Annonaceae

Guinea of Ethiopian pepper, spice tree

L In Nigeria the fruits are used as a cough cure, a carminative and a stimulating additive to other remedies. A fluid extraction or a decoction of the fruit or bark is recommended in the treatment of bronchitis, dysentery and biliousness. An extract of the seeds is also used to eliminate roundworm. The fruit is used as a condiment (Dalziel, 1937).

C From the fruit of the Nigerian species xylopic acid, a new diterpenic acid (15 /3-acetoxy(—)kaur-16ene-19-oic acid), three diterpenic alcohols, one of them identified as kauran-16-a-ol, 4 diterpenic acids, including kaurenoic and 15-oxo-kaurenoic acid, two acyclic compounds, fats, oils and an essential oil have been obtained and cuminal (isopropylbenzaldehyde) has been obtained from the seeds (Ekong and Ogan, 1968; Ekongeia/., 1969a; Ogan, 1971).

P An extract of the fruit has been found to have some antibiotic effect on Sarcina lutea and Mycobacterium phlei (Malcolm and Sofowora, 1969) and on Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Candida albicans. It is, however, inactive against Escherichia coli (Boakiji Yiadom et al., 1977). This action seems due mainly to xylopic acid and to a lesser extent to two other diterpene isolates. The effect of xylopic acid is comparable to that of chloramphenicol.

Azadirachta indica A. Juss syn. (Melia azadirachta L., M. indica (Juss.) Brandis) (Fig. 4.5) MELIACEAE

Neem, margosa tree

(Considerable confusion between this tree and Melia azedarach is found in the literature and must be watched!)

L Introduced and now naturalized in West Africa and Nigeria, this tree is mainly ornamental. The seed oil (margosa oil or neem oil) is used in India for the treatment of skin diseases and as a hair tonic (Indian Pharmacopoeia). The dried flowers find use as a tonic and stomachic and an infusion or tincture of the dried bark as a tonic and antipyretic.

C In India the seed oil has been found to contain bitter constituents. Those reported have been mainly 1.1% nimbidin (containing sulphur) and 0.1% nimbin and 0.01% nimbinin (both free from sulphur), which also occur in the stembark (Chatterjee el al., 1948). Meliacins found in the seeds include gedunin, 7-desacetylgedunin, desacetylnimbin and azedarachtin (Manske and Holmes, 1950-71, Vol. 5, p. 423).

From the flowers a flavonoid, nimbicetin, later found to be identical with kaempferol, has been isolated, together with a bitter substance and a pungent bitter essential oil. In the dried bark the same bitter components as in the seed oil have been found, and in the pericarp of the fruit a bitter principle, bakayanin, has been found (Narayanan and Iyer, 1967). From the Nigeria species El Said et al. (1968) isolated nimbin, nimbidol and other bitter tetra-nor-triterpenoids as well as a resin and a tannin. Ekong etal. (1969b) obtained two new meliacin cinnamates, nimbolin A and B, from the wood of the trunk besides a small quantity of nimbin, fraxinellose and gedunin. In the fresh leaves they found deacetylnimbine and a lactone, nimbolid.

Fig. 4.5. Azadirachta indica A. Juss.

Fig. 4.5. Azadirachta indica A. Juss.

P In India, a marked antibacterial action of the seed oil on Gram-positive and Gram-negative organisms and even against resistant strains of tuberculosis has been reported. The growth of all strains of Mycobacterium tuberculosis and Micrococcus pyogenes var. aureus was inhibited by a concentration of 1:800000 and the growth of Shigella typhosa, Salmonella paratyphi and Vibrio cholerae inaba was notably inhibited by a concentration of 2 mg/1; that of Klebsiella pneumonia by concentrations of 5 mg/1 (Murthy and Sirsi, 1957; 1958). Nimbin and nimbidin also inhibited potato virus X (Verma, 1974). The leaves appear to be insecticidal and are used in India to protect woollen fabrics and books against insects (Chopra et al., 1956). The triterpenoids of the seeds have been reported to repel certain parasites of cultivated plants and to have antiviral as well as antibacterial properties (Rai and Sethi, 1973; Anisimov et al., 1974; Kraus et al., 1978).

Azedarachtin, together with warburganal from East African Warburgia cyanensis, is considered one of the strongest antifeedants of African army worms hitherto discovered (Kubo et al., 1977).

An aqueous extract of the root has been reported to reduce sarcoma 180 (Abbot et al., 1966). An aqueous extract (1:1000) of the leaves of the Nigerian tree was found to act on the isolated guinea pig intestine, to contain a histamine-like substance (Oladele Arigbabu and Don Pedro, 1971) and to cause, on intravenous injection in the dog, an initial increase in blood pressure followed by a prolonged decrease with accelerated breathing (Luscombe and Taha, 1974; Thompson and Anderson, 1978). The fresh leaf extract has also been shown to have hypoglycaemic and anti-hyperglycaemic effects in dogs. When injected intravenously it prevented adrenaline-induced, as well as glucose-induced, hyperglycaemia. This action lasted from 30 min to 4 h after administration (Satyanarayan Murty et al., 1978). Anti-inflammatory and antipyretic properties of Azadirachta leaf extract have been reported in Nigeria by Okpanyi and Ezeukwu (1981).

Acalypha wilkesiana Mull. Arg. EUPHORBIACEAE

Cultivated (from tropical Asia)

L In Nigerian local medicine the plant is administered in the form of a tincture, a decoction or an infusion. The leaf juice, obtained by rubbing the leaves between the palms of the hands, is smeared on parts affected by Pityriasis versicolor or similar types of fungal skin infections. Alternatively, the decoction of the leaves may also be drunk by itself or in combination with other remedies.

C The active principle responsible for the antimycotic and antimicrobial action is being investigated by the agar diffusion method (Adesina etal., 1980b).

P Five different extracts have been tested (the preparation of each extract including a number of chemical operations) against seven test organisms and marked antimicrobial properties (inhibition zone over 15 mm) have been displayed against Bacillus subtilis, Staphylococcus aureus and B. cereus by extract B and to a certain extent against Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris and Serrata marcescens. (Adesinaetal., 1980b).

Eclipta prostrata (L.) L. syn. (E. alba (L.) Hassk., Verbesina prostrata L.)

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