Plants have the ability to synthesize a wide variety of chemical compounds that are used to perform important biological functions, and to defend against attack from predators such as insects, fungi and herbivorous mammals. Many of these phytochemicals have beneficial effects on long-term health when consumed by humans, and can be used to effectively treat human diseases. At least 12,000 such compounds have been isolated so far; a number estimated to be less than 10% of the total. These phytochemicals are divided into (1) primary metabolites such as sugars and fats, which are found in all plants; and (2) secondary metabolites – compounds which are found in a smaller range of plants, serving a more specific function. For example, some secondary metabolites are toxins used to deter predation and others are pheromones used to attract insects for pollination. It is these secondary metabolites and pigments that can have therapeutic actions in humans and which can be refined to produce drugs—examples are inulin from the roots of dahlias, quinine from the cinchona, morphine and codeine from the poppy, and digoxin from the foxglove. Chemical compounds in plants mediate their effects on the human body through processes identical to those already well understood for the chemical compounds in conventional drugs; thus herbal medicines do not differ greatly from conventional drugs in terms of how they work. This enables herbal medicines to be as effective as conventional medicines, but also gives them the same potential to cause harmful side effects.
Modern medicine now tends to use the active ingredients of plants rather than the whole plants. The phytochemicals may be synthesized, compounded or otherwise transformed to make pharmaceuticals. Examples of such derivatives include Digoxin, from digitalis; capsaicine, from chili; and aspirin, which is chemically related to the salicylic acid found in white willow. The opium poppy continues to be a major industrial source of opiates, including morphine. Few traditional remedies, however, have translated into modern drugs, although there is continuing research into the efficacy and possible adaptation of traditional herbal treatments.
Açai (Euterpe oleracea) Although açai berries are a longstanding food source for indigenous people of the Amazon, there is no evidence that they have historically served a medicinal, as opposed to nutritional role. In spite of their recent popularity in the United States as a dietary supplement, there is currently no evidence for their effectiveness for any health-related purpose.
Belladonna (Atropa belladonna), although toxic, was used historically in Italy by women to enlarge their pupils, as well as a sedative, among other uses. The name itself means "beautiful woman" in Italian.
Coffee senna (Cassia occidentalis) is used in a wide variety of roles in traditional medicine, including in particular as a broad-spectrum internal and external antimicrobial, for liver disorders, for intestinal worms and other parasites and as an immune-system stimulant.
Comfrey (Symphytum officinale) has been used as a vulnerary and to reduce inflammation. It was also used internally in the past, for stomach and other ailments, but its toxicity has led a number of other countries, including Canada, Brazil, Australia, and the United Kingdom, to severely restrict or ban the use of comfrey.
Kratom (Mitragyna speciosa) Kratom is known to prevent or delay withdrawal symptoms in an opiate dependent individual, and it is often used to mitigate cravings thereafter. It can also be used for other medicinal purposes. Kratom has been traditionally used in regions such as Malaysia, Thailand, and Indonesia.
Kanna (Sceletium tortuosum) African treatment for depression. Suggested to be an SSRI or have similar effects, but unknown MOA.
Oregano (Origanum vulgare) Used as an abortifacient in folk medicine in some parts of Bolivia and other north western South American countries, though no evidence of efficacy exists in Western medicine. Hippocrates used oregano as an antiseptic, as well as a cure for stomach and respiratory ailments. A Cretan oregano (O. dictamnus) is still used today in Greece as a palliative for sore throat. Evidence of efficacy in this matter is also lacking evidence.
Syrian Rue (aka Harmal) (Peganum harmala) - MAOI. Can be used as an anti-depressant, but carries significant risk. Used in traditional shamanistic rites in the amazon, and is a component of Ayahuasca, Caapi or Yajé (which is actually usually Banisteriopsis caapi but has the same active alkaloids).
Thyme (Thymus vulgaris) is used to treat bronchitis and cough. It serves as an antispasmotic and expectorant in this role. It has also been used in many other medicinal roles in Asian and Ayurvedic medicine, although it has not been shown to be effective in non-respiratory medicinal roles.
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