Polianthes tuberosa L.

Agave polianthes (L.) Thiede & Eggli, Agave tuberosa (L.) Thiede & Eggli nom. illeg., Crinum angustifolium Houtt., Polianthes gracilis Link, Polianthes tuberosa var. gracilis (Link) Beurl., Polianthes tuberosa f. plena Moldenke, Tuberosa amica Medik.

Asparagaceae, also placed in Agavaceae, Amaryllidaceae

Tuberose

It is indigenous to Central and southern Mexico. The plant was distributed all over the world as an ornamental and is grown in tropical, subtropical and subtemperate areas. Kenya and Egypt are the leading producers of tuberose for the export market.

Tuberose grows best in mild climate without extremes of high or low temperatures. It thrives in warm humid areas with mean temperatures of 20–32 °C. It is sensitive to low temperatures and frost. High temperatures close to 40 °C reduces flower spike length and quality. Tuberose prefers a sunny position. Although it can grow in a wide range of soils including saline and alkaline soils, it prefers well-drained and aerated sandy loams rich in organic matter with pH of 6–7.5. It requires copious watering during the growth stage. The plant can also be grown in pots and in greenhouses in temperate areas.

The flowers are eaten as vegetables (Burkill 1966; Uphof 1968; Tanaka 1976; Kunkel 1984; Facciola 1990; Roberts 2000). In Java, the Chinese cook the flowers in a kind of soup. The cooked flowers are also added to the substrate of ‘kecap’, an Indonesian soy sauce. Fragrant flowers are added along with other ingredients to the favourite beverage prepared from chocolate and served either hot or cold as desired. The flowers are the source of tuberosa-flower water.

Tuberose is a hardy perennial, erect herb, 45–70 cm high with tuberose rootstock and shallow adventitious roots and a short stem. It has elongated linear, bright green leaves clustered at the base of the plant (Plate 1) and smaller clasping leaves along the stem. The flowers in a long (up to 45 cm), simple, unbranched terminal racemous spike with 4–6, waxy, fragrant white flowers borne in pairs (Plate 2). The perianth is tubular or funnel-shaped with short subequal, curved oblong-lanceolate tepals, 10–15 mm long. Stamens 6 with filaments adnate to the upper part of the perianth tube, anthers dorsifixed. Ovary 3-loculed with numerous ovules, stigmas 3 ovate. Fruit a capsule.

Besides the normal ‘single-tepal’ flower, ‘double-tepal’ tuberose flowers have been developed in white and various colours such as reddish purple, pale purple, pale red, reddish pink, yellow and orange (Huang et al. 2001a, b) and also tuberose with variegated yellow-striped leaves.

Polianthes tuberosa tuber was found to contain lycorine, an alkaloid that causes vomiting (Gorter 1919). A glucofructosan (Srinivasan and Bhatia 1954), transfructosidase (Bhatia and Srinivasan 1954) and sucrose (Wali and Hasan 1965) were found in the plant. Chandravadana et al. (1995) found indole in the absolute from various varieties and hybrids, varying in contents ranging from 0.36 to 2.15 %. Several steroid sapogenins, such as hecogenin, 9-dehydroxyhecogenin and tigogenin (Zhou et al. 1965), as well as glycosides, 29-hydroxystigmast-5-en-3β-yl β-d-glucoside (Rashid et al. 1999), (22S)-2β,3β,22-trihydroxycholest-5-en-16β-yl β-d-glucoside (Firdous et al. 1999b) and diribofuranosylethyleneglycol (Firdous et al. 1999a) and spirostanol pentaglycosides (Mimaki et al. 2002) were identified from the underground parts of P. tuberosa. Four new spirostanol saponins with five monosaccharides (1–4) were isolated from P. tuberosa underground parts (Mimaki et al. 2002). Three glycosides and a long-chain alcohol were isolated from the bulbs of Polianthes tuberosa; these were identified as 3,29-dihydroxystigmast-5-ene-3-O-β-d-galactopyranoside (1), ethyl β-d-galactopyranoside (2), ethyl-α-d-galactopyranoside (3) and 1-tricosanol (4) (Khan et al. 2002). None of the compounds showed any significant cytotoxicity, antibacterial and antifungal activities.

A bisdesmosidic cholestane glycoside (1) and three new spirostanol saponins (2–4), along with a known cholestane glycoside, were isolated from the aerial parts of Polianthes tuberosa (Mimaki et al. 2000).

