Description Générale

Arbrisseaux, arbustes ou arbres.

Répartition en Nouvelle-Calédonie

En NC, ce genre indo-australien est représenté par 13 espèces endémiques et 2 variétés

Répartition hors Nouvelle-Calédonie

Ailleurs il comprend une quarantaine d'espèces répandues en Birmanie et en Australie

Feuille

Feuilles alternes.

Phénologie (Fleur)

Fleurs 5-mères; sépales et pétales libres; étamines nombreuses groupées en 5 faisceaux opposés aux pétales.

Fruits

Fruits en capsules exsertes au-dessus du calice, avec 2 - 4 loges; graines nombreuses, réniformes.

Particularité

Tristaniopsis calobuxus - Tristaniopsis glauca - Tristaniopsis yateensis
Aucun nom vernaculaire, aucune réputation médicinale traditionnelle ne sont connues jusqu'à présent pour ces trois espèces néo-calédoniennes.
(Or, ces 3 plantes contiennent des substances antipaludiques et un brevet italien a été déposé sur les propriétés in vitro de ces substances...)

Tristaniopsis callobuxus Brongniart & Gris, les extraits d'écorce testés à 50µg/ml, inhibent la xanthine oxydase (56%) et l'élastase (51%) (Gariboldi & al. 1998). L'extrait méthanolique d'écorces et divers composés inhibent la métalloprotéinase-9 (Bellosta & al. 2003).
L'activité antipaludique in-vitro de deux constituants de Tristaniopsis callobuxus est due à l'acide ellagique (qui interviendrait par ailleurs dans le 'french paradox') et à un composé nouveau, le 3,4,5-trimethoxyphenyl-(6'-O-galloyl)-O-beta-D-glucopyranoside (Verrota & al. 2001).

Bibliographie :
Gariboldi E, Mascetti D, Galli G, Caballion P, Bosisio E. - LC-UV-electrospray-MS-MS mass spectrometry analysis of plant constituents inhibiting xanthine oxidase. Pharm Res. 1998 Jun;15(6):936-43. - Erratum in: Pharm Res 1999 Jun;16(6):972 (Cabalion)
PURPOSE: A previous screening showed that Amyema scandensi [corrected] Danser (Loranthaceae) efficiently inhibited XOD. The aim of this study was to identify the compounds with anti-XOD properties. For this purpose, Electrospray Tandem Mass Spectrometry (ESI-MS-MS) coupled with UV and Diode Array LC techniques were employed.
METHODS: Leaves were delipidized with petroleum ether and extracted with acetone:water 70:30, v:v. The extract was fractionated into the ethyl acetate and water soluble phases. Chemical investigation was performed following the bioactivity guided fractionation. Two fractions with anti-XOD activity were isolated by silica gel column chromatography of the ethyl acetate phase and analyzed by LC-UV-ESI-MS-MS.
RESULTS: The compounds identified with authentic standards were: catechin, epicatechin, epicatechin-3-gallate, quercetin-3-O-glucoside, quercetin-3-O-rhamnoside, and isorhamnetin-3-O-glucoside. Other constituents, only partially characterized, were a procyanidin dimer, a procyanidin trimer, three dimers epi/catechine-epi/catechine gallate and isorhamnetin-O- deoxyhexose. The anti-XOD activity was mainly due to galloyl-containing oligomeric proanthocyanidins.
CONCLUSIONS: The coupling of UV Diode Array-HPLC with ESI-MS-MS represents a versatile tool for the rapid characterization of compounds in complex mixtures, avoiding time-consuming previous isolation.

Verotta L, Dell'Agli M, Giolito A, Guerrini M, Cabalion P, Bosisio E. - In vitro antiplasmodial activity of extracts of Tristaniopsis species and identification of the active constituents: ellagic acid and 3,4,5-trimethoxyphenyl-(6'-O-galloyl)-O-beta-D-glucopyranoside. - J Nat Prod. 2001 May;64(5):603-7.
Screening of plants from New Caledonia for antiplasmodial activity against Plasmodium falciparum revealed that methanolic extracts of the leaves and bark of Tristaniopsis calobuxus, T. yateensis, and T.glauca inhibited the growth of chloroquine-sensitive and -resistant clones. Ellagic acid and the new compound 3,4,5- trimethoxyphenyl-(6'-O-galloyl)-O-beta-D-glucopyranoside were identified as the active constituents (IC50 0.5 and 3.2 microM, respectively). The growth inhibition of both clones was comparable. The compounds showed negligible or very low cytotoxicity to human skin fibroblasts and Hep G2 cells when tested at concentrations ranging from 0.5 to 100 microM.

Bellosta S, Dell'Agli M, Canavesi M, Mitro N, Monetti M, Crestani M, Verotta L, Fuzzati N, Bernini F, Bosisio E. Inhibition of metalloproteinase-9 activity and gene expression by polyphenolic compounds isolated from the bark of Tristaniopsis calobuxus (Myrtaceae). Cell Mol Life Sci. 2003 Jul;60(7):1440-8.
Excessive breakdown of extracellular matrix by metalloproteinases (MMPs) occurs in many pathological conditions, and thus inhibition of MMP activity might have therapeutic potential. The methanolic extract and the identified compounds from the bark of Tristaniopsis calobuxus Brongniart & Gris (Myrtaceae) were tested on the activity, production, and gene expression of MMP-9. The extract produced a concentration-dependent inhibition (50-95% at 10-50 microg/ml) of MMP-9 activity. The inhibitory activity was retained in the ethyl acetate-soluble fraction (50-95% inhibition at 10-50 microg/ml) which also reduced the release of MMP-9 by mouse peritoneal macrophages up to 80%. In the ethyl acetate-soluble fraction, two active fractions, 5A and 5B were identified. HPLC-MS and NMR analyses of these fractions indicated the presence of gallocatechin, ellagic acid, and its glycoside derivatives. Since the absolute configuration of gallocatechin was not determined, in the next experiments both (+)-gallocatechin (2R,3S) and (-)-gallocatechin (2S,3R) were tested, and (-)-epigallocatechin (2R,3R) was included for comparison. 5A and 5B inhibited MMP-9 secretion, an observation which correlated with the decrease of MMP-9 promoter activity and the downregulation of mRNA levels. All compounds decreased MMP-9 mRNA levels and secretion. Ellagic acid, (+)-gallocatechin and (-)-epigallocatechin, but not (-)gallocatechin inhibited promoter-driven transcription. Thus configuration at C2 (R) of the flavanol seem to be critical for the interaction with the promoter.
Aussi un brevet italien sur l'activité antipaludique in vitro de l'acide ellagique et du 3,4,5-trimethoxyphenyl-(6'-O-galloyl)-O-beta-D-glucopyranoside.
P. Cabalion.