Novel bioactive homoisoflavonoids from Madagascan Rhodocodon species (Hyacinthaceae, sensu APG II)

Rhodocodon species are endemic to Madagascar and their circumscription has been a topic of much debate. Speta [1] treated Rhodocodon as synonymous with Rhadamanthus and Manning [2] included the species in Drimia. Knirsch et al. [3] have recently presented evidence for a separate genus, Rhodocodon. In this work, three novel homoisoflavonoids (compounds 1, 3 and 5) were isolated from the dichloromethane extract of the bulbs of Rhodocodon aff. intermedius (Hyacinthaceae, sensu APGII). The structures of these compounds together with the acetates (compounds 2 and 4A and 4B) were determined by spectroscopic techniques. Known homoisoflavanoids (compounds 6 and 7) have also been extracted from R. cryptopodus and R. rotundus. Compounds 1, 3 and 4B were tested for antiangiogenic activity on human retinal microvascular endothelial cells (HREC) and gave GI₅₀'s of 17.6µM, 17.1µM and 15.8µM respectively. Compounds 6 and 7 are still undergoing testing and synthetic methods are being developed in order to obtain more material for animal studies. Compounds inhibiting angiogenesis are of interest to treat eye diseases characterized by neovascularization of the retina, as well as being of interest as novel anticancer therapies.

References:

[1] Speta F. Hyacinthaceae. The Families and Genera of Vascular Plants. Springer, Berlin; 1998: 261 – 285

[2] Manning J C, Goldblatt P, Fay M F. A revised synopsis of Hyacinthaceae in Sub-Saharan Africa, based on molecular evidence, including new combinations and the new tribe Pseudoprospereae. Edinburgh J Bot 2004; 60: 533 – 568

[3] Knirsch W, Martìnez-Azorìn M, Pfosser M, Wetsching W. The reinstatement and rediagnosis of the Madagascan genus Rhodocodon (Asparagaceae, Scilloideae), with validation and remarks on H. Perrier's taxa. Phytotaxa 2015; 195: 101 – 133