Millettia (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Millettia Wight & Arn.

Protologue: Prodr. fl. Ind. orient. 1: 263 (1834).

Family: Leguminosae

Chromosome number: x= 10, 11; M. extensa, M. pachycarpa: 2n= 22; M. pinnata: 2n= 20, 22

• Millettia pinnata (L.) Panigrahi,
• M. sericea (Vent.) Wight & Arn.

Millettia consists of about 150 species found in the Old World tropics and subtropics, and 5 species in California and Mexico. One species (M. pinnata) extends from India to northern Australia and the West Pacific.

Roots or seeds of many Millettia species are traditionally employed as a fish poison throughout South-East Asia. Roots and seeds of M. pachycarpa Benth. from India, Burma (Myanmar), Thailand and China, are used likewise to poison fish and birds, and possess considerable insecticidal activity. The plant is locally employed as a tonic and to treat swellings. Roots of M. racemosa Benth. from India, Burma (Myanmar), Thailand and the Philippines, are used as a fish poison and applied to cattle sores.

M. ichtyochtona Drake from Vietnam and M. piscidia (Roxb.) Wight & Arn. from India are both used as fish poison, the former species is even being locally cultivated for its piscicidal properties. In Peninsular Malaysia, pounded leaves of M. xylocarpa Miq. (syn. M. hemsleyana Prain) are placed in a hollow tooth to relieve toothache. The West African M. thonningii (Schumach. & Thonn.) Baker is effectively applied as a molluscicide and cercaricide. In Sudan, the dried whole plant is used as an antimalarial. Leaves and branches of M. extensa and M. pinnata are applied as green manure or as fodder. The bark of various Millettia species is used for rough cordage. Sometimes Millettia is planted as an ornamental, for its showy drooping inflorescences.

Millettia is of local importance only, therefore no information on production and international trade is available.

Many Millettia species are characterized by the presence of isoflavones and rotenoids, which are isoflavone derivatives. For instance, M. ichtyochtona contains isoflavones in the leaves, and rotenone in the seeds. The latter compounds are also isolated from the roots and seeds of M. pachycarpa, which also contains isoflavones in the fruits, and other aerial parts. M. extensa is known to contain isoflavones and rotenoids in roots and seeds, M. thonningii in the seeds and roots, and M. racemosa isoflavones in the stem. Rotenone is a powerful mitochondrial inhibitor of the electron transport. It exhibits a considerable degree of selective toxicity; for example it is very toxic to insects, but only slightly to mammals.

Preliminary studies with ethanolic seed extracts of M. pinnata exhibited an anti-inflammatory effect in rats. M. pinnata seed extracts prepared with several other solvents were also evaluated for anti-inflammatory effects in chemically (bradykinin and PGE-1) induced hind paw inflammations in the rat; the predominant action appears to be a modulation of eicosanoid-events in inflammation. In contrast, minimal effects were seen against histamine and 5-HT-induced inflammations.

M. pinnata roots have been advocated in Ayurvedic medicine for treatment of various inflammatory and infective conditions including ulcers. Sequential petroleum ether, benzene, chloroform, acetone and ethanolic extracts of M. pinnata roots, when administered at a dose of 50 mg/kg intra peritoneal (i.p.) in rats, were found to have anti-inflammatory and analgesic activity. Pentobarbitone-induced "sleeping time" was reduced by all the extracts except for petroleum ether, which enhanced it. The extracts were also found to possess anti-ulcer effects when administered either by i.p. (45 min before) or oral route (45 min before or for 4 days) against restraint-stress or pylorus-ligated gastric ulcers in rats, the maximum protection being afforded by petroleum ether and ethanol extracts. The mechanism of the anti-ulcer effect could be due to decrease in acid-pepsin secretion and augmentation of mucin secretion as observed with the ethanol extract, while the petroleum ether extract might be producing the effect by virtue of its anti-stress activity.

The traditional Indian use of M. pinnata seeds for treatment of clinical lesions of skin and genitalia, prompted an evaluation of antiviral properties against herpes simplex virus type-1 (HSV-1) and type-2 (HSV-2) by in-vitro studies in Vero cells. A crude aqueous seed extract of M. pinnata completely inhibited the growth of HSV-1 and HSV-2 at concentrations of 1 and 20 mg/ml (w/v), respectively, and cytopathic effects were completely absent.

Other pharmacological effects of compounds and extracts of Millettia include: inhibition of the interleukin-1 production by pongapinone A, a phenylpropanoid isolated from the bark of M. pinnata, and inhibition of murine retroviral transcriptase and human DNA-polymerase by extracts from M. pachycarpa.

The inedible fatty seed oil of M. pinnata which has a disagreeable odour, and is difficult to refine, was tested as an antifeedant and insecticide against several insects, e.g. Oryzaephilus surinamensis and Tribolium castaneum (both storage pests of rice) and Nephotettix virescens (a vector of the virus causing tungro disease in rice).

Rotenoids are also obtained from the roots of other legumes such as Derris, Lonchocarpus, Paraderris, Piscidia and Tephrosia species. Other insecticides of plant origin used in South-East Asia are present in the seeds of Croton tiglium L., roots of Derris and Paraderris species, stem and roots of Tinospora species, leaves of Vitex negundo L., Nicotiana tabacum L. and Azadirachta indica A.H.L. Juss. Other piscicidal plants include Croton tiglium, Derris species, Myrica esculenta Buch.-Ham., Paraderris species and Sapindus saponaria L.

