Uniquely identifiable characteristics
Distinguishing Feature :
Lookee-Likees : Brazilian Giant-Rhubarb and Chilean Giant-Rhubarb
Flowers very much like those of Russian Vine which belongs to the same Dock and Knotweed Family.
No relation to : Brazilian Giant-Rhubarb or Chilean Giant-Rhubarb or [plants with similar names and that look a little like Rhubarb, but which belong to the Giant-Rhubarb Family (Gunneraceae)]
Is related to:
Monk's Rhubarb which belongs to the same Family as Rhubarb, but is in a different Genera (Rumex).
Besides Rhubarb, there exists another related species, Ornamental Rhubarb (Rheum palmatum), which is grown in gardens and parks as an ornamental plant rather than as plant for consumption.
Rhubarb is grown as a crop plant by both farmers and especially by cottage gardeners. The leaves are more toxic (and not eaten) than are the red (or green) crescent-shaped stems. Both contain poisonous Oxalic Acid but the leaves about 40 times more (by weight) and also contain another toxic component thought to be an anthraquinone glycoside.
The edible stalks (petioles) are very bitter because of the presence of Malic Acid, but when boiled with a sugary solution in water become much more palatable.
In the UK it is grown mainly in the so-called 'Wakefield Triangle' which lies between Wakefield, Leeds and Morley, which is where some of the above photographs were taken. It is grown both outdoors, and indoors within darkened sheds when it is harvested by candle-light to keep the best taste. The stalks are sold either green, or in the more popular red; both are as edible after cooking. There are normally two harvests, April to May, and June to July.
One cultivator within the 'Wakefield Triangle' sells a hundred different varieties of Rhubarb, some for consumption, others as a decorative ornamental plant. Some of the ornamentals can be as tall as 8 feet.
ANTHRAQUINOID DYES in RHUBARB
Chrysophanic Acid and
Emodin are two anthraquinoid dyes that are present in the roots of Rhubarb. Chrysophanic Acid (also called
Rheic Acid, Chrysophanol and
Rhubarbarin) is a yellow crystalline substance that is also present in Curled Dock (Rumex crispus) (aka Yellow Dock in the USA) and is used in the treatment of skin diseases. As a dye, it can be used to make yellow, orange and red shades with suitable mordants and is sometimes used as a dye for hair, since Chrysophanic Acid will bind to the
keratin in hair. Chrysophanic Acid has spectral absorption peaks at 256nm, 278nm, 288nm and 436nm.
Emodin (1,6,8-Trihydroxy-3-methylanthraquinone) is closely related chemically to Chrysophanic Acid, and is also present in Buckthorn and
Japanese Knotweed. The crystals are dull-orange in colour and it is another anthraquinone dye. It may be useful in the treatment of Type 2 Diabetes, and also exhibits anti-cancer effects and has a neuroprotective function against glutamate toxicity.
Aloe Emodin was first found in the leaves of the non-native plant
Aloe Vera. It differs from Emodin (shown directly above) in the omission of a CH3 on the left and and extra CH3 on the right. Not only is it found in the latex of
Aloe Vera, but also in the underground rhizome of Rhubarb, in the leaves of
Senna (Cassia angustifolia) which is native to the tropics, and in the bark of the shrub Alder Buckthorn (Frangula alnus) (formerly Rhamnus frangula) as well as some other plants. Aloe Vera sap (rather than Aloe Emodin) is found in many cosmetics and skin lotions for burns etc, but there is little scientific evidence that it is either effective nor of its safety. This is probably because Aloe Vera contains a plethora of differing substances, many of them toxic. Indeed, if taken orally in commercially available yoghurts and some desserts, then its many toxic components could have severe consequences! Indeed, Aloin, a glycoside of a similar Anthraquioid dye related to Aloe Emodin which is also found in Aloe Vera, has been banned for use in some foodstuffs in America due to its toxicity! Indeed, no product derived from Aloe Vera has been scientifically proven to be effective in curing any disease or condition! User/imbiber beware!
Rhein (aka Casseic Acid or Rhein-9-Anthrone) is an anthraquinoid acid that is also present in Rhubarb. It is being evaluated as an anti-bacterial agent against Staphyococcus aureus. Both Emodin and Rhein are cathartic and laxative, which helps explain why Rhubarb has been used as a dieting foodstuff in times past.
Physcion aka Parietin is another anthraquinone found in Rhubarb. It has anti-tumour and anti-fungal properties and is orange-yellow in colour. It is the orange pigment found in lichens of the Genus Caloplaca and in Golden Shield Lichen and is also found in the roots of Curled Dock. More recent research suggests it should be useful in treating leukaemia and it also inhibits the growth of lung head and neck tumours. Parietin inhibits the enzyme 6PGD (6-phosphogluconate dehydrogenase) which is part of the pentose-phoshate pathway responsible for constructing the cellular building blocks necessary for rapid growth. Without these building blocks cancer cells cannot grow, but then, neither can new non-cancerous cells. Clearly, if approved for use in humans (and trials have not yet begun) treatment cannot continue indefinitely.
A STILBENOID in RHUBARB
Stilbenoids are related to Stilbene, the old name for Resveratrol found in grapes and in wine, and was once thought to provide a certain health benefits.
Rhaponticin is the glycoside of the stilbenoid
Rhapontigenin and is found in the rhizome roots of Rhubarb. In tests on diabetic mice, Rhaponticin had beneficial effects, but it remains to be determined whether it will exhibit much the same effects in humans. Acting also on beta amyloid plaques within the brain it may also be helpful for use in the treatment of Alzheimers disease. It is not reported whether Rhapontigenin is also found within Rhubarb but this compound shows activity against prostrate cancer cells due to its inhibitory effect on human cytochrome P450, an enzyme thought to transform some cardiogenic and immunotoxic compounds.