New phenolic compounds from Dendrobium capillipes and Dendrobium secundum

Abstract

Phytochemical investigation of the stem of Dendrobium capillipes resulted in the isolation of a new flavonol glycoside namely quercetin-3-O-α-l-rhamnopyranosyl-(1 → 2)-β-d-xylopyranoside, along with seven known phenolic compounds which included two flavonol glycosides and five bibenzyls. From the stem of Dendrobium secundum, a new compound named 5-hydroxy-3,4,3′,4′,5′-pentamethoxybibenzyl was characterized, together with two known bibenzyls and three glycosidic flavonoids. Some of the isolated bibenzyls showed cytotoxicity against KB, NCI-H187, and MCF-7 cancer cells, whereas all of the glycosidic flavonoids were devoid of activity.

Keywords:

• cytotoxicity
• chemical constituents
• bibenzyls
• flavonoids
• Dendrobium

Acknowledgments

T.P. is grateful to the Graduate School of Chulalongkorn University for a research grant. Thanks are also due to the Research Instrument Center of Faculty of Pharmaceutical Sciences, Chulalongkorn University, for providing research facilities.