Phaeanthus (PROSEA)

Plant Resources of South-East Asia
Introduction

List of species

Phaeanthus Hook.f. & Thomson

Protologue: Fl. ind. 1: 146 (1855).

Family: Annonaceae

Chromosome number: x= 9; P. ebracteolatus: 2n= 18

Major species

Phaeanthus ebracteolatus (C. Presl) Merr.,
P. splendens Miq.

Vernacular names

Indonesia: pisang-pisang (used for most Annonaceae)
Malaysia: mempisang (used for most Annonaceae)
Vietnam: thuốc thượng.

Origin and geographic distribution

Phaeanthus consists of eight species and occurs in tropical and subtropical regions of South-East Asia. The species are distributed from Vietnam, Peninsular Malaysia, Sumatra, Borneo, Sulawesi, the Lesser Sunda Islands, the Moluccas, New Guinea and the Philippines.

Uses

The inner bark or the leaves of P. ebracteolatus, P. splendens and P. vietnamensis are a traditional medicine for sore eyes. P. splendens is used in folk medicine to lower blood pressure.

A solution of the quaternary alkaloids, total fluid extracts as well as tinctures of P. ebracteolatus similarly have been shown to produce an important pharmacodynamic effect, lowering blood pressure and relaxing smooth muscles. The quaternary alkaloids in aqueous or alcoholic solution depress the smooth muscles, especially of the blood vessels, and as a result blood pressure falls. Sufficiently large doses also depress the intestine, the enterine tracheal muscles and uterus.

The wood of Phaeanthus is used for light house construction and the bark is used for tying purposes.

Production and international trade

Phaeanthus is mainly used on a local scale.

Properties

Two bisbenzylisoquinoline alkaloids have been isolated from the bark of P. ebracteolatus. The first is a tertiary nonphenolic crystalline, called phaeanthine, which is similar to oxyaeanthine and berbamine. This compound has been credited with anti-tuberculotic effects. The second, a quaternary alkaloid, was named phaeantharine.

A solution containing only phaeantharine has practically the same effect as a solution of the bark, i.e. direct depression of the smooth muscles in vascular, intestinal, tracheal and uterine preparations. The most prominent effect of moderate or large doses of the alkaloid solution, hypotension, is partly attributed to a depression of the heart, together with the direct vasodilating action of phaeantharine. With sufficient large doses it also depresses the intestine, tracheal muscles and uterus, and is able to counteract the stimulant effects produced by pilocarpine and histamine in the excised uterus. The fall in blood pressure was of longer duration than that produced by nitroglycerine and acetylcholine, two well-known drugs that lower the blood pressure. With fatal doses, respiration was first increased then decreased and stopped. Blood pressure fell to zero through cessation of the heart beat a few minutes after the failure of respiration. When artificial respiration was applied the heart kept beating and after some time blood pressure increased again. On the basis of these effects, both phaeanthine and phaeantharine are said to be similar to the curare alkaloids.

Furthermore, phaeantharine also has a potent larvicidal effect in mosquitoes, due to ganglionic blocking action, cholinesterase inhibition and a neuromuscular blockade. It has no effect on the pupae and adult stages. Being water-soluble it can be dissolved easily in water where mosquitos breed.

Another tertiary alkaloid in the form of crystals has now also been isolated and given the name kalimatine. All three compounds from P. ebracteolatus, phaeanthine, phaeantharine and kalimatine, can also be extracted from the leaves.

Limacine and phaeanthine isolated from P. splendens show a certain degree of antibacterial activity against both gram-negative and gram-positive bacteria. Phaeanthine and limacine were active against Streptococcus faecalis, Streptococcus pneumoniae, and Escherichia coli, whereas phaeanthine was also active against Staphylococcus aureus.

The alkaloid extract of the leaves of P. vietnamensis contains monomeric and dimeric isoquinoline alkaloids, and exhibits anti-microbial activity. The main alkaloid 1S,1'R-(-)-7,7'-O,O’-dimethylgrisabine showed a potent in vitro activity against Bacillus subtilis.

Adulterations and substitutes

Certain plant families such as the Menispermaceae are well-known for the presence of (bis-)benzylisoquinoline alkaloids. It is therefore very possible that the alkaloids present in Phaeanthus, or closely related compounds, are also available in members of this family. Examples of these are phaeanthine, which is also present in Triclisia patens Oliv. from Africa, and limacine, which can be isolated from several species, including Cyclea barbata Miers.

