Not to be confused with : Spanish Broom (Spartium junceum) [which is more poisonous but has round stems rather than 5-angled, deeper yellow flowers and leaves that are never trefoil and seed pods that are hairy all-around],
Broom exists as one of two sub-species :
The above photographs are of the ssp. scoparius since they are not prostrate.
Prostrate Broom (Cytisus Scoparius ssp. maritimus) which is a low-lying plant that often grows near the sea, but that is restricted to the far west coasts of Wales and Devon & Cornwall.
Broom (Cytisus Scoparius ssp. scoparius), which is much more widespread than Prostrate Broom.
Uniquely identifiable characteristics
Distinguishing Feature : a shrub with thin fluted 5-angled stems, and yellow or yellow & orange pea-type flowers.
No relation to :
Broomrapes such as Common Broomrape (Orobanche minor) nor to Butcher's Broom (Ruscus aculeatus) [plants with similar names belonging to differing families].
Broom, gathered in bunches, was once used to sweep the floor, hence the name of 'broom' for this kind of brush. It has also been used as a source of fibre and can be made into both paper and cloth. The wood of Broom was once highly acclaimed for use in furniture as a veneer. Broom twigs have been used in basket-weaving. Like a great many other things, Broom was also added to beer as the bitter component instead of Hops, and the ground seeds once used as a 'coffee', although it must have caused some distress because of the constituent poisonous alkaloids.
Whereas Broom has five-sided fluted stems, Spanish Broom has ten, and this is the main difference between them. Broom has either wholly yellow or yellow with red flowers. It spreads by seeds which are flung up to 10 feet out of the seed pods. It is also bird-sown.
It can be confused with garden varieties specially bred to enhance the two-tone colour aspect. Unlike Broom itself which stops flowering after June, these cultivars flower from June to September, rather than April to June of a true Broom. The cultivars can also be readily bird-sown.
Scotch Broom (or just Broom) is of only low toxicity. In particular, it contains no
Cytisine unlike Spanish Broom. But it does contain other toxic alkaloids, amongst them l-Sparteine (up to 0.22% in the flowers, and over 1.5% in other parts of the plant) plus
Sarothamnine (possibly now called iso-Sparteine), Genisteine, Lupanine and Oxysparteine. The yellow pigmented flavone glycoside
Scoparoside now better known as
Scoparin has been found in both the leaves and branches of this plant. Another flavone glycoside,
Vitexin is also present, which is the glycoside of the flavone Apigenin.
The isoflavone Genisteine, which despite many pages to the contrary on the internet, is not an alkaloid!. Isoflavones are secondary metabolites of members of the Pea Family and many exhibit phyto-oestrogenic activity, mimicking the female mammalian sex hormone (
oestrogen). Some other isoflavones are induced in plants after infection by pathogens, and behave as phytoalexins (chemical deterrents for plants). Note that Genisteine is an isomer of Apigenin, shown below. One is a flavone, the other an isoflavone.
It is hoped that Genisteine may prove useful to treat a rare brain disease called Sanfilippo which aflicts youngsters who usually die of the condition before their 15th birthday. There is otherwise no cure for the fatal condition. The brains of youngsters with the condition are unable to process the glucose the brain requires and which is transported there in the bloodstream. The brains of such youngsters are deficient in one of the four enzymes involved in the lysomal degradation of glycosaminoglycan heparan sulfate, which otherwise accumulates to dangerous proportions. There are four diseases in the sanfilippo syndrome group, each corresponding to a deficiency in each of the four enzymes.
The yellow pigmented flavone glycoside
Scoparoside now better known as
Scoparin has been found in both the leaves and branches of this plant.
Another flavone glycoside,
Vitexin is also present, which is the glycoside of the flavone
Apigenin. Vitexin possesses pharmacological properties such as being an anti-histamine, anti-serotonin and anti-bradykinin. It may find use as an anti-inflammatory, a potent hypotensive and an anti-spasmodic.
The two flavone glycosides differ only in a methoxy group on the flavone. Another flavonol glycoside present is that of the 4'-O-Glycoside of Quercetin called Spiraeoside, which was also found in Meadowsweet, from which it derives its name (Meadowseeet used to have the scientific name Spiraea ulmaria until it was changed to Filipendula ulmaria. Unfortunately, the name of the secondary metabolite did not follow suit~).
Apigenin is an isomer of Genisteine, shown above. One is a flavone, the other an iso-flavone. Apigenin is the aglycone (without a sugar) of several different glycosides of Apigenin. It is responsible for the cancer prevention characteristics of several vegetables and fruits. It puts mammalian cells into autophagia, a kind of protective dormancy. Apigenin is a potent inhibitor of an enzyme responsible for the metabolization of many pharmaceutical drugs within the human body, so should be regarded with care. It also induces resistance against chemotherapy.
OxySparteine is Sparteine (a lupanane alkaloid) with an added ketonic oxygen atom. Sparteine has the effect of restoring a feeble irregular heartbeat back to normal, particularly useful for stubborn cases of arterial fibrillation. The chemically related Oxysparteine, |
Anagyrine and Lupanine have similar actions. Note that if it wasn't for the single ketone group (=O), then OxySparteine would be a dimer; indeed, Sparteine itself is a dimer.
Cytisine (not to be confused with the amino acid Cysteine) is an alkaloid with two nitrogen atoms and three fused
pyridine-type rings, one sharing the same nitrogen atom, forming three six-membered (albeit fused) rings. Shown above are two possible ways of depicting it pictorially, with the second diagram more clearly showing its relationship to Oxysparteine above. It is found naturally in many members of the
Faboideae Family (which is a sub-family of the Pea Family (Fabaceae)) including Anagyris, Cytisus, Genista, Laburnum, Thermopsis and the non-native Sophora as well as in some trees that are not native to the UK.
Cytisine is poisonous to humans, but possibly not to sheep or goats. Some caterpillars are able to sequester the toxin where it is deployed against predators. Such caterpillars usually have conspicuous aposematic colouring to warn predators of their poisonous nature, after all, the purpose is to avoid being eaten rather than to kill predators and die doing so, but some will inevitably succumb which helps revitalise the poisonous legend.
Cytisine binds to and blocks the same nicotinic acetylcholine receptors to which Nicotine binds and activates. It is therefore used as a drug to help tobacco addicts quit smoking. It mimics some of the effects of Nicotine, which is shown below for comparison only - Nicotine is not found in Broom.
A synthetic derivative of Cytisine called
Varenicline (shown alongside) is more widely prescribed to help quit smoking and is used in skin-patches. As far as is known, Varenicline does not occur naturally and is an alkaloid containing three nitrogen atoms and four fused rings of 6, 6, 5 and 6 members, respectively.