A robust method of extraction and GC-MS analysis of Monophenols exhibited UV-B mediated accumulation in Arabidopsis

Abstract

AbstractStudies on specialised metabolites like phenolics are of immense interest owing to their significance to agriculture, nutrition and health. In plants, phenolics accumulate and exhibits spatial and temporal regulations in response to growth conditions. Robust methodologies aimed at efficient extraction of plant phenolics, their qualitative and quantitative analysis is desired. We optimised the analytical and experimental bottlenecks that captured free, ester, glycoside and wall-bound phenolics after acid or alkali treatments of the tissue extracts and subsequent GC-MS analysis. Higher recovery of phenolics from the methanolic extracts was achieved by through a) Ultrasonication assisted extraction along with Methyl tert-butyl ether (MTBE) enrichment b) nitrogen gas drying and c) their derivatisation using MSTFA for GC-MS analysis. The optimised protocol was tested on Arabidopsis rosette exposed to UV-B radiation (280-315 nm) which triggered enhanced levels of 11 monophenols and might be attributed to photoprotection and other physiological roles. Interestingly, coumaric acid (308 m/z) and caffeic acid (396 m/z) levels were enhanced by 12-14 folds under UV-B. Other phenolics such as cinnamic acid (220 m/z), hydroxybenzoic acid (282 m/z), vanillic acid (312 m/z, gallic acid (458 m/z), ferulic acid (338 m/z), benzoic acid (194 m/z), hydroxycinnamic acid (368 m/z) and protocatechuic acid (370 m/z) also showed elevated levels by about 1 to 4 folds. Notably, vanillin (253 m/z) was detected only in the UV-B exposed tissues. The protocol also comprehensively captured the variations in the levels of ester, glycoside and wall-bounded phenolics with high reproducibility and sensitivity. The robust method of extraction and GC-MS analysis can readily be adopted for studying phenolics in plant systems.