Mitragyna speciosa Korth Havil

[From Latin, mitragyna = mitriform female organ and speciosus = beautiful]

Physical description: It is a timber tree which grows to a height of 25 m in the lowland forests of Malaysia, Thailand, Indonesia, the Philippines and New Guinea, by the streams and swamps.The bark is smooth and grey. The inner bark is pinkish. Leaves: simple, 3cm-20cm x 2cm-12cm, decussate and stipulate. The stipules are lanceolate and 1cm x 4 cm. The blade is thick, elliptic, ovate or obovate, slightly hairy below, shows 11-17 pairs of conspicuous secondary nerves, pointed at the

Common names: Ketong (Malay); krathom, ithang, kakuam, thom (Thai); puri (Indonesian).

apex and round at the base. The flowers are grouped in solitary, globose and 9 mm-1.3cm heads. The interflorale bracteoles are 4mm-6mm long, pale, hairy and conceal the calyces of flower buds in the young stage. The calyx is 2 mm long. The corolla is tubular, yellow, hairy on the inside of the throat and develops 5 val-vate lobes. The fruiting heads are 2cm-3cm in diameter and consist of several, 7 mm-9 mm x 4 mm-5 mm fruitlets. The seed are 1 mm long with a papery wing at each end (Fig. 351).

Uses: In Burma, the leaves cause drowsiness. In Malaysia, the leaves are chewed or infused to make a drink ingested to fight addiction to opium.The leaves are used to heal wounds and Fig. 351. Mitragyna speciosa (Korth.) Havil. enter in an external remedy to treat From: KLU Herbarium 25409. Flora of Tereng-enlarged spleen. InThailand, the leaves ganu. Comm. Ex. Herb. Hort. Bot. Sing. Geo-are chewed to assuage addiction to graphical localization: Jungle path to Gunong opium and to invigorate health. ^^ ^ altitude: 2000 ft Malaysia. Field co|-

-—- lectors & botanical identification: Mohd. Shah,

Ahmad Shukor, Mahmud Awang, 1 June 1974.

Pharmaceutical interest: Mitragyna speciosa (Korth.) Havil. is interesting because it produces several sorts of monoterpenoid indole alkaloids (Beckett AH etal., 1966), among which mitragynine binds to n- and 5-opioid receptors, responsible for the control of morphine addiction and pain.

Mitragynine

Morphine

Mitragynine

Morphine

(n = 5). Naloxone (10nM-300nM) reverses the inhibitory effect of mitrag-ynine on electrically-stimulated contraction and shifts the concentration-response curve of mitragynine to the right. Mitragynine (3 ^M-10 ^M) inhibits naloxone-precipitated withdrawal contraction, following a brief (5 min) exposure of the ileum to morphine (Watanabe K etal., 1997).

Central analgesic properties: Intrac-erebroventricular injection of mitragynine (10 ng) protects mice against the pain caused experimentally in the tail-pinch and hot-plate tests, but these effects are annihilated by the selective ^-opioid antagonist cyprodime (1 mg-10 ng) and the pretreatment with the selective m-opioid antagonist naloxonazine (1 mg-3 mg) and the selective 5-opioid antagonist naltrindole (1 ng-5ng) (Fig. 352). Nor-binaltorphimine, a selective k-opioid antagonist, significantly attenuates the analgesic property of mitragynine in the tail-pinch test, but not in the hot-plate test at the dose of 1 mg (Thongpradichote S etal., 1998). 7-Hydroxymitragynine is analgesic orally in mice (Matsumoto K et al., 2004).

Fig. 352. Mechanism of analgesic action of mitragynine. Mitragynine (M) binds to f- and 5-opioid receptors which mediate pain. PF: pain fiber, DRG: dorsal root ganglion, PS: presynaptic, PO: post-synaptic, DH: dorsal horn, N: neurotransmitter, B: brain.
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