Among the members of the Genus Pueraria, it is Pueraria lobata that contains the largest amount of tannins and other fine chemicals. Pueraria lobata produces very large amounts of simple phenolics (tannins) and highly complex, condensed polyphenolics, having a very high molecular weight. Not all leguminous plants produce tannins. However, legumes that are highly evolved, perennial, deciduous, dicotyledons often contain large quantities of these types of chemicals relative to their biomass. This is the case with Pueraria lobata.
Generally, plants that are perennial and have been forced to develop their defenses against numerous enemies over long periods of evolution contain the greatest amounts and largest numbers of chemical substances. Phytochemicals are used by plants to enhance their survival. Tannins are simple phenols and polyphenols, which bind to proteins specifically. These chemicals are believed to protect the plant from digestion by herbivores, among their benefits to the host plant. They are also believed to direct the conversion of glucose, the primary product of photosynthesis. Tannins are found in all parts of plants and have been found to perform a variety of specific defensive tasks in plants.
P. lobata is among the most highly evolved plants, having developed a sophisticated defense system, permitting it to grow successfully under a wide variety of adverse conditions, including in soil contaminated with pollutants, in heavy air pollution, in acid rain, in bogs and semi-arid climatic conditions. It is difficult to eradicate using herbicides because it isolates and takes dormant rhizome segments affected by chemicals in the ground until the contaminants have dissipated in the soil before resprouting. P. lobata rhizomes are not damaged by nematodes and other pests found living in the soil in the Southeast United States. Few other plants can co-exist with P. lobata in the Southeast. Those that grow along with it on the same site are usually in limited amounts, generally along the fringes of a field.
All parts of a P. lobata plant contain valuable chemicals. Often, the same chemicals found in different parts of the plant exist in different forms. Whilst chemical extraction from P. lobata appears best made from its rhizomes, the leaves, vines, seeds and flowers may also be used for chemical extractions. Chemical content varies with seasons. Chemical content of P. lobata growing in the United States appears to be at its highest and most concentrated level during late summer to early fall.
The largest single chemical component of P. lobata rhizomes appears to be coumarin. This powerful anti-coagulant is the primary ingredient of human anti-coagulant drugs and also the primary ingredient of rat poison. Coumarin is also used as a newly mown hay scent in cheese, cosmetics and perfume and as a beige to tan and yellow dye, including as a laser marker dye. Among flavors found in P. lobata, the major component appears to be palmitate.
Chemicals found in P. lobata can be roughly separated into two major groups: (1) those that dissolve in water (also soluble in methanol, ethanol and/or butanol) are usually polar compounds of small molecular weights, and (2) those that dissolve in organic solvents such as acetone, chloroform, etc. are usually larger, featuring additional side groups or attached sugars. In general, the skeletons of the water-soluble compounds can also be found in a more complex form in the water-insoluble fraction of P. lobata extracts. Usually, smaller compounds can be obtained by chemical synthesis and mass-produced in factories at a cost much lower than that by the cultivation of and isolating from the natural plant. However, larger compounds with more complex structures can be difficult to make and isolation from natural source may be preferred.
P. lobata contains large amounts of polyphenolics. Unlike simple phenols, polyphenols have complex chemical structures, may be extremely condensed, and have high molecular weights. Thus, they may be difficult and costly to synthesize chemically. A natural substance may be preferred for that reason. Certain flavonoids can be chemically modified to yield more potent drugs. It is likely that extractions of natural chemicals from P. lobata may serve as the starting point for the discovery of more potent, commercially useful, therapeutics.
Pueraria lobata leaves can be separately used for the production of phytochemicals. Inherent chemicals in P. lobata leaves have been found to be unique and to differ from the chemicals in the rhizome. Among others, chemicals found in P. lobata leaves include a tobacco flavoring and others identical to certain food flavoring components. The leaves also contain a high level of chlorophyllin, a chlorophyll derivative that is able to inhibit the action of certain mutagens.
