Acacia (PROSEA Medicinals)
- Protologue: Gard. Dict., abr. ed.: 4 (1754).
- Family: Leguminosae
- Chromosome number: x= 13; A. concinna, A. pennata: 2n= 26
Origin and geographic distribution
Acacia is a very large genus of over 1300 species and occurs throughout tropical and subtropical regions. Australia is richest with about 700 species occurring naturally. In Malesia, about 30 species have been found.
The 4 Acacia species treated here are all used medicinally in South-East Asia. In traditional medicine in Peninsular Malaysia a poultice of leaves is applied to the head for headache, and in Java leaves are used to treat fever. Boiled roots are applied as a poultice against rheumatism and smallpox in Malaysia, and the roots are used against cough and in a complex mixture of dart poison. The stem juice is used in Sumatra to treat sprue. Ash from the pods has been used in Peninsular Malaysia to treat itch. In Thailand the roots are used as an antipyretic and pods as an expectorant and to treat cough.
Acacia species are economically important as sources of timber (e.g. A. mangium Willd.), gum (e.g. A. nilotica (L.) Willd. ex Del.), tannin (e.g. A. catechu (L.f.) Willd. and A. mearnsii De Wild.) and essential oil (e.g. A. farnesiana (L.) Willd.). Moreover, they may be useful in reafforestation (e.g. A. auriculiformis A. Cunn. ex Benth.), for fire protection, to prevent soil erosion, to rehabilitate poor and degraded soils as nitrogen-fixing plants, and as ornamentals. Several of these species have medicinal importance. For example, cutch isolated from the heartwood of A. catechu is used to treat cough and sore throat, and its bark is said to be effective against dysentery, diarrhoea and in healing wounds. A. farnesiana has numerous medicinal applications in South-East Asia, e.g. the bark is used to treat cough, bleeding gums, gonorrhoea and bladder complaints, the leaves are applied to ulcers and sores, the roots are used against sore throat and tuberculosis, and the fruits against dysentery and inflammation of the skin and mucous membranes.
The seeds of A. pennata contain the biogenic amine N-methyltyramine (about 0.5% on a dry weight basis). This compound increased blood pressure in anaesthetized rats, relaxed guinea-pig ileum and increased the force and rate of contraction of guinea-pig right atrium by inducing the release of noradrenaline. It has similar pharmacological properties to tyramine, which is a known cause of dietary migraine. The fruit pulp of A. concinna and A. pennata has fish stupefying properties and is used in India to catch fish in ponds. The bark contains lupeol, Œ±-spinasterol and tannin (about 9%), and the stem contains sitosterol. The fruit pulp of A. concinna contains about 5% saponin. A saponin fraction of the bark showed strong cytotoxic activity against KB cells, as well as spermicidal activity in vitro. Upon alkaline hydrolysis this saponin mixture gave prosapogenols. A monoterpenoidal amide, concinnamide, was isolated from the seeds; it can be synthesized from (-)-linalool, which has antimicrobial activity. Kinmoonosides A-C were isolated as cytotoxic saponins from the fruits.
Extracts of A. nilotica bark and pods showed inhibitory effects against HIV-1 replication, and also antibacterial and molluscicidal activities. They inhibited platelet aggregation and had inhibitory effects on paw oedema and pyrexia in rats; they also produced a significant increase in the hot plate reaction time in mice. Triterpenoid saponins isolated from A. auriculiformis showed anthelmintic properties and antifilarial activity. Several species (e.g. A. nilotica and A. farnesiana) showed antimicrobial effects. Some of the pharmacological properties of Acacia species are reported to be at least partly due to the presence of tannins.
The following description is applicable to the 4 species treated here.
- Scandent shrubs or woody climbers up to 40 m long; branchlets armed with prickles.
- Leaves alternate, bipinnate, stipulate; petiole and rachis with extrafloral nectaries; leaflets opposite, numerous, small, asymmetrical at base.
- Inflorescence consisting of pedunculate glomerules aggregated into a raceme or panicle.
- Flowers bisexual or male, 5-merous, yellowish or creamy, with numerous stamens. Fruit a pod, brownish.
- Seeds flattened, with a hard blackish-brown testa with pleurogram.
In Malesia, A. pennata flowers from November to March and fruits have been found from April to August, A. concinna and A. pluricapitata can be found flowering and fruiting throughout the year.
A. concinna, A. pennata, A. pluricapitata and A. pseudointsia all belong to the subgenus Aculeiferum. They are closely related and sometimes confused. A. pennata is a variable species in which 4 subspecies have been distinguished; only subsp. kerrii Nielsen is found in Malesia.
A. concinna , A. pluricapitata and A. pseudointsia occur in primary and secondary rain forests, often at riversides, the former two species also in forest margins and clearings, up to 1000 m altitude. A. pennata is found in the drier parts of Malesia in monsoon forest and scrub vegetation, up to 1200 m altitude.
In tests in India, vegetative propagation by cuttings proved successful. Terminal branch cuttings treated with indole-butyric acid (1500 ppm) showed the highest percentage of rooting (54%).
The 4 Acacia species treated here do not seem to be endangered because they often occur in secondary forest and scrub vegetation and are widespread. However, in some regions a species can be rare, e.g. A. pluricapitata and A. pseudointsia in Thailand.
The bioactivity of the saponins present in the Acacia species treated here deserves more attention, particularly the antimicrobial and cytotoxic activities.
239, 247, 263, 541, 542, 711, 760.
Selection of species
- S. Aggarwal