Plumbago (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Plumbago L.

Protologue: Sp. pl. 1: 151 (1753); Gen. pl. ed. 5: 75 (1754).

Family: Plumbaginaceae

Chromosome number: x= unknown; P. indica: 2n= 14, P. zeylanica: 2n= 28

• Plumbago indica L.,
• P. zeylanica L.

• Leadwort (En)
• Vietnam: duôi công.

Plumbago consists of about 24 species from tropical and warm temperate regions. For the Malesian region 4 species are reported, 2 of which are indigenous to the region.

P. indica and P. zeylanica are widely considered a vesicant and abortifacient, and are further used in the treatment of rheumatism and skin problems. Although both are generally reported to have similar applications, P. zeylanica is said to be milder and less dangerous than P. indica. Some Plumbago species are widely cultivated ornamentals in tropical and subtropical regions. In the Malesian region, P. aphylla Bojer ex. Boiss. originating from Madagascar and P. auriculata Lamk (synonym: P. capensis Thunb.) from southern Africa are planted as ornamentals.

Dried roots of Plumbago are often the basis of the drugs used in traditional medicine and are found as such in the market. They are traded in pieces of usually less than 1.3 cm thick, with a shrivelled, yellowish to reddish-brown bark. The activity of preparations of P. indica and P. zeylanica can be largely attributed to the presence of plumbagin (2-methyl-5-hydroxy-1,4-naphthoquinone), which is mainly extracted from the roots and is only found in Plumbaginaceae. The Plumbago species from which plumbagin has been isolated not only include P. indica and P. zeylanica, but also P. auriculata, P. caerulea Humb., Bonpl. & Kunth, P. europaea L., P. pearsonii L. Bolus, P. pulchella Boiss. and P. scandens L. Analysis of dried and powdered P. zeylanica roots from Sri Lanka revealed the presence of naphthoquinone derivatives such as plumbagin (0.036%), isoshinanolone (0.035%), droserone (0.0013%) and 1,2(3)-tetrahydro-3,3'-biplumbagin (0.005%), and the steroid sitosterol (0.08%).

Plumbagin has been reported to have anti-implantation and abortifacient activity in rats, without having teratogenic effects, whereas it produces testicular lesions and testis weight reduction in dogs. It has shown antigonadotropic activity in rats, causing a decrease in weight of ovaries, and blocking the effect of applied gonadotrophin. It has also shown antiprogestational activity in rats.

Furthermore, in lower concentrations, plumbagin has an antimitotic activity comparable to that of colchicine. In larger doses, plumbagin also has nucleotoxic and cytotoxic effects. It has also been found that P. indica extracts have inhibitory activity on indirect mutagens and are not mutagenic themselves.

In small doses, plumbagin stimulates the central nervous system of frogs, mice and rabbits, whereas larger doses lead to convulsions and paralysis. In rabbits, it caused a decreased respiration and blood pressure, but no diuresis. In frogs, it paralysed muscular tissue and caused dilation of perfused blood vessels. Furthermore, it seems that plumbagin is a strong irritant and/or hepatotoxic.

Plumbagin has shown antibacterial activity against both gram-positive (e.g. Staphylococcus, Streptococcus, Pneumococcus spp.) and gram-negative (e.g. Salmonella) bacteria, whereas it is also active against certain fungi (Trichophyton, Epidermophyton and Microsporum spp.) and protozoa (Leishmania). It has been found to prevent Escherichia coli and Staphylococcus aureus developing resistance to antibiotics and it eliminated multidrug-resistant plasmids from E. coli strains, resulting in loss of resistance to the antibiotics tested. In low concentrations, it augments the bacterial activity of mouse macrophages against Staphylococcus aureus, whereas at higher concentrations it has shown inhibitory effects. Furthermore, plumbagin shows antitumour activity in mice, especially in combination with gamma radiation.

