Ethnobotanical Characteristics

Description

Small evergreen tree, up to 10m high, stem erect with fine pale gray scales. Leaves simple leathery, opposite, ovate, petiolate with entire margin and acute tip, dark glossy green on the upper surface, dull greyish on the lower surface with excreted salt crystals. Inflorescence cymose, in small terminal or axillary clusters on short stalks, flowers bracteate, scented; calyx lobes 2-4 mm long, obtusish, fine fimbricatemarginated; corolla dark yellow, exceeding the calyx with 4 unequal spreading lobes exceeding the tube. Fruit 2-valved capsule, globose, pale green, 1.5-2.5cm long; seeds 2-4 large. As Avicennia is growing in a specialized habitat, which is poorly aerated, it is adapted to life in this habitat by the presence of erect leafless outgrowths of the roots called pneumatophores or breathing roots up to 50 cm long, they stick out above water and absorb air, which thought to oxygenate the roots.

Habitat & Distribution

Avicennia is found growing in the inter- tidal mudflats with extremely limited wave action i.e. below the high watermark along the shores of the seas and oceans from east Africa to New Zealand. In U.A.E it inhabits nearly all shores and Khor Kalba on the east coast; now it is planted in many coasts, creeks and islands throughout the country.

Part(s) used

Leaves, flowers, bark, fruits.

Traditional & Medicinal Uses

Bark astringent and used as aphrodisiac, for scabies, antifertlity agent and has tanning properties. Flowers for perfumes. Leaves are aphrodisiac and used for toothache, Leaves and seeds forage for camels and animals. Wood was used as fuel and in traditional buildings. The plant is known for the quality of its honey and the charcoal has special uses.

Pharmacognosy and Phytochemistry

Part(s) studied

Leaves

Microscopical Description

Leaves

The upper epidermis is covered with a fairly thick cuticle. The upper epidermal cells are compact, polygonal with thick straight cell walls and they are rich in plastids and granular contents. Attached to the epidermis are few unicellular oblong tapering covering trichomes with unicellular or multicellular basal cells. The upper epidermis also bears few short glandular trichomes each with a large flat or mushroom-shaped glandular head and two to three basal cells. The epidermal cells are slightly papillose. The hypoderims is composed of cells having slightly sinuous thin walls of various sizes containing yellow pigments. The palisade cells are of different shapes and sizes and they have thin cell walls and are loosely arranged. The spongy mesophyll is composed of inconspicuous small semi-round cells filled with dark yellow and brown pigments. The spongy mesophyll is embedding normal, long, short, oblong and semi-triangular spirally and annularly thickened vessels. The lower epidermis is bearing several, compactly arranged, long unicellular covering trichomes. No starch granules or stomata have been observed and water pores are expected to exist. In the powder, few fragments of the air shoots are represented by compact vascular strands containing fibers and boarderly pitted vessels together with layers of oblong and semi-round pitted sclerenchymatous cells (DPS ZCHRTM unpublished results).

• (a) Surface view of the upper epidermis of the leaf showing the relatively small polygonal cells with their straight cell walls and cicatrices of detached covering trichomes.
• (b) A fragment of the leaf showing a portion of the hypodermal cells (top left) containing yellowish pigments underlain by cylindrical palisade cells followed by cleared semi-rounded spongy mesophyll cells.
• (c) Adjacent spirally and annularly thickened vessels of the leaf midrib with accompanying short fibers ( Magnifications: All x 250).

Organoleptic characteristics

Appearance:              Coarse powder
Colour:                       Brownish gray
Odour:                       Aromatic
Taste:                        Saltish

Physicochemical constants

Loss in weight on drying at 105°C (%) :      8.40-8.80

Solubilities (%)

Alcohol solubility:                                      12.00
Water solubility:                                        8.00-18.40
10% ethanolic extractive:                         46.00

Ash values (%)

Total ash:                                               12.40-12.60
Water soluble ash:                                 9.20-9.60
Acid-insoluble ash:                               0.20

Successive extractive (%)

Petroleum ether (60-80°C):                  3.30
Chloroform:                                         2.20-2.30
Absolute alcohol:                                13.00-13.50
Distilled water:                                   19.40-19.60

pH values

pH of 1% solution:                              5.88-5.90
pH of 10% solution:                            5.76

Chemical constituents

Contains betulic acid, taraxerol, taraxerone and hydrocarbon. Sterols (β sitosterol & stigmasterol), triterpene alcohols, iridoid glycosides and high amount of carbohydrates, lipids and proteins (Ghazanfar 1994; DPS, ZCHRTM un published results).

Pharmacological and Toxicological studies

Avicennia marina (Mangrove), being main forage for camels has been studied for on its ecological and phytochemical aspects. In folklore medicine mangrove plants have proven activity against human, animal and plant pathogens but only limited investigations have been carried out to identify the metabolites responsible for their bioactives. Little work has been carried out on pharmacology ad toxicology of the plant. Subchronic treatment with the extract did not affect significantly the body and liver weights, the water intake, faecal and urinary output, leucocyte count, hemoglobin or haematocrit. No significant changes in plasma biochemistry were observed except for a 15% increase in AST activity. Histopathological findings showed no changes as compared to the control values (Ali & Bashir 1998). The pharmacological and toxicological studies carried out in our laboratory and the results in brief, on Avicennia marina (10% ethanolic extract) have been given below. The results presented without references showed unpublished data (unpublished results, ZCHRTM, DBMS).

Summary of the results

Avicennia marina (10% ethanolic extract) showed no significant anti-inflammatory activity, antinociceptive activity, locomotor activity, Cardiotonic activity, and vasorelaxant activity. The extract also did not show antihypertension activity. Acute toxicity evaluations reveal no toxic signs and symptoms.

Antimicrobial activity

An aqueous extract exhibited a moderate antifungal activity. Seeds of Avicennia marina elaborate antifungal enzymes “compounds” (beta-1,3-glucanase and chitinase) that might suppress fungal proliferation during hydrated storage (Mahasneh AM, 2002).

References

• Ali, B.H. & Bashir, A.K. (1998). Toxicological studies on leaves of Avicennia marina (Mangrove) in rats. J. Appl Toxicol 18 (2) 111-6.
• Department of Biomedical Sciences, Zyed Complex for Herbal Research and Traditional Medicine, Unpublished results.
• Department of Pharmacognostic Sciences, Zyed Complex for Herbal Research and Traditional Medicine(ZCHRTM ), unpublished results.
• El-Ghonemy, A. A. Encyclopedia of Medicinal Plants of the United Arab Emirates. (1993)1st Edition, University of U.A.E.
• Ghazanfar S A. Handbook of Arabian Medicinal Plants, CRC Press, p.210, 1994.
• Jongbloed, M.V. The Comprehensive Guide to the Wild Flowers of the united Arab Emirates, Erwda, (2003), Emirates Printing Press, Dubai, U.A.E.
• Kotb, T. F. Medicinal Plants in Libya.(1985) Arab Encyclopedia House. Tripoli-Libya.
• Mahasneh AM. (2002) Screening of some indigenous Qatari medicinal plants for antimicrobial activity. Phytoth. Res. 16(8): 751-3.
• Western, A. R. The Flora of United Arab Emirates, an introduction. (1986) Publication of the U.A.E University, Al Ain.