Recent Advances in Polyphenol Research. Группа авторов

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Recent Advances in Polyphenol Research - Группа авторов


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used these clues to guide their own use of polyphenol‐rich plants as medicines for specific ailments. For animals, is it assumed that nutritional wisdom or use of plant resources for healing is a combination of post‐ingestive hedonic feedback and individual learning. Animals can use hedonic feedback to find ways of removing the unpleasant sensations of disease and injury. Some research has asserted that there is a purgative effect on the animal’s intestines that helps alleviate parasitic infections (see details below), whereas other theories maintain that the natural antimicrobial/wound‐healing effects provided by plant polyphenols are impetus for a wild animal’s tendency to seek berries or other polyphenolic resources, especially after they’ve incurred defensive wounds.

      Zoopharmacognosy is defined as the use of plant medicines/medicinally active herbs by animals—specifically when an animal seeks out a plant that is not normally part of its diet (and may have no nutritive value) in order to cure injury or disease (Moerman 1996). Mammals and even birds and insects are able to self‐medicate using plant resources for both physical and psychological treatments. Native Americans revered the bear as one of the most advanced animals in terms of self‐medication, as they use their clawed paws to dig for medicinal root crops (Densmore 1974).

      Native American traditional ecological knowledge observed that animals tend to “self‐regulate” tannin content via the diet (Moerman 1996; Engel 2007). Feeding deterrents (like tannins) are deliberately sought out by animals when the bioactive benefits outweigh the adverse tastes. For example, wild deer deliberately select plants not with very low tannin content, but those with moderate tannin content, as an adaptive taste preference, presumably because of the impact of the tannins on intestinal parasites. Repeated evidence suggests that animals attempt to self‐regulate tannin consumption to optimal levels. Similarly, the Asiatic two‐horned rhinoceros periodically will consume copious amounts of mangrove bark (tannin‐rich) to the point where their urine turns orange, to self‐medicate against endemic dysentery, just as a common medication for human dysentery (clioquinol) has a 50% tannin content (Engel 2007). During the coevolution of plants and animals, animals developed receptors for plant‐produced bioactive chemicals (benzodiazepine, opioid, and vanilloid), which had direct effects on the sensations of pain or of consciousness; the animal‐to‐plant relationships provided a template by which herbalists could treat human patients for seizures, anxiety, and pain.

      Enthusiastic consumption of other polyphenol‐rich plants, including wild berries, is a typical behavior for dogs (Sueda et al. 2008). Anecdotal evidence suggests that dogs will mimic humans when foraging for berries and harvesting from gardens. Dogs apparently love all types of berries—blueberries, strawberries, blackberries, and raspberries have all been scavenged, often to the chagrin of their owners, as well as peas, fallen apples, and corn on the cob from gardens. Sled dogs routinely accompany their owners during wild berry harvesting in Alaska, as a safeguard to keep foraging bears at bay, and these dogs routinely scavenge the berries from the lower branches in a berry stand. In a formal study on the antioxidant status of sled dogs fed wild blueberries, berries were initially mixed into the kibble and fed to the treated animals; however, it soon became apparent that the dogs preferred the berries and if placed on top of the kibble, they’d eat the berries first (Dunlap et al. 2006).

Schematic illustration of the wild wolf feeding on Alaskan salmonberries.

      Source: Illustration by Ginger Dunlap.

      Grizzly and black bears in Alaska are also notorious for copious consumption of wild berries, necessitating that Alaska Native and aboriginal Canadian berry harvesters must carry firearms for protection (as well as their domesticated sled dogs). Hunters have reported that during berry ripening season, grizzly bears actually have blue coloration from the berries interlaced in their fat deposits, and the meat acquires a sweeter flavor (Dr. Arleigh J. Reynold, DVM, PhD, University of Alaska Fairbanks, 2018, personal communication, 10 August).

      Nonhuman primates frequently make use of plants and other natural resources to self‐medicate. The most frequent observations are ingestion of natural products to purge intestinal parasites. Chimpanzees in Tanzania have been observed to fold, and then swallow, whole Aspilia spp. leaves without mastication; there is no known nutritional value but the undigested rough textured leaves help to expel parasitic worms into the feces. Similar cases where monkeys have ingested certain plants to dislodge parasites have been recorded. Primate behavior of this kind has helped to guide scientists to previously unscreened plant material that may have antimicrobial or antiparasitic properties. One very intriguing recent discovery with primates involves lemurs in Madagascar who deliberately chew on and vigorously rub millipedes, causing them to release secreted toxins in defense. Only then, once the toxins containing benzoquinones are released, the lemurs eat the crushed insects and rub them on their genitalia in order to kill parasitic worms (Bittel 2018).

      Traditional ecological knowledge concerning the medicinal use of polyphenol‐rich plants reaches back many hundreds and even thousands of years, but the naturopathic doctors and healers who routinely rely on wildcrafted plants are frequently loath to share their knowledge with anyone from outside the native communities. The reason for this reluctance has been the exploitation (and resultant overharvesting and/or theft) of native resources by outsiders in the past, which has undermined the authority and historical access of traditional healers (Andrae‐Marobela et al. 2012). The reductionist paradigm of Western science marginalizes the holistic approaches of wildcrafted medicine, and was imposed on top of indigenous knowledge systems during colonialism, which has made “bioprospecting” a disrespected term in the opinion of many elders in native tribal groups (Kellogg et al. 2010).


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