Recent studies on chemical constituents of Ophiorrhiza plants

Abstract

Ophiorrhiza plants (Family Rubiaceae) are known to produce diverse monoterpenoid indole alkaloids including camptothecin with potent antitumor activity. This review contains a summary of recent chemical studies reported over the past 10 years regarding alkaloids (monoterpenoid indole and tetrahydroisoquinoline alkaloids, and cyclopeptide) in Ophiorrhiza plants. In addition, the alkaloid biosynthetic pathways based on their reported structures were proposed.

Keywords: Alkaloid; Biosynthesis; Camptothecin; Ophiorrhiza; Rubiaceae.

Fig. 1

Structures of ophiorrhisides A–F (1–6) and alkaloids 7–10 isolated from Ophiorrhiza trichocarpon

Fig. 2

Structures of ophiorrhisine A (11), 7’,10-dide-O-methylcephaeline (12), and alkaloids 8, 9, and 13–16 isolated from Ophiorrhiza nutans

Fig. 3

Asymmetric total synthesis of ophiorrhisine A (11)

Fig. 4

Structures of ophiorrhisine A derivatives having cytotoxicity against human cancer cell lines

Fig. 5

Structures of ophiorrhines A (23), B (24), F (26), and G (27) and alkaloid 25 isolated from Ophiorrhiza japonica

Fig. 6

Structures of ophiorrhines C–E (28–30) and alkaloids 31 and 32 isolated from Ophiorrhiza cantoniensis

Fig. 7

Structures of camptothecin (33) and harmaline (34)

Fig. 8

Plausible biosynthetic pathways of some monoterpenoid indole alkaloids in Ophiorrhiza plants (* not isolated from Ophiorrhiza plants but found in other plants)

Fig. 9

Proposed biosynthetic pathways for monoterpenoid tetrahydroisoquinoline alkaloids in Ophiorrhiza plants (* not isolated from Ophiorrhiza plants but found in other plants)