Stemonaceae

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Stemonaceae

Description

Twining (to several metres long), trailing or erect perennial herbs, mostly with fasciculate tubers, or with a short rhizome. Plants glabrous, or with uniseriate hairs. Leaves papyraceous when dry, alternate, or opposite, or verticillate (China, Japan); Inflorescences axillary, sessile, or peduncled cincin-nae, appearing as short racemes, rarely one-flowered; Flowers consisting of 4 similar segments, representing two rows of two tepals, these free, valvate, out-curved at anthesis, persistent; Stamens 4, epitepalous; Ovary superior or half superior, small, one-celled, ovules few to many, basally (Stemona) or apically (Stichoneuron) attached, anatropous or semi-anatropous; Fruit a 2-valved capsule;

Distribution

Asia-Temperate: Asia-Tropical:, Malaya (Peninsular Malaysiapresent) Georgia: present Indo-Malesia: present Japan: present Northern America:, Florida (Floridapresent) SE United States: present Southern Japan: present continental Asia: present continental SE Asia: present northern Australia: present
Three genera, two of which occur in Indo-Malesia; Stemona (c. 20 species) occurs in Japan and Continental Asia, extending through Malesia to northern Australia, Stichoneuron (2 species) in continental SE Asia and the Malay Peninsula. The genus Croomia (c. 3 species) has a disjunct distribution in eastern China, southern Japan, and SE United States (Florida, Georgia). The genus Pentastemona, described by Van Steenis (1982) in Stemonaceae, has been removed from this family and raised to family-rank (see under Pentastemonaceae).

Taxonomy

An isolated family because of various special morphological features of the flower. Its affinity has generally been accepted as being with the Liliaceae s.l., although not closely. Burkill (1960) and Ayensu (1964) suggested an affinity with Dioscoreaceae.

Cytology

Stemona japonica: 2n = 14 (Suzuka & Koriba 1949); Stichoneuron caudatum: 2n = 18 and Croomia pauciflora: 2n = 24 (counted by Gitte Peterson, Copenhagen, unpubl.). Dahlgren et al. (1985) mentioned for the family x = 7.

Phytochemo

As far as I am aware nothing is known about the chemistry of the gdnera Pentastemona and Stichoneuron. The roots of several species of Stemona are used in Southeast Asia, China and Japan as insecticides and therapeutical agents (e. g. Perry & Metzger 1980). The chemistry and the chemotaxonomic aspects of Stemona and Croomia were discussed twice during the past 30 years (Hegnauer 1963, 1986). In these two treatises many references are available. Subterranean parts of both genera contain several in-secticidal alkaloids which represent a special type hitherto only known from these taxa. Tuberostemonin, C22H33NO4, is the best known of the Stemonaceae alkaloids. It was originally isolated from roots of Stemona tuberosa and also occurs in other Stemona taxa and is accompanied by a series of biogenetically related bases. Stems and leaves of S. japonica yielded the alkaloids stemofoline and stemospironine and roots and rhizomes of Croomia heterosepala contain croomine. Recently roots of Stemona species growing in the Southwest of China are investigated for insecticidal and therapeutically useful alkaloids: Stemona mairei (Wen-Han Lin et al. 1992), S.parviflora (Wen-Han Lin et al. 1991, 1992), S. sessilifolia (Dongliang Cheng et al. 1988) and S. tuberosa (Gwangdong Prov.; Wen-Han Lin et al. 1992).

Hitherto Stemonaceae were thoroughly investigated for alkaloids only. All other classes of secondary metabolites were neglected, including their phenolic compounds. Apparently there is one exception to this statement. In 1974 isolation of three non-prenylated munduserone-type rotenoids from a Thai medicinal crude drug ascribed to S. collinsae was reported (Shiengthong et al. 1974); these compounds were called stemonacetal, stemonal and stemonone. Later, however, Taguchi et al. (1977) investigated the same crude drug purchased on the Bangkok market and found it to be free of alkaloids, but yielding the known rotenoid stemonacetal and a new one, clitoriacetal. These workers detected that the Thai medicinal crude drug used to treat skin diseases and called 'Non-tai-yak' or 'Non-taai-yaak' has two different botanical sources, namely roots of Stemona burkillii, collinsae and tuberosa on the one hand, and roots of Clitoria macrophylla (= C. hanceana) on the other; pharmacognostical investigation of their crude drug sample convinced them that they were working with roots of the papilionaceous substitute Clitoria macrophylla. This makes it highly probable that also Shiengthong et al. (1974) investigated Clitoria macrophylla and not a Stemona taxon. Therefore, statements that Stemonaceae contain rotenoids (Shiengthong et al. 1974; Hegnauer 1986; Ponglux et al. 1987) are suspicious.

Saponins were recorded for roots of S. cochinchinensis which also contain alkaloids. Unfortunately the chemistry of these saponins is still unknown. If Stemonaceae are remotely connected with Dioscoreaceae (e.g. Van Steenis 1982) or belong to Asparagales (Huber 1991) one would guess that Stemona saponins are of the steroidal type, i.e. have a C27-sapogenin. (R. Hegnauer)