Adenia (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Adenia Forssk.

Protologue: Fl. Aegypt.-Arab.: 77 (1775).

Family: Passifloraceae

Chromosome number: x= 12

Adenia comprises almost 100 species and is distributed in the tropical and subtropical regions of the Old World. Africa is richest in species (about 60), followed by Madagascar (about 20) and southern Asia (about 15). In Malesia, 6 species occur, of which A. heterophylla is the most widespread, occurring from Indo-China to the Solomon Islands and northern Australia.

In South-East Asia Adenia is used medicinally for various complaints. The stem juice of A. cordifolia is applied as an eyewash against conjunctivitis, and the leaves are used to treat convulsions. A decoction of A. heterophylla roots has been used to treat stomach troubles. A poultice of leaves of A. macrophylla is applied to treat headache, and a lotion of the roots to treat ringworm. A. penangiana is used to treat chest and body pain.

A. hondala (Gaertner) W.J. de Wilde from southern India and Sri Lanka possesses antiseptic properties. The juice is used to treat chest complaints. The roots are an ingredient of tonics, and the juice of roots and leaves is applied externally against skin troubles.

Several Adenia species are important medicinal plants in Africa, the most important being A. cissampeloides (Planchon ex Hook.) Harms, A. lobata (Jacq.) Engl. and A. volkensii Harms. The most common uses include external application of stem decoctions as a sedative, and internal application of stem and leaf decoctions to treat gastro-intestinal troubles, chest complaints, cough and fever.

The poison present in various plant parts is sometimes used in hunting. In Indo-China, rice grains soaked in a maceration of A. cardiophylla (Masters) Engl. are used to capture birds; the birds die almost immediately after ingesting the rice, but their meat remains edible. In Africa, pounded stems and roots of several species are applied as fish poison.

The stems are sometimes used as binding material.

In an in-vitro test, an extract of stems and leaves of A. cordifolia showed antibacterial activity, i.e. total inhibition of growth of Staphylococcus aureus and partial inhibition of growth of Escherichia coli . However, biological screening of a 1:1 ethanol-water extract showed negative results for antiviral, antibacterial, antifungal and spasmolytic activities. Toxicity tests showed a LD₅₀of 681 mg/kg body weight when administered intraperitoneally to mice.

Cyanogenic compounds and toxic proteins are the cause of the poisonous properties of roots and stems. Several of these compounds are pharmaceutically interesting and have been studied in African Adenia . The polyacetylenic di-epoxide gummiferol isolated from the leaves of A. cissampeloides exhibits significant activity against the KB human cell line and a broad spectrum against other human cancer cell lines. Volkensin is a highly toxic compound from the roots of A. volkensii ; it is a galactose-specific lectin and a potent inhibitor of eukaryotic protein synthesis. This ricin-like toxin resembles modeccin, which is purified from the roots of the African A. digitata (Harv.) Engl. Modeccin agglutinates erythrocytes of several mammalian species. Furthermore, the cyanogenic glycosides tetraphyllin B and epi-tetraphyllin B have been isolated from the roots of A. cissampeloides , A. glauca Schinz and A. volkensii .

Woody or herbaceous perennial climbers, usually dioecious, often with tubers. Leaves simple, entire or lobed, pinnately or palmately veined; petiole with 1-2 glands at apex; stipules minute. Inflorescence axillary, cymose, often with 1(-3) tendrils. Flowers unisexual, (4-)5(-6)-merous, mostly greenish to yellowish, with saucer-shaped, cup-shaped or tubiform hypanthium; sepals free or partially connate; petals free or partially connate with the calyx tube, corona present or absent; disk mostly composed of 5 strap-shaped or clavate appendages; stamens 5, free or partially connate, anthers mostly acute or acuminate, reduced to staminodes in female flowers; ovary superior, vestigial in male flowers, with 3(-5) styles. Fruit a 3-valved capsule, leathery or woody, stipitate, red when mature. Seeds compressed, with pitted testa, enclosed in an aril. Seedling with epigeal germination; cotyledons foliaceous.

All species treated here can be found flowering and fruiting throughout the year, but flowering occurs mostly in the rainy season. Pollination is probably carried out by insects; bees and ants have been observed visiting the flowers.

In Adenia , 6 sections have been distinguished. The species found in Malesia belong to section Erythrocarpus (e.g. A. cordifolia , A. heterophylla , A. macrophylla ) and section Microblepharis ( A. penangiana ).

Adenia occurs in primary and secondary forest, also in scrub vegetation and forest edges and clearings, up to 1200(-2000) m altitude. All species are found in regions with per-humid climatic conditions, except A. heterophylla , which shows a preference for seasonal climates.

The species treated here have fairly large areas of distribution, are locally common, and occur in various habitats. They do not seem to be at risk of genetic erosion. However, two other Malesian species, A. kinabaluensis W.J. de Wilde from Sabah and A. crassa Merr. from the Philippines, have very restricted distributions and may easily become endangered.

Very little is known about the properties and pharmacological activity of South-East Asian Adenia . There is more information available on the African species, and as several pharmacologically interesting compounds have been found, research on South-East Asian Adenia seems worthwhile.

120, 182, 247, 296.

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Muhammad Mansur