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The Uncaria genus is an important source of medicinal natural products, particularly alkaloids and triterpenes. The collected information is an attempt to cover the more recent developments in the ethnobotany, pharmacology and phytochemistry of this genus. During the past 20 years, alkaloids, terpenes, quinovic acid glycosides, flavonoids and coumarins have been isolated from Uncaria. Fifty-three novel structures are reported in this review. The species in which the largest number of compounds has been identified is the Peruvian Uncaria tomentosa or 'cat's claw.' Pharmacological studies are described according to cytotoxicity, anti-inflammatory, antiviral, immunostimulation, antioxidant, CNS-related response, vascular, hypotensive, mutagenicity and antibacterial properties. The potential for development of leads from Uncaria continues to grow, particularly in the area of immunomodulatory, anti-inflammatory and vascular-related conditions. The information summarized here is intended to serve as a reference tool to practitioners in the fields of ethnopharmacology and natural products chemistry.

The leaves of the plant Mitragyna parvifolia have afforded two alkaloids, 16,17-dihydro-17beta-hydroxy isomitraphylline (1) and 16, 17-dihydro-17beta-hydroxy mitraphylline (2), together with two known alkaloids, isomitraphylline (3) and mitraphylline (4). The structures of 1 and 2 were elucidated using 1D and 2D NMR spectral methods, including (1)H-(1)HCOSY, DEPT, HSQC, and HMBC. Mitraphylline was the main alkaloid constituent.

Ajmalicine, formosanine, isomitraphylline and mitraphylline have been isolated from the bark of Uncaria elliptica . Differences in alkaloid content within the species have been observed. © 1997 Elsevier Science Ltd. All rights reserved

3-Iso-19-epi-ajmalicine, epiallo-corynantheine and dihydrocorynantheine pseudoindoxyl, not previously known as natural products, have been isolated from samples of U. attenuata. Akuammigine, dihydrocorynantheine, hirsutine, hirsuteine, mitraphylline, speciophylline, uncarines A and B, isorhynchophylline rhynchophylline, isocorynoxeine, corynoxeine, corynoxine B, rotundifoline, speciofoline, two yohimbine isomers, a yohimbine oxindole and an unidentified indole alkaloid (M+, m/e 347) have been obtained from samples of the same species. 3-Iso-ajmalicine, harmane, isopteropodine, pteropodine, uncarine F, speciophylline, isomitraphylline, mitraphylline and N-oxides of these six oxindole alkaloids have been isolated from samples of U. orientalis. Several samples of U. canescens have yielded harmane while one sample contained the four pteropodine isomers. The variation in the alkaloid content of these three species is discussed.

A new alkaloid roxburghine X, along with roxburghine D, formosanine and mitraphylline, has been isolated from the bark of Uncaria elliptica. Sitosterol, quinovaic acid, acetylquinovaic acid and scopoletin were isolated from the bark of Canthium dicoccum.