Characterisation of galloylated cyanogenic glucosides and hydrolysable tannins from leaves of Phyllagathis rotundifolia by LC-ESI-MS/MS.

Introduction: Phyllagathis rotundifolia (Jack) Bl. (Melastomataceae) is a creeping herb found in Peninsular Malaysia and Sumatra. Traditionally, a decoction of the leaves is used in the treatment of malaria, fever and stomach ache.

Objective: To provide ESI-MS(n) data which are applicable for chemical fingerprinting of P. rotundifolia to obviate laborious isolation and purification steps.

Methodology: The mass spectral data for the compounds isolated from the leaves of P. rotundifolia were obtained by liquid chromatography-electrospray ionisation tandem mass spectrometry.

Results: The MS fragmentation patterns were obtained for galloylated cyanogenic glucosides based on prunasin (prunasin 6′‐O‐gallate 1, prunasin 2′,6′‐di‐O‐gallate 2, prunasin 3′,6′‐di‐O‐gallate 3, prunasin 4′,6′‐di‐O‐gallate 4, prunasin 2′,3′,6′‐tri‐Ogallate 5, prunasin 3′,4′,6′‐tri‐O‐gallate 6 and prunasin 2′,3′,4′,6′‐tetra‐O‐gallate 7), gallotannins (6‐O‐galloyl‐D‐glucose 8, 3,6‐di‐O‐galloyl‐D‐glucose 9, 1,2,3‐tri‐O‐galloyl‐β‐D‐glucose 10, 1,4,6‐tri‐O‐galloyl‐β‐D‐glucose 11, 3,4,6‐tri‐O‐galloyl‐D‐glucose 12, 1,2,3,6‐tetra‐O‐galloyl‐β‐D‐glucose 13 and 1,2,3,4,6‐penta‐O‐galloyl‐β‐D‐glucose 14), ellagitannins [6‐O‐galloyl‐2,3‐O‐(S)‐hexahydroxy‐diphenoyl‐D‐glucose 15, praecoxin B 16 and pterocarinin C 17], ellagic acid derivatives (3′‐O‐methyl‐3,4‐methylenedioxyellagic acid 4′‐O‐β‐D‐glucopyranoside 18 and 3,3′,4‐tri‐O‐methylellagic acid 4′‐O‐β‐D‐glucopyranoside 19) and gallic acid 20 that were isolated from the leaves of P. rotundifolia.

Conclusion: The ESI-MS(n) technique facilitates identification of galloylated cyanogenic glucosides, hydrolysable tannins and ellagic acid derivatives that were isolated from the leaves of P. rotundifolia. It yields MS(n) spectra that are useful for identification of these compounds in complex samples and permit more complete fingerprinting of plant materials.