A new cholestane glycoside, (22S)-cholest-5-en-1β,3β,16β,22,25-pentaol 1-O-β-d-glucopyranosyl-16–O-β-d-apiofuranoside which was named tuberoside A, together with two known cholestane glycosides were isolated from the tubers of Polianthes tuberosa (Jin et al. 2003a). The two known cholestane glycoside 1 and 2 were identified as (22S)-cholest-5-en-1B, 3B, 16 B, 22-tetraol 1-O-B-d-glucopyranosyl-16-O-B-d-apiofuranoside (Mimaki et al. 2000) and (22S)-cholest-5-en-1B, 3B, 16 B, 22-tetraol 3, 16-di-O-B-d-glucopyronoside (Mimaki et al. 1995), respectively.

Six new steroid glycosides comprising two spirostanols, polianthosides B and C (1, 2) and four furostanols, polianthosides D–G (3–6) together with eight known saponins (7–14), were isolated from the fresh tubers of P. tuberosa (Jin et al. 2004). Polianthoside B (1) was characterised as tigogenin 3-O-β-d-xylopyranosyl-(1 → 3)-β-d-glucopyranosyl-(1 → 2)-[β-d-glucopyranosy-(1 → 3)]-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside and polianthoside C (2) as tigogenin 3-O-β-d-glucopyranosyl-(1 → 3)-β-d-glucopyranosyl-(1 → 2)-[β-d-glucopyranosyl-(1 → 3)]-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside. Polianthoside D (3) was elucidated as 26-O-β-d-glucopyranosyl-(25R)-5R-furost-3β,22R,-26-triol-12-one 3-O-β-d-glucopyranosyl-(1 → 2)-[β-d-xylopyranosyl-(1 → 3)]-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside. Polianthoside E (4) was elucidated as 26-O-β-d-glucopyranosyl-(25R)-5R-furost-3β,22R,-26-triol-12-one3-O-β-d-xylopyranosyl-(1 → 3)-β-d-glucopyranosyl-(1 → 2)-[β-d-xylopyranosyl-(1 → 3)]-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside. Polianthoside F (5) was deduced to be as 26-O-β-d -glucopyranosyl-(25R)-5R-furost-3β,22R,-26-triol 3-O-β-d-xylopyranosyl-(1 → 3)-β-d-glucopyranosyl-(1 → 2)-[β-d-xylopyranosyl-(1 → 3)]-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside and polianthoside G (6) deduced to be 26-O-β-d-glucopyranosyl-(25R)-5R-furost-3β,22R,-26-triol 3-O-β-d-xylopyranosyl-(1 → 3)-β-d-glucopyranosyl-(1 → 2)-[β-d-glucopyranosyl-(1 → 3)]-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside. The eight known steroid saponins were identified as hecogenin 3-O-β-d-glucopyranosyl-(1 → 2)-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside (7) (Xu et al. 2000), hecogenin 3-O-β-d-glucopyranosyl-(1 → 2)-[β-d-xyloyranosyl-(1 → 3)]-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside (8) (Mimaki et al. 1995), hecogenin 3-O-β-d-xyloyranosyl-(1 → 3)-β-d-glucopyranosyl-(1 → 2)-[β-d-xyloyranosyl-(1 → 3)]-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside (9) (Mimaki et al. 2000), agamenoside F (10) (Jin et al. 2003b), tigogenin 3-O-β-d-glucopyranosyl-(1 → 2)-[β-d-xyloyranosyl-(1 → 3)]-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside (11) (Wang et al. 1996), tigogenin 3-O-β-d-xyloyranosyl-(1 → 3)-β-d-glucopyranosyl-(1 → 2)-[β-d-xyloyranosyl-(1 → 3)]-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside (12) (Mimaki et al. 2000), chlorogenin 3-O-β-d-xyloyranosyl-(1 → 3)-β-d-glucopyranosyl-(1 → 2)-[β-d-xyloyranosyl-(1 → 3)]-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside (13) (Mimaki et al. 2000) and 26-O-β-d-glucopyranosyl-(25R)-5R-furost-3β,22R,-26-triol 3-O-β-d-glucopyranosyl-(1 → 2)-[β-d-xylopyranosyl-(1 → 3)]-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside (uttroside B) (14) (Sharma et al. 1983), respectively.