Influence of Bracken Fern (Pteridium caudatum L. Maxon) Pre-treatment on Extraction Yield of Illudane Glycosides and Pterosins

Introduction Bracken (Pteridium spp) illudane glycosidess are labile biologically active terpenoids that undergo decomposition in mild alkali or acid, heat and enzymatic reactions. Hypothetically, quantitation of these weakly chromophoric carcinogens may be challenged by plant sample preparation procedures that may alter the yield of isolates. Objective To study the influence of common plant sample pre-treatments on the recovery of Pteridium caudatum illudane glycoside carcinogens, ptaquiloside (1a), caudatoside (1c) and ptaquiloside Z (1d), and associated pterosins A, B and Z (2a, b, c) using HPLC-DAD. Method Bracken fronds were divided in equal left/right sections. One section was subjected to high vacuum desiccation (VD) and the other to freeze-drying (FD), air drying at room temperature (AD) for 7days, air drying at 70 degrees C for 72h (HD), or no treatment (fresh frond, FF). Quantitation was achieved by brief hot-water extraction, base-acid transformation of 1a, 1c and 1d to 2a, b, c and HPLC-DAD analysis against standards. Results Substantial differences in extraction yields were found for all illudane glycosides in the order FF>FD approximate to VD>AD>HD. Illudane instability to HD was 1c>1d>1a. Significant losses also were recorded in yields of Pterosins A, B and Z. Conclusion Glycoside extraction suffers from substantial yield loss of all illudane glycosides and indigenous pterosins in all sample pre-treatments studied relative to fresh frond material. Copyright (c) 2012 John Wiley & Sons, Ltd.