Phytochemistry


All or a combination of the compounds below may be found in many flowering plants, including acacias. This is however a rather simplified treatment of a very complex subject, there being literally thousands of different compounds and metabolites in pl ants. The role or function, if any, is still debatable, protection against predation, end metabolites, plant hormones, pheromones, anti-fungal/ viral etc.

Carbohydrates, sugars and gums - Carbohydrates (sugars) are the products of photosynthesis that plants use as starting material for most of the other compounds in plants. Cellulose is a carbohydrate that most plants make and contain that gives p lants their structure and strength, some parts of plants may be more than 50% cellulose. Gums are polysaccharidic (made from sugars) compounds, where various different sugars are joined together to form polymer like structures. Some acacias produce quite large amounts of gum from injuries or insect attack, some are edible, they can vary greatly in their water solubility, some becoming gelatinous and not really dissolving.

Terpenes, oils and resins - Generally water insoluble organic compounds, originally applied to substances made up of two 5-carbon units, the so called isoprene unit. Mono-terpenes are two units, sesquiterpenes are three units, diterpenes are four units, triterpenes six units etc. Different oils and terpenes may be found in the flowers and foliage, some acacia flower essential oils are used in perfumery. Most essential oils are mono or sesqui terpenes, resins are often more complex terpenoid mixt ures that may also contain gums.

Tannins - tannins are complex compounds based on tannic and gallic acid, very common in the wood, bark and foliage that are water soluble but react with proteins, this is what causes the astringency of many plants and is utilised to preserve lea ther in the tanning process. Acacia bark has been used as a source of tannins, some species having large amounts in the bark.

Glycoside - Is a general term for substances made up of of a sugar residue (glucose unit) and another compound, such as a flavanoid, coumarin, steroid or terpene, collectively known as the aglycone. Glycosides are common in plants, there are qui te a few that have a strong action on the body, including the heart, digestive and peripheral nervous system. ‘Cyanogenetic glycosides’ produce free HCN (cyanide) when reduced (digested?), and along with other glycosides, like the cardioactive glycosides can produce toxic even fatal results if enough is ingested, which may not be very much..About forty species from sub-genus Phyllodineae have been recorded as being cyanogenetic.
The glycoside kaempferol has been isolated from the flowers of a. discolour, a. linifolia, a. decurrens and a. longifolia, kaempferol is water soluble and yellow, and in these cases responsible for the colour of the flowers ( J Petrie, Proc. Linn. Soc. NSW, #48: 356-67, 1923), and this may be the case with many, if not most acacia flowers. This compound has been found to be a diuretic (promotes urination) and natriuretic (causes sodium loss), increasing urine secretions and the functioning of the kid ney cells, increasing in turn, their permeability and circulation. The general result is that kidney function improves which helps the body to positively react to water retention and excessive blood glucose levels, both of which are secondary symptoms of diabetes (Winkelman, Ethnobotanical treatments of diabetes in Baja California norte. unpublished report, Arizona state uni, Tempe, Ariz. 1991).

Flavanoids - This is a term that is applied to compounds common in many plants and quite often responsible for the colours in wood, fruit and flowers. The flavanoids of the heartwoods of Australian acacias has been the subject of some study. The se studies have found that Australian acacias can be broadly divided into different groups depending on the flavanoids present in the wood. These groupings did not correspond exactly with the classification based on morphological differences. There were h owever some correlations with the Botrycephaleae forming a distinct group and Phyllodineae species with flowers in racemes having a similar flavanoid pattern. The Juliflorae and Plurinerves had a similar flavanoid pattern, the Juliflorae being a fairly well defined group, with a further small group in the Juliflorae having unique but related flavanoids. There was also a distinct group in the Phyllodineae that had unique flavanoids that give members of this group distinctively purple heartwood. There were some mixed results for some species in sections Phyll odineae, Plurinerves and Juliflorae, especially the tropical northern species.

Other studies of the free amino acids in the seeds of different species found that sub-genus Acacia was a distinct group different to sub-genus Phyllodineae and Acueiliferum, a sub-genus of mostly Asian, African and Central American species. There seem ed to be some relationship between sub-genus Phyllodineae and Acueiliferum, with the addition of two more amino acids, one toxic, in the Acueiliferum species seeds compared to sub-genus Phyllodineae. Three extra Australian species of sub-genus Phyllodinea e, a. confusa, a. simplex and a. kuauiensis also have been found contain these extra amino acids.

Alkaloids - is a general term for basic (alkaline) nitrogen containing organic compounds, generally bitter in taste and strong physiological action, many plant derived drugs and medicines are alkaloids, eg quinine, scopolomine, codiene, morphine, ephedrine, tryptamines etc. A lot of them can be potentially toxic, even fatal, especially when in the form of purified alkaloids extracted from plants, quite often only a small amount of the alkaloids can have a strong effect. Obviously some, or at least the plants that contain them have proved immensely useful to people for disease and illness, for thousands of years.
Alkaloids are relatively common in the leguminosae as a whole, and within the genus acacia in Australia alkaloids that have been reported include N,N-dimethyltryptamine, N-methyltryptamine, tryptamine, tetrahydroharman, N-methyl-tetrahydroharman, b-phe nethylamine, N-methyl-b-phenethylamine, hordenine (N,N-dimethyl-4-hydroxy-b-phenethylamine ), N-cinnamoylhistamine.....
For the number of species, there has been little research on the alkaloids of Australian acacias, and like many studies of Australian plants there has been quite alot of variability in the results. For example the root bark of acacia holoserica is repo rted in a few publications as containing the B-phenethylamine alkaloid hordenine, up to 1.22% of the dry weight. Yet in a recent study of aboriginal medicinal plants all parts of this species were found to give a negative result for alkaloids. It was stil l used medicinally and another species, acacia auriculiformis, which was used in a similar way was found to give a positive test for alkaloids, both are members of section Juliflorae. Other studies have found that there can not o nly be variation in the amount, but also in the type of alkaloids present, eg a. baileyana has been found to contain both B-carboline and tryptamine alkaloids at different times of the year.
Qualitative studies of the alkaloids have found that B-phenethylamine alkaloids are quite common in the uninerved members of section Phyllodineae with flowers in racemes, with some specimens found to contain more than 1% alkaloi ds. B-phenethylamines have been found in other species from section Phyllodineae. N-cinnamoylhistamine has been isolated from at least one member of section Juliflorae. Tryptamine or it’s N-methyl and N, N-dimethyl derivatives have been found in a number of members of section Juliflorae, and a single species from the Botrycephalae. An extra-Australian member of sub-genus Phyllodineae is recorded as contain ing methylated tryptamine and B-carboline alkaloids together. A member of section plurinerves is reported to contain B-carboline alkaloids.
So the picture regarding alkaloids seems complex, with much variation from different areas or amongst types or chemical races. Other plants in the Australian flora exhibit this sort of phenomena, with great variation in the amount and even the constitu ents of the volatile oils (Eucalyptus, Melaleuca ), alkaloids (Duboisia) or other compounds between types or localities. Many Aboriginal people recognised this trait in the Australian bush by using plants from one area, and claim that the same plant from a different spot would not be effective, or may even be toxic.

alkaloids of acacias