P. lobata contains volatile chemicals as indicated by the sweet grape-like scent of its flowers (Kinjo etal., 1988a). Rhizome and other components of P. lobata contain volatile compounds as well. The chemicals in the flowers are not very different from those in the rhizome. The vines contain most of the same chemicals found in the rhizome and some chemicals that have not yet been found in the rhizome. It is likely that most, if not all, of the chemicals found in P. lobata will be found in its rhizomes.
Historically, P. lobata has been used in the Orient as a medicinal herb and food supplement. Koreans are fond of a P. lobata tannin tea as a healthful tonic. Small quantities of this tea are exported to the United States from Korea, usually flavored with orange or lemon and spices such as cinnamon and clove then highly sweetened with refined sugar. Japanese offerings exported to the United States tend to rely most upon starch-based recipes for foods, including a "kuzu crème" for dessert. Chinese most often describe the use of decoctions made by steeping the dried P. lobata rhizome for medicinal treatments, frequently describing it in mixtures also including peony and Siberian ginseng extracts.
Historic Chinese and Japanese medicine each reports extensive successful use of P. lobata extracts to treat a variety of ills. Among these are skin diseases, baldness, insect bites, digestive problems, strokes, drunkenness, and hangover after drinking alcoholic beverages, alcoholism, liver, and heart and kidney diseases. Their skin treatments from P. lobata are reported to be useful for moisturizing, skin-lightening, sun-screening, stimulating hair growth, preventing the formation of melanin deposits (age spots), treating and easing the symptoms of wounds, burns, insect bites, rashes, allergic skin reactions and similar conditions.
More recently, modern scientific methods have been used to study the pharmacological activity of these treatments, isolate and identify their active ingredients, and reveal their mechanism of actions. Among the biological activities reported in animals using P. lobata extracts are ones which are anti-spasmodic, (spasmolytic, muscle relaxing, musculatropic); anti-oxidative; anti-pyretic (hypothermic); cholinergic; anti-dyar-hythmic; analgesic; anti-fertility; vasodilative (hypertension); anti-inflammatory (Kimura etal., 1992); immune-stimulating; fungitoxic; herbicidal; anti-tuberculin; cardiovascular; anti-coronary artery disease; anti-mutagenic; anti-coagulant (Yu etal., 1997); anti-alcohol abuse (Keung etal., 1997); anti-liver intoxication/injuries (Nohara etal, 1998; Shinho etal, 1989); otolaryngologic (Xuan etal, 1999); opthalmic; anti-hypoglycemic; anti-diabetic; preventive of melanin formation; edema preventive, uro-logical (Yasuda etal, 1995); anti-viral (Kumai, 1996; Nohara and Kinjo, 1999); neurological (Shen etal, 1996; Oishi etal, 1998); and others.
Among chemicals already identified in Pueraria lobata are the following: Chlorophyll; Chlorophyllin; Coumarin; Coumestrol; Puerarin; Biochanin-A; Genistin; Genistein; Daidzin; Daidzein; Formononetin; Oononin; Tectorigenin; Glycitein; Chryin; Puerarols 1, 2, 3, and 6 Puerasol; Glycosyl-tryptophan; Rutin; Robinin; Nicotiflorin; Kakalide; Kakatin; Palmitate; di-methyl-Sucherate; di-methyl-Azelate; Acetylcarbinol; Paenol; Furfural; Furfuryl alcohol; 2-Furfuryl-methyl-ketone; Isoliquirtigen; Allantoin; B-sito-strerol; 5-Methyl-hydantoin; Ephedra; 7-0-eanenne sapogenols, including P. lobata sapogenol, P. lobata sapogenol A, P. lobata sapogenol B, and P. lobata sapogenol methyl ester. Among sugar moieties in Pueraria lobata rhizomes, glucose, xylose and other sugars have been identified (Kubo etal., 1973, 1975; Yokoyama, 1976; Sayed and Borisov, 1978; Shibata etal, 1978; Inatomi etal, 1979; Sajad etal, 1979; Yamagishi and Houma, 1980; Chen and Zhang, 1985; Kinjo etal, 1985, 1987, 1988b; Miyazawa and Kameoka, 1988; Oshima etal, 1988; Hirakura etal, 1989; Park etal, 1992; Nohara etal, 1993; Rong and Stevens, 1998).
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