Plumbagin also has insecticidal activity. It has shown strong insect antifeedant activity against larvae of army worms (Spodoptera exempta, S. littoralis), toxicity to nymphs of red cotton bug or cotton stainer (Dysdercus koeningii) and mosquito larvae (Culex quinquefasciatus), whereas it retarded growth, delayed metamorphosis and reduced fertility in housefly (Musca domestica). It also produced morphogenetic effects in Dysdercus koeningii and various other insects. These effects are probably due to its interference with the neuro-endocrine system and the system which regulates metamorphosis.

Besides plumbagin, phytochemical analysis has revealed the presence of other naphthoquinones and their derivatives in the roots of P. zeylanica including 3-chloroplumbagin and 2-methylnaphtazarin, the plumbagin dimers 3,3'-biplumbagin, 3,6'-biplumbagin (= chitranone), 6,6'-biplumbagin (= elliptinone), maritinone, methylene-3,3'-diplumbagin, zeylanone and isozeylanone, and the plumbagin trimer plumbazeylanone. Further compounds include: nonyl-nonanoate and nonyl-8-methyl-dodec-7-enoate (long-chain aliphatic esters), benzyl-2,5-dihydroxy-6-methoxybenzoate and 2,2-dimethyl-5-hydroxy-6-acetyl-chromene (aromatic derivatives), steroids (e.g. stigmasterol, stigmasterol acetate, sitosterone) and triterpenes (lupeol, lupeol acetate, lupanone, friedelinol). The leaves of P. zeylanica are reported to contain leucodelphinidin and quercetin-3-rhamnoside, and the petals azaleatin-3-rhamnoside. Compounds isolated from the aerial part of P. indica include 6-hydroxyplumbagin, plumbaginol (a flavonol), leucodelphinidin and steroids (e.g. β-sitosterol, stigmasterol, campesterol). The petals are reported to contain delphinidin, cyanidin and pelargonidin-3-rhamnosides, kaempferol-3-rhamnoside, galloylglucose and digalloylglucose.

P. indica and P. zeylanica are sometimes used as a substitute for Rauvolfia serpentina (L.) Benth. ex Kurz. Different naphthoquinone derivatives have been prepared from plumbagin, with halogenated plumbagin showing stronger ichthyotoxicity than plumbagin itself.

• Shrubs or perennial herbs, rarely annual, often straggling or subscandent.
• Leaves alternate, simple, entire, older ones often pale lepidote underneath as a result of carbonate exudations, or reduced in flowering stems, petiole often semi-amplexicaulous auriculate; stipules absent.
• Inflorescence composed of 1-flowered spikelets grouped in a terminal raceme or spike, often united in a leafy panicle.
• Flowers subtended by 2-3 bracts, 5-merous; calyx tubular, 5-ribbed, often with sessile or stalked glands outside, teeth erect, not enlarged in fruit; corolla funnel-shaped, lobes spreading, blue, red, white or violet; stamens 5, free, filaments broadened at the base; ovary superior, 1-locular, style 1, stigma lobes 5.
• Fruit a 1-seeded capsule, included in the calyx and corolla, often splitting from the base with 5 valves.
• Seed long, narrowly ovoid, slightly flattened, tapering towards apex, dark brown or black, surface colliculate, hilum small, oval, in a longitudinal depression.

In South-East Asia, both P. indica and P. zeylanica flower throughout the year, which explains their success as ornamentals. No fruit of P. indica has ever been found. The fruits of P. zeylanica are easily dispersed because of the sticky glands on the persistent calyx.

Plumbago is placed together with Ceratostigma in the subfamily Plumbaginoideae, characterized by inflorescences consisting of spikes, racemes or heads, as opposed to the other subfamily Staticoideae (inflorescence a thyrse with cincinnate partial inflorescences) comprising e.g. Armeria and Limonium which are both mainly saltmarsh and maritime genera. P. europaea from the Mediterranean region and West Asia used to be used in traditional medicine to treat eye diseases. One of the side-effects of this rather poisonous plant is a discoloration of the skin resembling the colour of lead, from which the Latin name Plumbago and the popular name leadwort are derived.

