subsistence diets throughout history, even prerecorded history (Buttriss 2012; Schmidt and Klaser Cheng 2017). Foraging wild edible plants for foods and therapeutic applications is an ancient tradition that was considered obsolescent by most modern urban consumers, but now is enjoying a resurgence in interest. Thanks to some new insights into the composition and resiliency of endemic wild plants, and the quest for novel flavors and textures—especially in niche, fine dining establishments—wild foraging has become “cool” again. Foraged cuisine and indigenous ingredients are coveted, trendy options in high‐end restaurants, where the tannic astringency of wildcrafted leaves and fruits can complement blander foods or flavor botanical‐infused gins and vodkas, and consumers are keen to experience new foods that they perceive as healthier, natural, and unadulterated (Reyes‐Garcia et al. 2015; Schatzker 2015; Soukand 2016; Sebag‐Montefiore 2017; Pinela et al. 2017). But what is the real history of human use for polyphenol‐rich biologically active edible wild plants? Where were they discovered and which species were preferentially targeted as medicinally relevant?
3.2 The Wildcrafting Tradition
Our hunter‐gatherer ancestors were opportunistic omnivores, combining indigenous plant‐based foods and ingredients and wild‐caught fish and game. Today, wildcrafted plant foods are still part of the cultural and genetic heritage in many nonurbanized regions of the world. They can form the mainstay of the traditional diet, complement staple agricultural foods, help to alleviate poverty, and provide food security, especially in rural villages during times when food is scarce (Soukand 2016; Pinela et al. 2017).
Historically, wild plants, including polyphenol‐rich berryfruits, were put to use as both food and medicines as well as for dyes and preservatives in the Americas, Europe, Africa, and Asia, and in most cases, responsibility for wildcrafting fell to the female villagers (Densmore 1974; Alarcomicronn et al. 2015; Soukand 2016; Pinela et al. 2017). Some of the earliest historic records from Native Americans and Alaska Natives not only describe the sources and preparation of polyphenol‐rich food sources, but also stress the importance of collecting the wild plants in proper season and stage of development, in order to ensure bioactive efficacy, palatability, and resource sustainability (Burns Kraft et al. 2008; Wapner 2012; Allkin 2017). Traditional ecological knowledge and folk medicine provide an ethnobotanical record that guides current discovery efforts (Joseph et al. 2014; Pinela et al. 2017).
Regular consumption of plant‐based diets supports health maintenance by regulating the balance between cellular (endogenous) and dietary (exogenous) antioxidants to maintain cell redox homeostasis, (Al‐Gubory and Laher 2018) whereas plant medicines are generally prepared by extraction and concentration of the active compounds from medicinal species prior to administration either orally or topically to humans (Moerman 1996; Allkin 2017; Pinela et al. 2017). Herbal teas, for example, were social/recreational beverages used without restriction, but more concentrated decoctions were taken only for a limited time to treat a health condition such as a digestive disorder or respiratory symptoms.
Phytotherapy, the integration of traditional practices and scientific method, supports the biological basis for traditional ecological medicines, and traditional knowledge is increasingly evolving as evidence‐based medicine. In the past, the generally potent antioxidant capacities of polyphenolic resources were credited with the multifaceted uses of these plants, however, research now suggests that the diverse health benefits coincident with plant polyphenol intake are more related to their anti‐inflammatory, prebiotic, vasodilation and signaling pathways’ influences (Cordova and Sumpio 2009; Margina et al. 2015). In each case, specific dosages and controlled periods of intake are recommended, often combined with cultural healing rituals (Pinela et al. 2017). Interestingly, Native Americans used only a small percentage of available polyphenol‐containing flora as medicines, and with the exception of several genera (i.e. Ribes, Vaccinium, Malus, Fragaria, Rubus, Crataegus, Prunus, and Arctostaphylos) the species used for medicines excluded those used for foods. This makes some sense, as medicines can be toxic and proper attention to homeopathy implies that the lowest possible effective doses should be used, as is the case for prescription synthetic drugs (Moerman 1996). Even so, there is some recorded overlap. For example, American tribes used wild strawberry fruits as a medicinal for diarrhea, stomach pain, and irregular menstruation, as well as a dietary item (Schmidt and Klaser Cheng 2017).
Plant medicines were used to treat a wide range of human symptoms, including liver conditions, urinary infection, skin problems, inflammation, toothache, diabetes, flu, and bronchitis. Other plant preparations were valued primarily as disinfectants. Historical records reveal that single plants could serve as resources for prescribed treatments against a wide range of diseases, because the diverse phytochemical profiles in wild herbal species enable single plant species to have bioactivities relevant against multiple potential disease targets.
Edible medicinal and dietary polyphenolic resources are usually processed/preserved today, for year‐round use, by freezing the plant material. In traditional cultures, where freezing is (or in the past, was) not an option, materials are preserved and used after (i) desiccation, (ii) preparation of infusions, (iii) decoction and maceration, or (iv) tincture (Pinela et al. 2017). Dried plant materials were either ground into a powder form or pressed between stones into dried cakes. In some cases, berries were pressed and pounded into wild game meats before co‐drying (with a low fire or just hot sun) into a protein/fat/polyphenol‐rich high‐energy food called pemmican or wasna, used in Native American Lakota and Cree cultures. This method not only preserved the polyphenol‐rich berries for year‐round consumption, but served as a natural antimicrobial additive for the meats. Infusions were prepared by soaking dried leaves or powders in (usually boiling) water so that the water‐soluble polyphenols were released (tea‐like preparations). Decoction/maceration is applied especially to tougher plant tissues (woody plant materials), which can be cut into small sections and crushed, then boiled in water for 10–20 minutes to fully extract the phytochemicals from the intractable matrix. When the volume of liquid has been reduced and cooled, additional water can be added and the process repeated. The replicated simmering and boiling cycles can concentrate some of the more stable phytoactive components. Tincture involves extraction of plant materials with alcohol, and storage in the same medium. A still‐popular preservation method in Alaska and northern Canada is the preparation of Eskimo ice cream or agutuk, which is made by whipping fresh wild berries into animal fats (caribou, moose, or walrus tallow, or seal oil). Copious amounts of sugar are typically added (and sometimes fish are added) to the shelf‐stable mixture, which is most often stored in a freezer prior to consumption (Wapner 2012).
The Native American traditional diet was one that many nutritionists would consider a healthy gold standard (consisting of fruits/berries, lean meat, fish, and wild vegetables), and the active hunter/fisher/gatherer lifestyle contributed to lean body mass. Polyphenol‐rich plant intake contributed to the very low incidence of diabetes and other pathologies of metabolic syndrome in Native communities. The forced relocation of Native American tribal communities to reservations in the 1800s separated people from their traditional food sources, and made them dependent on government rations of high‐carbohydrate commodity foods (Goetz 2012). Consequently, the modern incidence of obesity is now 1.6 times higher in Native communities than in the general population, and health conditions including diabetes and heart disease are running rampant (American Diabetes Association 2018). Poverty, lack of access to healthy food options (food