• Shrubs, lianas or trees up to 25 m tall.
• Leaves alternate, imparipinnate; stipules small, caducous; leaflets (sub)opposite, 1-35; stipellae absent or present.
• Inflorescence terminal or axillary, pseudopaniculate or pseudoracemose.
• Flowers bisexual, 5-merous; calyx tube usually truncate with 4-5 teeth or short lobes or with 4-5 distinct valvate lobes; corolla papilionaceous, much longer than the calyx, white, pink, blue or violet, standard broadly ovate to obovate, glabrous or silky pubescent outside, wings adherent to keel petals and equally long, (sub)falcate; stamens 10, upper filament free or adnate; ovary superior, 1-loculate, 1-7(-11)-ovuled.
• Fruit a flattened, sometimes inflated pod, without wings or with 2 wing-like crests, tardily dehiscent, 1-more seeded.
• Seed generally flat, lens-shaped or quadrate, in a few species ellipsoid.

Millettia is placed in the tribe Millettieae within the subfamily Papilionoideae. It seems closely related to Aganope, Derris, Lonchocarpus, Ostryocarpus and Paraderris. Millettia differs from Derris and Paraderris in the pods being wingless and dehiscent. Millettia can be easily distinguished from Callerya, the latter having large paniculate inflorescences and a diadelphous staminal tube. The Malesian M. dasyphylla (Miq.) Boerl. has been recombined in Callerya dasyphylla (Miq.) Schot. The Chinese and Indo-Chinese M. dielsiana Harms ex Diels, M. reticulata Benth. and M. speciosa Champ. have been recombined in Callerya cinerea (Benth.) Schot, C. reticulata (Benth.) Schot and C. speciosa (Champ.) Schot, respectively. C. cinerea is used as an anti-anaemic in China. C. reticulata is applied to cure wounds and as an insecticide. The roots of C. speciosa are used for their reconstituent and antitussive properties. They are utilized in the form of a decoction or powder in the treatment of general debility, anorexia, headaches, coughs and dysuria.

Millettia species are generally found in rather open habitats. M. pinnata is very tolerant of saline conditions and also tolerant of alkalinity. It nodulates and fixes atmospheric nitrogen with Rhizobium of the cowpea group.

Most Millettia species are propagated by seed. M. pinnata can easily be propagated by seed and cuttings. Germination takes 10-30 days. Seedlings reach a height of 60 cm about 1.5 years after sowing and are easy to transplant. Direct sowing is common and mostly successful.

Trees of M. pinnata coppice well and can also be pollarded.

Millettia hosts a large number of fungi and insects, but serious damage has not been observed. Flowers and flower buds of Millettia species of section Fragiliflora (e.g. M. pinnata) often suffer from gall formation: the section can be easily identified by this phenomenon.

Leaves of Millettia can be picked whenever the need arises, whereas pods are collected when mature. Tuberous roots are harvested from plants at least 1 year old.

Pod production in M. pinnata starts 5-7 years after sowing. Individual trees yield 9-90 kg of pods annually. Mature trees yield 8-24 kg seed annually. Air dried roots of M. pachycarpa contain 0.9-1.6 % rotenone and 2.8-4.3% ether extractives, roots less than 2.5 cm in diameter being richer in rotenone. Average yield of rotenone-rich roots amounts to 1 kg/plant. The seeds contain up to 0.65% rotenone and deguelin and 12% ether extracts.

Ripe pods of Millettia are collected and subsequently dried in the sun. Seeds are extracted by light hammering or by splitting the pod with a knife along the sutures and winnowing them out of the husks. Tuberous roots are washed, sliced and dried for further storage.

Medicinally important Millettia have a preference for relatively open habitats, and tend to be adapted to disturbance. Therefore the risk of genetic erosion is likely to be limited. However, the natural distribution of a considerable number of species is rather limited.

The presence of rotenoids in Millettia may be of interest for their application as an insecticide in local communities, being cheap, simple and convenient. The anti-inflammatory, anti-ulcer and antiviral effects might be of interest for development of future lead compounds, and thus merit further research.

• Adema, F., 2000. Notes on Malesian Fabaceae (Leguminosae-Papilionoideae) 6. The genus Milettia. Blumea 45: 403-425
• Elanchezhiyan, M., Rajarajan, S., Rajendran, P., Subramanian, S. & Thyagarajan, S.P., 1993. Antiviral properties of the seed extract of an Indian medicinal plant, Pongamia pinnata, Linn., against herpes simplex viruses: in-vitro studies on Vero cells. Journal of Medical Microbiology 38(4): 262-264.
• Ono, K., Nakane, H., Meng, Z.M., Ose, Y., Sakai, Y. & Mizuno, M., 1989. Differential inhibitory effects of various herb extracts on the activities of reverse transcriptase and various deoxyribonucleic acid (DNA) polymerases. Chemical and Pharmaceutical Bulletin Tokyo 37(7): 1810-1812.
• Schot, A.M., 1994. A revision of Callerya Endl. (including Padbruggea and Whitfordiodendron)(Papilionaceae: Millettieae). Blumea 39: 1-40.
• Singh, R.K., Joshi, V.K., Goel, R.K., Gambhir, S.S. & Acharya, S.B., 1996. Pharmacological actions of Pongamia pinnata seeds - a preliminary study. Indian Journal of Experimental Biology 34(12): 1204-1207.
• Singh, R.K. & Pandey, B.L., 1996. Anti-inflammatory activity of seed extracts of Pongamia pinnata in rat. Indian Journal of Physiology and Pharmacology 40(4): 355-358.

• J.L.C.H. van Valkenburg