In general, Plumbago prefers semi-arid conditions. P. indica is reported to be a short-day plant. It prefers rich, moist and well-drained soils, with a pH between 5.5 and 6.0, whereas a pH below 5.0 or above 7.0 may lead to stunted growth. In Indian experiments with P. zeylanica, the largest and heaviest roots were obtained from plants grown in loamy soils.

Shrubby Plumbago species are usually propagated through cuttings. P. indica is propagated through offsets and root cuttings. In vitro micropropagation from stem segments, nodes and leaves is also possible. However, in vitro plants may not transplant successfully into a soil medium.

P. zeylanica cell strains derived from stem explants and grown in vitro have been found to have a different potential of plumbagin synthesis.

Leaf poultices of P. zeylanica can be dried and stored for several months without losing their vesicant properties. However, dried roots of P. indica and P. zeylanica contain less plumbagin and show less activity than fresh ones.

In view of their wide distribution, neither P. indica nor P. zeylanica appear to be endangered. No breeding programmes are known to exist.

Although plumbagin may have medicinal potential, e.g. for its antimicrobial and antitumour activity, the use of plumbagin or plumbagin-containing plant material as medicine for humans is not devoid of danger. Plumbagin may have potential as a compound in synthetic insecticides.

• Devi, P.U., Solomon, F.E. & Sharada, A.C., 1994. In vivo tumor inhibitory and radiosensitizing effects of an Indian medicinal plant, Plumbago rosea on experimental mouse tumors. Indian Journal of Experimental Biology 32(8): 523-528.
• Dhar, S.K. & Rao, P.G., 1995. Hormonal profile of plumbagin. Fitoterapia 66(5): 442-446.
• Gunaherath, G.M.K.B., Gunatilaka, A.A.L. & Thomson, R.H., 1988. Studies on medicinal and related plants of Sri Lanka. Part 18. Structure of a new naphthoquinone from Plumbago zeylanica. Journal of the Chemical Society. Perkin Transactions 1, Organic and Bio-organic Chemistry 1988: 407-410.
• Gupta, M.M., Verma, R.K. & Gupta, A.P., 1995. A chemical investigation of Plumbago zeylanica. Current Research on Medicinal and Aromatic Plants 17: 161-164.
• Harborne, J.B., 1967. Comparative biochemistry of the flavonoids - IV. Correlations between chemistry, pollen morphology and systematics in the family Plumbaginaceae. Phytochemistry 6: 1415-1428.
• Heble, M.R., Narayanaswamy, S. & Chadha, M.S., 1974. Tissue differentiation and plumbagin synthesis in variant cell strains of Plumbago zeylanica L. in vitro. Plant Science Letters 2: 405-409.
• Karnick, C.R., Tiwari, K.C. & Majumber, R., 1982. Cultivation trials, pharmacognosy and ethnobotanical investigations of Plumbago zeylanica L. (Chitraka) of the Indian system of medicine. International Journal of Crude Drugs Research 20: 193-199.
• Valsaraj, R., Pushpangadan, P., Smitt, U.W., Adsersen, A. & Nyman, U., 1997. Antimicrobial screening of selected medicinal plants from India. Journal of Ethnopharmacology 58: 75-83.
• van Steenis, C.G.G.J., 1949. Plumbaginaceae. In: van Steenis, C.G.G.J. (General editor): Flora Malesiana. Series 1, Vol. 4. Noordhoff-Kolff N.V., Djakarta, Indonesia. pp. 107-112.
• Wilmot-Dear, C.M., 1976. Plumbaginaceae. In: Polhill, R.M. (Editor): Flora of Tropical East Africa. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. 12 pp.

• Plumbago indica
• Plumbago zeylanica

• Wongsatit Chuakul, Noppamas Soonthornchareonnon & Promjit Saralamp