Description

Shrubs or trees up to 25 m tall; branches often glabrescent, but sometimes also glabrous.
Leaves distichous, simple and entire, obovate to elliptical, papyraceous to coriaceous, base obtuse to cuneate, apex acuminate, pinnately veined with tertiary veins not very clear, often turning black when dried; petiolate; stipules absent.
Inflorescence extra-axillary or sometimes terminal, cymose.
Flowers solitary or up to 4 together on short, bracteolate peduncle, bisexual, 3-merous with 3 free valvate sepals and two dissimilar whorls of 3 free valvate petals, outer petals sepal-like, inner petals triangular with a broad base and occasionally a glandular-like spot at the base; stamens many, truncate with very short filament and flat connective prolongation that usually covers the thecae; anthers 2, extrorse; carpels many, cylindrical, pubescent, style short or absent, stigma ellipsoidal or club-shaped, ovules 1-2.
Fruit a berry-like monocarp, many (up to 30), ellipsoidal to globose, black when dry, stipitate.
Seeds 1-2, ellipsoidal, with lamellate ruminations in 4 parts, seed coat papyraceous.

Growth and development

Phaeanthus can be found flowering and fruiting throughout the year. The flowers may be pollinated by small flies and beetles. These insects are probably attracted by the sweet apple-like smell of the flowers. Birds may disperse the monocarps as they mature from green to dark red (purple).

Other botanical information

The classification within the Annonaceae is still not resolved. According to a recent classification based on a phenetic analysis of both flower and fruit characters of Annonaceae from all over the world, Phaeanthus is placed in the same informal group as Annickia (African), Enicosanthum (Asian), Ephedranthus (South American), Malmea (South American), Marsypopetalum (Asian), Neo-uvaria (Asian), Pseudephedranthus (South American), Trivalvaria (Asian), and Woodiellantha (Asian). In another classification, Phaeanthus was doubtfully placed in a large group which also includes the Asian genera Anomianthus, Fissistigma, Friesodielsia, Goniothalamus, Melodorum, Mitrella, Mitrephora, Neo-uvaria, Oreomitra, Papualthia, Petalolophus, Popowia, Pseuduvaria, Pyramidanthe, Richella, Schefferomitra and Trivalvaria. The nomenclature of P. nutans remains somewhat unclear as at this moment it can not be proven that Uvaria ophthalmica Roxb. belongs to the genus and/or has been used by Hooker and Thomson to describe the genus.

Ecology

Phaeanthus species are understorey shrubs or trees in primary or secondary lowland forest, and sometimes freshwater swamp. They may occur on steep hills, in particular on ridges, along riversides and in open locations, on various soils, up to 800 m altitude.

Propagation and planting

Phaeanthus is rarely planted. Initial trials with cuttings of P. ebracteolatus proved rather disappointing.

Harvesting

Leaves of Phaeanthus are plucked whenever the need arises. Strips of bark are simply cut and torn from the trunk.

Yield

Fresh leaves of P. splendens may yield 0.72% crude alkaloids consisting of 0.09% limacine and 0.03% phaeantine. Total crude alkaloids found in the stem bark amount to 0.78%. In dried plant material of P. vietnamensis the content of the main alkaloid, 1S,1’R-(-)-7,7’-O,O’-dimethylgrisabine, is 0.01%.

Handling after harvest

After stripping the bark of P. ebracteolatus the inner bark is scraped off into very thin pieces, placed in a glass containing a little clean water, and later filtered. The liquid is used as drops. The scrapings or shavings left over, packed in a banana leaf, heated, cooled and then squeezed, can be used again in the same manner.

Genetic resources and breeding

Most Phaeanthus species treated here are widely distributed and may even occur in disturbed forest. This may indicate that they are not very liable to genetic erosion. P. vietnamensis is not widely distributed and since it is confined to primary forest, it is more liable to genetic erosion.

Prospects

Although several alkaloids have been detected in Phaeanthus several still need to be isolated and identified, and their specific properties assessed. Several alkaloids, however, show interesting pharmacological properties, which might be of interest in future medicine (muscle relaxant, vasodilatating effects), medical research (tuberculosis, anti-microbial) or in agriculture (anti-microbial, larvicidal).

Literature

Fasihuddin, B.A., Shanty, V. & Atan, M.S., 1991. Phaeanthine and limacine from Phaeanthus crassipetalus Becc. Pertanika (Malaysia) 14(3): 355-358.
Garcia, F., 1940. Pharmacological study of quaternary alkaloids and fluid extract of Phaeanthus ebracteolatus (Presl) Merrill (Kalimatas). Philippine Journal of Science 71(4): 361-372.
Mols, J.B. & Kessler, P.J.A., 2000. Revision of the genus Phaeanthus (Annonaceae). Blumea 45: 205-233.
Nguyen Thi Nghia, Valka, I., Weigl, E., Simanek, V., Cortes, D. & Cave, A., 1991. Alkaloids from leaves of Phaeanthus vietnamensis. Fitoterapia 62(4): 315-318.
Robillos, Y.U., 1976. Some medicinal forest trees in the Philippines. Forpridecom Technical Note 169. 3 pp.
Van Beek, T.A., Verpoorte, R., Baerheim Svendsen, A., Santos, A.C. & Olay, L.P., 1983. Revised structure of phaeantharine. Journal of Natural Products 46(2): 226-231.

Selection of species

Authors

N.O. Aguilar & J.B. Mols